Comparison of Late Toxicity After Whole-pelvis Versus Prostate-only VMAT for Prostate Cancer

To evaluate whether whole-pelvis (WP) volumetric modulated arc therapy (VMAT) is associated with increased late toxicity compared with prostate-only (PO) VMAT in patients with localized prostate cancer.

Participants comprised 384 consecutive patients treated with definitive VMAT to 78 Gy in 39 fractions from July 2011 to August 2016. Of these, 183 patients received PO-VMAT and 201 patients received initial WP-VMAT to 46.8 Gy in 26 fractions using a simultaneous integrated boost technique. Gastrointestinal (GI) and genitourinary (GU) toxicities were prospectively scored using Common Terminology Criteria for Adverse Events version 4.0.

Median follow-up was 49 months (range=16-88 months) in the PO-VMAT group and 52 months (range=10-85 months) in the WP-VMAT group. Frequencies of Grade 3 late GI and GU toxicities were ≤3% across both groups. No patients experienced Grade 4+ toxicity. Cumulative incidences of Grade 2+ late GI and GU toxicities were similar between PO- and WP-VMAT groups (p=0.508 and p=0.838, respectively). Five-year cumulative incidences of Grade 2+ late GI and GU toxicities were 12.2% and 6.6% for the PO-VMAT group and 12.3% and 8.9% for the WP-VMAT group, respectively.

WP-VMAT did not increase late GI and GU toxicities. This suggests that concerns about increasing toxicity profile are insufficient reason for omitting WPRT for patients with high-risk prostate cancer.