Disease Markers
Volume 2018 (2018), Article ID 7860494, 15 pages
https://doi.org/10.1155/2018/7860494

Research Article

Prognostic Factors and Survival in Primary Central Nervous System Lymphoma: A Population-Based Study

Yudong Shan and Yilan Hu

Department of Neurosurgery, Affiliated Cixi Hospital of Wenzhou Medical University, Ningbo, Zhejiang Province, China

Correspondence should be addressed to Yudong Shan; zenki_zheng@yeah.net

Received 20 March 2018; Revised 20 May 2018; Accepted 5 June 2018; Published 28 June 2018

Academic Editor: Timo Sorsa

Copyright © 2018 Yudong Shan and Yilan Hu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Objective. This study sought to explore the prognostic factors in a large retrospective cohort of patients with primary central nervous system lymphoma (PCNSL) from the Surveillance, Epidemiology, and End Results database. Methods. There were 5903 patients with PCNSL who had complete clinical information and were identified in the Surveillance, Epidemiology, and End Results program between 1973 and 2014. The epidemiology, therapeutic measures, and clinical characteristics were listed as descriptive statistics. They were grouped into 4 categories: immunocompetent individual with diffuse large B cell lymphoma (DLBCL), immunocompetent individual with non-DLBCL, immunocompromised individual with DLBCL, and immunocompromised individual with non-DLBCL based on different subtypes and immunological status. Survival analysis was conducted with Cox regression models. Results. Different demographics and clinical characteristics were identified as independent factors in different groups. In survival analysis, for patients with DLBCL, chemotherapy involving treatments was associated with the most favorable survival. Received-only radiation could be considered as a primary treatment in immunocompetent patients with non-DLBCL. These differences were statistically significant (). Conclusion. PCNSL patients treated with appropriate chemotherapy treatments may receive stable tumor control.

1. Introduction

Primary central nervous system lymphoma (PCNSL) is a rare type of extranodal non-Hodgkin’s lymphoma (NHL), which is a rare and heterogeneous disease that accounts for approximately 1–3% of all central nervous system (CNS) tumors [1]. The estimated annual incidence of PCNSL, as calculated by the rate session of SEER statistics, is 0.7 cases per 100,000 person-years in the United States. It is well known that PCNSL occurs more commonly in immunosuppressed populations, particularly among people with human immunodeficiency virus (HIV) infection. However, an increasing incidence among immunocompetent adults requires more attention. Improved diagnosis with ascertainment bias and increasing health awareness may explain this situation [2, 3]. Different etiologies appear in immunocompetent and immunosuppressed individuals. Epstein-Barr Virus (EBV) is the major cause of PCNSL in HIV-infected people and transplant recipients, but it is less common in immunocompetent individuals [4, 5]. The heterogeneity of the disease leads to different clinical outcomes and diverse therapeutic approaches.

For decades, radiation and chemotherapy have gained wide recognition as the main treatments for cancer. Cancer-directed surgical procedures have become an unorthodox treatment [6, 7]. Unfortunately, high rates of disease control or cures have not been proven by the sensitivity of radiation and chemotherapy. Traditionally, whole brain radiation therapy (WBRT) was the primary treatment option, but currently, physicians rarely use radiation alone as the primary treatment. Regardless of whether these treatments are performed alone or in combination, high rates of neurotoxicity, particularly in patients over 60 years of age, should be considered [8]. Some studies have indicated that the combination of radiation with chemotherapy was better than a single treatment, whereas another study demonstrated that radiation should not be included in combinations [9, 10]. The prognostic role of radiation in treating PCNSL remains controversial. Therefore, in this study, we intend to explore the prognostic factors for survival in patients with PCNSL from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) database.

2. Materials and Methods

2.1. Data Source

The data source for this study is the SEER database from 1973 to 2014, which was released in November 2016. The SEER program provides clinical data, such as patient demographics and tumor characteristics, annually and openly. The National Center for Health Statistics is responsible for mortality data collection and updates [11]. The necessary data were obtained by the National Cancer Institute’s SEERStat software (Surveillance Research Program, National Cancer Institute SEERStat software, http://www.seer.cancer.gov/seerstat) (Version 8.3.4).

2.2. Inclusion Criteria

The inclusion criteria for the study were as follows: patients who were diagnosed between 1973 and 2014 with complete clinical manifestations, patients who had CNS listed as the primary disease lesion (International Classification of Diseases for Oncology, 3rd Edition (ICD-O-3) topography codes C70.0–C72.9), and patients who were diagnosed as having NHL subtypes (ICD-O-3 histology codes 9590, 9591, 9670–9699, 9701–9705, 9714, 9719, and 9727–9729). All diagnoses were histologically confirmed. All patients included were regularly followed up. Immunological status was not provided directly in the SEER database, and it was presumed by cause of death. Thus, on some level, “uncertain criteria” were included in the inclusion criteria. Patients with an insufficient clinical profile, unknown cause of death, and unknown survival months were excluded. Finally, 5903 patients were enrolled. This study was conducted based on the Public Data Base, and all methods were carried out in accordance with the Declaration of Helsinki. No experiments on humans or the use of human tissue samples were used in this study.

2.3. Variables for the Analyses

Age at diagnosis, sex, race, lymphoma subtypes, tumor primary sites, tumor laterality, lymphoma stage, therapy modality, immunological status, insurance status, marital status, and overall survival (OS) were extracted from original data and considered primary variables. Age at diagnosis was categorized as less than 60 years and 60 years or older. Race was classified into African American, non-Hispanic Caucasian, and others. Lymphoma subtypes were dichotomized as diffuse large B cell lymphoma (DLBCL) and non-DLBCL. Primary sites were located in the brain, meninges/cranial nerves, spine, and other locations. Tumor laterality was defined as a binary variable, with a nonpaired site and a paired site (left/right—origin of primary). According to SEER research data record description, tumor laterality describes the side of a paired organ or side of the body on which the reportable tumor originated. Laterality is coded for select invasive, benign, and borderline primary intracranial and CNS tumors. Lymphoma stage was stratified according to the Ann Arbor stage [12, 13]. The therapeutic modality included surgery, radiation, and chemotherapy. Detailed surgical information was not reviewed because its role in PCNSL was mainly limited to biopsy for tissue diagnosis. The immunological status was not provided directly in the SEER database. However, the cause of death was available. One of these causes was defined as “Other Infectious and Parasitic Diseases, including HIV.” Patients with this cause were strongly assumed to be immunocompromised. Further information involving HIV-positive, transplantation, or other causes were not supplied by SEER Database. This is similar to the approach taken by previous studies [14, 15]. Patients living with an immunocompromised status were rather difficult to identify by the records. However, this status had a limited impact on the total conclusion because patients with this status did not have an absolute predominance in terms of quantity. Insurance status was defined as uninsured, insured, or any Medicaid and insurance status unknown. Marital status was categorized as never married, married, ever married (including divorce, separated, and widowed), and marital status unknown.

2.4. Outcome Measurement

OS was the observed indicator of outcomes. OS was determined by the “vital status,” which represents the time from the date of diagnosis to the date of death. Death was considered a separate event. Censored observations included patients who were still alive at the time of the last follow-up. We only performed analysis on OS because we found that the results for cancer-specific survival were the same as those obtained for OS in the univariate and multivariate analyses.

2.5. Statistical Analysis

All statistical analyses were calculated by Statistical Package for the Social Sciences (SPSS) software version 22 (SPSS Inc., Chicago, IL, USA). Univariate and multivariate Cox proportional hazard models were used to estimate the association between various covariates and survival outcome. Kaplan-Meier curves and the log-rank (Mantel-Cox) test were used to compare the OS rates. Differences were considered statistically significant when .

3. Results

3.1. Baseline Characteristics

A total of 3353 males and 2550 female patients were included in the analysis. Of the total, 5138 patients were considered immunocompetent, and 765 were immunocompromised. The majority of them (4685, 79.4%) were diagnosed between 1996 and 2014. The median age at diagnosis was 61 years. Patients with ages ranging from 0 years to 98 years (Q25 47 years, Q75 71 years) were analyzed, in which patients with ages ≥ 60 years were the most common (53.7%). The immunocompromised cohort was substantially younger than the immunocompetent cohort was (for patients ≥ 60, 3.7% versus 61.1%). More blacks (28.2%) and males (88.9%) were included in the immunocompromised cohort than in the immunocompetent cohort (6% and 52%, resp.). DLBCL was the primary subtype in both cohorts. The tumor was usually located in the brain as the primary lesion. More azygous lesions than paired lesions were detected in patients. Patients had a larger proportion stratified as Ann Arbor stages I–II. More patients in the immunocompromised cohort (60.8%) underwent radiation than did those in the immunocompetent cohort (45.2%). In contrast, the patients in the immunocompetent cohort were more likely to receive chemotherapy than were those in the immunocompromised cohort (61.9% versus 19.2%). The insurance status of most patients was unknown. Most immunocompromised patients never got married (74%), while most immunocompetent patients were or ever got married. For immunocompromised patients, radiation only (49.3%) and neither but conservative treatment (30.5%) were the main therapeutic approaches. In contrast, most immunocompetent patients received chemotherapy treatments. The demographics and clinical characteristics are summarized in Table 1.

Table 1: Summary of characteristics for the patient population. SEER 1973–2014 ()a.

Characteristic
All patients number (%) ()
Immunocompromised patients number (%) ()
Immunocompetent patients number (%) ()

Age

    <60
2735 (46.3)
737 (96.3)
1998 (38.9)

    ≥60
3168 (53.7)
28 (3.7)
3140 (61.1)

Sex

    Male
3353 (56.8)
680 (88.9)
2673 (52.0)

    Female
2550 (43.2)
85 (11.1)
2465 (48.0)

Race

    Black
523 (8.9)
216 (28.3)
307 (6.0)

    White
4816 (81.5)
525 (68.6)
4291 (83.5)

    Other (American Indian/AK native, Asian/Pacific Islander)
564 (9.6)
24 (3.1)
540 (10.5)

Dates of diagnosis

    1973–1984
188 (3.2)
5 (0.7)
183 (3.6)

    1985–1995
1030 (17.4)
386 (50.5)
644 (12.5)

    1996–2006
2265 (38.4)
250 (32.7)
2015 (39.2)

    2007–2014
2420 (41.0)
124 (16.1)
2296 (44.7)

Lymphoma subtypes

    DLBCL
4342 (73.6)
527 (68.9)
3815 (74.3)

    Non-DLBCL
1561 (26.4)
238 (31.1)
1323 (25.7)

Primary site

    Brain
4768 (80.8)
684 (89.4)
4084 (79.5)

    Meninges/cranial nerves
110 (1.9)
7 (0.9)
107 (2.0)

    Spine
364 (6.1)
18 (2.4)
346 (6.7)

    Other
661 (11.2)
56 (7.3)
605 (11.8)

Laterality

    Not a paired site
4197 (71.7)
662 (86.5)
3535 (68.8)

    Paired site (left/right—origin of primary)
1706 (28.9)
103 (13.5)
1603 (31.2)

Lymphoma Ann Arbor stage

    I–II
4324 (73.3)
585 (76.5)
3739 (72.8)

    III–IV
116 (19.6)
147 (19.2)
1015 (19.8)

    Unknown
417 (7.1)
33 (4.3)
384 (7.5)

Radiation

    No
3015 (51.1)
289 (37.8)
2726 (53.1)

    Yes
2785 (47.2)
465 (60.8)
2320 (45.2)

    Unknown
103 (1.7)
11 (1.4)
92 (1.8)

Chemotherapy

    Yes
3325 (56.3)
147 (19.2)
3178 (61.9)

    No
2578 (43.7)
618 (80.8)
1960 (38.1)

Immunological status

    Immunocompromised
765 (13.0)
—
—

    Immunocompetent
5138 (87.0)

Vital status

    Dead
4382 (74.2)
765 (100.0)
3617 (70.4)

    Alive
1521 (25.8)
0 (0.0)
1521 (29.6)

Insurance status

    Uninsured
101 (1.7)
12 (1.6)
89 (1.7)

    Insured/any Medicaid
2271 (38.5)
107 (14.0)
2164 (42.1)

    Insurance status unknown
3531 (59.8)
646 (84.4)
2885 (56.2)

Marital status

    Never married
1409 (23.9)
566 (74.0)
843 (16.4)

    Married
3170 (53.7)
107 (14.0)
3063 (59.6)

    Ever married (divorced, separated, and widowed)
1142 (19.3)
63 (8.2)
1079 (21.0)

    Unknown
182 (3.1)
9 (3.8)
153 (3.0)

Multiple modalities

    Neither but conservative treatment
1104 (18.7)
233 (30.5)
871 (17.0)

    Chemotherapy involving
3270 (55.4)
144 (18.8)
3126 (60.8)

    Only radiation
1426 (24.2)
377 (49.3)
1049 (20.4)

    Missing
103 (1.7)
11 (1.4)
92 (1.8)

SEER: Surveillance, Epidemiology, and End Results; DLBCL: diffuse large B cell lymphoma; PCNSL: primary central nervous system lymphoma. aData are presented as the number (percentage) of patients.

3.2. Univariate and Multivariate Analyses in Patients according to Lymphoma Subtypes and Immunological Status

The variables that were validated as independent prognostic factors in immunocompromised patients with DLBCL included Ann Arbor stage (stages III–IV, hazard ratio (HR): 1.499, 95% CI: 1.187–1.892, ), received radiation therapy (yes, HR: 0.662, 95% CI: 0.548–0.800, ), and received chemotherapy (yes, HR: 0.554, 95% CI: 0.434–0.709, ) (Table 2). The independent prognostic factors in immunocompetent patients with DLBCL included age (range of over 60 years, HR: 1.834, 95% CI: 1.679–2.004, ), primary site (primary lesion of meninges/cranial nerves, HR: 0.470, 95% CI: 0.313–0.706, ; primary lesion of spine, HR: 0.428, 95% CI: 0.342–0.535, ; and other primary lesion, HR: 0.715, 95% CI: 0.620–0.824, ), tumor laterality (paired primary site, HR: 0.905, 95% CI: 0.825–0.994, ), received chemotherapy (yes, HR: 0.442, 95% CI: 0.407–0.480, ), and marital status (ever married, HR: 1.354 95% CI: 1.183–1.549, ) (Table 3). Received chemotherapy (HR: 0.384, 95% CI: 0.273–0.539, ) was the only risk factor in immunocompromised patients with non-DLBCL (Table 4). In immunocompetent patients with non-DLBCL, age (range of over 60 years, HR: 2.389, 95% CI: 2.052–2.780, ), primary site (primary lesion of meninges/cranial nerves, HR: 0.349, 95% CI: 0.238–0.511, ; primary lesion of spine, HR: 0.452, 95% CI: 0.362–0.565, ; and other primary lesion, HR: 0.515, 95% CI: 0.428–0.618, ), received chemotherapy (yes, HR: 0.724, 95% CI: 0.433–0.828, ), and marital status (married, HR: 0.821 95% CI: 0.677–0.994, ) were identified as risk factors (Table 5). These results were calculated based on multivariate analysis.

Table 2: Univariate and multivariate survival analysis in immunocompromised patients with DLBCL.

Variable
Univariate analysis
Multivariate analysis

HR (95% CI)

HR (95% CI)

Age (years)

    <60
Reference

    ≥60
0.727 (0.453–1.166)
0.186

Race

    White
Reference

    Black
1.194 (0.988–1.443)
0.067

    Other (American Indian/AK native, Asian/Pacific Islander)
0.921 (0.573–1.480)
0.734

Gender

    Female
Reference

    Male
1.185 (0.908–1.546)
0.212

Dates of diagnosis

    1973–1984
Reference

Reference

    1985–1995
3.253 (1.027–10.304)
0.045
2.701 (0.472–15.466)
0.264

    1996–2006
2.270 (0.718–7.179)
0.163
1.881 (0.329–10.747)
0.477

2007–2014
2.740 (0.858–8.756)
0.089
2.376 (0.411–13.728)
0.334

Primary site

    Brain
Reference

Reference

    Meninges/cranial nerves
0.313 (0.076–1.287)
0.107
0.603 (0.073–5.004)
0.640

    Spine
0.465 (0.254–0.852)
0.013
0.487 (0.262–0.906)
0.023

    Other
0.593 (0.709–1.541)
0.824
1.052 (0.692–1.600)
0.811

Laterality

    Not a paired site
Reference

    Paired site (left/right—origin of primary)
0.901 (0.709–1.145)
0.393

Lymphoma Ann Arbor stage

    I–II
Reference

Reference

    III–IV
1.452 (1.157–1.824)
0.001
1.499 (1.187–1.892)
0.001

    Unknown
1.269 (0.833–1.935)
0.267
1.177 (0.735–1.886)
0.497

Radiation

    No
Reference

Reference
<0.001

    Yes
0.673 (0.562–0.806)
<0.001 0.569
0.662 (0.548–0.800)
0.925

    Unknown
0.823 (0.422–1.607)

0.968 (0.490–1.914)

Chemotherapy

    No
Reference

Reference

    Yes
0.585 (0.465–0.735)
<0.001
0.554 (0.434–0.709)
<0.001

Insurance status

    Uninsured
Reference

    Insured/any Medicaid
0.708 (0.378–1.328)
0.282

    Insurance status unknown
0.735 (0.403–1.339)
0.315

Marital status

    Never married
Reference

    Married
0.847 (0.660–1.087)
0.192

    Ever married (divorced, separated, and widowed)
0.877 (0.647–1.189)
0.399

    Unknown
1.097 (0.731–1.646)
0.654

OS: overall survival; HR: hazard ratio; CI: confidence interval; SEER: Surveillance, Epidemiology, and End Results; DLBCL: diffuse large B cell lymphoma; PCNSL: primary central nervous system lymphoma.

Table 3: Univariate and multivariate survival analysis in immunocompetent patients with DLBCL.

Variable
Univariate analysis
Multivariate analysis

HR (95% CI)

HR (95% CI)

Age (years)

    <60
Reference

Reference

    ≥60
2.084 (1.916–2.267)
<0.001
1.834 (1.679–2.004)
<0.001

Race

    White
Reference

Reference

    Black
0.759 (0.628–0.918)
0.004
0.854 (0.703–1.037)
0.111

    Other (American Indian/AK native, Asian/Pacific Islander)
0.890 (0.788–1.006)
0.062
0.912 (0.806–1.031)
0.140

Gender

    Female
Reference

    Male
0.947 (0.878–1.021)
0.153

Dates of diagnosis

    1973–1984
Reference

Reference

    1985–1995
1.937 (0.761–1.153)
0.536
1.124 (0.912–1.386)
0.272

    1996–2006
0.727 (0.600–0.879)
0.001
1.048 (0.861–1.275)
0.642

    2007–2014
0.636 (0.525–0.770)
<0.001
1.031 (0.841–1.265)
0.767

Primary site

    Brain
Reference

Reference

    Meninges/cranial nerves
0.467 (0.312–0.698)
<0.001
0.470 (0.313–0.706)
<0.001

    Spine
0.403 (0.323--0.503)
<0.001
0.428 (0.342–0.535)
<0.001

    Other
0.682 (0.594–0.783)
<0.001
0.715 (0.620–0.824)
<0.001

Laterality

    Not a paired site
Reference

Reference

    Paired site (left/right—origin of primary)
0.885 (0.815–0.961)
0.003
0.905 (0.825–0.994)
0.036

Lymphoma Ann Arbor stage

    I–II
Reference

    III–IV
0.967 (0.877–1.067)
0.504

    Unknown
1.254 (1.073–1.465)
0.004

Radiation

    No
Reference

    Yes
1.038 (0.962–1.120)
0.338

    Unknown
0.815 (0.615–1.081)
0.156

Chemotherapy

    No
Reference

Reference

    Yes
0.402 (0.372–0.434)
<0.001
0.442 (0.407–0.480)
<0.001

Insurance status

    Uninsured
Reference

    Insured/any Medicaid
0.880 (0.646–1.198)
0.416

    Insurance status unknown
1.090 (0.802–1.481)
0.581

Marital status

    Never married
Reference

Reference

    Married
1.254 (1.118–1.406)
<0.001
1.070 (0.949–1.207)
0.271< 0.001 0.472

    Ever married (divorced, separated, and widowed)
1.823 (1.603–2.074)
<0.001
1.354 (1.183–1.549)

    Unknown
1.632 (1.283–2.075)
<0.001
1.093 (0.857–1.394)

OS: overall survival; HR: hazard ratio; CI: confidence interval; SEER: Surveillance, Epidemiology, and End Results; DLBCL: diffuse large B cell lymphoma; PCNSL: primary central nervous system lymphoma.

Table 4: Univariate and multivariate survival analysis in immunocompromised patients with non-DLBCL.

Variable
Univariate analysis
Multivariate analysis

HR (95% CI)

HR (95% CI)

Age (years)

    <60
Reference

    ≥60
0.599 (0.305–1.176)
0.136

Race

    White
Reference

    Black
1.029 (0.766–1.382)
0.848

    Other (American Indian/AK native, Asian/Pacific Islander)
2.129 (0.936–4.841)
0.071

Gender

    Female
Reference

    Male
0.874 (0.568–1.346)
0.541

Dates of diagnosis

    1973–1984
Reference

    1985–1995
1.396 (0.344–5.661)
0.641

    1996–2006
1.056 (0.257–4.347)
0.939

    2007–2014
2.218 (0.518–9.505)
0.283

Primary site

    Brain
Reference

    Meninges/cranial nerves
1.068 (0.439–2.598)
0.885

    Spine
0.784 (0.363–1.690) 0.620
0.534

    Other
(0.414–0.929)
0.021

Laterality

    Not a paired site
Reference

    Paired site (left/right—origin of primary)
1.383 (0.905–2.115)
0.134

Lymphoma Ann Arbor stage

    I–II
Reference

    III–IV
0.968 (0.708–1.322)
0.836

    Unknown
0.938 (0.495–1.779)
0.846

Radiation

    No
Reference

    Yes
0.803 (0.617–1.046)
0.104

    Unknown
0.454 (0.111–1.846)
0.270

Chemotherapy

    No
Reference

Reference

    Yes
0.384 (0.273–0.539)
<0.001
0.384 (0.273–0.539)
<0.001

Insurance status

    Uninsured
Reference

    Insured/any Medicaid
0.349 (0.046–2.631)
0.307

    Insurance status unknown
0.222 (0.031–1.605)
0.136

Marital status

    Never married
Reference

    Married
0.635 (0.430–0.936)
0.022

    Ever married (divorced, separated, and widowed)
0.885 (0.531–1.477)
0.641

    Unknown
2.138 (0.788–5.799)
0.136

OS: overall survival; HR: hazard ratio; CI: confidence interval; SEER: Surveillance, Epidemiology, and End Results; DLBCL: diffuse large B cell lymphoma; PCNSL: primary central nervous system lymphoma.

Table 5: Univariate and multivariate survival analysis in immunocompetent patients with non-DLBCL.

Variable
Univariate analysis
Multivariate analysis

HR (95% CI)

HR (95% CI)

Age (years)

    <60
Reference

Reference

    ≥60
2.399 (2.085–2.759)
<0.001
2.389 (2.052–2.780)
<0.001

Race

    White
Reference

    Black
0.777 (0.608–0.993)
0.043

    Other (American Indian/AK native, Asian/Pacific Islander)
1.016 (0.793–1.300)
0.902

Gender

    Female
Reference
0.946

    Male
1.005 (0.880–1.147)

Dates of diagnosis

    1973–1984
Reference

    1985–1995
1.165 (0.876–1.549)
0.294

    1996–2006
0.761 (0.577–1.002)
0.052

    2007–2014
0.847 (0.633–1.135)
0.266

Primary Site

    Brain
Reference

Reference

    Meninges/cranial nerves
0.358 (0.245–0.524)
<0.001
0.349 (0.238–0.511)
<0.001

    Spine
0.443 (0.355--0.553)
<0.001
0.452 (0.362–0.565)
<0.001

    Other
0.555 (0.463–0.666)
<0.001
0.515 (0.428–0.618)
<0.001

Laterality

    Not a paired site
Reference

    Paired site (left/right—origin of primary)
0.962 (0.804–1.150)
0.670

Lymphoma Ann Arbor stage

    I–II
Reference

    III–IV
0.980 (0.835–1.152)
0.810

    Unknown
1.008 (0.832–1.220)
0.936

Radiation

    No
Reference

    Yes
0.894 (0.780–1.023)
0.104

    Unknown
1.978 (1.198–3.267)
0.008

Chemotherapy

    No
Reference

Reference

    Yes
0.684 (0.599–0.781)
<0.001
0.724 (0.633–0.828)
<0.001

Insurance status

    Uninsured
Reference

    Insured/any Medicaid
1.457 (0.685–3.096)
0.328

    Insurance status unknown
1.522 (0.722–3.208)
0.270

Marital status

    Never married
Reference

Reference

    Married
1.153 (0.961–1.383)
0.126
0.821 (0.677–0.994)
0.043

    Ever married (divorced, separated, and widowed)
1.689 (1.363–2.094)
<0.001
1.048 (0.833–1.319)
0.689

    Unknown
1.206 (0.805–1.805
0.364
0.809 (0.538–1.217)
0.309

OS: overall survival; HR: hazard ratio; CI: confidence interval; SEER: Surveillance, Epidemiology, and End Results; DLBCL: diffuse large B cell lymphoma; PCNSL: primary central nervous system lymphoma.

3.3. Impact of Treatment Options for Patients with DLBCL

To compare the efficacy of different treatments, we grouped them as follows: received radiation only, received chemotherapy treatments (chemotherapy only or chemotherapy plus radiation), and received neither. In many countries, PCNSL patients first undergo chemotherapy. When the therapeutic response is good, the patients may be followed up without radiotherapy, but when complete remission is not obtained or the tumor recurs, radiation therapy may be added. Patients who receive chemotherapy plus radiation may thus have an apparently worse background than those who receive chemotherapy alone. Therefore, it is not appropriate to separate these two groups. Stratification analysis made the results more accurate. Survival analysis beyond different treatments was conducted according to different immunological statuses and dates of diagnosis. For immunocompromised patients, the median OS for those who received radiation only was 2 months (1985–1995), 4 months (1996–2006), and 2 months (2007–2014), respectively. The median OS for those who received neither was 0 months (1985–1995, 1996–2006, and 2007–2014). The median OS for those who received chemotherapy involving treatments was 2 months (1985–1995), 9 months (1996–2006), and 3 months (2007–2014). For immunocompetent patients, the median OS for those who received radiation only was 12 months (1973–1984), 6 months (1985–1995), 6 months (1996–2006), and 2 months (2007–2014). The median OS for those received neither was 0 months (1973–1984), 2 months (1985–1995), 1 month (1996–2006), and 1 month (2007–2014). The median OS for those who received chemotherapy treatments was 18 months (1973–1984), 20 months (1985–1995), 28 months (1996–2006), and 34 months (2007–2014). These differences were statistically significant (). The Kaplan-Meier-estimated OS distributions are shown in Figures 1 and 2.

(a)

(b)

(c)

Figure 1: Kaplan-Meier survival curves of immunocompromised patients with diffuse large B cell lymphoma (DLBCL) in 1985–1995 (a), 1996–2006 (b), and 2007–2014 (c) according to treatment options.

(a)

(b)

(c)

(d)

Figure 2: Kaplan-Meier survival curves of immunocompetent patients with DLBCL in 1973–1984 (a), 1985–1995 (b), 1996–2006 (c), and 2007–2014 (d) according to treatment options.

3.4. Impact of Treatment Options for Patients with Non-DLBCL

For immunocompromised patients, the median OS for those who received radiation only was 3 months (1985–1995), 2 months (1996–2006), and 1 month (2007–2014). The median OS for those who received neither was 1 month (1985–1995), 0 months (1996–2006), and 0 months (2007–2014). The median OS for those who received chemotherapy treatments was 5 months (1985–1995), 14 months (1996–2006), and 2 months (2007–2014). For immunocompetent patients, the median OS for those who received radiation only was 57 months (1973–1984), 11 months (1985–1995), 57 months (1996–2006), and 62 months (2007–2014). The median OS for those who received neither was 3 months (1973–1984), 3 months (1985–1995), 4 months (1996–2006), and 4 months (2007–2014). The median OS for those who received chemotherapy treatments was 18 months (1973–1984), 35 months (1985–1995), 74 months (1996–2006), and 46 months (2007–2014). These differences were statistically significant (). The Kaplan-Meier-estimated OS distributions are shown in Figures 3 and 4. The median OS of each group in each period was summarized and are shown in Figure 5.

(a)

(b)

(c)

Figure 3: Kaplan-Meier survival curves of immunocompromised patients with non-DLBCL in 1985–1995 (a), 1996–2006 (b), and 2007–2014 (c) according to treatment options.

(a)

(b)

(c)

(d)

Figure 4: Kaplan-Meier survival curves of immunocompetent patients with non-DLBCL in 1973–1984 (a), 1985–1995 (b), 1996–2006 (c), and 2007–2014 (d) according to treatment options.

(a)

(b)

(c)

(d)

Figure 5: The median OS (months) of each group of patients in any periods are displayed using line charts: (a) immunocompromised patients with DLBCL, (b) immunocompromised patients with non-DLBCL, (c) immunocompetent patients with DLBCL, and (d) immunocompetent patients with non-DLBCL

4. Discussion

Previous studies focused mostly on either immunocompetent patients or the impact of demographic factors [14, 16–18]. Chemotherapy data were first available in population-based data collected in the United States in 2017, which made it possible to analyze the merits and demerits of diverse therapeutic approaches for PCNSL to demonstrate an improvement in survival over time. Some predictors of survival, such as age, immunological status, and gender, have been confirmed in this study. However, some well-known predictors have been challenged. Receiving radiation seemed to be beneficial only for survival, which contradicts Norden et al.’s conclusion [14] based on the SEER database up to 2004. Being married at diagnosis did not have a favorable impact on survival compared to being unmarried, but ever being married (including divorce, separated, and widowed) actually negatively influenced survival in patients with DLBCL. Survival over time has improved for years and has mainly been attributed to the increasing use of methotrexate-based chemotherapy regimens and improved supportive care. The standard therapeutic approaches for incipient patients or relapsed or refractory patients are a high-dose methotrexate-based regimen or (low-dose or standard-dose) WBRT according to the NCCN Clinical Practice Guidelines in Oncology: Central Nervous System Cancers Version 1.2016. However, several patients who received radiation therapy showed a decreased survival time [15, 19, 20]. Presumably physicians and elderly patients, who represent approximately half of the PCNSL population, are aware of the fact that radiation therapy is neurotoxic. This change in benefit affects physicians’ decisions. Here, we sought to retrospectively identify evidence about the impact of radiation on survival from a population-based database.

In immunocompromised patients, regardless of whether they have been diagnosed with DLBCL or non-DLBCL, chemotherapy treatments could prolong survival in all time periods. It is better to choose this as the primary treatment. Additionally, some benefit could be observed in patients who received radiation only. Without these two approaches, immunocompromised patients have little chance of survival. It is obvious that the immunocompromised patients who received neither chemotherapy nor radiation had a median OS of 0 months. How could this occur? Detailed analysis showed that this population of patients was mainly male (possibly homosexual), black, single, young, or having poor economic and education conditions, which may prevent them from receiving further treatment. Furthermore, faint medical awareness, which can lead to a long duration before seeking medical assistance and concerns about basic immunodeficiency diseases (almost HIV), from the physician may also be a cause. This type of patient unexpectedly represents one-third of all immunocompromised patients, and it has been a general social phenomenon in the US. The results became more interesting in immunocompetent patients. Chemotherapy treatments provide more benefits over time in DLBCL patients, which is mainly attributed to the improvement of chemotherapy drugs and regimens. Only radiation therapy is below the therapeutic need and may cause central neurotoxicity. The relevant survival time is relatively shorter than that in those who received chemotherapy treatments in recent years. However, the results were the reverse in non-DLBCL patients. Although great advancements have been made in chemotherapy treatments, it was still seen that the efficacy of radiation therapy was not inferior to that of chemotherapy treatments and became even better in the last 7 years. It is well known that non-DLBCL has a less aggressive evolution than DLBCL does, so less radical therapeutic approaches may be associated with favorable survival. In any case, receiving neither chemotherapy nor radiation is not recommended. We observed that most patients were at Ann Arbor stages I–II, which is considered an early stage of NHL, but only less than 30% cases survived, regardless of treatment. There is still a long way to go in cancer control.

Previous studies have collected relevant results based on a limited population. Chalise et al. [21] indicated that a dexamethasone-based chemotherapy regimen is comparable with that of an HD-MTX-based chemotherapy regimen plus WBRT. Korfel et al. suggested no worsening of OS without WBRT in the primary therapy of PCNSL, even although statistical proof of noninferiority in OS was not given [22]. Thiel et al. showed that no significant difference in OS was recorded when WBRT was omitted from first-line chemotherapy in patients with newly diagnosed primary CNS lymphoma [10]. Our result further consolidates their conclusion. It actually does not mean that radiation could be neglected. Dose-reduced WBRT or partial-brain radiotherapy has been studied and evaluated. Early results have shown their potential [23, 24]. Even the role of surgery as an unorthodox treatment should be reconsidered [25].

The latest data and the relatively large cohort are the major strengths of this study, which closely represents the current situation in the US. Conclusions about mortality and the outcomes of rare malignancies could be found only in studies of large populations but not for collaborative or single institutions. However, the known limitations of the study may weaken these conclusions. Our effort to identify immunocompromised patients has inherent flaws, although there are no better methods. In addition, this classification scheme relies primarily on the causes of death. A few surviving immunocompromised patients might be classified as immunocompetent. The inability to accurately classify immunocompromised patients in the SEER data has the potential to introduce bias. However, this situation cannot be solved until a marker of immunological status, such as HIV and transplantation status, is clearly labelled in the SEER database. In addition, detailed information about chemotherapy and radiation was not captured. This information is not currently available from the SEER database.

In summary, these data indicate that radiation alone should not be recommended as the primary therapeutic approach for PCNSL patients with the DLBCL subtype. In non-DLBCL cases, it may provide an excellent outcome. Receiving neither chemotherapy nor radiation led to poor survival. The use of proper chemotherapy regimens greatly improved survival over time. Novel adjuvant therapies should be developed.

Data Availability

The data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest

The authors declare no conflicts of interest.

Authors’ Contributions

Yudong Shan wrote the main manuscript text, and Yilan Hu prepared Figures 1–5. All authors collaborated in the collection and interpretation of the data and contributed to the manuscript.

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