Time to BCR and cancer-specific mortality after radiotherapy or prostatectomy: implications for risk stratification and follow-up

Purpose: To evaluate the association between time to biochemical recurrence (ttBCR) and cancer-specific mortality (CSM) after prostatectomy or radiotherapy. Methods: This population-based study included 3606 patients experiencing BCR after prostatectomy or radiotherapy in Stockholm, Sweden, between 2003 and 2019. We tested the association between ttBCR and CSM using Cox models adjusted for clinical and pathological characteristics and estimated conditional cancer-specific survival by ttBCR and EAU risk group. Results: Among prostatectomy (n = 2392) vs radiotherapy patients (n = 1214), 589 vs 170 (25 vs 14%), 1205 vs 387 (50 vs 32%), 598 vs 657 (25 vs 54%) were low, intermediate, and high EAU risk group, respectively. The median ttBCR was 29 (interquartile range (IQR):11, 58) and 33 months (IQR:16, 60) among prostatectomy and radiotherapy patients, respectively. At a median follow-up for survivors of 52 months after BCR, 823 patients died, including 394 of PCa (104 in the prostatectomy and 290 in the radiotherapy group). At Cox multivariable models, ttBCR was associated with CSM in prostatectomy patients (HR:0.87; p:0.012) and radiotherapy patients (HR:0.69; p < 0.001). Adjusted cancer-specific survival probability was strongly influenced by ttBCR and EAU risk group. For instance, intermediate-risk patients with BCR after prostatectomy had a 10-year survival probability ranging from 0.74 to 0.98 for a ttBCR of 0 to 10 years. Limitations included the retrospective nature of the study. Conclusions: These findings demonstrate a strong association between ttBCR and CSM. These results suggest that ttBCR should be used to risk-stratify patients experiencing BCR after either RP or RT. The high survival probability observed in low- and intermediate-risk PCa patients who experience BCR after a prolonged period post-treatment should inform decisions regarding the intensity and duration of oncological follow-up for these patients.