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SGO Annual Meeting Takes Closer Look at Impact of Obesity on Cancer

DiGiulio, Sarah

doi: 10.1097/01.COT.0000451723.75475.9c


The role of obesity was the topic of several studies in gynecological cancers presented at this year's Society of Gynecologic Oncology (SGO) Annual Meeting on Women's Cancer.

“Obesity is having a big impact on health care—through the mechanisms resulting in disease, and then in how we apply our health care tools. The question becomes: is obesity changing patient outcomes?” said Pamela J.B. Stone, MD, a gynecologic oncologist at Rocky Mountain Cancer Center in Boulder, Colorado, who co-moderated a Focused Plenary session on obesity-induced challenges in endometrial cancer.

“Because most of our studies are in normal weight patients, now we're having to say: What's the safest way to treat obese patients without resulting in more complications?” she added in an interview after the meeting. “Are our assumptions about treatment even correct? Are we dosing chemotherapy correctly? Are there modifiable risk factors, and what are the costs for changing those?”



The following are some of the highlights on these topics addressed in the research presented at the meeting.

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Bariatric Surgery Associated with Lower Endometrial Cancer Risk

Women who had bariatric surgery to lose weight had a 71 percent lower risk of uterine cancer compared with women who were obese who had not had the procedure, according to a plenary study (Abstract 4). And for the women who had undergone the procedure and maintained a normal weight, the risk reduction was 81 percent.

“Obesity is the second leading cause of preventable death, and this research adds to the growing evidence that reducing obesity reduces cancer,” the study's lead author Kristy Ward, MD, MAS, a Gynecologic Oncology Fellow at the University of California San Diego Moores Cancer Center, said in a news release. “After women had bariatric surgery, their risk of uterine cancer plummeted and became the same or perhaps even a little less than in women who were not obese.”



The retrospective cohort study analyzed 7,431,858 women admitted at University HealthSystem Consortium hospitals between 2009 and 2013—which included 103,797 patients who had had bariatric surgery and 44,345 patients who had developed a uterine malignancy.

Of the women who developed a uterine cancer, the incidence was 2.8 times higher among patients who were obese (1,409 per 100,000 patients) than for those who were not obese (496 per 100,000 patients). And, among the patients who had undergone bariatric surgery, the risk of uterine malignancy was 408 per 100,000 patients—682 per 100,000 patients with persistent obesity, and 270 per 100,000 who were no longer obese.

The finding that women who had undergone bariatric surgery actually had an even lower risk of uterine cancer than the non-obese women in the study (who had not undergone bariatric surgery) was an unexpected finding, which should be explored in additional research, Ward noted via email.

Another next step for the research, she added, is working with bariatric specialists to prospectively evaluate risk reduction in this population of patients: “We should all be cognizant about counseling our patients on weight-related issues, and consider how gynecologists and gynecologic oncologists can work together with bariatric specialists and nutritionists in an effective, patient-centered manner.”

The findings are significant, Stone noted, because—given the rising trend of obesity in the U.S. and the association between obesity and type I uterine cancer—they suggest that bariatric surgery could modify that risk factor. Still, the study is retrospective, so it does not necessarily show causality, but it does warrant designing a prospective study.

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Endometrial Cancer Staging in the Morbidly Obese

Another study reported findings from the Gynecologic Oncology Group (GOG) LAP2 trial (a randomized comparison of laparoscopic versus open surgical staging in patients with clinically early-stage endometrial cancer) (Abstract 76). The data showed that (1) obese women were more likely to have lower-risk, earlier-stage uterine cancer; (2) there was an association between normal body mass index (BMI) and high-risk disease; and (3) obese women had shorter overall survival rates than non-obese women, despite having similar disease-specific survival.



“We found that as BMI increased, women were much more likely to have an early-stage tumor—particularly stage 1A, the very earliest—and they were also more likely to have a well-differentiated tumor,” said the study's lead author, Camille G. Gunderson, MD, a gynecologic oncology fellow at the University of Oklahoma. But, the women with higher BMIs had similar rates of recurrence and all-cause mortality—and had greater complications, despite having low-risk disease, she explained: “Which leads us to believe that [the women with higher BMIs] are dying from other things—most likely cardiovascular disease.”

The study, which analyzed 2,596 women with endometrial cancer or uterine cancer, showed:

  • Obese women were less likely than non-obese women to have any positive lymph nodes (4.6% of women with a BMI greater than 40 vs. 10.4% of women with a BMI less than 25) or positive pelvic nodes (3.4% vs. 10.5%);
  • Intraoperative complications were similar within each surgical approach group despite BMI;
  • Postoperative complications were more frequent with obesity (occurring in 23.8% of women with a BMI greater than 40 vs. 13.7% of women with a BMI less than 25);
  • Obese women more often needed postoperative antibiotics (30.3% of the women with a BMI greater than 40 vs. 15.8% of women with a BMI less than 25) and more often needed hospitalization longer than two days (78.9% of women with a BMI greater than 40 vs. 60.7% of women with a BMI less than 25);
  • After controlling for surgical approach, wound infection and postoperative antibiotic use were higher in obese women; and
  • All postoperative complications were more frequent in obese women converted to laparotomy compared with open or laparoscopic groups.

“Our findings are really a call to action for gynecologic oncologists to not hurt these patients who have lower-risk disease by putting them through a laparotomy in order to stage them,” Gunderson said. “The better route for patients with type 1 endometrial cancers (i.e., grades 1 and 2) is to do minimally invasive procedure and perform a laparotomy only for high-risk disease—and to also focus on the importance of overall health, weight management, and exercise programs.”

The data confirm that more obese patients tend to present with this disease at a younger age with lower-stage and lower-grade uterine cancers, Stone noted. “The results are reassuring—these patients were the ones who tend to fail in terms of being able to be completely staged laproscopically, so it is reassuring that with further analysis, these patients tended to have lower-risk disease and lower nodal involvement.”

And, Stone added, the conclusion that all-cause mortality was increased for the obese patients is further reason why talking about comorbidities factoring into patients' survival is important: “Survival is not clearly based on just their cancer.”

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Discussing Costs

Another study reported the financial implications of treating obese patients. Estimates—based on actual mean hospital charges—showed that morbidly obese patients with endometrial cancer incurred an additional $5,000 in total hospitalization charges per case (Abstract 75).

The study is one of the first to give detailed demographic and socioeconomic data for these morbidly obese patients, the study's lead author, John Chung-Kai Chan, MD, a gynecologic oncologist at the Palo Alto Medical Foundation, explained in an interview after the meeting. “It also gave us an idea of how these patients are utilizing our health care resources—in terms of the kind of surgery we are performing on these patients, how and where they are operated on, and the economic impact.”

The intention is that these findings could potentially be used to better allocate resources to handle these patients—to support hospitals and care centers that serve these patients, he noted.

“The patients we generally see are overweight—and many of them have comorbidities that will then require medical treatment on top of surgery. This ultimately results in longer hospitalization and potentially more procedures, not necessarily related to their endometrial cancer, but potentially related to cardiac problems, diabetes, or risk of infection.”

The other takeaway, he added, is that patients who are morbidly obese put a significantly greater cost strain on the health care system than patients categorized as “just” obese: “We can handle obese patients—doctors are good at that, hospitals are good at that, and it doesn't incur significant costs,” he said. “But it's when patients are in the morbidly obese category that the costs significantly increase.”

The study sought to determine those actual costs by analyzing data on 6,560 patients with endometrial cancer who were part of the National Inpatient Sample from 2010. The data showed:

  • The mean postoperative stay for the morbidly obese was four days, compared with 3.5 for patients who were non-morbidly obese;
  • Morbidly obese patients required more intensive care with mechanical ventilation (5.5%) than non-morbidly obese patients (1.6%);
  • The median total hospital charges were higher for the morbidly obese patients compared with the non-morbidly obese patients ($46,654 vs. $41,164) and
  • Using a multivariate linear regression model adjusted for charges associated with insurance type, hospital type, and surgery performed, the incremental costs of treating the morbidly obese patients were $5,096 per patient.

Of the patients in the sample:

  • Most patients were white (78%), with the remainder black (10%), Hispanic (8%), Asian (3%), and Native American (1%);
  • 5% of the patients were uninsured, 45% had Medicaid, 43% had Medicare, and 7% had private insurance; and
  • 1,088 (17%) of the patients were morbidly obese.
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‘We're Seeing a Huge Impact’

Chan's study is further evidence that the impact of obesity on cancer care is expensive, Stone noted: “We're seeing a huge impact. It takes additional staffing and equipment to address the size of the patients. And, we don't have a breakdown of where those costs come from—which is the next part to look at.”

As Chan suggests, the solution may be in reallocating resources to have more specialized care centers, or—considering findings such as Ward's—another solution may be in creating more support for bariatric programs, Stone added.

“Seeing this much talk about gynecological tumors and obesity is a reflection of our society,” she said, noting the rising rates of obesity and morbid obesity across the U.S. “It's the norm now. And physicians practicing in those areas need to become more comfortable taking care of obese and morbidly obese patients because that becomes their population.”

© 2014 by Lippincott Williams & Wilkins, Inc.
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