Prophylactic Extended-Field Irradiation vs. Pelvic Irradiation in Cervical Cancer Patients With 2018 FIGO IIIC1 Diseases

Abstract

The role of prophylactic extended-field radiation therapy (EFRT) has not been established, and the indications for prophylactic EFRT in patients with cervical cancer are not clear. In the present study, we compared the survival rates and toxicities of prophylactic EFRT and pelvic radiation therapy (PRT) among cervical cancer patients with 2018 FIGO stage IIIC1 disease.We retrospectively analyzed patients with 2018 FIGO stage IIIC1 disease who were treated with definitive concurrent chemoradiotherapy at our institute between 2011 and 2015. A dose of 50.4 Gy in 28 fractions was delivered to the pelvic region (by PRT) or the pelvic plus para-aortic lymph node region (by EFRT) with intensity-modulated radiation therapy. The first-line regimen of concurrent chemotherapy was weekly cisplatin. As the baseline characteristics were not balanced between the two groups, we conducted propensity score matching.A total of 280 patients were included, with 161 patients treated with PRT and 119 patients treated with EFRT. The median follow-up periods were 47.2 months. After propensity score matching (1:1), 71 pairs of patients were selected. The 5-year rates of the patients treated with PRT and EFRT were 61.9% and 85.0% for overall survival (OS, P = 0.025), 53.0% and 77.9% for disease-free survival (DFS, P = 0.004), 89.7% and 98.4% for para-aortic lymph nodes (PALN) control (P = 0.053). In the subgroup analysis, patients were grouped into a high-risk group (122 patients) and a low-risk group (158 patients) based on three factors: positive common iliac lymph nodes, 3 or more pelvic lymph nodes and T3 disease. Patients with one or more risk factors were grouped to the high-risk group. In high-risk group, 32 pairs of patients were selected after matching. Over 5 years, the rates for patients treated with PRT and EFRT after matching were 65.1% and 84.3% for OS (P = 0.135), 54.9% and 84.4% for DFS (P = 0.018), 91.8% and 100.0% for PALN control (P = 0.132). In low-risk group, 39 pairs of patients were selected after matching. Over 5 years, the rates for patients treated with PRT and EFRT after matching were 61.8% and 91.1% for OS (P = 0.028), 53.8% and 80.3% for DFS (P = 0.017), 88.4% and 100.0% for PALN control (P = 0.043). The rates of grade 3 or greater chronic toxicities were 1.2% and 5.9% in the PRT and EFRT groups, respectively (P = 0.067).Compared to PRT, prophylactic EFRT improved OS, DFS and PALN control in cervical cancer patients with pelvic MLNs. In the subgroup analysis, patients in both the high-risk group and low-risk group benefited from prophylactic EFRT. The incidence of grade 3 or higher toxicities was higher in the EFRT group than in the PRT group, although the difference was not significant. 2018 FIGO stage IIIC1 can be used as an inclusion criterion in clinical trials comparing PRT to prophylactic EFRT in patients with cervical cancer.