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CME / ABIM MOC / CE

Can Prolonged Obesity Increase the Risk for Cancer?

  • Authors News Author: Roxanne Nelson, RN, BSN
    CME Author: Laurie Barclay, MD
  • CME / ABIM MOC / CE Released: 9/28/2016
  • Valid for credit through: 9/28/2017
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  • Credits Available

    Physicians - maximum of 0.25 AMA PRA Category 1 Credit(s)™

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Target Audience And Goal Statement

This article is intended for primary care clinicians, diabetologists/endocrinologists, hematologists/oncologists, obstetrician-gynecologists, nurses, public health officials, and other members of the healthcare team involved in the care of women with prolonged obesity who may be at increased risk for cancer.

The goal of this activity is to provide medical news to primary care clinicians and other healthcare professionals in order to enhance patient care.

Upon completion of this activity, participants will be able to:

  1. Assess the association of overweight and obesity duration in adulthood and cumulative intensity on cancer risk among US women, based on an analysis from the Women's Health Initiative (WHI)
  2. Determine the clinical implications regarding the association of overweight and obesity duration in adulthood and cumulative intensity on cancer risk among US women, based on this analysis of WHI data


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Author(s)

  • Roxanne Nelson, RN, BSN

    Journalist, Medscape Oncology

    Disclosures

    Disclosure: Roxanne Nelson, RN, BSN, has disclosed no relevant financial relationships.

Editor(s)

  • Robert Morris, PharmD

    Associate CME Clinical Director, Medscape, LLC

    Disclosures

    Disclosure: Robert Morris, PharmD, has disclosed no relevant financial relationships.

CME Author(s)

  • Laurie Barclay, MD

    Freelance writer and reviewer, Medscape, LLC

    Disclosures

    Disclosure: Laurie Barclay, MD, has disclosed the following relevant financial relationships:
    Owns stock, stock options, or bonds from: Pfizer

CME Reviewer/Nurse Planner

  • Amy Bernard, MS, BSN, RN-BC

    Lead Nurse Planner, Medscape, LLC

    Disclosures

    Disclosure: Amy Bernard, MS, BSN, RN-BC, has disclosed no relevant financial relationships.


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CME / ABIM MOC / CE

Can Prolonged Obesity Increase the Risk for Cancer?

Authors: News Author: Roxanne Nelson, RN, BSN CME Author: Laurie Barclay, MD;Faculty and Disclosures

CME / ABIM MOC / CE Released: 9/28/2016

Valid for credit through: 9/28/2017

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Clinical Context

In high-income countries, high body mass index (BMI) is currently the leading risk factor of disease burden, offsetting or exceeding the decreasing disease burden related to tobacco smoking. Cancers that appear to have associations with high BMI include postmenopausal breast cancer; esophageal adenocarcinoma; and pancreatic, colorectal, renal, endometrial, ovarian, and gallbladder cancers.

Previous research suggests that time mediates cancer risk related to obesity, but evidence is limited regarding any dose-response relationship or cumulative lifetime effect of overweight and obesity on cancer risk. The goal of this analysis from the Women's Health Initiative (WHI) was to determine the effect of adulthood overweight and obesity duration and cumulative intensity on cancer risk among US women, as well as the modifying effect of smoking, postmenopausal hormone use, ethnicity, and other factors.

Study Synopsis and Perspective

A longer duration of being overweight during adulthood significantly increased the incidence of all cancers that are associated with obesity, a new study in postmenopausal women has concluded. The large population-based study was published August 16 in PLoS Medicine.[1]

"To our knowledge, this study is the first to assess the impact of adulthood overweight and obesity duration on the risk of cancer in a large cohort of postmenopausal women," write the authors, led by Melina Arnold, PhD, from the International Agency for Research on Cancer, Lyon, France.

Dr Arnold and colleagues found that for every 10 years of being overweight as an adult, there was an associated 7% increase in the risk for all obesity-related cancers.

The risk was highest for endometrial cancer (17%) and kidney cancer (16%).

For breast cancer, the increased risk was 5%, but no significant associations were found for rectal, liver, gallbladder, pancreatic, ovarian, and thyroid cancers.

When the authors took into account the degree of excess weight across time, the risks were further increased, and there were "clear dose-response relationships," they note.

Again, the risk was highest for endometrial cancer. For each additional decade spent with a BMI that was 10 units above normal weight, there was a 37% increase in the risk for endometrial cancer.

Overweight and obesity are also associated with an increased risk for other serious health conditions, including diabetes, stroke, and cardiovascular disease. Although the authors in this study looked only at the impact on cancer, it may be likely that the duration and degree of obesity could also play into the risk for other illnesses, explained study coauthor Hoda Anton-Culver, PhD.

"We are looking at these chronic conditions as well," she told Medscape Medical News.

The study also looked only at women, so it is unclear whether these results could extrapolate to men as well. "Mechanistically we can extrapolate for some cancer sites, but quantitatively and to look at other cancer sites we should replicate the study in men," Dr Anton-Culver said.

The findings also help bring home the message that excess body weight can affect health. "I think the results provide strength and ammunition to the healthcare providers to counsel their patients, particularly those at high risk, and also to apply intervention programs for weight control in those who are overweight," said Dr Anton-Culver.

Study Details

The researchers used data from the huge American WHI trial of postmenopausal women (ages 50-79 years at the time of study enrollment).

For this analysis, the team focused on a cohort of 73,913 postmenopausal women.

During a mean follow-up of 12.6 years, 6301 obesity-related cancers were diagnosed.

Approximately 40% (n=29,770) of women in the cohort were never overweight during their adult life.

The remaining 60% (n=44,143) were ever overweight; of this subgroup, almost half (n=19,654) were also ever obese.

Women who were ever overweight were, on average, overweight for approximately 30 years; those who were ever obese had been so for an average of 20 years.

The authors found that the risk of being diagnosed with an obesity-related cancer rose for every 10 years of being overweight (hazard ratio [HR], 1.07).

The association for obesity duration was even stronger for all cancers (multivariable-adjusted HR per 10-year increment, 1.10), as well as individually for colon, breast, endometrial, and kidney cancers; the HRs for every 10 years of being obese ranged from 1.07 for breast cancer to 1.23 for endometrial cancer.

In a discussion of the study,[2] NHS Choices, the official website of the National Health Service in England, notes that the "study's size and use of BMI measurements over time mean it is likely to be more reliable than smaller studies, or those that look at BMI only at one time point."

Despite the study's limitations, NHS Choices writes that "the study is a serious attempt to quantify the risk that overweight and obesity contribute to cancer risk. Obesity levels have been rising in recent decades and figures from Public Health England show 65% of men and 58% of women in England were overweight or obese in 2014."

The WHI program is funded by the National Heart, Lung, and Blood Institute, National Institutes of Health. Support for Dr Arnold's research came from the Department of Epidemiology in the School of Medicine and the Genetic Epidemiology Research Institute at the University of California, Irvine; the World Cancer Research Fund International; and the Union for International Cancer Control International Cancer Technology Transfer Fellowship. Coauthor Erin LeBlanc's institution has received grant funding from the National Institutes of Health, the Agency for Healthcare Research and Quality, Merck, Amgen, Bristol-Myers Squibb, and AstraZeneca for her research work that is unrelated to the current study. The other authors have disclosed no relevant financial relationships.

PLoS Med. Published online August 16, 2016.

Study Highlights

  • Researchers identified 73,913 WHI participants with 3 or more BMI measurements during follow-up. Participants were cancer free at baseline and had complete data on covariates.
  • Approximately 60% of participants were ever overweight or obese during adulthood.
  • Using a quadratic growth model, researchers estimated BMI trajectories across ages.
  • Using predicted BMIs, they calculated overweight (BMI ≥25 kg/m2) and obesity (BMI ≥30 kg/m2), and weighted cumulative overweight and obese years, which account for the degree of overweight and obesity across time (similar to pack-years for cigarette smoking).
  • Cancer risks linked to the duration of overweight and obesity were examined in Cox proportional hazard models.
  • Secondary analyses considered the influence of important effect modifiers and confounders (smoking, postmenopausal hormone use, diabetes history, and ethnicity).
  • During follow-up (mean, 12.6 years), 6301 obesity-related cancers were diagnosed.
  • Longer duration of overweight was significantly associated with the incidence of all obesity-related cancers (HR per 10-year increase, 1.07; 95% confidence interval, 1.06-1.09; 7% increase in risk), postmenopausal breast cancer (5% increase in risk), endometrial cancer (17%), and kidney cancer (16%). However, such duration was not associated with rectal, liver, gallbladder, pancreatic, ovarian, or thyroid cancers.
  • Adjustment for intensity of overweight increased these risks (per 10-year increase) to 8% for postmenopausal breast cancer and 37% for endometrial cancer.
  • Women who never used postmenopausal hormones had much greater risks for postmenopausal breast and endometrial cancers related to overweight duration.
  • On the basis of these findings, the investigators concluded that longer duration of overweight and obesity is associated with an increased risk for development of several forms of cancer, and that the degree of overweight during adulthood affected cancer risk, particularly endometrial cancer.
  • They suggest that reducing overweight duration in adulthood could reduce cancer risk, and that obesity prevention is important beginning early in life.
  • They recommend that healthcare teams recognize the potential of obesity management to help prevent cancer and the importance of managing excess body weight in women of all ages.
  • The findings correspond to those of previous studies on other chronic diseases, in which obesity duration was an important, independent risk factor for type 2 diabetes, cardiovascular disease, and all-cause mortality.
  • Possible mechanisms underlying the role of obesity in the risk for chronic diseases include greater risks for hypertension, insulin resistance, chronic inflammation, oxidative DNA damage, and changes in endogenous hormone metabolism.
  • Study limitations include observational design precluding causal inferences; reliance on retrospective self-reports for some of the anthropometric data, and missing data at various time points; limitations of BMI as a measure of body fatness; and possible residual confounders.

Clinical Implications

  • According to this analysis of WHI data, longer duration of overweight and obesity was associated with an increased risk for development of several forms of cancer. The degree of overweight during adulthood also affected cancer risk, particularly endometrial cancer.
  • The findings correspond to those of previous studies showing that obesity duration was an important, independent risk factor for type 2 diabetes, cardiovascular disease, and all-cause mortality.
  • Implications for the Healthcare Team: Healthcare teams should recognize the potential of obesity management to help prevent cancer and the importance of managing excess body weight in women of all ages.

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