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Phase II study of radiotherapy plus concurrent irinotecan (CPT-11) and infusional 5-fluorouracil (5FU) in the treatment of T3-T4 locally advanced inoperable rectal cancer.

3612 Background: Previously, we reported a Phase I study of radiotherapy with concurrent CPT-11 and 5FU for the treatment of locally advanced inoperable rectal cancer (Proc ASCO 2003, abst 1384). In combination with pelvic radiotherapy of 45 Gy in 25 daily fractions over five weeks, this established a recommended dose for CPT-11 of 60 mg/m2 given once per week, during weeks 1, 2, 3 and 4 as a 60 minute infusion, together with continuous infusional 5FU at 200 mg/m2 per day via a central line throughout radiotherapy, including weekends. This dose level was expanded to a cohort of thirty one patients for the present phase II assessment.


METHODS
All patients were initially staged using MRI. Patients with T3 (with threatened mesorectal edge on MRI scan) or T4 rectal cancer, were treated with the above regime. Surgery was performed 6 - 8 weeks following the completion of chemoradiation.


RESULTS
All patients completed chemoradiation as planned. There was only one grade 3 toxicity reported (diarrhoea) and the patient completed treatment successfully. Thirty-one patients entered, of whom twenty-nine (93%) underwent resection. Two patients were deemed inoperable because of unresectable pelvic disease. Sixteen patients (55%) had an anterior resection and thirteen patients (45%) had an abdomino-perineal resection. Twenty-six patients (87%) had complete excision of the tumour (Ro resection). Six patients (21%) had a complete response to chemoradiation (pCR). Four patients in addition (14%) had microfoci only of tumour remaining (near-pCR).


CONCLUSIONS
Radiotherapy with concurrent CPT-11 and 5FU is a well tolerated treatment for locally advanced inoperable rectal cancer leading to a high probability of complete resection of the cancer. This treatment regime is currently being studied (in the NWCOG-2 trial), in a similar cohort of rectal cancer patients, but substituting Capecitabine for 5FU. [Table: see text].