Introduction: We hypothesized that most contralateral breast cancers (CBCs) develop ≥5 years after the primary breast cancer (PBC) and that CBCs have more favorable tumor characteristics.
Methods: This is a single-institution retrospective review of 323 patients who were diagnosed with CBC from 1990 to 2014. CBCs were diagnosed at least 1 year after the diagnosis of PBC. Χ(2) tests and one-way analysis of variance were used to examine the time interval and pathologic features between the PBC and CBC.
Results: The median time interval between the PBC and CBC was 6.2 years (average: 7.1, range: 1.01-23.0), and 189 (58.5%) patients had a time interval ≥5 years. Patients ≥70 years old developed a CBC sooner than patients <50 years (median: 4.3 vs 6.6 years, P < .001). Patients with infiltrating lobular carcinoma developed their CBC in 9.0 years versus 6.2 years for infiltrating ductal carcinoma histology (P = .028). In comparison with the PBC, a greater proportion of CBCs were stage I (50.8%), T1 (72.1%), node negative (67.5%), and estrogen receptor positive (68.7%). Of the 252 patients with available tumor size information for both cancers, only 54 (21.4%) patients developed a CBC that was >1 cm larger than their PBC, and only 25 (9.9%) patients developed a CBC that was >2 cm larger than their PBC. Only 28 of 201 (13.9%) node-negative PBCs developed a node-positive CBC.
Conclusion: A majority of CBCs develop ≥5 years after the diagnosis of the PBC. CBCs have more favorable tumor characteristics than the PBC and tend to be smaller and node negative.
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