(S030) Utilization of Postprostatectomy Radiation Therapy at an NCI-Designated Comprehensive Cancer Center

Jeffrey M. Martin, MD, MS, Tianyu Li, MS, Matthew E. Johnson, MD, Colin M. Murphy, MD, Marc C. Smaldone, MD, Alexander Kutikov, MD, Eric M. Horwitz, MD; Fox Chase Cancer Center

Purpose: To characterize the utilization of postprostatectomy radiation for patients with prostate cancer (CaP) at a National Cancer Institute (NCI)-designated Comprehensive Cancer Center over the past decade, given the introduction of robotic prostatectomy and the publication of multiple phase III trials showing a benefit for adjuvant postprostatectomy radiation.

Methods: We queried our prospective database for patients with CaP who received radiation therapy (RT) to the prostate bed after prostatectomy from 1999–2011. Patients receiving a prescription dose of 60–68 Gy were included. Patients were excluded if they had metastatic disease. Adjuvant RT was defined as initiation of RT within 1 year of surgery and referral for a high-risk factor (T3, positive margin, or Gleason score 8–10). A detectable prostate-specific antigen (PSA) was allowed in the adjuvant definition as long as only a single postoperative PSA was obtained in the setting of the preceding high-risk factors and was < 0.2 ng/mL. Salvage RT was defined as RT in the setting of rising PSA, a single postoperative PSA ≥ 0.2 ng/mL, or documented clinical recurrence via imaging or digital rectal examination. The number of patients with an intact prostate treated with definitive RT was recorded by year as a control for the changing volume in total prostate patients in the department. Chi-square analysis was used to assess differences in patient population between adjuvant and salvage RT cohorts. Spearman correlation was used to assess yearly trends in PSA level at time of referral for RT.

Results: A total of 563 patients received postprostatectomy RT between 1999 and 2011: 465 as salvage and 98 as adjuvant. Over time, there was a trend for an increased number of patients treated with postprostatectomy RT. Of all patients treated with RT for localized CaP, postprostatectomy RT constituted a larger proportion, ranging from 5.3% to 9.4% from 1999–2003, 11.9% to 13.3% from 2004–2007, and 18.4% to 26.6% from 2008–2011. There was no increase in the proportion of patients treated with adjuvant RT compared with salvage RT (P = .5). Patients referred for adjuvant RT were younger (P = .001) and had higher pathologic Gleason score (P = .0372), higher pathologic T-stage (P < .0001), and higher rates of positive margins (P < .0001) than patients receiving salvage RT. Pre-RT PSA values were inversely correlated with year (P = .005).

Conclusion: Postprostatectomy RT utilization now constitutes a larger proportion of patients treated with RT for localized CaP. There has not been an increase in the proportion of patients treated with adjuvant compared with salvage RT. There is a trend over time for CaP patients to be referred for postprostatectomy RT with lower PSAs.

Proceedings of the 96th Annual Meeting of the American Radium Society - americanradiumsociety.org