In contrast to bone scan and computed tomography (CT), which depend on osteoblastic response to detect bone metastasis, whole-body magnetic resonance imaging (WB-MRI) may be able to directly detect viable tumors. A 75-year-old male who had progressive metastatic prostate cancer during primary androgen deprivation therapy was referred to our hospital. Although bone scan and CT showed multiple bone metastases, WB-MRI suggested nonviable bone metastasis and viable tumor of the primary lesion. Prostate needle biopsy demonstrated viable prostate cancer cells from 10 of 12 cores. In contrast, CT-guided needle biopsy from bone metastasis of the lumbar vertebra revealed no malignant cells. Based on these findings, we reasoned that viable tumor cells inducing disease progression may primarily exist in the primary lesions and not in the metastatic lesions, and combined prostate radiotherapy and systemic hormonal therapy resulted in successful clinical response and disease control. The use of WB-MRI to detect viable disease lesions may enable us to design optimal treatment strategies for patients with metastatic castration-resistant prostate cancer.
As the disease condition of metastatic prostate cancer may change over time, it is necessary to evaluate and adjust its corresponding treatment as necessary, according to the given circumstances. Although bone scan and computed tomography (CT) have been the most widely used methods of evaluating metastases of prostate cancer, accurately evaluating bone metastases is often difficult because bone scan and CT depend on the osteoblastic response induced by tumor cells infiltrating the bone. In addition, bone scan and CT cannot evaluate the prostate. In contrast, whole-body magnetic resonance imaging (WB-MRI) allows direct detection of viable tumors not only in the metastatic sites but also in the primary lesion, owing to the method’s excellent soft-tissue contrast, high spatial resolution, and lack of ionizing radiation [
A 75-year-old male visited a urological practitioner because of nocturia. An elevated serum prostate specific antigen (PSA) level of 76.2 ng/mL was observed, and digital rectal examination showed diffuse induration of the prostate. Pelvic MRI demonstrated extensive high signal of the prostate in diffusion-weighted imaging (DWI) (Figure
Image findings at initial diagnosis. Pelvic MRI (DWI) (a) showed extensive high signal of the prostate. FDG-PET/CT revealed multiple spine and pelvic bone (b) and para-aortic and pelvic lymph node metastases (c). MRI, magnetic resonance imaging; DWI, diffusion-weighted imaging; FDG-PET/CT, fluorodeoxyglucose-positron emission tomography/computed tomography.
To evaluate the patient’s current disease status, we performed CT, bone scan, and WB-MRI. We observed discrepancies between the WB-MRI, bone scan, and CT. CT showed multiple osteoblastic lesions in the spine and pelvic bone (Figures
Imaging findings at the time of CRPC diagnosis. CT showed multiple osteoblastic lesions in the spine (a) and pelvic bone (b). Bone scan confirmed multiple accumulations at the same bone sites as CT (c). CRPC, castration-resistant prostate cancer; CT, computed tomography.
WB-MRI at the time of CRPC diagnosis. Sagittal DWI of the spine (a), coronal DWI + T2 fusion (b), and whole-body DWI (c) showed few high signals. Coronal DWI + T2 fusion of the pelvis (d) revealed diffuse high signal in the prostate. WB-MRI, whole-body magnetic resonance imaging; CRPC, castration-resistant prostate cancer; DWI, diffusion-weighted imaging.
We then performed histopathological examinations of both the prostate and the vertebra. The prostate needle biopsy demonstrated that 10 of 12 cores had viable prostate cancer cells (Figure
Histopathological findings at the time of CRPC diagnosis. Prostate needle biopsy detected viable prostate cancer cells from 10 of 12 cores (a). Bone needle biopsy from the second lumbar vertebra demonstrated no malignant cells (b). CRPC, castration-resistant prostate cancer.
Imaging findings of MRI and CT in the second lumbar vertebra where CT-guided needle biopsy was performed. (a) CT revealed an osteoclastic lesion in the second vertebral body (885.4 HU).
Based on the findings of our WB-MRI and histopathological examinations, we reasoned that viable tumor cells inducing disease progression may primarily exist in the primary lesions and not in the metastatic lesions. Then, to control the overall disease, we changed the patient’s medication from bicalutamide to enzalutamide for potentially existing micrometastases and added prostate RT (74 Gy). After this, his elevated PSA immediately declined and was controlled at a level of <0.2 ng/mL.
The present case has demonstrated the diagnostic accuracy of WB-MRI in a patient with metastatic CRPC, whose histopathological examination results were consistent with the WB-MRI results but not with the bone scan and CT results. The results of WB-MRI and histopathological examinations enabled us to provide optimal treatment to the patient, including combining prostate RT and systemic hormonal therapy.
Several meta-analyses have shown that WB-MRI has greater diagnostic performance for bone metastasis than bone scan and CT. The sensitivity and specificity of WB-MRI in the detection of bone metastasis were found to be ≥95%, whereas the equivalent measures for bone scan were just 78% and 85%, respectively, and for CT, just 77% and 83%, respectively [
It has been reported that WB-MRI can directly detect tumor viability, with the support of DWI [
It is noteworthy that diagnosis using WB-MRI for both primary and bone metastases in a patient with metastatic CRPC was histopathologically proven. Regarding the consistency of MRI and pathological findings, Perez-Lopez et al. [
Recently, local therapy for metastatic prostate cancer has attracted attention because the median overall survival rate of metastatic prostate cancer is still only 42 months, despite the availability of several new drugs such as docetaxel, enzalutamide, abiraterone, cabazitaxel, and radium-223 [
There are two hypotheses as to why local therapy for metastatic prostate cancer can improve oncological outcomes. The first hypothesis is the “abscopal effect” of RT. This is a phenomenon where local irradiation causes the shrinking not only of the irradiated tumor but also tumors outside the irradiation field [
This case report has several limitations. First, we do not have access to pretreatment prostate biopsy, baseline WB-MRI, and bone scan results because the patient’s initial diagnosis and treatment occurred before his referral to our hospital. Second, we could not exclude the possibility of a false-negative result in the bone biopsy, although we performed the CT-guided bone needle biopsy via the osteoblastic lesion, which was diagnosed with bone metastasis by CT and bone scintigraphy, with an orthopedically appropriate technique to detect bone metastasis [
Accurate evaluation of the viability of both primary and metastatic lesions in patients with metastatic CRPC using WB-MRI may enable us to select patients who would benefit from local therapy. Prospective studies are needed to validate the treatment strategy associated with the use of WB-MRI for metastatic CRPC.
Informed consent for the publication of this report has been obtained from the patient.
The authors declare that there are no conflicts of interest regarding the publication of this article.
The course of treatment of the patient is demonstrated. His elevated PSA immediately declined and was controlled at a level of <0.2 ng/mL after the prostate RT and the administration of enzalutamide.