Neutron therapy (dT, 14 MeV) for recurrence of rectal cancer: interim analysis from Münster

For rectal recurrent cancer and macroscopic residual disease after surgery neutron radiotherapy has been suggested to be superior to photon radiotherapy. At the d,T generator in Münster (14 MeV) 20 patients have been treated with a combined photon-/neutron-radiotherapy: two patients with residual disease after surgery: among the 18 patients with rectal recurrence 15 for pain relief; all for tumor control. Tumor resection had been carried out in five recurrent tumors. Six patients presented with distant metastases. 30 to 40 Gy photons for tumor region and potential microscopic spread with 2 Gy per fraction and 5 to 10 Gy neutrons for macroscopic tumor volume with 0.7 to 1.6 Gy per fraction were applied using multiple fields (three to five). The mean follow-up period is nine months. Pain relief was achieved in eleven of 15 patients (73%), the onset of pain was fast, the probability for a pain-free period is 46% for nine months and for survival 56% for twelve months. Side-effects were slight to moderate beside a severe subcutaneous fibrosis in two patients. The superiority of neutrons to photons in rectal recurrent cancer remains questionable and is to be proven in a prospective trial comparing different schedules for frequency, onset and duration of pain relief, tumor control, survival and side-effects.