2783 - A Novel Combination of Carbon Ion Radiotherapy with Image-Guided Brachytherapy for Locally Advanced Cervical Adenocarcinoma
Presenter(s)
T. Kumazawa1, K. Ando1, K. Murata2, T. Kaminuma3, S. E. Noda4, A. Iwase5, and T. Ohno6; 1Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Japan, 2QST Hospital, National Institutes for Quantum Science and Technology, Chiba, Japan, 3Department of Radiation Oncology, Shibukawa Medical Center, Maebashi, Japan, 4Department of Radiation Oncology, Comprehensive Cancer Center, International Medical Center, Saitama Medical University, Saitama, Japan, 5Department of Obstetrics and Gynecology, Graduate School of Medicine, Gunma University, Maebashi, Japan, 6Department of Radiation Oncology, Graduate School of Medicine, Gunma University, Maebashi, Japan
Purpose/Objective(s): Conventional photon therapy has not shown satisfactory results for locally advanced cervical adenocarcinoma (LACA). Carbon-ion radiotherapy (CIRT), high linear energy transfer radiotherapy, is expected to be effective against tumors resistant to photon therapy such as LACA. At the prior facility, treatment for LACA was provided only with CIRT; the local boost irradiation with CIRT required limiting the dose to the tumor to prioritize dose constraints in the rectum or sigmoid colon. Therefore, a sufficient dose could not be administered to bulky tumors or tumors close to the rectum or sigmoid colon, which could lead to local recurrence. To solve this problem, Gunma University established a novel method for combining CIRT with image-guided brachytherapy (IGBT) as a boost irradiation in 2018. This study is the first to demonstrate the efficacy and safety of a combination of CIRT and IGBT for LACA.
Materials/Methods: This study included 30 patients with stage II–IVA cervical adenocarcinoma treated with the combination of CIRT and IGBT at Gunma Heavy Ion Medical Center from October 2013 to January 2023. CIRT was administered at 36.0 Gy (RBE)/12 fractions to the local and pelvic lymph node regions, followed by 19.2 Gy (RBE)/4 fractions to the primary local tumor and enlarged lymph nodes. Then, three IGBT fractions were given after CIRT. In IGBT, the treatment target was the high-risk clinical target volume (HR-CTV), which includes the tumor-infiltrated area and whole cervix. The aiming target dose for the absolute dose of CIRT and the biological equivalent dose of 2 Gy per fraction (EQD2) of IGBT was <64.1 Gy for the rectum and sigmoid D2cm3. The target accumulated dose of HR-CTV D90% was =76.5 Gy. In principle, cisplatin was concurrently administered at 40 mg/m2/week for patients aged <75 years, with a maximum of five courses.
Results: The median age was 53 years. The FIGO stages were I, III, and IV in 16, 15, and 2 patients, respectively. The median tumor diameter at the beginning of treatment was 56 (range, 33–84) mm. The median follow-up period was 49.9 months. The median accumulated doses to HR-CTV D90%, rectum D2cm3 and sigmoid D2cm3 were 85.1 (range, 77.5–96.6), 59.4 (range, 45.6–65.0), and 60.2 (range, 52.9–64.9), respectively. The 4-year local control, overall survival, and progression-free survival (PFS) rates after CIRT were 96%, 94%, and 66%, respectively. After 3 months of treatment, grade =3 late adverse events (CTCAE ver. 5.0) were observed only in two cases (bladder hemorrhage and ileus).
Conclusion: The results suggest that the combination of CIRT with IGBT is a promising treatment option for LACA. To improve PFS, we are proceeding with the clinical trial of this combination therapy with an immune checkpoint inhibitor.