Kazuhiko Sato - Department of Breast Oncology, Tokyo-West Tokushukai Hospital, Tokyo, Japan
Hiromi Fuchikami - Department of Breast Oncology, Tokyo-West Tokushukai Hospital, Tokyo, Japan
Naoko Takeda - Department of Breast Oncology, Tokyo-West Tokushukai Hospital, Tokyo, Japan
Takahiro Shimo - Department of Radiation Oncology, Tokyo-West Tokushukai Hospital, Tokyo, Japan
Masahiro Kato - Department of Radiation Oncology, Tokyo-West Tokushukai Hospital, Tokyo, Japan
Tomohiko Okawa - Preventive Medical Center, Sano City Hospital, Tochigi, Japan

Background: Breast-conserving therapy (BCT) with partial-breast irradiation(PBI) has become a standard alternative to whole-breast irradiation. Recently,neoadjuvant chemotherapy (NACT) has been widely performed for early breastcancer. Although BCT using perioperative PBI decreased invasiveness andgeographic miss, risks of adverse events and local recurrence remain a concern forpatients receiving NACT. Thus, a prospectively registered study, the ClinicalOutcome of Multicatheter BrAchyTherapy after NEOadjuvant chemotherapy(COMBAT-NEO), was conducted.Methods: Patients who underwent BCT using multicatheter-interstitialbrachytherapy (MIB) by intraoperative catheter implant were analyzed. Early andlate adverse events (AEs) including higher grade skin toxicities and woundcomplications, and tumor control of patients receiving NACT were evaluated incomparison with adjuvant chemotherapy (ACT) and no chemotherapy (no-CT).Results: Between April ۲۰۱۷ and February ۲۰۲۰, ۲۶۵ consecutive patients whoreceived single-stage BCT were evaluated, including ۱۳ NACT (۴.۹%), ۶۸ ACT(۲۵.۷%), and ۱۸۴ no-CT (۶۹.۴%). The median follow-up time and age were ۳۰.۰months and ۵۹.۰ years, respectively. All patients were followed up for at least ۱۲months. Although AEs in NACT, ACT, and no-CT were observed in ۱ (۷.۷%), ۵(۷.۴%), and ۱۱ (۶.۰%) patients, respectively (p = ۰.۹۱) and there was no acute AE inNACT patients. Overall, ۳ (۱.۱%) ipsilateral and ۱ (۰.۴%) contralateral breast tumorrecurrences were observed in no-CT patients. There were no regional and distantrecurrences.Conclusion: Although this pilot study was based on a small sample size withshort follow-up, these preliminary results support the study of a single-stage BCTwith MIB-PBI following NACT.

Breast cancer, breast conserving therapy, partial breast irradiation, neoadjuvant chemotherapy, multicatheter interstitial brachytherapy