By Cameron Johnston

SAN ANTONIO, TEX. | A small Australia-New Zealand study looking at the use of gefitinib(Iressa)in the treatment of hormone-resistant breast cancers has been halted early because patients were not responding to the treatment.

In in a poster session here at the San Antonio Breast Cancer Symposium, study co-author Dr. Prue Francis, a medical oncologist with the Peter McCallum Cancer Centre in Melbourne, Australia, said there appears to be an inverse relationship between epidermal growth factor receptor(EGFR)expression and estrogen receptor status. Cancer cells that were estrogen receptor-negative were more likely to express higher levels of EGFR and could potentially respond to anti-EGFR therapy. Cancer cells that were hormone receptor-positive generally had lower levels of EGFR, except in cases where they developed resistance to hormonal therapy. Then they, too, had an increased expression of EGFR.

This suggests that some, but not all, breast cancers could potentially be treated with gefitinib. Dr Francis's study compared 39 patients who had been treated with hormonal therapy but whose cancer progressed—i.e., they developed a resistance to the therapy—with 27 patient who did not over-express either the estrogen or progesterone receptors.

All had advanced disease and were treated with gefitinib 500 mg/day, which is approximately twice the dose normally used to treat patients with non-small cell lung cancer. There were no complete or partial responses and the mean time to progression in both groups was eight weeks. Two patients in the hormone receptor negative group showed signs of stable disease(7.7%)but both discontinued the therapy.

Enrolment in the trial was stopped.