= Full article availableScientists are debating the significance of a headline-grabbing study that seems to show a link between a low-fat diet and reduced recurrence of breast cancer. Researchers said this represented the first large, randomized clinical trial to show diet could have any impact on cancer outcomes. But experts cautioned that the findings, presented at the world’s largest cancer meeting, the American Society of Clinical Oncology, were only marginally statistically significant.
“We’ve been hearing about the potential of low-fat diets to affect cancer for decades,” commented Len Lichtenfeld, MD, deputy chief medical officer of the American Cancer Society. “Until now, we had no evidence this had a significant impact. Now we have some, but it really has to be confirmed in larger trials.”
The study, funded by the National Cancer Institute, involved 2,437 postmenopausal women participating in the Women’s Intervention Nutrition Study. After undergoing standard breast cancer treatment, 975 of the women received eight weeks of nutritional counseling about cutting dietary fat. They reduced their percentage of calories from fat from 29 to 20 percent, consuming an average of 33.3 grams of fat daily compared to 51.3 grams for women in the control group.
After an average of five years of follow-up, 9.8 percent of women in the low-fat group saw a recurrence of breast cancer, compared to 12.4 percent for the women who didn’t change their diets. That’s a 24 percent overall reduction in risk, but among women with estrogen-negative tumors the risk dropped by 42 percent. Estrogen-negative tumors don’t respond to hormonal treatments such as tamoxifen or aromatase inhibitors, so the results were particularly encouraging for this group. But women with estrogen-positive tumors did not see a statistically significant benefit from the low-fat diet.
“This study may well represent the first lifestyle change—namely lowering dietary fat intake—that can have a favorable effect on breast cancer outcome,” said lead researcher Rowan T. Chlebowski, MD, PhD, of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center. He acknowledged that it wasn’t clear how dietary fat might be associated with cancer recurrence. And he advised that women should not expect any sort of diet to take the place of traditional breast cancer treatment.
“It’s suggestive but definitely not a slam dunk in terms of statistical certainty,” Steven Goodman, MD, MHS, PhD, a professor of oncology and biostatistics at Johns Hopkins University School of Medicine, told The New York Times.
Other experts cautioned that even if diet can affect cancer recurrence, that doesn’t mean dietary changes can prevent cancer in the first place.
But scientists agreed that, in any case, there’s no downside to reducing dietary fat. Said Dr. Lichtenfeld, “There’s never any harm in following a balanced low-fat diet.”
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