The combination treatment of Herceptin and Tykerb for breast cancer is costly. (CBC)

Women with early-stage breast cancer were more likely to see their tumours shrink before surgery if they took two particular drugs in combination rather than one of them alone, doctors reported Friday.

The two drugs, Tykerb and Herceptin, are designed to block receptors linked to the growth and proliferation of tumours.

The study focused on women with HER2-positive tumours, found in about 20 per cent of breast cancers. It is thought that excessive amounts of the protein HER2, which stands for human epidermal growth factor receptor 2, increase the growth of breast cancer.

Herceptin blocks the protein on the cell's surface, while Tykerb blocks protein inside the cell.

In the international study, 455 patients with HER2-positive breast cancer taking the chemotherapy drug paclitaxel. Participants were randomly assigned to either a drug alone or in combination about four months before surgery to remove tumours and for nine months afterward.

The goal of the research was to shrink tumours before surgery.

Early data suggests half the women who received the combination of drugs had no signs of invasive cancer after surgery compared with 20 per cent for either drug alone, according to findings presented Friday at the San Antonio Breast Cancer Symposium in Texas.

"While further research is ongoing, our results indicate that we are on the right track to improve the therapy of HER2-positive disease," lead researcher Dr. Jose Baselga, chief of the division of hematology and oncology and associate director of the Massachusetts General Hospital Cancer Center, said in a release.

There were more side-effects with Tykerb, such as diarrhea.

The full study has not yet been peer reviewed to detect any flaws.

Treatment questions

British-based GlaxoSmithKline PLC makes Tykerb; its generic name is lapatinib. California-based Genentech, now part of the Swiss company Roche, makes Herceptin; its generic name is trastuzumab.

The research on the pre-surgery treatment, or neoadjuvants, may not predict how the drugs work after surgery, noted Dr. Karen Gelmon, a medical oncologist at the B.C. Cancer Agency and a professor of medicine at the University of British Columbia, who is attending the conference.

Tykerb is approved for use in Canada for advanced or recurrent disease, Gelmon said. Herceptin is approved for advanced or recurrent disease worldwide.

Only Nova Scotia and Saskatchewan cover the $5,000 to $6,000 US cost per month of Tykerb.

"These neoadjuvant studies provide very important information on biologic effects and will help us choose regimens to study in large-scale trials that have the potential to change practice," said Dr. Pamela Goodwin, a clinician-scientist at Toronto's Mount Sinai Hospital, who is also attending the conference.

A larger trial, called ALLTO, of 8,000 patients treated after surgery is underway to show whether the combination can be tied to improved relapse and survival rates. Doctors need those results to judge whether the research will change how they practise, Goodwin said.

"It would be good for it to be available for women who have had recurrences, especially once trastuzumab stops working," Goodwin said in an email from the conference.

Herceptin works for only a limited amount of time before cancer becomes resistant, said Jackie Manthorne, chief executive officer for the Ottawa-based Canadian Breast Cancer Network, a non-profit advocacy group.

"Many of the new drugs that are coming out, and not just for breast cancer but for any number of cancers, are fairly expensive," Manthorne said from San Antonio. "But they are necessary to keep people alive."

The group is working on changing what it calls the lengthy, complex and inequitable process of drug coverage in Canada.

With files from The Associated Press