Efficacy and safety of radiotherapy combined with raltitrexed and irinotecan for treating unresectable recurrent colorectal cancer: a single-arm phase II trial

BACKGROUND: Local recurrence of colorectal cancer is associated with poor prognosis and quality of life. For patients not eligible for curative surgery, chemoradiation could be a promising therapeutic option, but there is no consensus yet for the concurrent chemotherapy regimen. This study evaluated the effects and safety of intensity-modulated radiation therapy (IMRT) when administered concurrently with raltitrexed and irinotecan to patients with unresectable recurrent colorectal cancer. METHODS: Eligible patients developed unresectable recurrent colorectal cancer, and were refractory to, or intolerant of, chemotherapy with fluoropyrimidine and oxaliplatin. IMRT was delivered (total dose: 50–60 Gy in 25–30 fractions) concurrently with irinotecan and raltitrexed (200 and 3 mg/m(2), respectively, on days 1 and 22). After treatment completion, patients underwent surgery or continued the same regimen of chemotherapy and were assessed by a multidisciplinary team. The primary endpoint was the objective response rate, defined as the proportion of patients with a confirmed complete response or partial response, assessed by radiologist and investigator after the completion of radiotherapy and reconfirmed a month later, in accordance with the Response Evaluation Criteria in Solid Tumors version 1.1. RESULTS: All 30 patients enrolled in this study between January 2019 and July 2020 completed radiotherapy and received a median of five chemotherapy cycles (range, 2–10 cycles). Twelve patients (40.0%) experienced an objective response (two complete responses and ten partial responses) and 17 patients exhibited stable disease [disease control rate (DCR): 96.7%]. The median follow-up was 22 months (range, 4–35 months), by the end of follow-up, six (20.0%) patients had local failure in the irradiation field, four (13.3%) had regional progression outside the irradiation field, 13 (43.3%) had distant metastasis or metastatic progression and nine (30.0%) died. The median progression-free survival (PFS) and local PFS (LPFS) were 13.5 and 23 months, respectively. The incidence of grade 3 or 4 adverse events was 26.7%, the most common of which was neutropenia (13.3%). CONCLUSIONS: IMRT with concurrent raltitrexed and irinotecan is a feasible treatment for unresectable recurrent colorectal cancer, which allows good tumor response and local control with acceptable toxicity profile.