The regrowth of rectal adenocarcinoma after pre-operative radiotherapy with a report of two cases.

To evaluate the factors that contribute towards the regrowth of rectal carcinoma after pre-operative radiotherapy. Of 120 patients, we pre-operatively treated with intraluminal brachytherapy or external beam radiotherapy since 1986, two showed regrowth of rectal carcinoma. For them, the case reports and findings for the resected specimen obtained using immunohistochemical staining for the P53 tumor suppressor gene (P53) and proliferating cell nuclear antigen (PCNA) were retrospectively evaluated. The regrowth of rectal carcinoma was observed 40 days after intraluminal brachytherapy in one patient, and 33 days after external radiotherapy in the other. Both P53 and PCNA staining was seen in the recurrent tumors or during the examination of the resected specimen. These results suggest that polypoid tumors with regrowth have a malignant potential. The interval between radiotherapy and operation reported in the literature varies widely. The potential for regrowth should be considered in the preoperative radiotherapy for rectal cancer.