Concomitant boost radiotherapy and multidrug chemotherapy in the neoadjuvant treatment of locally advanced rectal cancer: results of a phase II study

BACKGROUND: An intensified multidrug chemotherapy regimen (raltitrexed plus oxaliplatin, Tom-Ox) plus concomitant boost radiotherapy, in the neoadjuvant treatment of locally advanced rectal cancer patients, was shown feasible in our previous study. The aim of this study was to evaluate the efficacy in terms of pathologic complete response to pre-operative therapy. MATERIAL AND METHODS: A Phase II study was designed and clinical stage T3-T4 and/ or N ≥ 1 patients were treated with concomitant boost radiotherapy (55 Gy/5 weeks) plus concurrent chemotherapy (Tom-Ox). The primary endpoint was the assessment of efficacy in terms of clinical and pathologic response to pre-operative therapy. According to the Gehan's design study, 25 patients were enrolled. Toxicity was assessed according to the RTOG-EORTC and CTCAE v.3.0 criteria. RESULTS: Twenty-five consecutive patients were treated. Twenty-two of the 25 (88%) patients had a partial clinical response at the time of pre-operative magnetic resonance imaging (MRI). Only one patient showed progressive systemic disease at pre-surgical revaluation and was subjected only to biopsy to evaluate pathological response. Twenty-four patients (96%) underwent surgery. Overall, pathologic complete response was observed in eight patients (32%; CI 0.95:12-55%) and only microscopic tumor foci (pTmic) in two patients (pT0-mic: 40%; CI 0.95:18-63%). Nineteen patients (76%) showed tumor down-staging. Proctitis and/or diarrhea were the most frequent acute side effects experienced. Eighteen patients had grade 1-2 toxicity (77%); whereas two patients experienced grade 3 toxicity (8%). Two-year Local control and actuarial Disease Free Survival were 100% and 91%, respectively. CONCLUSION. An intensified regimen of concomitant boost radiotherapy plus concurrent raltitrexed and oxaliplatin, can be safely administered in patients with locally advanced rectal cancer. This regimen produces high rates of pathological complete response. Based on available data, this type of treatment could be offered to patients with more advanced tumors (T4 or local recurrence).