[Lobular invasive breast cancer prognostic factors: About 940 patients]

To assess the prognostic factors of T1 and T2 infiltrating lobular breast cancers, and to investigate predictive factors of axillary lymph node involvement.

This is a retrospective multicentric study, conducted from 1999 to 2008, among 13 french centers. All data concerning patients with breast cancer who underwent a primary surgical treatment including a sentinel lymph node procedure have been collected (tumors was stage T1 or T2). Patients underwent partial or radical mastectomy. Axillary lymph node dissection was done systematically (at the time of sentinel procedure evaluation), or in case of sentinel lymph node involvement. Among all the 8100 patients, 940 cases of lobular infiltrating tumors were extracted. Univariate analysis was done to identify significant prognosis factors, and then a Cox regression was applied. Analysis interested factors that improved disease free survival, overall survival and factors that influenced the chemotherapy indication. Different factors that may be related with lymph node involvement have been tested with univariate than multivariate analysis, to highlight predictive factors of axillary involvement.

Median age was 60 years (27-89). Most of patients had tumours with a size superior to 10mm (n=676, 72%), with a minority of high SBR grade (n=38, 4%), and a majority of positive hormonal status (n = 880, 93, 6%). The median duration of follow-up was 59 months (1-131). Factors significantly associated with decreased disease free survival was histological grade 3 (hazard ratio [HR]: 3,85, IC 1,21-12,21), tumour size superior to 2cm (HR: 2,85, IC: 1,43-5,68) and macrometastatic lymph node status (HR: 3,11, IC: 1,47-6,58). Concerning overall survival, multivariate analysis demonstrated a significant impact of age less than 50 years (HR: 5,2, IC: 1,39-19,49), histological grade 3 (HR: 5,03, IC: 1,19-21,25), tumour size superior to 2cm (HR: 2,53, IC: 1,13-5,69). Analysis concerning macrometastatic lymph node status nearly reached significance (HR: 2,43, IC: 0,99-5,93). There was no detectable effect of chemotherapy regarding disease free survival (odds ratio [OR] 0,8, IC: 0,35-1,80) and overall survival (OR: 0,72, IC: 0,28-1,82). Disease free survival was similar between no axillary invasion (pN0) and isolated tumor cells (pNi+), or micrometastatic lymph nodes (pNmic). There were no difference neither between one or more than one macromatastatic lymph node. But disease free survival was statistically worse for pN1 compared to other lymph node status (pN0, pNi+ or pNmic). Factors associated with lymph node involvement after logistic regression was: age from 51 to 65 years (OR: 2,1, IC 1,45-3,04), age inferior to 50 years (OR 3,2, IC: 2,05-5,03), Tumour size superior to 2cm (OR 4,4, IC: 3,2-6,14), SBR grading 2 (OR 1,9, IC: 1,30-2,90) and SBR grade 3 (OR 3,5, IC: 1,61-7,75).

The analysis of this series of 940 T1 and T2 lobular invasive breast carcinomas offers several information: factors associated with axillary lymph node involvement are age under 65 years, tumor size greater than 20mm, and a SBR grade 2 or 3. The same factors were significantly associated with the OS and DFS. The macrometastatic lymph node involvement has a significant impact on DFS and OS, which is not true for isolated cells and micrometastases, which seem to have the same prognosis as pN0.