A 45-year-old white male presented to our department with postoperative recurrence of gastrointestinal poorly differentiated neuroendocrine carcinoma manifesting as lymph node dissemination and a solitary implantation metastasis in the rectovesical pouch. Following disease progression on chemotherapy, the patient was treated with radiotherapy using either a conventional daily treatment or an accelerated hyperfractionated protocol to separate sites of disease progression. Using serial CT scan assessment, changes in cross-sectional area of the separately treated metastatic lesions were evaluated for determination of therapy response. The accelerated hyperfractionated radiotherapy appeared to limit the rate of tumor growth to a greater degree than the conventional fractionation schedule. Of uttermost importance, in this palliative setting, the patient completed the intensified radiotherapy regimens with acceptable acute toxicity. Given the proliferative capacity of poorly differentiated neuroendocrine carcinomas of the gastrointestinal tract, radiotherapy may be a therapeutic supplement to chemotherapy, which represents the main treatment option in this tumor entity. Importantly, tumors with a capacity for rapid proliferation and regeneration may be particularly sensitive to the use of intensified fractionation protocols in clinical radiotherapy.