Radiotherapy of Oligometastatic Prostate Cancer: Experience of the Mohamed VI Center for Cancer Treatment in Casablanca, Morocco

Backgraound Oligometastatic disease is an intermediate stage between locally advanced disease and multi-metastatic disease. We report the experience of the Mohamed VI Center for the Treatment of Cancers in the management of oligometastatic prostate cancers in a retrospective series from 2016 to 2019. Method We collected cases of de novo metastatic prostate adenocarcinoma judged to be oligometastatic and having benefited from radiotherapy on the prostate. The primary endpoints were: progression-free survival and overall survival at 2 and 3 years. The proportions were compared by the CHI 2 test with a significance level of 0.05. The Kaplan Meier model was used to compare survivals. Result We had recruited 37 patients with a median age of 70 years. The initial PSA was between 11 ng/ml and 1635 ng/ml with an average of 160 ng/ml. The Gleason score was between 8 and 10 in 46 % of patients. A secondary bone location was present in 100% of cases and no patient had a visceral metastasis. The vertebral seat was the most common secondary bone site (55%). The maximum number of metastatic sites was 3. The median follow-up is 38 months. Overall survival at 24 months and 36 months, respectively, was 92% and 86%. The 2- year and 3-year progression-free survival was 84% and 79%, respectively. There was no statistically significant difference in either overall survival or progression-free survival between patients who received radiation to the prostate alone and those who received radiation to the prostate plus the pelvis (p = 0.86). No significant difference was observed in terms of survival between the patients who received in addition to local radiotherapy and primary palliative chemotherapy and those who received only local radiotherapy. The low statistical power of our sample did not allow us to obtain a significant difference between patients irradiated in hypofractionated and those irradiated in conventional fractionation. Conclusion The limit of our study lies in the small size of our sample but also in its retrospective nature. Prostate radiation therapy remains a treatment option for de novo oligometastatic prostate cancer