Bioscore: A Staging System for Breast Cancer Patients that Reflects the Prognostic Significance of Underlying Tumor Biology
Biologic factors guide treatment decisions and have a significant impact on prognosis for breast cancer patients. This study was undertaken to develop a staging system incorporating biologic factors in addition to standard anatomic factors in the American Joint Committee on Cancer (AJCC) pathologic stage (PS) to assess disease-specific survival (DSS).
Overall, 3327 patients treated with surgery as an initial intervention at MD Anderson Cancer Center from 2007 to 2013 were identified. Multivariate analyses of factors, including PS, T stage (T), nodal stage (N), grade (G), estrogen receptor (ER) status (E) and human epidermal growth factor receptor (HER2) status (H) were performed to identify associations with DSS. A score of 0–4 was assigned for each factor by considering the hazard ratio magnitude. Multiple staging system models were then constructed: PS, PS + G, PS + G + E, PS + G + E + H, T + N, T + N + G, T + N + G + E, and T + N + G + E + H. Model performance was quantified using Harrell’s concordance index, and the Akaike Information Criterion (AIC) was used to compare model fits. Comparable cases from California (n = 67,944) were used for validation.
Median follow-up was 5.0 years (range 0.1–8.8) and 5-year DSS was 97.9% (95% confidence interval 97.3–98.4). Models incorporating grade, ER status, and HER2 status were most precise with identical C-index (0.81) and comparable AIC (994.9 for PS + G + E + H and 987.8 for T + N + G + E + H). Both models were externally validated.
These results confirm the importance of biologic factors in determining prognosis for breast cancer patients. We propose the Bioscore, which incorporates grade, ER and HER2 status with AJCC PS, to provide more refined stratification of breast cancer patients undergoing surgery as an initial intervention with respect to DSS.
The collection of cancer incidence data used in this study was supported by the California Department of Public Health as part of the statewide cancer reporting program mandated by California Health and Safety Code Section 103885; the National Cancer Institute’s Surveillance, Epidemiology and End Results Program under contract HHSN261201000140C awarded to the Cancer Prevention Institute of California, contract HHSN261201000035C awarded to the University of Southern California, and contract HHSN261201000034C awarded to the Public Health Institute; and the Centers for Disease Control and Prevention’s National Program of Cancer Registries, under agreement U58dP003862-01 awarded to the California Department of Public Health. The ideas and opinions expressed herein are those of the authors and endorsement by the State of California, Department of Public Health and National Cancer Institute, and the Centers for Disease Control and Prevention, or their contractors and subcontractors, is not intended nor should be inferred. This work was supported in part by a cancer center support grant from the National Cancer Institute to the University of Texas MDACC (CA016672). Analysis of cancer registry data was supported by the National Cancer Institute under contract HHSN261201000140C awarded to the Cancer Prevention Institute of California. Elizabeth A. Mittendorf is an R. Lee Clark Fellow of The University of Texas MD Anderson Cancer Center, supported by the Jeanne F. Shelby Scholarship Fund. Sharon H. Giordano is supported by grants from the Cancer Prevention Research Institute of Texas (CPRIT RP140020) and the Komen for the Cure Foundation (SA150061).
Elizabeth A. Mittendorf, Mariana Chavez-MacGregor, Jose Vila, Min Yi, Daphne Y. Lichtensztajn, Christina A. Clarke, Sharon H. Giordano, and Kelly K. Hunt have no relevant financial disclosures to declare.
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