As many as one in four women who use the popular and pricey breast cancer drug Herceptin will develop heart failure, according to a St. Boniface Hospital researcher, a significantly higher number than earlier trials found.
Herceptin, a drug with the generic name of Trastuzumab, is commonly used alongside chemotherapy by the roughly 25 per cent of women whose breast cancer is marked by an aggressive receptor known as HER2.
The higher risk of heart failure - a weakening of the heart's ability to pump - is common knowledge for the drug's users, but earlier clinical trials put the chances at around one in 10.
Now the drug's first real-world study, conducted by the St. Boniface Research Centre's Dr. Davinder Jassal with Cancer Care Manitoba, found the risk is closer to one in four.
There's no other comparable drug on the market used to treat HER2 patients, said Jassal, the principal investigator in cardiovascular imaging at the St. Boniface Research Centre.
The new findings make the drug even more of a double-edged sword, with an increased likelihood of heart failure as a trade-off for becoming cancer-free.
Of the 152 Herceptin users tested in the Manitoba study, 36 of the women experienced heart failure, "which is quite high compared to the one in 10 clinical trials," said Jassal, who will present the findings Saturday in a public lecture at the research centre.
The women ranged in age from 31 to 78. Twenty recovered with medication, the study found, and another 16 are still experiencing heart failure at the same level or worse.
However, Jassal is still optimistic about treatment with Herceptin, a drug that can cut the odds of recurring cancer by as much as half and reduce mortality rates by up to a third, and costs up to $47,000 annually per patient.
The high risks of heart failure could be lessened by early detection or prevention, and Jassal said he's encouraged by a study he helped with at the St. Boniface Research Centre in which researchers used an imaging system called Tissue Doppler to hone in on muscle behaviour, and detect early-stage heart problems in mice.
He's currently recruiting a group of 50 women to see if the effects can be duplicated on humans. If so, researchers might ultimately be able to detect Herceptin-related heart problems before damage occurs.
Jassal said he expects the biggest impact of the one-in-four finding will be better patient screening.
"I think it's going to be more vigilant monitoring," he said.
Dr. Shaun Lucash, a Winnipeg pediatrician, used Herceptin after developing breast cancer, and finished her treatment last fall.
"My experience with Herceptin has thankfully been favourable so far," she said, noting that although her heart isn't quite as strong, it doesn't qualify as heart failure.
The increased risk of heart problems does give pause, she said, but she's more focused on the battle at hand than theoretical problems down the line.
"We're dealing with the devil that we know," she said. "There are many devils in our lives that we don't know. I think the right way to look at this is, we all live one breath at a time."
An estimated 400,000 Canadians live with congestive heart failure, according to a self-reported study cited by the Heart and Stroke Foundation of Canada. Although firm statistics on the chance of developing heart failure are hard to come by, it's the most common reason for people 65 and over to be hospitalized in North America.
lindsey.wiebe@freepress.mb.ca
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