Outcomes show a reduction in treatment failure associated with dose-escalated, hypofractionated radiation therapy for localized prostate cancer

Abstract

Long-term results of a phase 3 randomized trial comparing conventionally fractionated intensity-modulated radiation therapy (CIMRT) with dose-escalated, hypofractionated intensity-modulated radiation therapy (HIMRT) in patients with localized prostate cancer found considerable improvement in treatment failure rates among patients treated with HIMRT versus CIMRT according to a study published in the Journal of Clinical Oncology.¹

The findings add to the growing body of evidence supporting the use of hypofractionated IMRT and making it the current standard of care. Data from the current study show that at a median follow-up of 13.2 years, men undergoing HIMRT had less frequent treatment failure than those undergoing CIMRT (11% vs. 21%). The result shows improvement but was not statistically significant. When the analysis was limited to patients who did not receive androgen deprivation therapy (ADT), patients treated with HIMRT showed a significant improvement in treatment failure in comparison with patients treated with CIMRT (13% vs. 26%; p = .039).

The study also found that long-term distant metastases were rare and occurred primarily in the intermediate-risk cohort treated with CIMRT or HIMRT (8% vs. 4%).

A total of 222 patients with localized prostate cancer were included in the trial; 206 of the patients were evaluable. Most patients had intermediate-risk disease (71%), 90% had a PSA level ≤10 ng/mL, 48% had Gleason grade 2 disease, and 24% received ADT. Patients were randomized to CIMRT (n = 102) or HIMRT (n = 104). Patients treated with CIMRT received 75.6 Gy in 42 fractions (1.8 Cy per fraction) over 8.4 weeks. Patients treated with HIMRT received 72 Gy in 30 fractions (2.4 Gy per fraction) over 6 weeks.

The results build on an initial assessment of the trial at a median follow-up of 9.5 months that showed 8-year failure rates of 10.7% with HIMRT and 15.4% with CIMRT.² Similar to the initial results, the long-term results showed no statistically significant difference between HIMRT and CIMRT in grade 2 or higher late gastrointestinal adverse effects (10% vs. 4% at 10 years, p = .09) or grade 2 or higher genitourinary adverse effects (26% vs. 23% at 10 years, p = .5).

“These data represent one of the largest follow-ups published so far for hypofractionated regimens and provide the most robust long-term data on the safety and tolerability of hypofractionated regimens in prostate cancer, while potentially indicating that dose-escalated, shorter courses of radiation for prostate cancer may provide higher efficacy than traditional, conventionally fractionated radiation,” says the lead author of the study, Comron Hassanzadeh, MD, MPH, an assistant professor of genitourinary radiation oncology at The University of Texas MD Anderson Cancer Center.