Pathologic complete response (pCR) to neoadjuvant chemoradiation (CRT) of uT2uN0 rectal cancer (RC) treated by local excision (LE): Results of the ACOSOG Z6041 trial.

3510 Background: LE alone is an effective treatment for selected T1 RCs, however, for T2 RCs it results in unacceptable local recurrence and survival. The Z6041 phase II trial investigates the efficacy of CRT and LE for treating T2N0 RC. Methods: Patients (pts) with ultrasound-staged T2N0 RC and ECOG PS ≤ 2 were treated with capecitabine (825 mg/m2 days 1-14 and 22-35) and oxaliplatin (50 mg/m2 weeks 1, 2, 4 and 5) during radiation (RT) (total dose 54 Gy) followed by LE. Due to toxicity, the dose of RT was reduced to 50.4 Gy and capecitabine to 725 mg/m2 (5 days/week/5 weeks). Pts were evaluated for clinical and pathologic response. pCR was defined as ypT0N0. The association between pCR rate and pre-treatment pt and tumor characteristics were assessed by logistic regression. The agreement between clinical and pathologic assessment of response was evaluated by sensitivity and specificity. Results: Of the 90 pts accrued (66% male; age [mean ± SD], 63 ± 11; 83% ECOG PS 0, and 89% white), 6 pts did not receiv...