Abstract P3-07-03: Endocrine sensitivity is decisive for patient outcome in small node-negative breast cancers (BC) (pT1a,b) – Results from the Munich Cancer Registry

Abstract

Abstract PURPOSE In clinical routine, adjuvant systemic therapy (ADST) in small node-negative (N0) breast cancers is controversial, in particular in HER2-positive disease. We aimed to define the patient subgroups with tumors <1 cm which would benefit from ADST based on their risk of BC-recurrence and survival using population-based cancer registry data. METHODS From 2002-2009 (median follow-up 6 years), 9,707 primary breast cancer patients with N0 tumors <2 cm (pTis, pT1N0M0) were reported to the Munich Cancer Registry. Patients with pTis tumors (n= 1870) served as internal control. Time to progression, observed (OS) and relative survival rates (Kaplan-Meier estimates) are presented. Cox regression analysis was used to assess the influence of tumor size, age, HR-, and HER2-status. RESULTS 10-year-OS in HR-positive tumors was 91.9% in pT1a (n=537), 90.6% in pT1b (n=1958), and 86.8% in pT1c (n=4513). In HR-negative tumors, rates were 91.7% (n=78), 86.8% (n=134), and 86.8% (n=427), respectively. In HER2-positive, it was 81.2% for pT1a (n=116), 88.1% for pT1b (n=171), and 86.7% for pT1c (n=427), in HER2-negative tumors it was 93.1% (n=431), 90.6% (n=1751), and 86.0% (n=3942), respectively. In the multivariate model, age, tumor size, and HR-status showed a significant impact on OS, while HER2-status was not an independent prognostic factor. (tumor size >1 cm vs. pTis: hazard ratio 1.94, p<0.0001 (95% CI; 1.47-2.56) (HRneg. vs. HRpos.: hazard ratio 1.42, p=0.011 (95% CI; 1.09-1.87) In this epidemiological registry, patients between 60 and 69 years - compared to patients aged 50 to 59 years - are at a 1.66 fold higher risk of dying (p=0.0003; 95% CI 1.26-2.18), risk for patients aged 70-79 years was 3.99 fold (p<0.0001; 95% CI 3.03-5.27) and for patients 80 years and older it was 15.38 fold higher (p= <0.0001; CI 11.45-20.66). However, hazard ratio for death at ages < 50 years was 0.88; this was not statistically significant in the model (p=0.457; 95% CI 0.62-1.24). Even young age less than 40 years by itself did not turn out to be a significant risk factor. CONCLUSION Prognosis of pN0 tumors <1 cm is excellent, especially if they are HR-positive, even in HER2-positive cases. Weighing potential benefits vs. side-effects, there seems to be no need for chemotherapy in tumors <0.5 cm. In pT1b tumors, chemotherapy may be considered, if tumors are triple negative or HER2-positive and HR-negative. In pT1c guideline-based adjuvant therapy using all therapeutic options seems to be warranted. Citation Format: Thomas Kolben, Nadia Harbeck, Rachel Wuerstlein, Gabriele Schubert-Fritschle, Ingo Bauerfeind, Simone Schrodi, Jutta Engel. Endocrine sensitivity is decisive for patient outcome in small node-negative breast cancers (BC) (pT1a,b) – Results from the Munich Cancer Registry [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-07-03.