Predicting the clinical outcomes and benefit from letrozole after 5 years of treatment with aromatase inhibitors for early breast cancer: analysis from CCTG MA.17R

Purpose: Women with hormone receptor positive breast cancer may receive 5 years of treatment with aromatase inhibitors but the magnitude of benefit was relatively small. Our goal was to develop a tool for identification of women with limited treatment benefit.

Methods: Regression analyses were applied to women treated by placebo in CCTG MA.17R trial (NCT00754845) to identify important prognostic factors associated with distant recurrence and develop a nomogram for predicting 5-year likelihood of distant recurrence, which was internally validated using bootstrap resampling method. Differential treatment effects between risk categories derived from the nomogram were evaluated among all women enrolled through interaction test between treatment and risk category.

Results: A total of 1735 women were included and the final model from 866 women treated by placebo identified the following three factors associate with distant recurrence: tumor size, nodal status, and presence of cardiovascular disease. The nomogram derived from the final model exhibited good discrimination power with a bootstrap-corrected concordance index of 0.71 and, importantly, identified 64% of low risk patients in whom extended treatment has limited benefit. Interaction between treatment and risk category derived from the nomogram was significant (p = 0.04).

Conclusion: A nomogram with good performance may be used to accurately predict distant recurrence risk and also benefits with extended treatment after 5 years of aromatase inhibitors. Future independent validation of the proposed nomogram is warranted.

Trial registration number: NCT00754845.