TUESDAY, July 1 (HealthDay News) -- Compared to non-pregnancy-associated breast cancers, pregnancy-associated breast cancers present as larger tumors, at a more advanced stage, and are less likely to be hormone receptor-positive, according to an article published in the July issue of Obstetrics & Gynecology.
Anne O. Rodriguez, M.D., from the University of California Davis Medical Center in Sacramento, Calif., and colleagues used the California Cancer Registry and the California Patient Discharge Data Set to identify women with breast cancer occurring prenatally to one year after delivery. The case-control study used age-matched, non-pregnancy-associated breast cancer controls to identify predictive factors for death using proportional hazards modeling.
The investigators compared 797 pregnancy-associated breast cancer cases with 4,177 non-pregnancy-associated breast cancer controls. Pregnancy-associated breast cancers were associated with advanced stage (stage III presentation in non-pregnant controls was 8.6 percent versus 16.3 percent in pregnant subjects), larger tumor size (larger than 5 cm; 8.5 percent in non-pregnant controls versus 15.9 percent in pregnant subjects), and hormone receptor negativity (28 percent in non-pregnant controls versus 39.3 percent in pregnant subjects). Pregnancy-associated breast cancer also had a higher death rate than non-pregnancy-associated cancer (39.2 percent versus 33.4 percent, respectively).
"Although overall rates of treatment modalities such as radiation and chemotherapy are similar, it is not clear why there would be a difference in survival for pregnancy-associated cases," the authors write. They suggest one hypothesis is that "the elevated hormone levels of the pregnant state could accelerate tumor growth or metastasis through either an intrinsic effect on the tumor cell biology or by increasing vascularity and subsequently metastasis out of the breast."
Abstract
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