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Most women with the most common form of early-stage breast cancer can safely skip chemotherapy without hurting their chances of beating the disease, doctors are reporting from a landmark study that used genetic testing to gauge each patient’s risk.

The study is the largest ever done of breast cancer treatment, and the results are expected to spare up to 70,000 patients a year in the United States, and many more elsewhere, the ordeal and expense of these drugs.

“The impact is tremendous,” said the study leader, Dr. Joseph Sparano of Montefiore Medical Center in New York. Most women in this situation don’t need treatment beyond surgery and hormone therapy, he said.

The study was funded by the National Cancer Institute, some foundations, and proceeds from the U.S. breast cancer postage stamp.

Who can avoid chemo?

Cancer care has been evolving away from chemotherapy — older drugs with harsh side effects — in favor of gene-targeting therapies, hormone blockers and immune system treatments. When chemo is used now, it’s sometimes for shorter periods or at lower doses than it once was.

The breast cancer study focused on cases where chemo’s value increasingly is in doubt: women with early-stage disease that has not spread to lymph nodes, is hormone-positive (meaning its growth is fueled by estrogen or progesterone), and is not the type that the drug Herceptin targets.

The usual treatment is surgery followed by years of a hormone-blocking drug. But many women also are urged to have chemo to help kill any stray cancer cells. Doctors know that most don’t need it, but evidence is thin on who can forgo it.

The study gave 10,273 patients a test called Oncotype DX, which uses a biopsy sample to estimate the risk that a cancer will recur. It measures the activity of genes involved in cell growth and response to hormone therapy.

About 17 percent of women had high-risk scores and were advised to have chemo. The 16 percent with low-risk scores now know they can skip chemo, based on earlier results from this study.

The new results are on the 67 percent of women at intermediate risk. All had surgery and hormone therapy, and half also got chemo.

After nine years, 94 percent of both groups were still alive, and about 84 percent were alive without signs of cancer, so adding chemo made no difference.

Certain women 50 or younger did benefit from chemo. Slightly fewer cases of cancer spreading far beyond the breast occurred among some of them given chemo, depending on their risk scores on the gene test.

Who needs less Herceptin?

A different study suggests that many women with a common and aggressive form of breast cancer that is treated with Herceptin (a drug designed to block the growth and spread of cancer cells) can get by with six months of that drug instead of the usual 12, greatly reducing the risk of heart damage Herceptin sometimes can cause.

It’s good news, but it comes nearly two decades after the drug first went on the market, and many patients have suffered that side effect.

The study was done in the United Kingdom and funded by UK government grants. Results were released by the American Society of Clinical Oncology.

Herceptin transformed care of the dreaded disease when it was approved in 1998 for women with advanced breast cancers whose growth is aided by a faulty HER2 gene, as 15 percent to 20 percent of cases are.

It was later approved for treatment of those cancers in earlier stages, too, based on studies that had tested it in patients for 12 months. That guess, that the drug should be taken for a year, became the standard of care.

Shorter use appears sufficient

But over time, the drug can hurt the heart’s ability to pump. That often eases if treatment is stopped, but the damage can be permanent and lead to heart failure.

Some studies tested shorter use periods, but results conflicted. The new study is the largest so far, and involved more than 4,000 women with early-stage cancers who were given usual chemotherapy plus Herceptin for either six or 12 months.

After four years, about 90 percent of both groups were alive without signs of the disease. Only 4 percent on the shorter treatment dropped out due to heart problems versus 8 percent of those treated for a year.

“It’s great news” for patients, said the study leader, Dr. Helena Earl of the University of Cambridge in England. Earl has consulted for Herceptin’s maker, Roche. The company had no role in the study.

“There’s no reason to not immediately change practice. The findings are persuasive,” said Dr. Richard Schilsky, chief medical officer for the oncology society. Most of Herceptin’s cancer-fighting benefit seems to come in the early months of use, he said.

Others said that because so few women have died or relapsed after being treated with the drug, longer follow-up may be needed to make sure the findings hold up before guidelines should be changed.

Doctors also want to see results published, and to study them to see if certain groups of women need longer treatment.

—AP