RGPT for Prostate Cancer Is Generally Effective

A new study showed that real-time-image gated spot-scanning proton therapy (RGPT) is reliable in terms of safety and short-term clinical outcomes in patients with prostate cancer. The results were presented at the 2022 American Society for Radiation Oncology Annual Meeting.

To conduct their analysis, presenting author Kentaro Nishioka, MD, PhD, and colleagues assessed 45 patients with an Eastern Cooperative Oncology Group performance status of 0 to 2 and no lymph node or distant metastasis. The primary outcome of interest was defined as the frequency of an early adverse event (AE) of grade 2 or higher within 90 days following RGPT. The biological relapse-free survival rate and frequency of late AE was the secondary end point. Based on the findings of previous studies, the frequency of grade 2 or higher AE was 12.6%, the frequency of early AE of RGPT was assumed to be 7.6%, and the noninferiority margin was set at 10%. The threshold AE occurrence rate was set at 22.6%. Based on the data, the researchers assumed that “the noninferiority of early safety of RGPT would be verified if the number of grade 2 or higher early AE occurrence cases is 5 or less.”

According to the results, the number of patients with low, favorable intermediate, unfavorable intermediate, and high/very high risk was 9, 7, 12, and 17, respectively. The investigators observed that the frequency of a grade 2 or higher early AE was 8.9%, thus verifying the noninferiority of early safety with RGPT.

These findings “allow the conclusion that the RGPT for prostate cancer was as safe as conventional proton beam therapy in early AE, and its efficacy was suggested to be comparable with previous studies,” the researchers said.

Source: Nishioka K, Hashimoto T, Mori T, et al. A single-institution prospective study to evaluate the safety and efficacy of real-time-image gated spot-scanning proton therapy (RGPT) for prostate cancer. Abstract 2526. Presented at the 2022 ASTRO Annual Meeting; October 23-26, 2022; San Antonio, TX.