Is there a favorable subset of patients with metastatic prostate cancer who have oligometastases

Abstract

Purpose/Objective: The outcome of prostate cancer is largely determined by the development of metastases with an early predilection for bone. It appears that patients with a large number of metastatic lesions (>5) or spread of disease beyond bones do less well compared with those with fewer lesions or lesions confined to bones alone. Therefore, the prognosis of the disease may vary as a function of the number of metastatic lesions. It is our hypothesis that, those patients with oligometastatic disease, or disease spread to only a few sites (especially if the lesions are ≤5 in number), form a select group of patients, having extremely favorable prognosis. The objective of this retrospective study was to look at metastatic patterns, their clinical behavior, and the outcome in our patients. We were particularly interested in the disease behavior in patients with ≤5 metastatic lesions. Materials/Methods: Three hundred and sixty nine consecutively treated patients with Stage T1-3a NX-0 M0 disease were accrued to this study. All patients were treated between January 1970 and December 1990, with a 10 year minimum follow-up period. All patients had biopsy proven cancer. Pretreatment evaluation was done on most of the patients with CT staging and Gleason scores. Serum PSA levels were available for a limited number of patients. Bone scans were done with elevated alkaline phosphatase, elevated PSA, or bone pain. All patients were treated with a curative intent and at a mean dose of 65 Gy. The full natural history of metastatic disease was documented. This included documentation of the organ or bones initially involved, the progression over the time to other organs or bones, and survival. The Kaplan Meier method was used for calculating survival, and the logrank test was used for calculating the significance of statistical values. Results: Seventy-four (20%) patients developed documented bony metastases. Distant metastases to other sites were seen in fewer patients: brain (n=2), lung (n=4), liver (n=6), and lymph nodes (n=11). The overall survival for all patients was 75% at 5 years and 45% at 10 years. The disease specific survival at 5 and 10 years was 95% and 83%, respectively. The patients without metastasis had significantly improved survival compared with those with metastasis (p < 0.0001). The overall survival for patients who developed bone metastases was 58% at 5 years and 27% at 10 years. Survival rate from the date of documented bone metastases were 73% at 5 years, and 36% at 10 years among patients who developed ≤5 metastatic lesions compared with 45% at 5 years and 18% at 10 years for those patients who developed >5 metastatic lesions (p = 0.018). Patients with bone metastases to the pelvis did worse compared with those with vertebral metastases. Once the metastatic disease was reported in these patients, the original stage of the disease, Gleason score and serum PSA level at diagnosis seemed to have no impact on ultimate survival. Patients with lung metastasis had dismal survival compared with those with bone, lymph node, liver, or brain metastases (p = 0.0001). Conclusions: In conclusion, patients with metastatic disease involving ≤5 metastatic sites survived significantly longer than patients with >5 lesions. This sub-group of patients, despite presence of metastatic disease, may be considered having particularly favorable outcome.