CHICAGO—Gene expression arrays have extended the identification of molecular subtypes of breast cancer beyond the presence or absence of the estrogen receptor (ER) and revealed the multiplicity of diseases within the breast cancer umbrella that have different prognoses. One of these subtypes is the so-called triple-negative form of breast cancer, or basal-like breast cancer, which occurs in 10% to 20% of tumors. Such cancers have low expression of HER2, ER, and progesterone(Drug information on progesterone)-receptor (PR), and are highly proliferative.
The other molecular subtypes are commonly described as luminal A (ER+, HER2–); luminal B (ER+, HER2+); HER2 (HER2+, ER–), and normal-like (negative for all markers) (see Table on page 29).
While endocrine and HER2-targeted therapies have been effective in the treatment of patients with luminal A, luminal B, and HER2 subtypes of breast cancer, only chemotherapy has been an option for patients with basal-like breast cancer.
The Good News
“The only treatment is chemotherapy. That’s the bad news. The good news is that it does work,” Lisa A. Carey, MD, associate professor of medicine, University of North Carolina School of Medicine, The Good News “The only treatment is chemotherapy. That’s the bad news. The good news is that it does work,” Lisa A. Carey, MD, associate professor of medicine, University of North Carolina School of Medicine, Chapel Hill, said at the 8th Annual Lynn Sage Breast Cancer Symposium.
Less than 10% of patients with luminal A/B or normal-like subtypes of breast cancer have a pathological complete response to paclitaxel followed by fluorouracil(Drug information on fluorouracil), doxorubicin(Drug information on doxorubicin), and cyclophosphamide(Drug information on cyclophosphamide) (T-FAC) or doxorubicin and cyclophosphamide followed by paclitaxel(Drug information on paclitaxel) or docetaxel(Drug information on docetaxel) (Taxotere) (AC-T), compared with 26% to 45% of patients with basal-like breast cancer.
In a study of 82 patients treated with T-FAC, a pathological complete response was detected in only 2 of 30 (7%) patients with luminal A/B breast cancer and 0 of 10 (0%) patients with normal-like disease. However, 10 of 22 patients (45%) with basal-like breast cancer had a documented complete response to the regimen, as did 9 of 20 (45%) HER2+ patients.
In a study of 107 breast cancer patients who were treated with AC-T, only 4 of 62 (7%) patients with luminal A/B breast cancer had a complete response, compared with 9 of 34 (26%) patients with basal-like breast cancer.