Imaging Evaluation of Recurrence in Treated Prostate Cancer

Prostate cancer is the most common cancer in men and although most prostate cancers are slow growing but aggressive prostate cancers cases are seen too. Prevalence of prostate cancer vary widely across the world, it is more common in the developed countries. It is the second leading cause of cancer-related death in men in the United States and the sixth cause of cancer-related death globally in the world. Many cases of prostate cancer remain subclinical and never have symptoms until late progressive stages of the disease. About 85% of patients diagnosed with prostate cancer have localized disease and could be treated by definitive radiation therapy or radical prostatectomy. In 3050% of patients who had radical prostatectomy, PSA relapse happens at 5 years. Diagnosis and treatment of patients with PSA relapse are difficult. Detection of local recurrence of prostate cancer is important because it could be treated by local radiation therapy. Local treatment of local recurrence of prostate cancer have higher rate of complications in comparison to treatment of primary prostate cancer, hence, accurate detection of local recurrence and excluding distant metastasis is important. Distant metastasis is treated by hormone therapy. Imaging studies play an important role in detection of local recurrence of prostate cancer and its differentiation with distant metastasis. The main imaging studies that are used for evaluation of patients after radical prostatectomy are transrectal ultrasonography (TRUS) and magnetic resonance imaging (MRI). The patients with local recurrence of prostate cancer could be divided to three groups based on imaging studies. 1- Patients who have a mass lesion in surgical bed that is detectable by both MRI and TRUS. TRUS is useful for obtaining biopsy from these mass lesions. 2- Patients who have residual prostate tissue detectable by both MRI and TRUS. The residual tissue may be tumoral and responsible for local recurrence or may be non-tumoral. MRI functional studies including dynamic contrast study, diffusion weighted imaging (DWI) and MR spectroscopy (MRS) is able to confirm presence of tumoral tissue within the prostate glands remnant. Differentiation of tumoral and non-tumoral prostate remnant is not possible by means of TRUS but TRUS is useful for doing biopsy from the prostate remnant. 3- There is no mass lesion in surgical bed and anastomotic site and surrounding tissues have normal appearance in both TRUS and conventional MRI but local tumor recurrence is detected by functional MR studies like abnormal early phase enhancement in surgical bed structures, restrictive pattern in DWI or rise in choline to creatine ratio in MRS. There is no role for TRUS in detection and management of this third group of patients. CT scan is not useful for evaluation of prostate gland itself but is beneficial for evaluation of lungs and abdominal organs and can detect skeletal metastasis.