Long-term follow-up results of endorectal balloon-assisted helical tomotherapy for localized prostate cancer patients in the high-risk group of gastrointestinal adverse events

Background: Endorectal balloon (ERB) has been shown to reduce rectal radiation dose and late gastrointestinal toxicities in patients with prostate cancer. However, the usefulness of ERBs for patients with prostate cancer whose rectal shape or size is suboptimal has not been investigated. The purpose of this study was to present the long-term follow-up results of ERB-assisted helical tomotherapy for localized prostate cancer patients whose initial radiation treatment planning (RTP) was unacceptable due to suboptimal rectal shape or size. Materials and methods: Of 541 consecutive patients with localized prostate cancer, 10 were included in this study whose RTPs without ERBs did not meet dose constraints due to: 1) Intestinal intrusion, 2) Small rectum; or 3) Unstable rectal shape. We re-planned using ERBs and delivered 76 Gy in 38 fractions, and evaluated the long-term usefulness and safety of ERB-assisted helical tomotherapy. Results: At a median follow-up of 109 months, there were no local recurrences of prostate cancer. The overall, cause-specific, and progression-free survivals at 10 years were 90.0%, 100%, and 83%, respectively. Adverse events of grade 3 or higher were not observed during or after ERB-assisted helical tomotherapy. Conclusions: When intestinal intrusion, a small rectum, or an unstable rectal shape is an obstacle for administering helical tomotherapy, ERBs might be the solution.