Pencil Beam Proton Therapy for Recurrences in Anal Cancer Patients Previously Treated With Radiotherapy (DACG 5)

This study tests proton therapy — an advanced and more precise type of radiation treatment — for people with anal cancer that has come back after having already received radiation therapy. Because these patients can't safely receive conventional re-irradiation, proton therapy offers a way to deliver radiation again with less damage to surrounding healthy tissue. **You may be eligible if...** - You are 18 or older with confirmed recurrent squamous cell carcinoma of the anus - You have previously received radiation (more than 30 Gy) and a dose plan from the first treatment is available - Your case has been reviewed by a specialist team (MDT conference) - You are in reasonable health (performance status 0–2) with adequate organ function **You may NOT be eligible if...** - Your cancer has spread to distant organs without any curative treatment options - You are unable to have MRI or PET-CT scans - You cannot complete the full course of radiation and follow-up appointments Talk to your doctor to see if this trial is right for you.