Tailoring treatment for ductal intraepithelial neoplasia of the breast according to Ki-67 and molecular phenotype

BACKGROUND: The post-surgical management of ductal intraepithelial neoplasia (DIN) of the breast is still a dilemma. Ki-67 labelling index (LI) has been proposed as an independent predictive and prognostic factor in early breast cancer. METHODS: The prognostic and predictive roles of Ki-67 LI were evaluated with a multivariable Cox regression model in a cohort of 1171 consecutive patients operated for DIN in a single institution from 1997 to 2007. RESULTS: Radiotherapy (RT) was protective in subjects with DIN with Ki-67 LI ≥14%, whereas no evidence of benefit was seen for Ki-67 LI <14%, irrespective of nuclear grade and presence of necrosis. Notably, the higher the Ki-67 LI, the stronger the effect of RT (P-interaction <0.01). Hormonal therapy (HT) was effective in both Luminal A (adjusted hazard ratio (HR)=0.56 (95% CI, 0.33–0.97)) and Luminal B/Her2neg DIN (HR 0.51 (95% CI, 0.27–0.95)). CONCLUSION: Our data suggest that Ki-67 LI may be a useful prognostic and predictive adjunct in DIN patients. The Ki-67 LI of 14% could be a potential cutoff for better categorising this population of women at increased risk for breast cancer and in which adjuvant treatment (RT, HT) should be differently addressed, independent of histological grade and presence of necrosis.