Clinical outcomes of external beam radiotherapy in patients with localized prostate cancer: Does dose escalation matter?

Background: To report outcomes of localized prostate cancer treated with radical external beam radiation therapy (EBRT) in our institution over a 14-year period, and to determine the impact of dose escalation of prostate cancer outcomes.

Methods: Patients with T1-T4 N0 M0 prostate cancer who received radical EBRT between January 2002 and December 2015 were reviewed retrospectively. Clinical data were obtained via the institutional electronic medical records. The primary endpoint was 5-year overall survival (OS). The secondary endpoints were 5-year freedom from biochemical failure (FFBF) and treatment toxicities.

Results: A total of 200 eligible patients were identified. Median follow-up duration was 48 months. 13%, 36% and 51% of patients had low-, intermediate- and high-risk disease. Median dose was 79.2 Gy. The 5-year OS were 90%, 87% and 78% and FFBF were 94%, 100% and 81% for low-, intermediate- and high-risk patients, respectively. Multivariable analysis showed that Eastern Cooperate Oncology Group performance status 2 and Gleason grade group 5 were independent predictors of worse OS. The incidence of grade ≥2 proctitis was 24.5%. Dose escalation was significantly associated with increased incidence of grade ≥2 proctitis (odd ratio, 4.42; 95% confidence interval, 1.95-10.08; P < 0.01).

Conclusion: Men with localized prostate cancer treated with EBRT in our population had excellent 5-year OS and biochemical outcomes. Dose escalation did not significantly improve these outcomes but was associated with significantly increased risk of grade ≥2 proctitis in our population. Future studies should be performed to identify patients who will benefit the most from dose-escalated EBRT.