Radiotherapy plus concurrent irinotecan (CPT-11) and capecitabine (CAP) as preoperative downstaging treatment for locally advanced inoperable rectal cancer: A phase I/II study

Abstract

13519 Background: Preoperative downstaging chemoradiation has become standard treatment for locally advanced unresectable rectal cancer. Oral CAP is potentially more convenient as a radiation sensitiser than infusional fluoropyrimidine regimes. This study evaluated the dose-limiting toxicity (DLT), maximum tolerated dose (MTD) and recommended dose (RD) of daily CAP plus weekly i.v. CPT-11 when used in combination with RT in locally advanced rectal cancer. Methods: Patients had an adenocarcinoma of the rectum (lower limit within 12 cm of the anal verge) which on MRI was T3 within 2 mm of the mesorectal outer edge, T4, or any T3 within 5 cm of the anal verge. There were no distant metastases on staging investigations. Patients received planned pelvic RT to 45 Gy in 25 daily fractions over five weeks, concurrent with oral CAP daily throughout RT (including weekends) and a 60 minute infusion of i.v. CPT-11 weeks 1, 2, 3 and 4. Doses of CAP and CPT-11 were gradually escalated in cohorts of three patients. Results: The most common DLT was diarrhoea. Initially dose level (D/L) 3 was chosen as the recommended dose for phase II. However, unacceptable toxicity was encountered in the first 12 patients treated at D/L 3 (see Table). Thus D/L 2 is now being expanded to 60 patients for phase II. 40 patients have thus far potentially been eligible for resection: 5 (13%) could not be resected (2 deteriorated, 2 developed metastases, 1 died during treatment), 32 (80%) had R0 and 3 (7%) R1 resection. 9 (25%) had a pathological complete response (pCR) and 7 (20%) ‘near’ pCR. 5 (9%) of 57 patients had a defunctioning stoma pre-RT. Conclusions: The RD for this regime is 60 mg/m2 i.v. CPT-11 weeks 1, 2, 3, 4 and 650 mg/m2 bd of oral CAP daily. This demonstrates promising signs of efficacy. The RD is currently being studied in an expanded phase II cohort of 60 patients. D=diarrhea; F=febrile neutropenia; A=anorexia; L=lethargy; N=nausea/vomiting. [Table: see text] No significant financial relationships to disclose.