Researchers from the M. D. Anderson Cancer Center have reported that the addition of Iressa® (gefitinib) to Arimidex® (anastrozole) improves progression-free survival (PFS) in postmenopausal women with hormone receptor-positive metastatic breast cancer. The details of this study were published in the March 15, 2010 issue of Clinical Cancer Research.[1]

Arimidex is a hormone therapy that prevents the formation of estrogen in the body. It is commonly used among postmenopausal women with hormone-positive breast cancer. Unfortunately, some women can become resistant to Arimidex, and others may never respond to Arimidex. Reasons for this lack of response are not clear. Researchers continue to evaluate ways to work around this resistance, such as targeting other biologic pathways associated with cancer.

Previous studies have suggested that Nexavar® (sorafenib) helps restore sensitivity to Arimidex among women with breast cancer. Researchers have also shown that the addition of Herceptin® (trastuzumab) to Arimidex improves PFS. Iressa has also been shown to produce responses in tamoxifen (Nolvadex®)-resistant hormone-positive breast cancer.

The current study involved 93 postmenopausal women with hormone-positive metastatic breast cancer who had not been treated with hormonal therapy. Some women, however, had failed adjuvant tamoxifen therapy. Patients were randomly allocated to receive Arimidex and Iressa or Arimidex and placebo.

• PFS was 14.7 months for Iressa patients versus 8.4 months for the placebo group.
• Clinical benefit rate was 49% for patients receiving Arimidex and Iressa versus 34% for patients receiving Arimidex and placebo.

Comments: These authors suggest that further studies should be performed evaluating epidermal growth factor inhibition in combination with endocrine  therapy.

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