Abstract PO1-09-01: Patient Advocates, Oncologists & Research Scientists Collaborate to Address PostPartum Breast Cancer

Abstract The incidence of young women (YW= 45) with aggressive breast cancer (BC) has been increasing and BC in younger women tends to be diagnosed in more advanced stages1. A group of advocates, oncologists and scientists have established an advocate-researcher dialogue to address this. A key finding we are highlighting and sharing with the community is that postpartum BC (PPBC) is a "free biomarker" for increased risk of metastatic disease. We report our efforts to understand the biologic underpinnings of PPBC, strategize to disseminate information, and accomplish our longterm goals to reduce BC incidence and mortality in YW. Interactions Between Childbirth 30 at the time of their last baby, this increased risk converts to a protective effect about 10 years after childbirth, such that in later life they have a lower risk of getting BC in comparison to women who have not given birth. However for women who have children after 30, the risk remains increased for many decades. The peak window of time for YW to get BC is within 10 years after childbirth and diagnoses during this window are PPBC. The global trend of women delaying childbirth until they are older is one factor contributing to increased PPBC2. While lactation can be protective, this protection is seen most robustly against triple negative BC (TNBC). This protective effect is seen most strongly in women who nurse for about 6 months. In some who do not nurse, especially black women, risk for TNBC can be increased3. When women get diagnosed with PPBC several things are known4: The frequency of the different subtypes of BC (ER+,PR+,Her2+) is similar to BC diagnosed in YW overall, so most PPBC is ER+ Her2- While there is no difference in the % of women who will have Her2+ or TNBC among PPBC cases, more women with PPBC will have + lymph nodes at diagnosis Of women who get diagnosed with BC 45, about half will occur in this PP window accounting for about 50% of all early onset BC Studies have shown that PPBC has a higher tendency towards developing metastatic disease in comparison to BC in women without children or in women diagnosed more than 10 years since last childbirth4. Research is ongoing to identify why this increased risk is occurring and how treatment can be tailored to eliminate this risk. Adherence to therapy and participation in clinical trials is crucial. Clinical trials should capture when a woman had her last child as a routine datapoint so PPBC can be researched more broadly. This datapoint - age of her youngest child when she was diagnosed - is essentially a "free biomarker" indicating risk for metastasis. Advocate-Researcher Outreach Efforts Production of a podcast episode "Rising Rates of BC 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-09-01.