Population Trends in Lobular Carcinoma of the Breast: The Ontario Experience.

BACKGROUND: Invasive lobular carcinoma (ILC) is less common that invasive ductal carcinoma (IDC), and more challenging to diagnose by examination and screening mammography. This study evaluated current trends in ILC incidence, and described the 5-, 10-, and 15-year survival probabilities for women diagnosed with ILC in Ontario, Canada. METHODS: This retrospective cohort analysis included all women aged 18 years and older diagnosed with breast cancer between 1991 and 2015. Health administrative data from the Institute of Clinical Evaluative Sciences and the Ontario Cancer Registry were used to identify breast cancer cases. Age-adjusted incidence was plotted by year. Crude proportions were plotted by year of diagnosis for stage and hormone receptor status. Kaplan-Meier curves were generated to determine the 5-, 10-, and 15-year survival probabilities for ILC and IDC. RESULTS: From 1991 to 2015, there were 194,065 cases of breast cancer in Ontario, 14.7% of which were ILC. The age-adjusted incidence of breast cancer increased 1.04-fold, while ILC rates increased 1.53-fold. All bilateral breast cancers were of lobular origin. The proportion of stage 1 ILC decreased, while the proportion of stage 2-4 ILC increased. The 5-, 10-, and 15-year overall survival probabilities for women diagnosed with ILC were 82.7%, 65.3%, and 50.2%, respectively. CONCLUSIONS: This study contains the largest population dataset of ILC evaluated to date. While total breast cancer incidence rates in Ontario are largely unchanged, ILC incidence rates are steadily increasing and there is a trend towards diagnosis of ILC at a later stage. These trends highlight the ongoing diagnostic and treatment challenge ILC presents for patients and clinicians.

Predictors of Residual Disease After Breast Conservation Surgery.

INTRODUCTION: Breast-conserving therapy is the standard of care for early-stage breast cancer. In the era of multimodality therapy, the debate on the value of revision surgery for compromised margins continues, and high re-excision rates persist despite updated guidelines. Our study sought to identify the local re-excision rate for compromised margins after lumpectomy, and identify predictors of residual disease at re-excision. METHODS: This population-based retrospective cohort study included women with breast cancer who underwent a lumpectomy between 2009 and 2012 in Manitoba, with close (≤ 2 mm) or positive margins that led to re-excision. Patient demographics and tumor characteristics were identified through provincial cancer registries and chart reviews. For patients with invasive cancer, the six anatomical margins were reported for margin status, width, and pathology type at the margin. RESULTS: Of the 2494 patients identified, 556 women underwent re-excision, yielding a re-excision rate of 22.29%. Of our 311 patients with invasive cancer who underwent re-excision, 62.7% had residual disease identified on revision. On univariable analysis, the size and grade of the invasive component, nodal stage, and the number of positive margins were associated with residual disease on re-excision (p < 0.05). With the exception of nodal stage, the same variables remained statistically significant on multivariable analysis. CONCLUSIONS: Our results suggest that even in the absence of 'no ink on tumor', the cancer size and grade in lumpectomy specimens are high-risk factors for residual disease, and this subgroup of patients may benefit from re-excision. Long-term follow-up of this cohort is required to determine their risk of recurrence after adjuvant treatment.