Pathology of rectal adenocarcinoma following preoperative adjuvant radiotherapy and chemotherapy.

The study group comprised 13 patients (mean age 68 years) with clinically fixed and biopsy proven moderately differentiated rectal adenocarcinoma (8 high rectal, 5 low-mid rectal) who received synchronous courses of preoperative combination chemotherapy and pelvic radiotherapy (radiotherapy alone in 3 cases) over a period of 8-20 weeks prior to surgical resection. All cases showed varying degrees of mural and mesorectal fibrosis. Three cases did not differ otherwise from usual rectal adenocarcinoma while 4 had a 20-30% diminution in expected tumour area. In 6 cases tumour could not be definitely identified grossly--1 showed a 50% reduction in tumour bulk while 5 had only residual microscopic foci from 0.6-4 mm in maximum dimensions. Only 3 cases had involvement of the mesorectal circumferential radial margin. Four involved lymph nodes in 2 cases were partially hyalinised and calcified. Preoperative combination adjuvant therapy can produce marked regressive morphological changes in rectal adenocarcinoma. The implications of this are discussed.