PURPOSE

To determine the acute toxicity, post-operative complications, pathologic response and extent of downstaging to high dose pre-operative radiation using a hyperfractionated radiation boost and concurrent chemotherapy in a prospective Phase I trial.

MATERIALS & METHODS: To be eligible for this study, patients had to have adenocarcinoma of the rectum less than 12 cm from the anal verge with either Stage T4 or T3 but greater than 4 cm or greater than 40% of the bowel circumference. All patients received 45 Gy pelvic radiation (1.8 Gy per fraction). Subsequent radiation was given to the region of the gross tumor with a 2 cm margin. This "boost" treatment was given at 1.2 Gy twice daily to a total dose of 54.6 Gy for Level I, 57 Gy for Level II, and 61.8 Gy for Level III. 5-FU was given at 1g/m2 over 24 hours for a four day infusion during the first and sixth weeks of radiation, with the second course concurrent with the hyperfractionated radiation. Surgical resection was carried out 4-6 weeks following completion of chemoradiation (in curative cases) and additional adjuvant chemotherapy consisting of 5-FU and Leucovorin was given for an additional 4 monthly cycles Days 1 through 5 beginning four weeks post surgery.

RESULTS

Twenty-seven patients, age 40-82 (median 61), completed the initial course of chemoradiation and are included in the analysis of toxicity. The median follow-up is 27 months (range 8-68). Eleven patients were treated to a dose of 54.6 Gy, nine patients to 57 Gy, and seven patients to 61.8 Gy. Twenty-one patients had T3 tumors, and six patients T4 tumors. Grade III acute toxicity from chemoradiation included proctitis (5 patients), dermatitis (9), diarrhea (five), leukopenia (1), cardiac (1). Grade IV toxicities included one patient with diarrhea (on dose Level I) and one patient (on dose Level III) with cardiac toxicity (unrelated to radiation). Surgical resection consisted of abdominal perineal resection in 16 and low anterior resection in 7. Four patients did not undergo a curative resection; three initially presented with metastases and one developed metastasis during the pre-operative regimen. Post-operative complications included pelvic or perineal abscess in two (on dose Levels I & II), and delayed wound healing in two (one of whom, on dose Level III, developed perineal wound dehiscence requiring surgical reconstruction). Of the 23 patients who had a curative resection, four manifested pathologic complete responses (17.4%). Thirteen of 23 patients (57%) had evidence of pathologic downstaging and only 1/23 patients (on dose Level I) had a positive resection margin. Of these 23 patients (with a minimum follow-up of 8 months), the patient with positive margins was the only one who developed a local failure (Fisher's Exact p=.04). The 3-year actuarial OS, DFS and LC rates are 82%, 72% and 96%, respectively. Twelve of 13 patients (92% at 3 years) > or = 61 years vs. 5/10 patients (45% at 3 years) < 61 years remained disease-free (log-rank p=0.017).

CONCLUSION

This regimen of high dose pre-operative chemoradiation employing a hyperfractionated radiation boost is feasible and tolerable and results in significant downstaging in locally advanced rectal cancer. The vast majority of patients (96%) achieved negative margins, which appears to be a prerequisite for local control (p= 0.04). Older age (> or =61 years) was a significant predictor for improved DFS. This regimen (at dose Level III, 61.8 Gy) is currently being tested in a Phase II setting.