Stereotactic ablative body radiotherapy boost for cervical cancer when brachytherapy boost is not feasible.

Background: The purpose of this study was to analyze the treatment efficacy and safety of stereotactic ablative body radiotherapy (SABR) boost for cervical cancer patients not amenable to brachytherapy.

Methods: A retrospective review of the medical records from single institution of 25 eligible patients was performed. The patients underwent pelvic radiotherapy (RT) in 25 or 28 fractions with a median dose of 45 Gy (range 44-50.4 Gy). SABR boost was delivered after pelvic RT, with a median dose of 25 Gy (range 20-33 Gy), and a median fraction number of 5 (range 4-6). 21 patients with a follow-up period of more than one year were included in the toxicity analysis, and hematuria and hematochezia that occurred later than 3 months after the RT were graded.

Results: The median follow-up period after radiotherapy was 2.85 years (range 0.33-6.60). The 3-year local control, locoregional control, disease-free survival, and overall survival rates were 80.9%, 75.8%, 40.9%, and 77.1%, respectively. 5 patients experienced grade 3 toxicity (3 genitourinary, 3 gastrointestinal), and no grade 4-5 toxicity was reported. Univariate analysis showed that cumulative D in equivalent dose in 2 Gy fractions (EQD2) of rectum was marginally predictive for any grade of hematochezia (P = 0.051). Cumulative D EQD2 of bladder was not predictive for hematuria. In the receiver operating characteristic (ROC) curve analysis, the optimal threshold of cumulative rectal D EQD2 was 81.2 Gy for any grade of hematochezia.

Conclusion: SABR boost for cervical cancer was effective and tolerable. Although it cannot substitute brachytherapy, it can be a treatment option when brachytherapy is not possible.