Impact of timing on radiation therapy adverse events following radical prostatectomy, an analysis of the RTOG 9601 cohort
Baumgarten LC, Borchert A, Delela D, Sood A, Arora S, Keeley J, Trinh Q, Rogers CG, Peabody JO, Menon M, and Abdollah F. Impact of timing on radiation therapy adverse events following radical prostatectomy, an analysis of the RTOG 9601 cohort. Eur Urol Suppl 2019; 18(1):e2200-e2201.
Eur Urol Suppl
Introduction & Objectives: Approximately 30% of patients who undergo radical prostatectomy (RP)harbor aggressive pathologic features and would benefit from early adjuvant radiation therapy (RT). However, less than 10% of this population receive such a treatment, due to concerns of overtreatment and worsening of functional outcomes with early delivery of RT to the pelvis after surgery. We sought to investigate the impact of timing between RP and RT on adverse events rate. Materials & Methods: Using the Radiation Therapy Oncology Group (RTOG)9601 trial cohort, we performed post-hoc analysis of 760 men who developed biochemical recurrence after RP, and received subsequent RT (randomized to concomitant bicalutamide vs. placebo). Bowel adverse events (rectal urgency, diarrhea, and hematochezia); bladder adverse events (urinary frequency, dysuria, hematuria, and incontinence); and new onset of erectile dysfunction were documented as acute (<90 days after starting RT)or chronic, at each visit, per trial protocol. Regression analysis tested the impact of time between RP and RT on the aforementioned adverse events, after adjusting for potential confounders. Results: The majority of men aged 60 years or above (75.3%), were white (87.9%), and had a Karnofsky Performance Score (KPS)of 100 (75.8%). Likewise, most patients had Gleason scores ≥ 7 (71.8%), T3 disease (67.4%), and positive surgical margins (74.9%). The median time from RP to initiating RT was 2.1 years (interquartile range [IQR]: 1.1-4.0). Patients were followed for a median (IQR)of 13 (11.9-14.0)years following RP. Sixty-seven (8.8%)patients underwent RT <6 months following RP. On multivariable analysis, time was evaluated as a continuous variable and as a dichotomous variable (at 6 months and at the median time of 2.1 years between RP and RT). As shown in the table, timing was not a significant predictor of adverse events in this cohort. [Table Presented]Conclusions: Based on post-hoc analysis of the RTOG 9601 clinical trial cohort, there was no impact of timing between RP and RT on urinary, bowel, and erectile adverse events related to RT. Given the rigorous and accurate capturing of complications in this trial cohort, our findings challenge the current belief that early post-surgical RT compromises functional outcomes more than late RT and support the utilization of such a treatment if indicated.