Colorectal cancer (CRC) is the third most common cancer in the world. The curability of CRC has been improving in recent years, due to the progress made in surgical techniques and in chemotherapy, including molecular targeted drugs. However, the prognostic risk factors for CRC are still under debate. Recently, several biomarkers have been reported to be the risk factors of CRC recurrence; however, lymphatic metastasis, which Dukes discovered more than 80 years ago [
However, the risk of recurrence in CRC patients with node-negative disease is not clear. Accordingly, we aimed in this study to investigate the correlations between preoperative IL-6 levels and various clinicopathological parameters and to determine whether preoperative IL-6 is a prognostic factor for recurrence in CRC patients, with particular focus on stage II CRC.
Two hundred thirty-three patients with CRC were enrolled in this study. Written informed consent to participate was provided by all patients. Operations were performed between April 2010 and November 2013. The male : female ratio was 139 : 94, and the mean age was 69.1 years (±10.2). The mean body mass index (BMI) was 22.2 kg/m2 (±3.8). The exclusion criteria included the presence of a second cancer or the presence of inflammatory conditions such as abscess, perforation, or pneumonia. The primary lesion was located in the rectum in 78 patients and in the colon in 155 (sigmoid colon: 65, descending colon: 11, transverse colon: 26, ascending colon: 42, and cecum: 11). The levels of biomarkers (serum IL-6, CRP, albumin, carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9)), and plasma vascular endothelial growth factor (VEGF) were measured preoperatively. Serum IL-6 level was measured using a standard chemiluminescent enzyme immunoassay, and plasma VEGF level was measured using an enzyme-linked immunosorbent assay, as suggested by the manufacturer (SRL Tokyo Laboratories Inc., Tokyo, Japan). CEA and CA19-9 levels were measured using standard chemiluminescent enzyme immunoassays. CRP level was measured using the latex agglutination reaction method. Albumin level was measured using the modified bromocresol purple method. Synchronous metastasis was evaluated using preoperative computed tomography (CT) and/or postoperative pathological examinations. According to the TNM classification, 13/233 (5.6%), 52/233 (22.3%), 60/233 (25.8%), 63/233 (27.0%), and 45/233 (19.3%) cases were classified as stages 0, I, II, III, and IV, respectively. In 32 patients, liver metastasis was observed, and 10 patients were discovered to have lung metastasis during the primary operation. All patients underwent surgery. Among them, 207 (all 188 stages I–III patients and 19/45 stage IV patients) underwent curative resection, while 26 of the 45 stage IV patients underwent palliative resection.
The correlations between preoperative serum IL-6 and the patient characteristics (age, gender, and BMI), preoperative blood test findings (serum albumin, serum CRP, serum CEA, serum CA19-9, and plasma VEGF), and tumor characteristics (tumor location, differentiation, degree of lymphatic and venous invasion, TNM classification, and obstruction) were analyzed (Table
Characteristic of the study patients (
Number of patients | Mean values (±SD) | % | |
---|---|---|---|
IL-6 (pg/mL) | |||
Colorectal cancer | 233 | 6.6 (±9.9) | 94.7 |
Healthy control | 13 | 2.6 (±2.5) | 5.3 |
Age (years) | 69.1 (±10.2) | ||
BMI | 22.2 (±3.8) | ||
Albumin (g/dL) | 4.0 (±0.5) | ||
CRP (mg/dL) | 0.5 (±1.0) | ||
CEA (ng/mL) | 54.6 (±451.6) | ||
CA19-9 (U/mL) | 66.1 (±344.1) | ||
VEGF (pg/mL) | 92.9 (±128.5) | ||
Tumor location | |||
Rectum | 78 | 33.5 | |
Colon | 155 | 66.5 | |
TNM classification | |||
0 | 13 | 5.6 | |
1 | 52 | 22.3 | |
2 | 60 | 25.8 | |
3 | 63 | 27.0 | |
4 | 45 | 19.3 |
IL-6: interleukin-6; BMI: body mass index; CRP: C-reactive protein; CEA: carcinoembryonic antigen; CA19-9: carbohydrate antigen 19-9; VEGF: vascular endothelial growth factor.
All statistical analyses were performed with EZR (Saitama Medical Center, Jichi Medical University, Saitama, Japan), which is a graphical user interface for R (The R Foundation for Statistical Computing, Vienna, Austria). More precisely, it is a modified version of the R-commander designed to add statistical functions frequently used in biostatistics [
The measured serum IL-6 values ranged from 0.7 to 68.0 pg/mL. The mean values were 6.6 (±9.9) pg/mL in CRC patients and 2.6 (±2.5) pg/mL in healthy controls (Figure
Measured serum interleukin-6 (IL-6) values. (a) Preoperative serum IL-6 values for all patients (
Univariate analyses revealed that an increase in the IL-6 level was associated with low levels of albumin (<4.0 g/dL), high serum CRP (≥0.5 mg/L), high serum CEA (≥5.0 ng/dL), high serum CA19-9 (≥37 ng/dL), venous invasion, tumor depth of pT4 disease, distant metastasis, and colorectal obstruction (Table
Results of the univariate analyses (
High IL-6 levels |
Low IL-6 levels |
|
||
---|---|---|---|---|
Age (years) | ≥75 | 24 (32.4) | 50 (67.6) | 0.07 |
<75 | 33 (20.8) | 126 (79.2) | ||
Sex | Female | 20 (21.3) | 74 (78.7) | 0.44 |
Male | 37 (26.6) | 102 (73.4) | ||
BMI | ≥25 | 10 (19.2) | 42 (80.8) | 0.37 |
<25 | 47 (26.0) | 134 (74.0) | ||
Albumin (g/dL) | ≥4.0 | 19 (14.4) | 113 (85.6) | <0.01 |
<4.0 | 38 (37.6) | 63 (62.4) | ||
CRP (mg/dL) | ≥0.5 | 34 (63.0) | 20 (37.0) | <0.01 |
<0.5 | 23 (12.8) | 156 (87.2) | ||
CEA (ng/mL) | ≥5.0 | 30 (32.3) | 63 (67.7) | 0.03 |
<5.0 | 27 (19.3) | 113 (80.7) | ||
CA19-9 (U/mL) | ≥37.0 | 19 (38.0) | 31 (62.0) | 0.02 |
<37.0 | 38 (20.8) | 145 (79.2) | ||
VEGF (pg/mL) | ≥145 | 12 (30.0) | 28 (70.0) | 0.42 |
<145 | 45 (23.3) | 148 (76.7) | ||
Tumor location | Right | 24 (30.4) | 55 (69.6) | 0.15 |
Left | 33 (21.4) | 121 (78.6) | ||
Pathological findings | ||||
Differentiation | Poor | 6 (42.9) | 8 (57.1) | 0.11 |
Others | 51 (23.3) | 168 (76.7) | ||
Lymphatic invasion | Positive | 48 (26.4) | 134 (73.6) | 0.27 |
Negative | 9 (17.6) | 42 (82.4) | ||
Venous invasion | Positive | 50 (29.9) | 117 (70.1) | <0.01 |
Negative | 7 (10.6) | 59 (89.4) | ||
TNM classification | ||||
T | <4 | 28 (16.3) | 144 (83.7) | <0.01 |
4 | 29 (47.5) | 32 (52.5) | ||
N | Positive | 31 (30.4) | 71 (69.6) | 0.07 |
Negative | 26 (19.8) | 105 (80.2) | ||
M | Positive | 19 (42.2) | 26 (57.8) | <0.01 |
Negative | 28 (15.7) | 150 (84.3) | ||
Liver metastasis | Positive | 11 (37.9) | 18 (62.1) | 0.27 |
Negative | 46 (22.5) | 158 (77.5) | ||
Obstruction | Positive | 23 (57.5) | 17 (42.5) | <0.01 |
Negative | 34 (17.6) | 159 (82.4) |
The analyses were performed using Fisher’s exact test. The results are presented as the number of patients.
IL-6: interleukin-6; BMI: body mass index; CRP: C-reactive protein; CEA: carcinoembryonic antigen; CA19-9: carbohydrate antigen 19-9; VEGF: vascular endothelial growth factor.
Logistic multivariate analysis for the associations with interleukin-6 for all patients (
OR | 95% CI |
|
|
---|---|---|---|
CRP | 2.270 | 1.100–4.690 | <0.01 |
CEA | 9.530 | 4.490–20.200 | 0.04 |
Obstruction | 0.255 | 0.110–0.595 | <0.01 |
T4 | 0.446 | 0.207–0.960 | 0.04 |
OR: odds ratio; CI: confidence interval; CRP: C-reactive protein; CEA: carcinoembryonic antigen.
During the follow-up period, 24 (10.0%) of the 233 patients died of cancer, and 1 of another, unrelated disease. Kaplan-Meier survival curves showed that patients with high IL-6 levels had a worse OS rate than those with low levels of IL-6 (
Three-year overall survival (OS) rates according to the preoperative serum interleukin-6 (IL-6) status (Kaplan-Meier analysis). (a) OS of all 233 patients. (b) OS of the 188 stages I–III colorectal cancer patients. (c) OS of the 45 stage IV patients.
During follow-up, recurrence occurred in 37/233 patients (17.9%); among them, 12 of 37 patients had high preoperative IL-6 levels. The sites of metastasis were the liver, lung, and pelvis in 13, 10, and 5 patients, respectively. The DFS rate according to the serum IL-6 status was analyzed among the 207 CRC patients who underwent curative intent resection (Figure
Disease-free survival (DFS) rates according to the preoperative serum interleukin-6 (IL-6) status. (a) DFS of all 207 patients who underwent curative resection. (b) DFS of 188 patients with stages I–III colorectal cancer. (c) DFS of the 60 stage II patients.
Based on this finding, we further investigated the correlations between each clinicopathological parameter and DFS by using the Cox proportional hazard model in TNM stage II patients (
Results of the multivariate Cox hazard model for disease-free survival in stage II colorectal patients (
Hazard ratio | 95% CI |
|
|
---|---|---|---|
CEA | 5.1 | 0.9–30.6 | 0.07 |
CRP | 8.2 | 1.1–61.2 | 0.04 |
IL-6 | 0.1 | 0.01–0.6 | 0.01 |
Obstruction | 2.0 | 0.4–10.2 | 0.4 |
T4 | 6.7 | 1.4–31.6 | 0.02 |
OR: odds ratio; CI: confidence interval; CEA: carcinoembryonic antigen; CRP: C-reactive protein; IL-6: interleukin-6.
Clinically, significant correlations between elevated serum IL-6 levels and other clinical factors such as serum CEA [
On the other hand, a previous report demonstrated that endotoxin (lipopolysaccharide) production was induced by bowel obstruction. Endotoxins are found in the outer membrane of Gram-negative bacteria and are released by the destruction of the bacterial cell walls. They are known to cause various biological responses, including sepsis [
Furthermore, our results also showed a discrepancy regarding the order of the TNM stages and the IL-6 level. As shown in Figure
Previous studies have already reported a relationship between serum IL-6 levels and disease status in CRC patients [
In this study, patients with low preoperative levels of IL-6 experienced longer OS than those with higher levels of IL-6. However, we did not find a statistical difference in OS rates according to the serum IL-6 level. We believe that this lack of significance was likely a result of the shorter follow-up period in this study compared to that in other studies. On the other hand, we succeeded in showing that the DFS of patients with high IL-6 was significantly poorer than that of patients with lower IL-6, and we believe that the most important result of the present study was finding that high serum IL-6 was a risk factor for CRC recurrence, including stage II patients. In this study, obstruction did not significantly influence DFS in stage II patients, but the reason for this finding is unclear.
There are currently few reports investigating the correlation between IL-6 and DFS in CRC. In the present study, for all patients, and for stages I-III patients, low preoperative levels of IL-6 were significantly associated with a longer DFS; these results indicate that preoperative serum IL-6 is an independent risk factor for recurrence, and this information may aid in the decision-making regarding adjuvant chemotherapy.
Preoperative serum IL-6 influences CRC recurrence. Importantly, this result also applies to stage II cancer patients, and this finding may aid in the decision-making regarding adjuvant therapy in these patients.
The authors declare that there is no conflict of interests regarding the publication of this paper.