3727 - Long-Term Results of Stereotactic Body Radiotherapy Boost In Patients with Cervical Cancer Ineligible for Intracavitary Brachytherapy: Secondary Analysis of a Phase I/II Study
Presenter(s)
K. Ito1, Y. Nakajima2, H. Ogawa3, A. Furusawa1, S. Kito1, N. Kino1, T. Yasugi1, T. Uno4, and K. Murofushi1; 1Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Tokyo, Japan, 2Komazawa University Graduate School, Tokyo, Japan, 3Department of Radiation Oncology, Miyagi Cancer Center, Miyagi, Japan, 4Department of Radiology, Chiba University Hospital, Chiba, Japan
Purpose/Objective(s): Although stereotactic body radiotherapy (SBRT) boost represents a promising treatment option for patients with locally advanced cervical cancer who are ineligible for brachytherapy, its long-term efficacy and safety remain unclear. This study assessed long-term oncologic outcomes and late toxicities in a patient cohort from a previous phase I/II trial.
Materials/Methods: This secondary analysis of an open-label, multicenter, single-arm, prospective phase I/II trial included 21 patients enrolled from January 2016 to October 2020. Patients with untreated, intracavitary brachytherapy-ineligible cervical cancer received whole-pelvic radiotherapy (45 Gy in 25 fractions) followed by an SBRT boost to the primary tumor. SBRT was delivered as 21 Gy in three consecutive daily fractions. The planning goal was to deliver the prescription dose to PTV D90%, with a maximum dose between 140% and 160% of the prescription dose. A rectal planning organ at risk volume (rectum + 3 mm) constraint of D2 cc =71.3 Gy EQD2 was applied. Endpoints for this analysis included long-term oncologic outcomes and late radiotherapy-related toxicities.
Results: The cohort comprised 21 patients, of whom 52% were aged =75 years, 81% had clinical stage III disease, and 43% had a maximum primary tumor size =70 mm. The reasons for foregoing intracavitary brachytherapy included bulky tumors (n=7), patient refusal (n=6), advanced age (n=3), comorbidities (n=2), vaginal anatomical abnormalities (n=2), and permanent contraceptive device use (n=1). The median follow-up was 61.1 months (range, 10.4–111.0) for all patients and 71.9 months (range, 60.0–111.0) for surviving patients. The 5-year loco-regional control, progression-free survival, and overall survival rates were 84%, 62%, and 62%, respectively. Grade 3 late toxicity occurred in one patient (urinary tract obstruction), and no grade 4–5 toxicities were observed. Six patients experienced grade 2 late toxicities (proctitis, n=3; fractures, n=3).
Conclusion: This secondary analysis demonstrated that an SBRT boost has curative potential and an acceptable long-term safety profile, even in patients with poor prognostic features. These findings support SBRT boost as a viable treatment option for patients with locally advanced cervical cancer who are ineligible for brachytherapy.