Abstract P3-20-02: The association of clinicopathological variables and patient´s preference with surgical decision-making for early breast cancer

Abstract Background: Mastectomy (Mx) and breast conserving surgery (BCS) when combined with adjuvant whole breast radiotherapy (RT) have been shown to give equivalent outcome in randomized trials . In recent years, a number of retrospective population-based studies suggest that BCS offers superior survival compared to Mx. In these studies, treatment has not been randomized, but selected based on patient and tumour characteristics or patient´s own choice. The aim of this study was to compare clinicopathological variables in women with tumours less than 30mm in size treated with either BCS or Mx, where both surgical methods would have been feasible based on postoperatively recorded tumour characteristics. Our second aim was to explore the underlying reason for choosing Mx as surgical approach. Method: The study is a population-based retrospective analysis of prospectively collected data from the Swedish National Breast Cancer Register (NBCR). The source population are women registered with primary invasive breast cancer with a tumour size up to 30 mm and no more than four positive axillary lymph nodes, treated between 2013-2016 in the northern health care region in Sweden. During this time period, the reason for selecting Mx was registered in this region with five optional alternatives: 1.Age < 40 years, 2.Large tumour size/extent relative breast volume, 3.Multifocality/multicentricity, 4.RT contraindicated due to comorbidity and 5.Patient´s own choice. All cases with male breast cancer and patients treated with neoadjuvant therapy were excluded.Logistic regression analyses were performed to assess the association of tumour and patient characteristics with receiving a mastectomy shown as odds ratios with 95% confidence intervals (CI). Results: A total of 1860 women met our inclusion criteria, 1346 of which had undergone BCS (mean age 63) and 514 Mx (mean age 66). For 1309 women (97.1%) in the BCS group and 146 (27.6%) in the Mx group adjuvant RT was added to the breast, chest wall and/or ipsilateral regional lymph nodes after surgery. Clinical detection, OR 3.35 (95%CI 3.32-5.14), higher T stage OR 2.66 (2.00-3.54), N stage OR 1.84 (1.46-2.32) and multifocality, OR 4.59 (3.56-5.92) were associated with a higher likelihood of receiving Mx. Women treated with Mx had more lobular tumours, OR 1.42 (1.05-1.92), higher grade, OR 2.27 (1.65-3.13), more hormone receptor negative, 1.47 (1.09-1.98) and HER2 positive tumours, OR 1.61 (1.19-2.17) compared to women treated with BCS.The most common reason for choosing Mx was large tumour size and/or multifocality (52.8%). The second most common reason was the woman´s own preference (36.6%). In 9 % of the cases RT was considered contraindicated, hence Mx was recommended by the treating surgeon or tumour board. Conclusion: Women with invasive breast cancer up to 30mm selected for treatment with Mx have less favourable prognostic characteristics than those treated with BCS. Selection bias may largely explain the survival benefits of BCS compared to Mx demonstrated in observational studies. Table 1: Distribution of factors listed as reason of mastectomy as surgical treatment. Table based on a a total of 431 mastectomy cases where reason for Mx were listed. RT = Radiotherapy No. of patients%Age < 40 years61.4large tumour size/extent relative breast volume13531.3Multifocality/multicentricity9321.5RT contraindicated due to comorbidity399.0Patients own choice15836.6 Citation Format: Emma Söderberg, Malin Sund, Fredrik Wärnberg, Lars Holmberg, Greger Nilsson, Hans Garmo, Carl Blomqvist, Charlotta Wadsten. The association of clinicopathological variables and patient´s preference with surgical decision-making for early breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-20-02.