Gene clue may explain breast cancer drug response
German scientists have found a clue to why some women with breast cancer respond better to treatment with the drug tamoxifen than others.
German scientists have found a clue to why some women with breast cancer respond better to treatment with the drug tamoxifen than others, and say the finding could help doctors offer more personalised treatment.
In a study published on Tuesday, the researchers said about half of patients have a genetic variation of a certain enzyme which helps them metabolise the drug -- meaning they are likely to respond well.
The study also showed about 8 percent of people are likely to be unable to metabolise the drug, suggesting they should be given alternatives and all patients should be gene tested.
"If we had the opportunity to genotype patients before making a (treatment) decision, those who are not predicted to benefit from tamoxifen could go straight to other drugs," said Hiltrud Brauch, who conducted the study with colleagues at the Institute of Clinical Pharmacology in Stuttgart.
"But those who ... have the full capacity to metabolise tamoxifen, they actually have full capacity to benefit from it -- and that is about half of the patients."
About 1.3 million cases of breast cancer are diagnosed worldwide each year and it is the leading cause of cancer deaths in women, according to the American Cancer Society.
Tamoxifen, which works by blocking oestrogen from causing wild cell growth, is given to many women for five years after they are diagnosed to prevent the disease from returning.
It is estimated to have saved half a million lives and has been the "gold standard" for the past 25 years for hormone treatment of breast cancer, the researchers said.
Generic tamoxifen has been overtaken by a newer generation of so-called aromatase inhibitor drugs such as AstraZeneca's Arimidex, Novartis's Femara and Pfizer's Aromasin.
Doctors are increasingly being encouraged to switch from tamoxifen to a newer drug halfway through the five-year course -- a move Brauch said might not always be the right one.
The researchers, whose findings were published in the Journal of the American Medical Association, found that the enzyme CYP2D6, which aids metabolism of drugs, helped patients respond to tamoxifen.
They looked at data on DNA from tumour tissue or blood from 1,325 mainly postmenopausal patients diagnosed with early, mid-stage and advanced breast cancer and found higher breast cancer recurrence in patients with low or no CYP2D6 function, compared with patients who had high levels.
Poor metabolisers had nearly twice the risk of recurrence compared with good metabolisers, they said.
Reuters Last Mod: 06 Ekim 2009, 23:47