Phase 1/2 study of hypofractionated intensity-modulated radiation therapy for prostate cancer including...

This study evaluates the safety and efficacy of moderately hypofractionated radiation therapy (RT) with simultaneous integrated boost (HSIB) intensity modulated RT (IMRT) that includes coverage of the seminal vesicles (SVs) and pelvic lymph nodes (LNs).

Men with localized prostate cancer were prospectively enrolled in a phase 1/2 trial to receive HSIB-IMRT to the prostate, ± SV, ± pelvic LN using a risk-based method. Low-risk patients received 69.6 Gy to only the prostate in 29 fractions. Intermediate-risk (IR) and high-risk (HR) patients received 30 fractions with 72 Gy to the prostate, 54 Gy to the SV, and 50.4 Gy to the pelvic LN when risk of LN involvement exceeded 15% by the Roach formula. IR and HR patients received androgen deprivation therapy. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicity were prospectively evaluated with patient- and physician-reported surveys.

Fifty-five men were enrolled, and 49 had at least 1 year of follow-up with 19.2% low-risk, 40.4% IR, and 40.4% HR disease. The median age was 69 years; median follow-up time was 36.9 months. Twenty-six patients received pelvic nodal HSIB-IMRT. At 2 years, the cumulative incidence of physician-reported late grade 2+ GU and GI toxicity was 32.6% and 18.4% respectively. At 2 years, only 10.2% grade 2+ GU toxicities and 2.0% grade 2+ GI toxicities remained unresolved. At last follow-up, the prevalence of unresolved physician-reported late grade 2+ GU and GI toxicity was 4.1% and 0%. The median patient-reported American Urologic Association-International Prostate Symptom Score fell from 10 at baseline to 7.5 at 2 years. The 3-year biochemical relapse-free survival rate for the cohort was 96%.

HSIB-IMRT with risk-based nodal coverage results in excellent biochemical control. Although the cumulative incidence of physician-reported GU toxicity was higher than anticipated, late GI and GU toxicity was relatively transient.