Local Control and Use of External Beam Parametrial Boost in the Era of Image-Guided Brachytherapy for Locally...

Historically, external beam parametrial boost (EBPB) has been used in locally advanced cervical cancers to supplement radiation dose. However, it has become controversial in the era of image-guided brachytherapy. Modern 3D imaging and brachytherapy techniques have improved delineation and coverage of tumor. Outcomes with and without parametrial boost were analyzed.

Women with cervical cancer involving the parametria (clinically or radiographically) diagnosed between 2001 and 2017 were identified. Clinicopathologic and treatment features, survival and patterns of failure data were collected. Univariate and multivariable data analysis was performed to evaluate association of these variables, including parametrial boost, with local failure-free survival and overall survival. Competing risks analysis was performed for cumulative incidence of local failure, with death and other failures treated as competing events.

A total of 100 women were identified (median follow-up 26.8 mo). Forty-one (41%) received EBPB; these patients were less likely to have received magnetic resonance imaging, positron emission tomography, interstitial, or high-dose rate brachytherapy. Magnetic resonance imaging, positron emission tomography, dose rate, and treatment era were highly correlated (Cramer's V: 0.43 to 0.68, P<0.01). Two-year overall survival and local failure were 78% and 12% for the entire cohort. While the use of EBPB was not associated with any outcome on multivariable analysis, treatment year after 2009 was highly associated with improved outcomes in all models.

In this study, omission of EBPB did not compromise local control or survival in the modern era, supporting a decreased need for standardized use of parametrial boost.