Purpose: Primary unresectable and locally advanced recurrent rectal cancer presents a significant clinical challenge. Local failure rates are high in both situations. Under such circumstances, there is a significant need to safely deliver tumoricidal doses of radiation in an attempt to improve local control. For this reason, we have incorporated a new approach utilizing high dose rate intraoperative radiation therapy (HDR-IORT).
Methods and materials: Between 11/92-12/96, a total of 112 patients were explored, of which 68 patients were treated with HDR-IORT, and 66 are evaluable. The majority of the 44 patients were excluded for unresectable disease or for distant metastases which eluded preoperative imaging. There were 22 patients with primary unresectable disease, and 46 patients who presented with recurrent disease. The histology was adenocarcinoma in 64 patients, and squamous cell carcinoma in four patients. In general, the patients with primary unresectable disease received preoperative chemotherapy with 5-fluorouracil (5-FU) and leucovorin, and external beam irradiation to 4500-5040 cGy, followed by surgical resection and HDR-IORT (1000-2000 cGy). In general, the patients with recurrent disease were treated with surgical resection and HDR-IORT (1000-2000 cGy) alone. All surgical procedures were done in a dedicated operating room in the brachytherapy suite, so that HDR-IORT could be delivered using the Harrison-Anderson-Mick (HAM) applicator. The median follow-up is 17.5 months (1-48 mo).
Results: In primary cases, the actuarial 2-year local control is 81%. For patients with negative margins, the local control was 92% vs. 38% for those with positive margins (p = 0.002). The 2-year actuarial disease-free survival was 69%; 77% for patients with negative margins vs. 38% for patients with positive margins (p = 0.03). For patients with recurrent disease, the 2-year actuarial local control rate was 63%. For patients with negative margins, it was 82%, while it was 19% for those with positive margins (p = 0.02). The disease-free survival was 47% (71% for negative margins and 0% for positive margins) (p = 0.04). Prospective data gathering indicated that significant complications occurred in approximately 38% of patients and were multifactorial in nature, and manageable to complete recovery.
Conclusion: HDR-IORT using our technique is versatile, safe, and effective. The local control rates for primary disease compare quite well with other published series, especially for patients with negative margins. For patients with recurrent disease, locoregional control and survival are especially encouraging in patients with negative resection margins. Further follow-up is needed to see whether these encouraging data will continue.