Regression Discontinuity Analysis of Salvage Radiotherapy in Prostate Cancer.
Gild P, Pompe RS, Seisen T, Keeley J, Tang HJ, Bossi A, Tilki D, Menon M, and Abdollah F. Regression Discontinuity Analysis of Salvage Radiotherapy in Prostate Cancer. Eur Urol Oncol 2019.
Eur Urol Oncol
There is a lack of randomized evidence comparing early (eSRT) to late (lSRT) salvage radiotherapy (SRT) after radical prostatectomy (RP) for prostate cancer (PCa). Moreover, the existing evidence is often affected by lead-time bias. We sought to address this gap in a cohort of 1458 PCa patients undergoing SRT for biochemical recurrence (BCR) after RP in two tertiary care centers between 1992 and 2013. Using a quasi-randomized study design known as regression discontinuity (RD) and adjusting for lead-time bias, we compared metastasis-free survival (MFS) at 5 and 10years after surgery between eSRT (prostate-specific antigen [PSA] <0.5ng/ml) and lSRT (PSA>/=0.5ng/ml). Overall, 1049 patients (71.9%) underwent eSRT and 409 (28.1%) lSRT at a mean follow-up of 84 mo (interquartile range (IQR) 52-120.4). The MFS rate decreased nonsignificantly at the proposed cutoff by 0.04 (95% confidence interval [CI]: -0.06 to 0.19) at 5years and by 0.07 (95% CI:-0.12 to 0.32) at 10years. Cox regression analysis revealed a hazard ratio for the cutoff examined of 1.3 (95% CI: 0.8-2.4; p=0.2). In conclusion, in a quasirandomized study design accounting for lead-time bias, eSRT (PSA<0.5ng/ml) did not improve MFS. Our results underline the need for level-one evidence to compare eSRT and lSRT. PATIENT SUMMARY: We compared early versus late salvage radiotherapy (SRT) for biochemical recurrence after radical prostatectomy by simulating a randomized trial. We found that early SRT (initiated at prostate-specific antigen <0.5ng/ml) compared to late SRT did not improve metastasis-free survival.
ePub ahead of print