KEY POINTS
- The report describes a 28-month-old child with high-risk neuroblastoma previously treated with multi-agent induction chemotherapy followed by high-dose busulfan/melphalan and autologous stem-cell rescue.
- The child subsequently received anti-GD2 immunotherapy with dinutuximab. Transient diarrhea had occurred during both high-dose chemotherapy and immunotherapy but had resolved before radiotherapy.
- Proton therapy was planned to 30.6 Gy(RBE) to the tumor bed and regional disease, with a treatment volume that included a substantial segment of colon.
- Hematochezia developed after only 12.6 Gy(RBE). CT showed diffuse mural thickening from sigmoid colon to rectum, and colonoscopy demonstrated widespread mucosal erythema consistent with hemorrhagic colitis.
- Infectious causes were not identified, and no concurrent chemotherapy or antibiotics were being administered. The authors therefore considered radiation injury superimposed on pre-existing treatment-related mucosal vulnerability a plausible explanation.
- Proton therapy was paused for four weeks and then resumed with a modified field designed to reduce bowel exposure. The child ultimately received 28.8 Gy(RBE) without recurrent bleeding, but subsequently died from progressive neuroblastoma.
CLINICAL TAKEAWAY
A nominally modest bowel dose may not tell the full toxicity story after intensive multimodal paediatric therapy. This single case cannot define a new bowel constraint, but it is a useful reminder to consider preceding mucosal injury and treatment sequence when planning RT soon after high-dose chemotherapy and immunotherapy.