The first experiment ever to show that low fat diets could help prevent a return of breast cancer now reveals, with longer follow up, that the benefit was almost exclusively to women whose tumour growth was not driven by hormones.
SAN ANTONIO: The first experiment ever to show that low fat diets could help prevent a return of breast cancer now reveals, with longer follow up, that the benefit was almost exclusively to women whose tumour growth was not driven by hormones.
That could be huge — the new results suggest but cannot prove that these women might be able to cut their risk of dying by up to 66 percent with such diets.
“That’s as great or better than any treatment intervention that we’ve given for this type of cancer, which is notoriously hard to treat,” said Dr C Kent Osborne of Baylor College of Medicine in Houston, who had no role in the study.
However, for women whose cancers are fuelled by hormones — the vast majority of breast cancer patients — the diet change seemed to make little difference in the risk of recurrence or survival. Questions remained about whether those who did benefit truly were helped by cutting fat or by the weight loss that resulted. “Maybe it raises as many issues as it answers,” said John Milner, chief of nutrition science research for the National Cancer Institute.
Initial findings from the study were reported at a cancer conference in 2005 and will appear in this week’s Journal of the National Cancer Institute. The mixed results were a surprise because doctors had expected all women to benefit, said DrRowan Chlebowski of the University of California at Los Angeles, who led the work. Hormones might play such a strong role in some cancers that dietary changes have only weak impact on future risk, experts said.
The study involved 2,437 women with early stage breast cancer, average age 58. All had surgery followed by chemotherapy and five years of tamoxifen if their tumours were hormone-fuelled. At the start of the study, 29 per cent of their calories came from fat — 10 per cent to 12 per cent lower than the typical American diet. Doctors told 1,462 of them to continue their normal diets. The other 975 had counselling with dietitians to cut fat to around 20 per cent of daily calories. The diet group averaged 33.3 grams of fat a day compared to 51.3 grams for the others, and lost five to six pounds during the study.
Five years later, cancer had returned in 9.8 per cent of the diet group and 12.4 per cent of those on standard diets, which translated to a 24 per cent lower risk.
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