Pak, LM

Abstract Background Young women are more likely than older women to present with higher stage breast cancer (BC) and may benefit to a greater extent from downstaging with neoadjuvant systemic treatment (NST). Young age is also associated with greater likelihood of pathologic complete response (pCR). Using a large prospective cohort of young women with BC, we investigated response to neoadjuvant therapy, eligibility for breast conserving surgery (BCS) pre- and post-NST, and surgical treatment. Methods The Young Women's Breast Cancer Study (YWS) is a multi-center cohort of women diagnosed with BC at age ≤40, that enrolled 1302 patients from 2006 to 2016. Disease characteristics and treatment information were obtained through medical record and central pathology review. Surgical recommendation before and after NST, conversion from BCS borderline/ineligible to BCS eligible, surgery, documented reasons for choosing mastectomy (MTX) among BCS eligible women, and final pathologic response were independently reviewed. Results Among 1302 women enrolled in YWS, 801 (62%) presented with unilateral stage I-III breast cancer and 317(40%) received NST. Median age was 36 years old (22-40). Pre-NST, 85/317 (27%) were BCS eligible, 49 (15%) were borderline, and 169 (53%) were not eligible (16 inflammatory breast cancer (IBC), 88 large tumor size /cosmetic, 48 diffuse calcifications, and 83 multicentricity). Among the 218 patients who were BCS ineligible/borderline pre-NST, 82 (38%) became eligible for BCS after NST. 4 patients who were BCS eligible pre-NST became ineligible. Of all patients eligible for BCS post-NST (n=163), 80 (49%) attempted BCS, 74 (93%) of whom were successful, and 83 (51%) chose MTX. Reasons for choosing MTX included: patient preference (38/83 (46%)), BRCA or TP53 mutation (31 (37%)), family history (3 (4%)), unknown (11 (13%)). On final pathology, 75 (24%) patients had pCR. Among patients who achieved a pCR, 48 (64%) underwent MTX, fewer than half (21/48 (44%)) were for anatomic indications (IBC, large tumor at diagnosis, diffuse calcifications, multicentric disease). Conclusion While NST doubled the proportion of young women eligible for BCS, nearly half chose MTX regardless of response to NST, mostly for personal preference or high-risk preventative reasons. These data highlight that surgical decision making among young women with breast cancer is often driven by factors beyond extent of disease and clinical response to therapy. Table 1.Clinical-pathologic characteristicsCharacteristicsNumber%Pre NST surgical recommendation BCS eligible8526.8Borderline4915.5BCS ineligible16953.3Unknown144.4Clinical Response Complete20263.7Partial9229.0Stable30.9Progressing72.2Unknown134.1Pathologic Response pCR (No invasive or DCIS)7524No pCR24276Post NST Surgical recommendation BCS eligible16351.4BCS ineligible14445.4Unknown103.2Attempted surgery BCS8025.2MTX23674.1Unknown20.6Final Surgery BCS7423.3MTX24176unknown20.6 Citation Format: Kim HJ, Dominici L, Rosenberg S, Pak LM, Poorvu PD, Ruddy K, Tamimi R, Schapira L, Come S, Peppercorn J, Borges V, Warner E, Vardeh H, Collins L, King T, Partridge A. Surgical treatment after neoadjuvant systemic therapy in young women with breast cancer: Results from a prospective cohort study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr GS6-01.

Abstract Background: Synchronous bilateral breast cancer is rare, with reported incidence from 0.3-12%; the incidence and pattern of bilateral breast cancer among younger women is unknown. Here we report the incidence and phenotypes of bilateral breast cancer in women ≤40 years of age enrolled in the Young Women's Study (YWS) cohort. Methods: The YWS is a multi-center, prospective cohort study that enrolled women with newly diagnosed breast cancer at age ≤40 years from 2006-2016. Those with synchronous bilateral breast cancer (in-situ and/or invasive) formed our study cohort. Disease characteristics and treatment were obtained by medical record review. Central pathology review was performed to capture histologic features and categorize the tumor phenotype as either luminal A (hormone receptor (HR)+, HER2-, grade 1 or 2), luminal B (HR+, HER2+, or HER2- and grade 3), HER2-type (HR-, HER2+), or triple negative (TNC; HR/HER2-). Tumor phenotypes of bilateral breast cancers were compared and evaluated for concordance. Results: Among 1302 patients enrolled in the YWS, 20 (1.5%) patients presented with bilateral disease, with median age of diagnosis of 38 years (range 18-40). The majority of patients (13 (65%)) presented with unilateral symptoms and contralateral disease was identified on subsequent imaging. 12 (60%) reported a positive family history of breast cancer and 17 (85%) underwent genetic testing; resulting in the identification of 6 mutation carriers (2 BRCA1, 3 BRCA2, 1 TP53). The majority of patients (15 (75%)) underwent bilateral mastectomy, 1 underwent unilateral mastectomy with contralateral lumpectomy, and 4 underwent bilateral lumpectomy. On pathology, 2 patients had bilateral in-situ disease, 5 had unilateral invasive and contralateral in-situ disease, and 13 had bilateral invasive disease. Of those with bilateral invasive disease, all had concordant tumor histology (92% ductal, 8% ductal and lobular), 10 (77%) patients had bilateral luminal tumors and when fully characterized 6 were of the same luminal type. Only one patient had bilateral basal-like breast cancer. Patient ID ERPRHer2 amplifiedGradePhenotype1Left++-2Luminal A Right++-3Luminal B3Left++-3Luminal B Right++-3Luminal B6Left++-3Luminal B Right++-3Luminal B9Left++-2Luminal A Right++-2Luminal A10Left+++3Luminal B Right++-2Luminal A12Left+--3Luminal B Right+--2Luminal A13Left---NABasal-like Right++-NALuminal A or B14Left+++2Luminal B Right++-3Luminal B15Left++-3Luminal B Right+++3Luminal B16Left+++3Luminal B Right--+NAHEr2-type17Left---3Basal-like Right---3Basal-like19Left++-2Luminal A Right++-3Luminal B20Left++-1Luminal A Right++-2Luminal A Conclusions: Among a large cohort of young women, only 20 (1.5%) had bilateral disease, and the majority of the invasive tumors were of the luminal phenotype, yet frequently differed by grade or HER2 status; supporting the need for thorough pathologic evaluation of bilateral disease to determine risk and tailor treatment. Overall the low incidence of bilateral disease and preponderance of the luminal phenotype in this population is reassuring. Citation Format: Pak LM, Rosenberg SM, Ruddy KJ, Tamimi RM, Peppercorn J, Schapira L, Borges VF, Come SE, Warner E, Snow C, Collins L, King TA, Partridge AH. Tumor phenotype and concordance in synchronous bilateral breast cancer in young women [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-22-03.