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Drug Found to Slow Tumor Growth: New Medication for Advanced Breast Cancer Still in Experimental Phase

Posted on: Sunday, 4 June 2006, 03:00 CDT

By Kawanza Newson, Milwaukee Journal Sentinel

Jun. 4--Atlanta -- An experimental drug dramatically slowed tumor growth among certain patients with advanced-stage breast cancer, researchers reported Saturday, providing hope to women who don't respond to standard treatment options.

"This is really exciting," said Len Lichtenfeld, deputy chief medical officer for the American Cancer Society, which was not involved in the study.

Use of lapatinib, manufactured by GlaxoSmithKline, with the standard chemotherapy drug capecitabine prevented tumor growth among patients with HER2 positive breast cancer for 8 1/2 months, compared with 4 1/2 months for those taking only capecitabine. In addition, fewer women taking the combination had cancer spread to their brains, though more women had diarrhea and skin rashes.

The results were presented Saturday at a meeting of more than 30,000 cancer specialists.

"This is an effective new regime for women with advanced HER2 positive breast cancer and should be considered a new standard of care for women meeting the eligibility criteria of this trial," said Charles Geyer, director of breast medical oncology at Allegheny General Hospital in Pittsburgh and lead author of the study.

About 25% to 30% of breast cancers produce too much of a protein known as HER2, which stimulates cell growth. These cancers tend to be more aggressive and occur in younger women, Lichtenfeld said.

The standard treatment for advanced breast cancer, Herceptin, is a type of genetically engineered protein used to treat tumors that produce too much HER2. The new combination treatment is for women who don't respond to Herceptin.

Herceptin is expensive -- averaging $40,000 to $50,000 a year -- and has been shown to cause heart damage among users, particularly those taking a standard group of chemotherapy drugs, anthracyclines, which are also known to cause heart damage. Typically, Herceptin is given after chemotherapy, which can compound the cardiovascular risk.

Not approved yet

Lapatinib targets the same aggressive breast cancer as Herceptin, though previous studies have suggested lapatinib easily penetrates the brain. Lapatinib, however, has not been approved by the Food and Drug Administration.

"We've gone through this with many drugs -- interferon, interleukin -- certain drugs that get lots of hype," said James Stewart, an oncologist at the University of Wisconsin Comprehensive Cancer Center, which was involved in the study.

"The problem is that (patients and their family) will walk into doctors' offices wanting the drug now to save a life. It's just unfair to put doctors and patients in this position now."

Help for early-stage cancer

A large, international study also released Saturday shows that women with early-stage breast cancer can lower their risk of dying by 15% if they take tamoxifen for about two years and then switch to a different medication.

Researchers reported that the women who switched to exemestane also reduced the chance of their cancer spreading or returning. Exemestane blocks formation of estrogen, which can fuel growth of breast cancer cells. Tamoxifen blocks the effects of estrogen but increases the risk of uterine cancer or a life-threatening blood clot.

"For many years tamoxifen has been the gold standard," said Judith Bliss, director of the clinical trials and statistics unit at The Institute of Cancer Research in the United Kingdom and co-author of the study.

"But the amount of benefit per year of use (with tamoxifen) is greater in the beginning than later years of use," she said.

However, two separate studies show more evidence that women taking estrogen-blocking drugs are at increased risk for bone loss. UW's Stewart said that women taking these drugs should take vitamin D or calcium supplements and have their bone density checked yearly.

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Copyright (c) 2006, Milwaukee Journal Sentinel

Distributed by Knight Ridder/Tribune Business News.

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Source: The Milwaukee Journal Sentinel

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