In a multicenter study, led by researchers at the University of Michigan Comprehensive Cancer Center, it has been found that women whose breast cancer expressed a protein called HER-2 are most likely to benefit from adding Taxol to chemotherapy. On the other hand, women whose tumours are fuelled by oestrogen, but do not express HER-2, do not get any benefit from the added Taxol.
The scientists say that targeting treatment can help prevent the majority of patients from unnecessary side effects because about 15 to 20 per cent of breast cancers express HER-2, while three-quarters of breast cancers are so-called oestrogen-receptor-positive.
"In general, chemotherapy for breast cancer has been a one-size-fits-all approach. Our decision to recommend it is based on whether a woman is at high risk of the breast cancer recurring, without any idea of whether she would benefit from the additional therapy. With this data we hope we will be able to focus chemotherapy on patients whom it's most likely to help," the New England Journal of Medicine quoted lead study author Dr. Daniel Hayes, clinical director of the breast oncology program at the U-M Comprehensive Cancer Center, as saying.
During the study, the researchers looked at tissue samples and data from 1,500 women who had previously participated in a study looking at the benefit of adding Taxol after four cycles of the drugs Adriamycin and Cytoxan, so-called AC chemotherapy. Haft of the women had received four cycles of Taxol after completing four cycles of AC chemotherapy.
A previous analysis had shown that adding Taxol decreased the chances of cancer recurring, and improved survival when all patients were considered, with no consideration of HER-2 status. The analysis, however, also showed that women with oestrogen-receptor-positive tumours did not seem to benefit as much from chemotherapy as their counterparts whose tumours did not need oestrogen.
In the current analysis, it has been found that the addition of Taxol improves survival rates in women who are HER-2-positive, regardless of their oestrogen receptor status. The researchers have also found that women with tumours that are HER-2-negative and oestrogen-receptor-positive do not get any additional benefit from the paclitaxel.
However, the researchers have suggested that medical professionals do not introduce any change in treatment until further research confirms that Taxol does not benefit oestrogen-receptor-positive breast cancer.
"This is the first such observation that's been made, and it was made retrospectively, meaning we looked backwards instead of forwards. We are not recommending at this time that women with positive lymph nodes, for whom we would currently recommend Taxol, but who are oestrogen receptor positive and HER-2 negative not take the Taxol. We think the stakes are too high," Hayes says.
"We've seen mortality from breast cancer dropping in recently years because we've applied these new and better therapies. But now we believe, if these results are confirmed and validated in other studies, that perhaps we could pull out half the patients in that study and save them from the toxicities and the cost of receiving a drug that might not do them any good," he adds.