KEY POINTS
- The Reirradiation Collaborative Group systematically searched prospective studies of pelvic re-irradiation for recurrent rectal and anal cancer. Of 27 studies identified, 21 were eligible, and investigators from 9 trials completed a detailed 40-item protocol questionnaire.
- The nine participating trials included seven focused on rectal cancer, one including rectal and anal cancer, and one focused on anal cancer. Seven trials primarily used ESTRO/EORTC type 1 re-irradiation, involving overlap with previously irradiated volumes.
- Clinical intent differed substantially: 3 trials were preoperative only, 2 definitive only, and 4 allowed both approaches. Eight incorporated radiosensitizing fluoropyrimidine-based therapy, while one anal-cancer study used cisplatin.
- Dose and modality varied dramatically, ranging from conventional or hyperfractionated IMRT/VMAT to SBRT, proton therapy, carbon-ion therapy, MR-guided RT, brachytherapy, and intraoperative RT. Example schedules ranged from 30 Gy/15 to SBRT 35–40 Gy/5 and highly fractionated re-irradiation approaching 65 Gy.
- Studies also differed in target-volume margins, pelvic organs considered at risk, dose objectives, prior-RT reconstruction, image registration, and methods used to calculate cumulative dose—making cross-trial interpretation particularly difficult.
- Toxicity was graded with CTCAE in 8/9 trials, while patient-reported outcomes were included in 7/9; instruments and assessment timepoints nevertheless varied.
- ReCOG therefore proposed 12 pragmatic recommendations covering treatment intent, standardized re-irradiation definitions, retrieval of prior DICOM-RT, cumulative-dose methodology, planning and IGRT documentation, OAR reporting, endpoints, systemic therapy, toxicity, and PROs. These were developed iteratively by the working group rather than through a formal Delphi consensus process.
CLINICAL TAKEAWAY
This paper does not tell clinicians which pelvic re-irradiation regimen is best; instead, it shows why the prospective evidence remains so difficult to synthesize. Its main value is methodological: adoption of a common minimum reporting framework could make future rectal and anal re-irradiation trials far more comparable and clinically useful.
SOURCE
Technical Innovations & Patient Support in Radiation Oncology