BERKELEY, CA (UroToday.com) - A recent study observed a survival benefit in men diagnosed with metastatic prostate cancer (mPCa) and managed with local treatment of the primary tumor (LT, either radical prostatectomy plus pelvic lymph node dissection or radiation therapy). In this study we tested the hypothesis that only specific mPCa patients would benefit from LT, and that the potential benefit varies based on primary tumor characteristics.
A total of 8 197 mPCa patients at diagnosis (M1a, M1b, and M1c) were identified using Surveillance Epidemiology and End Results (SEER) database (2004–2011) and divided according to treatment type: LT vs. non-local treatment of the primary tumor (NLT, either androgen deprivation therapy, or observation). Multivariable Cox regression analysis was used to predict cancer specific mortality (CSM) in patients who received NLT. Predictors consisted of age at diagnosis, PSA level, Gleason score (≤ 6 vs. 7 vs. ≥ 8), T stage (≤ T2 vs. ≥ T3), N stage (N0/Nx vs. N1), and M stage (M1a vs. M1b vs. M1c). The discrimination of the model was corrected for over-fit using 10-fold cross-validation. We wished to assess whether the benefit of LT was different by baseline risk by testing an interaction with CSM-risk and LT. We plotted CSM-free survival rate at 3 years against predicted CSM-risk at 3 years, according to treatment option (LT vs. NLT). Finally, we explored the variation of the number needed to treat (NNT) according to the predicted CSM-risk at 3 years after diagnosis.
Of 8 197 mPCa patients, 628 (8%) received LT, while 7 569 (92%) underwent NLT. At multivariable analysis, all the predictors were significantly associated with CSM. Interaction test for the hypothesis that the impact of LT varies according to the predicted CSM-risk was statistically significant (p < 0.0001). Local treatment of the primary tumor, compared to NLT, conferred a higher CSM-free survival rate in patients with a predicted CSM-risk lower than 40%. Conversely, when the predicted CSM-risk exceeded 50%, LT did not provide a survival benefit. The NNT remained substantially constant from 10% to 30%, while it exponentially increased for predicted CSM-risk greater than 40%.
In conclusion, the potential and beneficial impact of local treatment of the primary tumor greatly depends on tumor characteristics, and patient selection is essential to avoid over/under treatment. If validated in future studies, our novel model can be of great help in selecting the optimal candidate for local treatment among metastatic prostate cancer patients.
Nicola Fossatia, b and Firas Abdollahc as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
aDept. of Epidemiology and Biostatistics, Memorial Sloan-Kettering Cancer Center, New York, NY USA
bDivision of Oncology / Unit of Urology, IRCCS Ospedale San Raffaele – Ville Turro, Milan, Italy
cVattikuti Urology Institute and VUI Center for Outcomes Research Analytics and Evaluation, Henry Ford Hospital, Detroit, MI, USA