In a peer-reviewed study believed to be the first of its kind published, a research team led by Johns Hopkins Medicine provides scientific evidence that a healthy diet may reduce the chance of low-risk prostate cancer progressing to a more aggressive state in men undergoing active surveillance.
The findings were reported in the journal JAMA Oncology.
In the newly published study, the researchers prospectively evaluated the histories of 886 men (median age at diagnosis: 66) diagnosed with grade group 1 prostate cancer from January 2005 to February 2017, all of whom were in the Johns Hopkins Medicine active surveillance program and whom, at the time of enrollment, completed a validated food frequency survey — the Block 1998 Food Frequency Questionnaire — regarding their usual dietary patterns. Of the participants, 55 were Black (6.2%), 803 (90.6%) were white and 28 (3.2%) identified as other races and ethnicities.
Based on their responses to the questionnaire, a Healthy Eating Index (HEI) score was calculated for each patient. The HEI ranges from 0 to 100.
“The HEI is a validated measure of overall diet quality, quantifying how well an individual’s dietary pattern adheres to the recommendations of the U.S. Department of Agriculture’s Dietary Guidelines for Americans,” says study lead author Zhuo Tony Su, M.D., a fifth-year resident at the Brady Urological Institute and the Johns Hopkins University School of Medicine. “We looked at each patient’s HEI score — as calculated from their dietary information recorded at enrollment in our active surveillance program — and assessed whether men with a higher quality diet were less likely to experience grade reclassification in the years afterward.”
Su says the researchers also evaluated the patients using an energy-adjusted HEI (E-HEI) score that takes into account a person’s daily caloric intake.
Along with those two metrics, Su says, the researchers calculated scores for each study participant using the Dietary Inflammatory Index (DII) and the energy-adjusted DII (E-DII).
“The DII and E-DII scores assess the inflammatory or anti-inflammatory potential of any diet, so higher scores indicate a diet that may cause more inflammation, which in turn, may contribute to the development and progression of prostate cancer,” says Su. “We evaluated whether higher inflammatory potential was associated with increased risk of grade reclassification.”
By a follow-up assessment at 6.5 years after diagnosis, 187 men (21%) had been reclassified as grade group 2 or greater, of whom 55 (6%) had extreme grade reclassification to grade group 3 or greater.
“When our team looked at the HEI and E-HEI scores in relation to the grade reclassification rates, we found a statistically significant inverse association between adherence to a high quality diet — as indicated by high HEI and E-HEI scores — and the risk of grade reclassification during active surveillance,” says study co-senior author Bruce Trock, Ph.D., a professor of urology, epidemiology and oncology at the Johns Hopkins University School of Medicine, and director of the Brady Urological Institute’s epidemiology division. “In other words, the higher the HEI and E-HEI scores, the more reduced the risk that a low-grade prostate cancer had progressed to a higher grade disease that mandated curative treatment.”
Study co-senior author Christian Pavlovich, M.D., a professor in urologic oncology at the Johns Hopkins University School of Medicine and director of the Brady Urological Institute’s prostate cancer active surveillance program says for patients adhering to a high quality diet, every increase of 12.5 points in the HEI score was associated with an approximately 15% reduction in reclassification to grade group 2 or greater, and a 30% reduction in reclassification to grade group 3 or greater.
The researchers say their findings also indicate that lower inflammation potential is among several possible risk lowering mechanisms as a result of a higher quality diet. However, they did not find an association between grade reclassification and baseline DII/E-DII scores.
“This lack of association with DII/E-DII may indicate that inflammation plays a role in driving the progression from a healthy prostate to one with cancer,” says Trock. “Whereas, in men who already have prostate cancer, the more subtle biological change from a lower to higher grade may reflect other mechanisms potentially influenced by diet.”
