By Marilynn Larkin
NEW YORK (Reuters Health) – A newly introduced breast cancer prognostic stage from the American Joint Committee on Cancer (AJCC) is more accurate than the anatomic stage and should be implemented in clinical practice, researchers say.
"We were able to show that the AJCC 8th edition prognostic stage - which incorporates the biologic factors of grade, estrogen receptor/progesterone receptor (ER/PR) and HER2 status - stratifies patients with respect to survival outcomes better than the anatomic stage, which is based solely on the size of the tumor (T category) and extent of nodal disease (N category)," Dr. Elizabeth Mittendorf of the University of Texas MD Anderson Cancer Center, Houston, told Reuters Health.
To validate the new prognostic stage, Dr. Mittendorf and colleagues identified breast cancer patients treated with surgery as an initial intervention from two large databases: 3,327 women from the University of Texas MD Anderson Cancer Center treated from 2007 to 2013 (median follow-up, five years) and 54,727 from the California Cancer Registry treated from 2005 to 2009 (median follow-up, seven years.
Compared with the AJCC anatomic stage, the prognostic stage upstaged 29.5% of patients and downstaged 28.1% in the MD Anderson cohort; and upstaged 31.0% of patients and downstaged 20.6% in the California registry cohort, according to the December 7 online report in JAMA Oncology.
The accuracy of the prognostic stage was better than that of the anatomic stage, as reflected by comparisons in the Harrell concordance index (0.8426 vs. 0.8097) and the Akaike information criterion.
"In completing this validation, we found that in 13.6% of patients in the MD Anderson cohort and 6.8% of patients in the California Cancer Registry cohort, a prognostic stage could not be assigned due to uncategorized combinations of T category, N category, grade, ER, PR and HER2 status," Dr. Mittendorf said by email.
"Based on these data, the AJCC expert panel revised the prognostic stage, which is now available online (http://bit.ly/2CxHxDx), " she added.
"This work, as well as the effort of the AJCC to revise the staging system to incorporate biologic factors into breast cancer staging, was a critically important step, in that we know that the biology of the disease dictates outcome," Dr. Mittendorf observed. "Incorporating biology into the staging system was therefore necessary for the system to maintain clinical relevance."
Dr. Francisco Esteva, director of breast medical oncology at Perlmutter Cancer Center, NYU Langone Health in New York City, told Reuters Health, "I agree the new staging improves prognosis assessment."
"A brief learning curve should be expected for oncologists to integrate anatomical features and molecular markers into the new staging system," he said by email. "It will be important for AJCC to integrate novel multi-gene prognostic assays as clinical data become available, to be consistent with national treatment guidelines."
JAMA Oncol 2017.
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