Androgen receptor expression linked to response to treatment

IMPAKT Breast Cancer Conference

Androgen receptor-negative tumors demonstrated an elevated pathological complete response rate to the combined treatment of docetaxel, doxorubicin and cyclophosphamide compared with androgen receptor-positive tumors, according to findings from a recent trial.

Researchers analyzed the relationship between androgen receptor and clinic-pathological parameters and pathological complete response in 682 patients with primary breast cancer. The patients were part of a larger cohort in the GeparTrio trial (n=1,711) in which all patients underwent treatment with docetaxel, doxorubicin and cyclophosphamide. Almost half of the 682 patients (47.8%) expressed androgen receptor, according to a press release.

“This group [of researchers] has looked for the expression of androgen receptor in breast cancer and found a subgroup of the population that does express it. [The researchers] have shown that these patients respond worse to chemotherapy than those whose tumors do not express androgen receptor,” José Baselga, MD, co-chair of the IMPAKT Breast Cancer Conference and director of the Division of Medical Oncology, Hematology and Radiation Oncology at the Vall d'Hebron University Hospital in Barcelona, Spain, said in a press release.

There was a significant correlation between androgen receptor and tumor grading (P<.001), age (P=.006), expression of estrogen/progesterone status (P<.001) and pathological complete response (P<.001).

A pathological complete response occurred in 14.2% of androgen receptor-positive patients vs. 31.9% of androgen receptor-negative patients (P<.001). The total pathological complete response was 21.4%, according to the researchers.

Among 86 triple-negative tumors available for analysis, 40.7% had a pathological complete response; 27.9% expressed androgen receptor. There were significant associations for tumor grading (P=.007) and age (P=.020). For triple-negative androgen receptor-negative tumors, the pathological complete response rate was 43.5% vs. 33.3% for the triple-negative androgen receptor-positive tumors (P=.387).

“We should undertake a study to investigate if an anti-androgen, bicalutamide or another can improve survival in the triple-negative androgen receptor-positive breast cancer,” Sibylle Loibl, MD, PhD, assistant professor at University Frankfurt in Germany and a co-author of the study, told HemOnc Today.

“We are seeing the birth of a new concept in breast cancer — the androgen receptor-positive breast cancer,” Baselga said. “This is an important development in finding new targets that we can attack with new drugs in the future.” – by Christen Haigh

For more information:

Loibl S. #1270. Presented at: IMPAKT Breast Cancer Conference; May 7-9, 2009; Brussels, Belgium.