E. L. Liederbach1, R. Piro1, R. Watkin1, K. Hughes1, C. Wang2, C. Pesce1, D. J. Winchester1, K. Yao1 1Northshore University Health System,Surgery,Evanston, IL, USA 2Northshore University Health System,Center For Biomedical Research Informatics,Evanston, IL, USA
Introduction: Multiple studies have shown that contralateral prophylactic mastectomy improves survival, but follow-up for most of these studies are five years or less and provide little data on tumor characteristics of the contralateral breast cancer (CBC). We hypothesized that most CBCs develop after five years and that these CBCs have favorable tumor characteristics.
Methods: This is a single institution retrospective review of 323 patients who were diagnosed with CBCs from 1990 to 2014. CBCs were diagnosed at least one year after the primary cancer diagnosis. BRCA mutation carriers were not excluded. Utilizing chi-square tests and one-way ANOVA tests, we examined the time interval and pathological features between the primary and contralateral cancer.
Results: The average time interval between the primary and CBC was 7.15 years (median: 6.2, range: 1.01-23.0), with 60.4% of patients having a time interval of >5 years. Older patients ≥70 yo developed a CBC sooner than patients <70 yo (5.0 and 7.6 years respectively, p<.001). A majority of stage III patients (69.2%) developed a CBC within 5 years compared to 51.9% of stage 0, 39.3% of stage I, and 36.6% of stage II patients (p=.039). On average, patients with ILC developed their CBC in 9.2 years compared to 7.1 years for IDC patients, 6.6 years for mixed histology patients, and 5.9 years for DCIS patients (p=.016). Factors that had no influence on the time interval between CBCs were race, body mass index, menopausal status, use of hormone replacement therapy, family history of breast/ovarian cancer, estrogen receptor (ER) status, BRCA status, tumor grade, and presence of lymphatic vascular invasion. In comparison to the first primary breast cancer, a higher proportion of CBCs were stage I (51.0% vs. 36.2%), T1 tumors (72.1% vs. 59.1%), node negative (67.5% vs. 62.2%), and ER(+) tumors (68.7% vs. 51.7%). Of the 252 patients with available tumor size information for both breast cancers, 54 (21.4%) patients developed a CBC that was >1cm larger than their original primary, and only 25 (9.9%) patients developed a CBC that was >2cm larger than their original primary. There were 201 (62.2%) patients with node negative disease for their first breast cancer, and only 28 (13.9%) of these patients developed a node positive CBC. Of the 300 patients with stage information, 85 (28.3%) patients had a higher stage CBC compared to their first primary. Of the 67 patients with an ER(-) primary, 44 (62.7%) developed an ER(+) CBC.
Conclusion: A majority of CBCs develop >5 years after the diagnosis of the first primary breast cancer. CBCs have more favorable tumor characteristics than the primary tumor because they tend to be smaller, less aggressive, and lower in stage compared to the primary breast cancer. Patient age, stage, and tumor histology significantly influence the time interval from primary to CBCs. It is unlikely that CBC would affect survival at five years of follow-up given this data.