Do Intermediate Radiation Doses Contribute to Late Rectal Toxicity? An Analysis of Data From Radiation Therapy Oncology Group Protocol 94-06

There is no evidence from these data that intermediate doses influence the risk of Grade ≥2 late rectal toxicity. Instead, the critical doses for this endpoint seem to be ≥75 Gy. It is hypothesized that cases of Grade ≥2 late rectal toxicity occurring among patients with V75 less than approximately 12% may be due to a “background” level of risk, likely due mainly to biological factors.