Background: Obesity or increased body mass index (BMI) has been shown to have two important adverse effects related to breast cancer. First, several studies have identified an association between increased BMI and advanced stage breast cancer. Second, increased BMI has been shown to be associated with poorer prognosis. In a previous report, we had identified low BMI as a risk factor for local reccurence at five years. The objectives of this study were to evaluate the relationship between BMI and local control and to confirm this prognostic factor in a larger population with an important follow-up.

Materials and methods: Between 1976 and 1988, 605 women with invasive breast carcinoma less than 4 cm in diameter underwent conservative surgery with axillary dissection and radiation therapy. The median follow-up time was 82 months. The risk of local recurrence and distant metastasis was evaluated by univariate retrospective analysis using Kaplan-Meier method for the main clinical and histologic factors. Those found to be significant were entered in a Cox model for multivariate analysis.

Results: Since the beginning of the study, 80 patients had developed local recurrence. The 5 years and 10 years local control rates were 91% and 83%, respectively. Four parameters were independent predictive factors of local recurrence: Age lower than 40 years (HR = 2.42 95% CI = [1.35-4.34]), BMI: elevation of one unit reducing the local recurrence of 0.92 95%CI = [0.85-0.99], multifocality of the tumor on pathological examination (HR = 2.12 95% CI = [1.16-3.88]) and positive axillary nodes HR = 0.54 95% CI = [0.31-0.95]. Size of the breast was not a predictive factor for local cancer recurrence. Low BMI did not increase risk of distant.

Conclusion: Our study offers new data concerning the possibility that thinness may be related to local recurrence of breast cancer.