Abstract P4-12-06: Long-term follow-up of patients with invasive breast cancer treated with catheter-based accelerated partial breast irradiation following lumpectomy

Abstract

Abstract Introduction: A large number of breast cancer patients who are eligible for breast-conserving therapy (radiation following complete resection via lumpectomy) elect to undergo mastectomy to avoid radiation - with treatment length being the most significant deterrent. The development of accelerated partial breast irradiation (APBI) tailored treatment to target tissue at greatest risk of recurrence, balancing treatment-associated benefits with radiation exposure risk while shortening therapy duration from 6 weeks to 5 days. This study analyzed rates of ipsilateral breast tumor recurrence (IBTR) in patients with invasive breast cancer treated with resection followed by APBI delivered via catheter-based brachytherapy. Methods: Retrospective data was collected on 406 patients with primary invasive breast cancer diagnosed from January 2007 to February 2014, treated with lumpectomy and adjuvant APBI catheter-based brachytherapy. Follow-up data was available for 390 patients (97.5%). Mean and median follow-up were 80.9 and 83.5 months respectively. 193 patients (49.4%) had at least 7 years of follow-up. Results: 21 patients (5.4%) were found to have an IBTR. Of these patients, 14 (66.7%) experienced an IBTR in the same quadrant as their index cancer. 7 patients (33.3%) experienced an IBTR in a different quadrant. Only one patient (4.8%) experienced an IBTR within the first two years after conclusion of their primary treatment. Of the entire cohort, 7 patients (1.8%) were found to have a metastatic recurrence (one which occurred within the first two years after primary treatment) and 7 patients (1.8%) experienced new primary cancers diagnosed in their contralateral breasts. Conclusion: The results of this investigation demonstrate catheter-based brachytherapy APBI delivered after breast-conserving surgery carries a relatively low risk for IBTR in patients with invasive breast cancer. We support its' use as an effective and valid alternative for selected early breast cancer patients desiring a significantly shorter, more convenient course of treatment in the adjuvant setting without increased risk of recurrence. Citation Format: Cynthia Chen, Chi Chi Do-Nguyen, Lisa Poole, Lina Sizer, William B Carter, Thomas G. Frazier. Long-term follow-up of patients with invasive breast cancer treated with catheter-based accelerated partial breast irradiation following lumpectomy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-06.