Preoperative Chemoradiation With VMAT-SIB in Rectal Cancer: A Phase II Study

Purpose: The aim of this study was to investigate the efficacy and toxicity of volumetric modulated arc therapy (VMAT)-simultaneous integrated boost (SIB) in preoperative combined treatment of locally advanced rectal cancer. Methods: Radiation therapy was performed using the VMAT-SIB technique. The dose to mesorectum and pelvic lymph nodes was 45 Gy (1.8 Gy/fraction). A concomitant boost was delivered on GTV + 2-cm margin with a total dose of 57.5 Gy (2.3 Gy/fraction). The following concomitant chemotherapy was administered: capecitabine (825 mg/m2 twice daily, 5 days per week) and oxaliplatin (130 mg/m2 on days 1, 17, and 35). Efficacy was evaluated in terms of complete pathological response (pCR). Acute toxicities were evaluated according to Common Terminology Criteria for Adverse Events version 3.0 criteria. Results: A total of 18 patients (7 women; median age 62 years; clinical stage: 4 local recurrences, 6 cT4, 5 cT3, 3 cT2, 2 cN0, 7 cN1, 9 cN2) were enrolled. Sixteen patients underwent surgical resection (9 low anterior resection, 6 abdominal perineal amputations; 1 transanal excision) and 2 patients did not undergo surgery for early metastatic progression or death from acute pulmonary edema. R0 resection was achieved in all patients who underwent surgery. Overall, 4 patients had a pCR and 7 patients only a microscopic residual of disease (pT0-Tmic: 11/18 = 61.1%; 95% CI, 36.2-86.1). Acute grade ≥ 3 toxicity was as follows: 1 case of leukopenia, 1 skin toxicity, 1 genitourinary toxicity, and 5 gastrointestinal toxicities, with an overall incidence of 8 (44.4%) of 18 patients. One-, 3-, and 5-year cumulative local control was 100%, 68.6%, and 68.6%, respectively. One-, 3-, and 5-year cumulative disease-free survival was 88.9%, 66.7%, and 66.7%, respectively. One-, 3-, and 5-year cumulative overall survival was 85%, 63.8%, and 63.8%, respectively. Conclusion: The regimen used in this study showed excellent results in terms of pathologic responses. However, despite the use of the VMAT technique, more than one-third of patients had severe acute toxicity.