Feasibility and full-course dosimetry of an intraoperatively placed multichannel brachytherapy catheter for accelerated partial breast irradiation

Abstract

PurposeDetermine feasibility and resultant dosimetry of an intraoperatively placed multichannel intracavitary brachytherapy catheter for accelerated partial breast irradiation (APBI). MethodsPatients with breast cancer underwent intraoperative brachytherapy catheter placement based on frozen section analysis with immediate postoperative APBI. The planning target volume evaluation (PTVEval) and organs at risk were contoured on daily pretreatment CT scans for each patient, and the original treatment plan was applied to assess full-course dosimetry. ResultsOf the first 21 patients consented for intraoperative catheter placement, 20 (95%) were able to proceed with treatment as planned. The mean volume of PTVEval receiving 90% of prescription dose (V90%) and mean percentage of prescription dose to 90% of the PTVEval (D90%) on initial planning were 96.7 (±1.1%) and 100.2 (±2.1%), respectively. Full-course dose coverage remained excellent with a mean PTVEval V90% and D90% of 95.0 (±4.4%) and 100.2 (±9.6%), respectively. Mean full-course maximum dose constraints for chest wall and skin were met by 70% and 95% of patients, respectively. Air accumulation >1 cc during treatment increased the risk of a daily fraction with PTVEval coverage below goal (odds ratio, 9.8; p = 0.05), whereas those with applicators <0.5 cm from the chest wall at planning were at risk of exceeding that organ's maximum dose constraint on a daily fraction (odds ratio, 45; p = 0.02). ConclusionsIntraoperative catheter placement and early initiation of APBI based on frozen section pathology is feasible, yields acceptable dosimetry, and is an option for completing breast conserving therapy in less than 10 days.