How much does diet and body weight influence the effectiveness of cancer treatment and reduce the risk of cancer recurrence? What is the optimal diet for patients with cancer and survivors to follow? There are currently no hard and fast rules, but some dietary clues are starting to emerge.
Search for Evidence
According to a prospective, observational study of more than 1,000 patients with stage III colon cancer published last year in the Journal of the National Cancer Institute,1 overweight and obese patients who consistently ate a high-carbohydrate diet that caused high levels of blood glucose and insulin had an increased risk of cancer recurrence and death. The diet did not adversely affect the outcomes of patients with a healthy weight.
Now, a new randomized controlled trial is underway to study whether calorie restriction through a low-carbohydrate diet can slow tumor growth in overweight or obese men with prostate cancer. Other studies looking at calorie restriction are also being planned or are already underway in breast, pancreatic, and lung cancers.
“We came through the age of chemotherapy, when chemotherapy was going to cure everyone. Then we needed to give high-dose chemotherapy with stem cell rescue, and we thought that would save everyone. Next the ideal treatment was going to be immunotherapy, and now it is small-molecule targeted therapies,” said Stephen Freedland, MD, Associate Professor of Urology and Pathology at Duke University Medical Center, Durham, North Carolina, and lead author of the prostate cancer study.
“While we are making major strides in our understanding of cancer and its treatment, we are not getting to where we want to go, and I think we need to take a more holistic approach,” he continued. “We are introducing nutritional approaches into standard treatment regimens and combining the best of both worlds. We want to use not just the medicine we pump into our patients’ veins, but also the food they put into their mouths as anticancer treatments.”
Dietary Confusion
Although numerous studies show that weight gain after a cancer diagnosis is associated with a higher risk of disease recurrence in several types of cancer, including breast and prostate cancers, there is not enough evidence-based data showing exactly which type of diet—low-fat/high-carbohydrate or high-fat/low-carbohydrate—is best to follow during cancer treatment and survivorship. The result is confusion among both physicians and patients looking for definitive answers.
In a study of 21 National Comprehensive Cancer Network (NCCN) member institution websites evaluating nutritional recommendations for patients with cancer undergoing treatment and during survivorship, only 4 sites provided nutritional guidelines. Half of the NCCN sites promoted a low-fat, high-carbohydrate diet, recommending 5:1 and 7:1 ratios of carbohydrate to fat food types, and half endorsed weight maintenance during treatment, recommending a 1:1 ratio of carbohydrate to fat.1 One-third of the NCCN sites had links to external websites, including commercial websites like WebMD, and many contained inconsistent dietary recommendations.
“The information was so varied,” said Colin E. Champ, MD, Assistant Professor in the Department of Radiation Oncology at the University of Pittsburgh, and the lead author of the website dietary recommendations study.2 “One site is telling readers to avoid all fat sources, and another site is saying to eat plenty of fat and eat as many calorically dense foods as possible—and that’s pretty worrisome,” he commented.
“For patients with gastrointestinal cancers or head and neck cancers who need to maintain weight during treatment, eating a high-calorie diet is fine,” he said. “But for patients with breast cancer or prostate cancer—many of whom are already overweight—giving recommendations to eat whatever you can to avoid losing weight could put them in a bad spot. Studies show that patients who gain about 10 lb during or after treatment have a higher rate of recurrence.”
The study result is especially alarming, said Dr. Champ, since data show that as many as 1 in 3 patients seek online dietary and nutritional advice during cancer treatment and survivorship.
Tailoring Diet Based on Cancer Type
Because cancer type, stage of disease, and treatment modalities (and their side effects) can all impact a patient’s nutritional requirements, dietary recommendations should be customized to fit those needs, also taking into account a patient’s cultural heritage and food preferences and the patient’s resources with regard to buying and cooking wholesome foods, according to Jody Gilman, MS, RDN, CDN, Outpatient Clinical Dietitian at Memorial Sloan-Kettering Cancer Center, New York City.
“Nutritional counseling is part art and part science. A diet plan and medical nutrition therapy will incorporate the clinical judgment of the provider but also be specifically tailored to the patient’s needs and challenges,” said Ms. Gilman.
“A patient with head and neck cancer receiving chemotherapy or radiation therapy who has damage to her esophagus and oral cavity is going to present with much different symptoms from treatment side effects than a patient with breast cancer on endocrine therapy,” she explained. “The former patient may require food consistency modifications, such as purees, or the need for nutrition through a feeding tube, for example. The latter may need a diet tailored to weight control. The ideal diet for a patient with cancer will be based on all these types of information.”
And because a patient’s nutritional needs may change during each step in the aftermath of a cancer diagnosis—while undergoing treatment and after cure, remission, or disease progression—the patient’s diet should be reevaluated and altered accordingly, said Ms. Gilman.
Managing Cancer through Diet
Although having cancer and going through treatment is often associated with severe weight loss, recent data show that only a small minority of patients actually experience severe weight loss. In fact, it is more common for patients to gain weight during treatment,3,4 a problem that can result in poorer responses to therapy, disease progression, and disease recurrence, according to studies.5,6
“Plenty of studies show that overweight patients have worse outcomes than normal weight patients and that obese patients are at higher risk of having elevated insulin and serum glucose levels, which can feed tumors and make treatment less effective. For cancers requiring radiation treatment, planning the course of therapy for obese patients is a lot more difficult, and we have to use higher radiation doses to penetrate the body fat and reach the tumor, which also creates problems,” said Dr. Champ.
Although there have not been many randomized studies examining whether a diet low in fat and high in carbohydrates or one that is low in carbohydrates and high in fat is best for patients with cancer, oncologists can consider the results of dietary studies in patients without cancer for guidance, noted Dr. Champ.
“I looked at a lot of studies examining the risk factors in obese patients in a number of diseases, including diabetes and heart disease, and found that a low-fat, high-carbohydrate diet may not be the right choice,” he said. “We need to start extrapolating these data in cancer and look at how we can reduce obesity as one of the risk factors for cancer incidence and recurrence.”
Study Diet
In Dr. Freedland’s observational prostate cancer study, patients are encouraged to eat a diet of less than 20 g of carbohydrates a day, few or no fruits, low or no sugar and mainly meat, cheese, beans, nuts, and vegetables, with no limit on the amount of those foods participants consume.
“In mouse studies, cutting calories by 20% slows cancer tumor growth,” said Dr. Freedland. “If you can get a patient on a diet of 2,500 calories per day to reduce his food intake to 2,000 calories a day, that’s enough of a reduction in the equivalent mouse model to slow tumor growth.”
“Now, I’ve treated a lot of mice with different diets, but I haven’t cured one, so diet is unlikely to be a cure,” he added. “But I would argue that medications don’t cure diabetes or heart disease either; they help manage these diseases, and that’s our goal with diet and cancer. I’m not trying to cure cancer with my diets. I’m trying to convert cancer to a chronic disease that doesn’t cause patients problems and won’t metastasize or kill them.”
The bottom line: “We need to invest more thought, time, and money into nutritional studies for patients with cancer,” said Dr. Champ. ■
Disclosure: Drs. Freedland and Champ and Ms. Gilman reported no potential conflicts of interest.
References
1. Meyerhardt JA, Sato K, Niedzwiecki D, et al: Dietary glycemic load and cancer recurrence and survival in patients with stage III colon cancer: Findings from CALGB 89803. J Natl Cancer Inst 104:1702-1711, 2012.
2. Champ CE, Mishra MV, Showalter TM, et al: Dietary recommendations during and after cancer treatment: Consistently inconsistent? Nutr Cancer 65, 430-439, 2013.
3. Demark-Wahnefried W, Rimer BK, Winer EP: Weight gain in women diagnosed with breast cancer. J Am Diet Assoc 97:519-529, 1997.
4. Kim HS, Moreira DM, Smith MR, et al: A natural history of weight change in men with prostate cancer on androgen-deprivation therapy (ADT): Results from the Shared Equal Access Regional Cancer Hospital (SEARCH) database. BJU Int 107:924-928, 2011.
5. Stebbing J. Sharma A, North B, et al: A metabolic phenotyping approach to understanding relationships between metabolic syndrome and breast tumor responses to chemotherapy. ASCO Annual Meeting. Abstract 10544. Presented June 6, 2011.
6. Goodwin PJ, Ennis M, Pritchard KI, et al: Fasting insulin and outcome in early-stage breast cancer: Results of a prospective cohort study. J Clin Oncol 20:42-51, 2002.
