There is a widespread belief that conventional use of pesticides, antibiotics and other factors in “industrial” farming may promote the incidence of cancers – a risk that could be avoided by eating “organic”.
According to a paper by Kathryn Bradbury and colleagues, published in the British Journal of Cancer, this may not quite be the case.
The researchers examined prospective data of 620,000 middle-aged UK women on the relationship between the incidence of a variety of cancers and self-reported consumption of organic foods.
Over the 9.3 years of follow-up, there was no relationship between the consumption of organic foods and the incidence of all cancers.
In a subset analyses there was a statistically ‘borderline’ reduction in non-Hodgkin lymphoma, a finding that is perhaps more attributable to statistical chance than to any plausible biological hypothesis.
So, while eating “organic” may have a certain “healthfulness” appeal, a lower risk of cancer may not be a notable benefit.
Bradbury KE, Balkwill A, Spencer EA, Roddam AW, Reeves GK, Green J, Key TJ, Beral V, & Pirie K (2014). Organic food consumption and the incidence of cancer in a large prospective study of women in the United Kingdom. British journal of cancer PMID: 24675385
Thus, a study by Rebecca Sedjo and colleagues, in a paper published in the Journal of Cancer Survivorship, notes significant weight gain in 665 overweight and obese women within five years of surviving breast cancer.
The average weight gain over five years was 4.5% with almost half the participants gaining significantly more weight.
Younger women and those with lower BMIs were more likely to gain significant amounts of weight over time.
Pharmacological treatment was also an important predictor of weight gain, with women treated with selective estrogen-receptor modulators twice as likely to gain weight compared to women prescribed aromatase inhibitors.
Clearly, post-diagnosis weight gain is common in breast cancer survivors and is influenced by a complex set of factors including age, ethnicity, weight, smoking status, time elapsed since diagnosis, and endocrine-modulating therapy.
It appears that exploration of effective strategies to prevent this weight gain or provide obesity management strategies to breast cancer survivors are long overdue.
Obesity is a risk factor for many cancers. But even if this were not the case, the increase in the number of people living with obesity means that more obese people will be diagnosed with cancer than ever before.
The many complex issues facing oncologists in managing their obese cancer patients are nicely summarized and reviewed in a paper by Wenjing Tao and Jesper Lagergren from the Karolinska Institute, Stockholm, Sweden, in a paper published in Nature Reviews Clinical Oncology.
As the authors point out, not only does a large body of epidemiological evidence link obesity to increased cancer incidence, but there is also evidence suggesting poorer survival in obese patients with cancer.
There are also a number of important challenges related to diagnosis including reduced participation of obese individuals in cancer screening programs, lower tumour-marker expression and problems with medical imaging among obese individuals.
Excess body weight also alters pharmacokinetics of chemotherapy and hormone therapy and precision of radiotherapy might be adversely affected by greater skin motility and increased motion of internal organs.
Obese patients can also face higher risks of complications with surgery and recovery times may be affected.
Finally, the authors discuss the importance of sarcopenic obesity and the problem of excess weight gain associated with cancer survival, both of which can affect long-term outcomes.
But, as the authors conclude,
“Although the number of obese patients with cancer is rapidly growing, there is a lack of evidence-based clinical guidelines specifically addressing diagnosis and treatment for these patients.”
Tao W, & Lagergren J (2013). Clinical management of obese patients with cancer. Nature reviews. Clinical oncology PMID: 23856746
In a paper just published in the Journal of Clinical Oncology, Lisa Martin and colleagues from the University of Alberta studied around 1,500 patients with various stages of lung or gastrointestinal cancer presenting with a wide range of BMI (17% obese, 35% overweight, 36% normal weight, and 12% underweight).
Patients in all BMI categories varied widely in weight loss, muscle index, and muscle attenuation (measured by CT).
Irrespective of BMI, high weight loss, low muscle index, and low muscle attenuation were independently prognostic of survival.
Compared to a survival model containing conventional covariates (cancer diagnosis, stage, age, performance status), a model ignoring these variables but including only BMI, weight loss, muscle index, and muscle attenuation proved a far better predictor of patient survival.
Patients who had higher weight loss and lower muscle indicators survived 8.4 months, regardless of whether they presented as obese, overweight, normal weight, or underweight, in contrast to patients who had none of these features, who survived 28.4 months.
From these finding the authors conclude that, regardless of BMI, cancer patients presenting with involuntary weight loss, muscle depletion and muscle attenuation share the poorest prognosis.
Thus, the authors note that,
“Our findings provide evidence in support of the proposed international consensus definition of cancer cachexia as a multifactorial syndrome defined by an ongoing loss of skeletal muscle mass with or without loss of fat mass.”
Once again, simply stepping on a scale appears to be a rather limited measure of health.
Martin L, Birdsell L, Macdonald N, Reiman T, Clandinin MT, McCargar LJ, Murphy R, Ghosh S, Sawyer MB, & Baracos VE (2013). Cancer Cachexia in the Age of Obesity: Skeletal Muscle Depletion Is a Powerful Prognostic Factor, Independent of Body Mass Index. Journal of clinical oncology : official journal of the American Society of Clinical Oncology PMID: 23530101
One of the consistent findings in the medical literature is the fact that although excess weight is associated with an increased risk for a wide range of medical problems (including the earlier onset of such complications), once people have these problems, excess weight appears to be either ‘protective’ (the so-called obesity ‘paradox’) or have little influence on long-term outcomes.
Thus, a study by Kai Bickenback and colleagues from the Memorial Sloan-Kettering Cancer Center, New York, NY, published in the Annals of Surgical Oncology, failed to find an impact of obesity on long-term survival of patients with gastric (stomach) cancer.
In their study, the researchers examined dat from about 1,800 patients who underwent curative intent resection for gastric carcinoma from 1985 to 2007.
Overall, there was no difference in survival between overweight or obese and normal weight patients.
However, overweight patients did have more proximal tumors and a lower tumor (T) stage at surgery.
Overweight and obese patients also had about twice the rate of wound infections and anastomic leaks than normal weight patients.
In multivariate logistic regression analyses, higher BMI, total gastrectomy, and use of neoadjuvant chemotherapy were all associated with increased wound infection and anastomotic leaks.
Thus, the authors note that although peri-operative complications may be more common in overweight and obese patients undergoing surgery for gastric cancer, their survival rates are no worse than those of normal weight individuals.
Obviously, given the higher peri-operative complication rates, costs for hospital stay and doctor visits may be higher in the overweight and obese patients (not analysed in this paper) – however, this should certainly not prove a barrier to providing the same care to overweight and obese patients with gastric cancer as one would to normal-weight individuals with this unfortunate condition.
Bickenbach KA, Denton B, Gonen M, Brennan MF, Coit DG, & Strong VE (2012). Impact of Obesity on Perioperative Complications and Long-term Survival of Patients with Gastric Cancer. Annals of surgical oncology PMID: 22976377