(ChemotherapyAdvisor) – Women ≤35 years of age are more likely to achieve a pathological complete response (pCR) after neoadjuvant chemotherapy for breast cancer, an effect driven primarily by the more common triple negative nature of their tumors, a study reported during the 2012 CTRC-AACR San Antonio Breast Cancer Symposium.

“Young women with breast cancer are rare, and some data indicate that their prognosis is worse than it is for older women,” said Sibylle Loibl, MD, PhD, of the German Breast Group, Neu-Isenburg, Germany, and an associate professor at the University of Frankfurt, Germany. “This is not only because their tumors tend to be more aggressive, but because breast tumors that arise in women who are young seem to be a special biological entity.”

Dr. Loibl analyzed a subgroup of 704 patients ≤35 years of age from a total of 8,949 women enrolled in eight German studies of neoadjuvant treatment for operable or locally advanced, nonmetastatic breast cancer. Rate of pCR and disease-free survival (DFS) in the younger patients was compared with older patients and in different histopathological subgroups.

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Among the younger women, 21% had luminal-A type disease vs 27% among the older women; they also had more triple-negative breast cancer (TNBC), 26% vs 19%.

The pCR rate was significantly higher in very young women, 23.6%, vs 15.7% among older women (P<0.0001), they found. However, this difference was confined to the TNBC subgroup, 45% vs 31% (OR 1.85; 95% CI 1.33–2.56; P<0.001).

Only in the TNBC cohort was age an independent predictive factor for achieving pCR. Compared with the older cohort, hormone receptor status and grade were independent predictive factors of pCR, but T-stage and nodal-stage were not. When patients had a pCR, DFS did not differ by age; however, those ≤35 years who did not attain pCR had a significantly worse DFS (HR 1.35; P=0.001) after adjusting for T-stage, nodal-stage, age, and pCR.

Within the TNBC cohort, pCR but not age was an independent prognostic variable for DFS and, within the luminal A-type group, age but not pCR was an independent prognostic variable for DFS. In the luminal A-type group, the worst DFS was observed in the group ≤35 years without a pCR, whereas the best DFS was observed in those ≤35 years with a pCR (log rank P=0.27; HR 0.05 wide CI due to small sample size; p=0.5).

“The most surprising finding was that young women with a luminal-type tumor—hormone receptor-positive and HER2-negative—who achieved a pathological complete response had a better survival rate than the patients with nonpathological complete response,” Dr. Loibl said. “This is not true for other age groups, which indicates that breast cancer in the young—even when a luminal-type breast cancer—is chemosensitive.”

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