Superficial high-dose-rate brachytherapy for primary tumors and relapses after surgery in patients with basal cell carcinoma of the head and neck region: results of a retrospective comparative cohort study - J. Chyrek, Artur; Chicheł, Adam; M. Burchardt, Wojciech; Bielęda, Grzegorz; Jankowska, Małgorzata; Moczko, Jerzy; Roszak, Andrzej (Journal of Contemporary Brachytherapy, 2022)