Carbon-ion radiotherapy for adenocarcinoma of the uterine cervix: clinical outcomes of a multicenter prospective registry-based study in Japan (2016-2020)

Purpose: Prognoses are poorer in cases of adenocarcinoma of the uterine cervix (AUC) than of squamous cell carcinoma. Carbon-ion radiotherapy (CIRT) outcomes for AUC have been reported in retrospective or single institutional prospective studies but not prospective multicenter studies. We present the results of CIRT for AUC in a prospective multicenter study utilizing a nationwide hospital-based registry in Japan.

Materials and methods: Patients with locally advanced untreated AUC who received CIRT at 4 Japanese centers between June 2016 and April 2020 were included in this study. In the absence of organ dysfunction, up to 5 weekly 40 mg/m² cisplatin courses were administered. The primary endpoints were 2-year overall survival (OS) and local control (LC) rates. The secondary endpoints were 2-year disease-free survival (DFS) rate and late adverse events (AEs).

Results: Forty-two patients were enrolled with a median age of 54 years (range, 34-76 years). Patients were diagnosed with Stage IIB (n=26), IIIB (n=12), or IVA (n=4) disease. The median follow-up period was 24 months. The 2-year OS, LC, and DFS rates were 97.5% (95% confidence interval [CI] 92.7-100.0%), 80.9% (95% CI 66.9-94.8%), and 64.3% (48.1-80.4%), respectively. Two patients developed Grade 3 rectum/sigmoid AE. One patient required urinary diversion surgery during a salvage operation for local tumor recurrence (Grade 3 genitourinary AE). No other Grade 3 or worse toxicities were reported.

Conclusion: CIRT is an effective treatment for locally advanced AUC. Further research is required to validate the safety and efficacy of CIRT for AUC.