Abstract PO4-02-07: Prevalence of distant metastases in High-Risk Operable Breast Cancer (HROBC) pT1-2 N2a orhigher at diagnosis

Abstract Introduction: Current standard guidelines do not recommend a routine staging workup in early breast cancer as incidence of de novo metastasis is only 1-2%. Some of these patients are found to have a higher axillary nodal burden after surgery. This prospective study evaluated the incidence of distant metastases in clinically high-risk operable breast cancer (HROBC) who have a higher nodal burden on histopathological report after surgery. The intent was to detect presence of subclinical distant disease that may have an impact on treatment offered and outcome. Currently, there is no compelling data to support a routine metastatic workup in these patients. Methodology: A single-centre study approved by Institutional Ethics Committee was carried out enrolling early breast cancer patients with high nodal burden (four or more axillary nodes positive) after definitive surgery. The HROBC group was defined as early breast cancer patients with pT1/2, N2a/N3 stage on surgical histopathology. They underwent a comprehensive metastatic workup, including ultrasound abdomen, bone scan, and CT scan (thorax-abdomen-pelvis) or PET scan before starting their adjuvant treatment. Burden of distant disease was classified into oligometastatic (M1o) or polymetastatic disease (M1p). The adjuvant treatment intent was redefined as curative or palliative based on the distant disease burden and treatment was modified accordingly. Result: The study accrued 100 HROBC women with pT1-2, pN2a-3 stage disease during 2015-2018 operated upfront for early breast cancer cT1-2 N0-1, of which 97 were included in final analysis. The 3 excluded patients had their surgery elsewhere with clinical diagnosis of early breast cancer with histopathology indicating heavy nodal burden; 2 of them had T3 tumor and 1 had cN3 disease and were deemed a higher stage and would anyway warrant a metastatic work-up and hence were ineligible for the study. Forty percent women were premenopausal, 54 (55.6%) had pN2a disease and 43 (44.4%) had pN3. Staging investigations identified distant metastatic disease (M1) in 8 of 97 women (8.24%). Interestingly, 5 of them had oligometastatic (M1o) disease (5.15%) and 3 had polymetastatic (M1p) disease (3.09%). Between the 2 nodal groups, no specific distribution of M1o or M1p disease was observed, but the pickup rate of overall distant disease was higher in pN3 (11.4%) as against N2a (5.6%) patients p=NS. The most common sites of metastases observed was bone (5/8) followed by liver (3/8). There was no correlation with ER, PgR or HER2neu status and extent of distant disease. The patients with M1o disease, completed their adjuvant treatment as planned along with treatment of oligometastatic sites. Only 3.09% patients who were detected with M1p disease, were treated with a palliative systemic therapy. Conclusion: Early detection of metastatic disease, M1o and M1p, in clinical HROBC could lead to improved treatment strategies. The findings have the possibility to optimize management of high-risk early breast cancer as a separate clinical entity, requiring staging post hoc after primary surgery, for adequate resource stratification and better outcomes, especially in those with 10 or more axillary nodes positive for metastases. This subset may get identified in the TNM classification for better understanding and management. Citation Format: Vani Parmar, Naveena Kumar AN, Basila Ameer Ali, Nita Nair, Shalaka Joshi, Purvi Thakkar, Garvit Chitkara, Varsha Gaikwad, Vaibhav Vanmali, Shabina Siddique, Palak Popat, Sneha Shah, Sangeeta Desai, Tanuja Shet, Meenakshi Thakur, Venkatesh Rangarajan, Rajendra Badwe. Prevalence of distant metastases in High-Risk Operable Breast Cancer (HROBC) pT1-2 N2a orhigher at diagnosis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-02-07.