This article is more than 5 years old. Information may no longer be current.
High protein intake yields modest advantage in breast cancer survival
Women with breast cancer who had a higher intake of protein showed a modest survival advantage, regardless of insulin receptor status, according to an analysis of data from the Nurses’ Health Study published in Journal of Oncology.
“We found a modest survival advantage with higher protein intake that was not associated with any particular foods,” Michelle D. Holmes, MD, associate professor in the department of epidemiology at Channing Division of Network Medicine at Brigham and Women’s Hospital, and colleagues wrote. “There is no clear mechanism for this surprising finding.”
Greater protein intake has been associated with better breast cancer survival in several prospective studies, including in the Nurses’ Health Study. Holmes and colleagues sought to extend this finding by proving that total protein, essential amino acid, branch-chain amino acid and leucine intakes were associated with improved survival after breast cancer. Researchers also anticipated a strong association between protein intake and tumors expressing insulin receptor.
The analysis included 6,348 women diagnosed with stage I to III breast cancer between 1976 and 2004 whose cancer had not recurred within one year of primary diagnoses.
Researchers used validated semiquantitative food frequency questionnaires to administer dietary assessments at various timepoints. For each food or beverage, participants were asked how often, on average, they had consumed a specific amount over the past year. Researchers then categorized patients into quintiles of protein intake.
Distant breast cancer recurrence served as the primary endpoint. Death resulting from breast cancer and total mortality were secondary endpoints.
Overall, there were 1,046 distant recurrences, 919 deaths resulting from breast cancer and 1,847 total deaths.
Researchers noted that physical activity increased with protein intake, from 14.4 hours per week in the lowest quintile to 16.9 hours per week in the highest quintile.
There was an inverse association between total protein intake and distant breast cancer recurrence. Multivariable RRs for increasing quintiles of intake ranged from 0.95 (95% CI, 0.79-1.15) for the second quintile vs. first quintile, to 0.84 (95% CI, 0.69-1.03) for the fifth quintile vs. the first quintile (trend P = .02).
For animal protein intake, the RRs increased from 0.88 (95% CI, 0.73-1.06) to 0.78 (95% CI, 0.63-0.95; trend P = .003).
Essential amino acids, branched-chain amino acids and any individual amino acid did not appear associated with breast cancer outcomes. The association also did not differ by insulin receptor status.
There was no clear association with any protein-containing foods, other than a borderline association with low-fat dairy.
The 5-year RFS was 94% for women in the highest quintile of protein consumption and was 92.1% for those in the lowest quintile of protein consumption. Corresponding rates of 10-year RFS were 87.4% vs. 83.3%.
“The modest survival advantage with higher protein intake has been found in several studies and we feel it is important that patients with breast cancer and their clinicians know this,” Holmes and colleagues wrote. “At the least, it may provide reassurance that consuming protein-containing foods is not likely to increase the risk of breast cancer recurrence.”– by Chuck Gormley
Disclosure: Holmes reports research funding from Bayer HealthCare Pharmaceuticals. One other researcher reports research funding from Bayer HealthCare Pharmaceuticals and royalties on patents licensed to UpToDate.