Preoperative downstaging chemoradiation with concurrent irinotecan and capecitabine in MRI-defined locally advanced rectal cancer: a phase I trial (NWCOG-2).

Background: The aim of this study was to investigate the safety of neoadjuvant chemoradiation using radiotherapy (RT) combined with concurrent capecitabine and irinotecan for locally advanced rectal cancer before surgery.

Methods: Forty-six patients were recruited and treated on the basis that MRI scanning had shown poor-risk tumours with threatening (< or =1 mm) or involvement of the mesorectal fascia. Conformal RT was given using 3 or 4 fields at daily fractions of 1.8 Gy on 5 days per week to a total dose of 45 Gy. Concurrently oral capecitabine was given twice daily throughout radiotherapy continuously from days 1 to 35 and intravenous irinotecan was given once per week during weeks 1 to 4 of RT. Dose levels were gradually escalated as follows. Dose level 1: capecitabine 650 mg m(-2) b.i.d. and irinotecan 50 mg m(-2); Dose level 2: capecitabine 650 mg m(-2) b.i.d. and irinotecan 60 mg m(-2); Dose level 3: capecitabine 825 mg m(-2) b.i.d. and irinotecan 60 mg m(2); Dose level 4: capecitabine 825 mg m(-2) b.i.d. and irinotecan 70 mg m(-2).

Results: Diarrhoea (grade 3, no grade 4) was the main serious acute toxicity with lesser degrees of fatigue, neutropenia, anorexia and palmar-plantar erythrodysesthesia. The recommended dose for future study was dose level 2 at which 3 of 14 patients (21%) developed grade 3 diarrhoea. Postoperative complications included seven pelvic or wound infections and two anastomotic and two perineal wound dehiscences. There were no deaths in the first 30 days postoperatively. Of 41 resected specimens, 11 (27%) showed a pathological complete response (pCR) and five (12%) showed an involved circumferential resection margin (defined as < or =1 mm). The 3-year disease-free survival (intent-to-treat) was 53.2%.

Conclusion: In patients with poor-risk MRI-defined locally advanced rectal cancer threatening or involving the mesorectal fascia, preoperative chemoradiation based on RT at 45 Gy in 25 daily fractions over 5 weeks with continuous daily oral capecitabine at 650 mg m(-2) b.i.d. days 1-35 and weekly IV irinotecan at 60 mg m(-2) weeks 1-4, provides acceptable acute toxicity and postoperative morbidity with encouraging response and curative resection rates.