Background: Current guidelines recommend counseling on risk-reduction strategies, including lifestyle modification, endocrine therapy, and bilateral mastectomy, for patients with classic-type lobular carcinoma in situ (LCIS) detected on core biopsy or surgical excision. Importantly, current diagnosis and treatment guidelines for classic-type LCIS do not include unilateral mastectomy for primary treatment or risk reduction. Prior studies reporting national practice patterns suggest increasing use of mastectomy for management of LCIS, with considerable variation by geographic region. However, these studies did not distinguish between uni- and bilateral mastectomies. This study aimed to investigate national practice patterns and factors associated with unilateral mastectomy. Methods: The study used the National Cancer Database to identify women with a diagnosis of LCIS from 2004 to 2013. Descriptive statistics were used to describe surgical treatment, and multinomial logistic regression was used to identify temporal, patient, and facility-level factors associated with receipt of uni- and bilateral mastectomy. Results: The study identified 30,105 women with LCIS. Of these woman, 5.4% received no surgery, 84.8% had surgical excision, 4% underwent unilateral mastectomy, and 5.1% underwent bilateral mastectomy. Adjusted analysis showed that young age, white race, insurance coverage, greater comorbidity, and geographic region (p < 0.001) were associated with receipt of both uni- and bilateral mastectomy. Additionally, more recent year of diagnosis was associated with receipt of bilateral mastectomy. Unilateral mastectomy rates within geographic regions ranged from 2.7% in New England to 8% in the South. Conclusions: Nearly as many patients underwent unilateral (4%) as bilateral mastectomy (5.1%), representing inappropriate care. These findings highlight an opportunity to reduce unnecessary care through improved provider and patient education regarding optimal management of LCIS.
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