Study findings should help tailor chemotherapy for breast cancer patients

TORONTO (CP) - Findings of a new Canadian study of younger women with breast cancer suggest better tailoring of chemotherapy regimens should be on the horizon, allowing some women to avoid a more difficult-to-endure and side-effect-ridden type of therapy.

"I think the broad message is that increasingly, by careful pathology, we're able to tailor the treatment more for individual patients," lead author Dr. Kathleen Pritchard of Toronto's Sunnybrook Health Sciences Centre said Wednesday in an interview.

"And that we're able to pick out patients who are likely to do well with more chemotherapy, more hormone therapy, something in-between or different types of chemotherapy."

The study, published Thursday in the New England Journal of Medicine, found that premenopausal women whose cancers overproduced a protein called HER2 (sometimes called HER2/neu) responded better to an aggressive type of chemotherapy containing agents from the anthracycline class of drugs.

But in women whose cancers were HER2-negative, this more toxic and more expensive form of chemotherapy did not produce better results than alternative regimens, Pritchard and her co-authors from the National Cancer Institute of Canada clinical trials group reported.

Increasingly, oncologists are testing women with breast cancer to check their HER2 status, largely because it helps doctors determine whether a patient ought to be put on a regimen of the drug Herceptin, which reduces the risk of breast cancer recurrence after they have completed their cancer treatment.

"These are really important findings. We're moving away from the era when it was one treatment that was given to all women with breast cancer and we're really trying to tailor treatment," said Dr. Pamela Goodwin, a researcher and head of the breast cancer treatment program at Toronto's Mount Sinai Hospital.

"And this helps us use HER2 status not only as an indicator that Herceptin needs to be given, but also when HER2 is not positive as an indicator that perhaps we don't have to use an anthracycline-based chemotherapy."

Goodwin was not involved in this research, which tested slivers of cancers for HER2 and compared those findings with the treatment-response profile of the women studied.

A series of earlier studies had failed to prove that HER2 status could predict response to different chemotherapy regimens. But Pritchard and her co-authors drew the link.

Being able to confidently steer HER2-negative women away from anthracycline-based chemotherapy would be beneficial because the drugs are associated with a small but real increased risk of congestive heart failure and leukemia, as well as worse short-term side-effects such as hair loss, nausea, vomiting and neutropenia, a decrease in white blood cells.

"We want to give regimens that are as effective as possible for a given patient, with as few side-effects (as possible)," Pritchard said.

"Chemotherapy's a bit of a blunt instrument, although it works amazingly well sometimes. But it may be that we're picking the types of chemotherapy to say that they may be better for one tumour than another - which is actually pretty neat."

An editorial in the journal suggested, however, that clinicians may think it is too soon to feel confident that HER2-negative women can forego anthracycline-based chemotherapy.

Dr. Martine Piccart-Gebhart of the Jules Bordet Institute at Brussels Free University in Belgium said additional research is showing that HER2-negative patients aren't one homogeneous group, but at least three subsets of patients whose tumours might respond in different ways to different drug regimens.

Goodwin agreed.

"I think practising oncologists are going to say until we actually figure out how to break down the HER2-negative patients to figure out exactly which ones of them don't benefit, we'll probably continue to use a lot of anthracycline-based chemotherapy," Goodwin said.

© The Canadian Press, 2006