Abstract PS2-03-11: Current Practices and Perspectives in the Management of Multicentric and Multifocal Breast Cancer: A Survey-Based Analysis

Abstract Background: Breast conservation for multifocal (MF) and multicentric (MC) breast cancer remains contentious, particularly with evolving surgical and radiotherapy techniques. We conducted a cross-sectional survey to assess current practices, definitions, and attitudes among surgical oncologists (SOs) and radiation oncologists (ROs) regarding MF/MC breast cancer. Methods: An online 28-item questionnaire was disseminated to consultant SOs and ROs. Responses from 82 participants across 76 institutions representing 16 Indian states and 3 union territories were analyzed descriptively. Items assessed included diagnostic definitions, indications for breast-conserving surgery (BCS), imaging, boost strategies, and multidisciplinary involvement. Results: ROs and SOs were equally represented (n=41 each), with 93% specializing in breast cancer. Most respondents were from private hospitals (74.4%), followed by government institutions (18.3%) and trust/NGO setups (7.3%).A high-volume cohort, 37% treated >50 breast cancer cases per month. MF disease was encountered ‘frequently’ or ‘very frequently’ by 40% of respondents, and MC by 34%. Most (76%) felt MF/MC incidence is rising due to advanced imaging. BCS was routinely offered for MF by 52% and conditionally by 40%; for MC, 13.6% offered it routinely, and 51% conditionally. Definitions of MC varied: 45% used quadrant-based criteria; 46% used the ≥5 cm separation rule; and 16% defined it as lesions requiring different incisions. Oncoplastic approaches were used to manage tissue deficits in 85% of MF and 76% of MC cases. Five surgeons had never offered BCS for MC, and extreme oncoplastic procedures were performed or encountered in 61% of practices. MRI was considered mandatory by 30%, while 26.5% used contrast-enhanced mammography. Biopsy of both lesions was deemed essential by 35%, with some emphasizing the importance of evaluating biological heterogeneity. Radiation strategies varied: for MF, 10% gave whole-breast irradiation (WBI) without boost, 60% gave a full boost, and 8.5% selectively boosted part of the bed. For MC, 57% boosted both tumor beds. Hypofractionated WBI (40 Gy in 15 fractions) was preferred (74%), while 11% used ultra hypofractionation selectively. IMRT/VMAT was the most commonly used boost technique (54.9%), followed by 3DCRT (38%), electrons (35.4%), and mini-tangents (20.7%). Boost decisions were typically based on tumor size, grade, nodal status, age, and receptor status, with 17.1% using all five factors. Key challenges included uncertainty in target delineation (73.2%), concerns about poor cosmesis (54.9%), and technical complexity (62.2%). Acute toxicity was also reported as a concern (42.7%). Multidisciplinary team (MDT) involvement before surgery was reported by 42.7% and postoperatively or selectively by 44%. Only 2.4% lacked access to an MDT. In 64.6% of practices, the surgical team was involved in boost planning only when the RO found it challenging; routine joint delineation was rare (7.3%). A majority (93.9%) expressed willingness to participate in a prospective study to develop consensus guidelines for boost contouring in MF/MC cases. Conclusion: This survey highlights substantial heterogeneity in surgical and radiation practices for MF/MC breast cancer across India. While breast conservation is cautiously expanding, standardized definitions and contouring guidelines are lacking. Multidisciplinary planning and tailored radiation strategies are essential. These findings underscore the urgent need for consensus protocols and prospective studies to unify practice. Citation Format: R. Krishnamurthy, S. Joshi, R. Pathak, A. Das Sheth, T. Wadasadawala, B. Kothari, D. Hoysal, A. Deshpande, R. Sarin. Current Practices and Perspectives in the Management of Multicentric and Multifocal Breast Cancer: A Survey-Based Analysis [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-03-11.