Abstract P3-07-13: Outcomes of women with small, early-stage breast cancer in Manitoba from 1995-2011
Authors: Aly-Khan Lalani, Katherine Fradette, Rashid Ahmed, Debjani Grenier, Marshall Pitz
Journal: Cancer Research (2015)

Abstract OBJECTIVES: The objectives of this study were to describe the distribution, management, and outcomes of women with early-stage breast cancer in Manitoba during the period from 1995-2011. Specifically, we looked at tumours 1cm or smaller in size (T1mic/T1a/T1b) across the spectrum of molecular phenotypes: estrogen-receptor (ER) status, progesterone-receptor (PR) status, and human epidermal growth factor receptor 2 (HER2) status. This is the first study to evaluate these objectives in Manitoba, and will contribute significantly to the limited data of long-term outcomes for smaller-sized breast tumours. METHODS: Using the Manitoba Cancer Registry, we created a retrospective cohort of all patients with primary breast cancer of 1.0 cm or less, between 1995 and 2011. Women with previous or synchronous contralateral breast cancers were excluded. Data included patient demographics, diagnostic procedure, tumour size, nodal disease, treatment modalities (surgery, radiotherapy, hormone therapy, and chemotherapy), ER status, PR status, and HER2 status. Linkage to the Manitoba Health Drug Program Information Network (DPIN) database allowed capture of all hormonal therapies. Patient outcomes were evaluated, including risk of recurrence, overall survival and relative survival. Risk of recurrence was illustrated using cumulative incidence of recurrence, accounting for the competing risk of death. Kaplan-Meier curves were used to illustrate overall survival. The relative survival estimate was used to estimate the probability of surviving from breast cancer while controlling for differences in mortality due to other causes. RESULTS: Our study captured 2,341 women. Mean age at diagnosis was 62. ER+, PR+, and HER2+ status were 71% (11% unknown), 61.6% (11% unknown), and 8.6% (31% unknown), respectively. Clinically, 78% were Stage I disease, and by tumour size overall: T1mic 11.5%, T1a 18.9%, and T1b 69.7%. Ninety-eight percent had primary surgery, 58% had primary radiation, 48% received hormone therapy, and 16% received chemotherapy. At last follow-up, 21% of all patients were deceased. Relative survival estimates revealed that the survival of the overall cohort was not different than the general population, when comparing based on age groupings for Manitoban females. Recurrence occurred in 6.6% (156) of all cases. ER+, PR+, and HER2+ status were 63% (4% unknown), 58% (4% unknown), and 48% (5% unknown), respectively. By staging, 65% were Stage I disease and by tumour size 60% were T1b. Overall, 64% of recurrences were node-negative. For the HER2+, node-negative subpopulation at diagnosis: 21% of the T1mic group recurred, 41% of T1a recurred, and 19% of T1b recurred. In all recurrences, 39% of patients were deceased at last follow-up. CONCLUSIONS: Small, early-stage breast cancers are common and a significant proportion of patients recur. HER2-positivity appears to be an important risk factor for recurrence and may independently warrant treatment with trastuzumab, regardless of primary tumour size. Citation Format: Aly-Khan Lalani, Katherine Fradette, Rashid Ahmed, Debjani Grenier, Marshall Pitz. Outcomes of women with small, early-stage breast cancer in Manitoba from 1995-2011 [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 P3-07-13.