How Obesity Affects Cancer Treatment, and How to Talk With Patients About Prevention

As obesity rates have climbed in the United States over the past 2 decades, so has the incidence of cancers related to obesity.^1,2 Debra Patt, MD, MPH, MBA, an oncologist who specializes in breast cancer and who serves as executive vice president at Texas Oncology, sees this phenomenon among her patients in the Austin, Texas, area. Patt spoke with Evidence-Based Oncology™ (EBO) about the effect that obesity has on cancer rates and how it can reduce the effectiveness of some therapies, as well as the need for clinicians to encourage patients to eat healthy food and exercise to both improve outcomes and prevent recurrence.

Patt, a member of the editorial board of EBO, is a national leader in healthcare policy and clinical informatics who has testified before Congress about the importance of protecting access to care for Medicare beneficiaries.³ She is the editor-in-chief of the Journal of Clinical Oncology—Clinical Cancer Informatics.

The interview is edited slightly for clarity.

EVIDENCE-BASED ONCOLOGY™ (EBO): The United States has made gains in cancer survivorship and preventing cancers related to smoking, but cancers related to obesity have climbed over the past 10 to 15 years. Do you think there is enough awareness of this challenge among primary care physicians, payers, and oncologists?

PATT:It’s a great point. We are seeing several trends. The first trend is that we are better at treating and preventing smoking-related malignancies, but the second is that obesity-related malignancies are growing as the epidemic of obesity is continuing to increase and also that obesity-related cancers are happening earlier and earlier in people’s lives, as obesity is happening earlier and happening in more of the country.

To your question, there is awareness of the obesity epidemic; what is harder is effective action. There are so many components in the [patient’s] lifestyle in which patients must engage in their health and wellness to have a lean body mass—things like exercise, diet, nutrition, healthy behaviors—that it becomes hard [for the clinician] to partner with patients effectively.

EBO: Is the health system addressing the issue of disparities in obesity-related cancers? Are some parts of the country doing a better job than others?

PATT: Yes, the health system is addressing the issue of disparities and obesity-related cancers. Interestingly, some early research suggests that sometimes obesity can act differently, contributing to risk among different ethnic groups.^4,5 So, there is research in that area, and I think that is really important. And yes, there are parts of the country that are doing a better job than others. I’m sure you’ve seen things that are simple, like wellness scores in communities.⁶ To what degree are individuals that live in [given] communities walking, exercising; is health and wellness part of their regular routine? Are some communities more obese than others? There certainly are places that tend to be more fit than others. A lot of those are manifestations of policies and interventions to have a healthier population.

EBO:

It can be difficult for a provider to address obesity with patients. Can you walk us through how you handle these conversations? We have heard from providers who worry about offending patients but also want to give them the facts.

PATT: It can be tricky talking to patients about a very sensitive subject like obesity. I tend to think of myself as a clinician as someone who provides facts and helps patients have a good outcome. In doing that, I try to be as fact based as possible, because I think people fear judgment about obesity or their body habitus in general. So, if you can be a fact-based partner on a collaborative strategy, that’s in the best interest of patients, and frequently [this] will diminish their likelihood of being offended. I may say something like, “I notice that your weight has increased on our scale, and your body mass index [BMI] is 31, which plots out as obese, and we know that is a risk for you as a breast cancer survivor. I want you to be happy and healthy. How do you think we can partner to reduce your risk?”

EBO:

There’s so much work being done with genetic testing and biomarkers in cancer. Is any work being done in biomarkers for obesity and how it can increase existing cancer risk?

PATT: There is a lot of thought around end points of obesity being inflammation, and there are a lot of markers of inflammation like IL-6, among others, that are surrogate end points for biomarkers of obesity. How that influences cancer risk is being evaluated. We are trying to understand it better because it is complex; there are so many factors that play in. It’s not only what you eat by caloric content or the composition of what you eat or how frequently you eat but also how much energy you are expending. What does your exercise platform look like? It’s important to use biomarkers to try to contribute to the understanding, as we want to know how the various features of things that contribute to obesity can influence cancer risk.

EBO:

In looking at different groups of women, can you discuss how obesity affects cancer risk in postmenopausal women?

PATT: In postmenopausal women, obese patients have an increased risk of recurrence of breast cancer and uterine cancer. That’s a different risk than for premenopausal patients. It may be multifactorial. There may be some inherent risk, and then some of our mechanisms of cancer treatment may be less effective in obese patients. So, for example, we know postmenopausal breast cancer patients who are obese have a higher risk of recurrence; it may be because when you make natural estrogen in a postmenopausal women, you’re converting androstenedione and testosterone to estrogens. And that reaction is catalyzed by an enzyme called aromatase, which we block with drugs called aromatase inhibitors to treat breast cancer. If you have more fat because you’re obese, we know that the same dose of aromatase inhibitors may not effectively block the enzymatic conversion to estrogen; those patients may not have their estrogen successfully blocked as well as a normal-weight patient.

EBO:

What supports should payers be offering women in menopause to help them address weight changes?

PATT: I think it’s complex. I know many payers have tried to have healthy living campaigns in many different ways—encouraging diet, encouraging weight loss among obese patients, and trying to facilitate exercise. I wish I knew what the right answer was. The truth is, I think it’s all very important.

Here’s what we know: Eating lean is important. I try to give people generic guidance. I will credit Michael Pollan for the guidance: Eat food like nonprocessed, real food, mostly green, and not too much.⁷ That’s a reasonable way to approach nutrition. I think in this society, we eat a lot of primary carbohydrates and breads that contribute to weight gain, and so I think following the Michael Pollan mantra is a really reasonable way to approach healthy eating.

But it’s not just about eating—it’s also about exercise, so I think trying to facilitate ways that patients will exercise 3 to 5 hours per week is important. Having some balance of cardiovascular training and strength training is important.⁸ I try to explore with patients what they’re interested in, because the truth is, any strategy that they’re not interested in—that they’re bored with, that they find too difficult—they’re just not going to do. I counsel people [to try] anything—[maybe] walking the mall, if window shopping seems exciting to them, or swimming. I live in Texas, where it’s frequently hot outside, so swimming seems attractive. But I try to discern from them what they think is appealing. Those are important features of fitness that influence health outcomes, but also exercise contributes, because for many patients who undergo surgery for the treatment of cancer, recovery is much faster if they had been exercising and their cardiovascular health is improved.

What we see here is that diet, exercise, and physical fitness can influence cancer outcomes in many ways.

EBO:

What do we know about the importance of weight loss once a patient survives cancer treatment? How do you address this with the breast cancer patients you see in clinical practice?

PATT: We know that postmenopausal patients who have survived breast cancer have a lower risk of recurrence if they are not obese, so I tend to give nutritional guidance and guidance around exercise. Again, I try to explore with them what will work, because I find any strategy that they are not interested in is going to be challenging, and any strategy that’s too difficult they might deem a failure and then not do anything. So, I try to see what they’re predisposed to do.

Again, I tend to give the guidance of: Eat food, mostly green, not too much, and try to exercise 3 to 5 hours per week. I try to find out what they’re doing and push them to do a little bit more. With every patient I see in clinic, we have some discussion about their wellness and what they are doing to make sure they get adequate sleep, are exercising, and are making good nutritional choices.

EBO:

Is there evidence that obesity limits the effectiveness of cancer therapies? If so, why does this occur?

PATT: There is evidence that obesity limits the effectiveness of some cancer therapies. A great example is that in postmenopausal women with breast cancer, we frequently treat estrogen-positive cancers with aromatase inhibitors—drugs like letrozole, or Femara; anastrozole, or Arimidex; exemestane, or Aromasin—those drugs act by preventing the peripheral conversion of testosterone or androstenedione into estrogens. It’s the same dose for every patient. If you have a 150-kg patient [330 lb] or a 60-kg patient [132 lb], you’re giving them the same dose of drug. What we’ve learned is that the obese patient is at higher risk of recurrence, and it appears to be directly related to this. If you have more fat, you can have more aromatization of testosterone products without being blocked appropriately.

EBO:

Does obesity’s effect on a person’s mental health also affect their cancer risk or survival if they receive a diagnosis?

PATT: It becomes very complex; we don’t understand as well today which part of obesity influences the outcome. Is it diet or is predominantly exercise? Is it predominantly percentage of fat? Is it BMI? I think we don’t know the answers to those questions yet, and I think that more research is very important in that area. At the end of the day, what we bring to practice as clinicians is an obligation to talk to our patients about nutrition, wellness, and exercise, to try to get them on the right path to having a good outcome.References

1. Flegal KM, Kruszon-Moran D, Carroll MD, Fryar CD, Ogden CL. Trends in obesity among adults in the United States, 2005 to 2014. JAMA. 2016;315(21):2284-2291. doi: 10.1001/jama.2016.6458.

2. Sung H, Siegel RL, Rosenberg PS, Jemal A. Emerging cancer trends among young adults in the USA: analysis of a population-based registry. Lancet Public Health. 2019;4(3):e137-e147. doi: 10.1016/S2468-2667(18)30267-6.

3. Debra Patt, MD, MPH, MBA. Texas Oncology website. texasoncology. com/doctors/debra-patt. Accessed September 30, 2019.

4. Obesity prevention source. ethnic differences in BMI and disease risk. Harvard School of Public Health website. hsph.harvard.edu/obesity-prevention-source/ethnic-differences-in-bmi-and-disease-risk/. Accessed September 30, 2019.

5. Wang L, Southerland J, Wang K, et al. Ethnic differences in risk factors for obesity among adults in California, the United States. J Obes 2017;2017:2427483. doi: 10.1155/2017/2427483.

6. Caffrey M. Sharecare, Boston University launch new community well-being index. The American Journal of Managed Care® website. ajmc.com/focus-of-the-week/sharecare-boston-university-launch-new-community-wellbeing-index. Published July 15, 2019. Accessed September 30, 2019.

7. Pollan M. In defense of food. CBC Radio website. michaelpollan.com/interviews/in-defense-of-food-3/. Published January 9, 2008. Accessed September 30, 2019.

8. President’s Council on Sports, Physical Fitness and Nutrition. Physical activity guidelines for Americans. HHS website. hhs.gov/fitness/be-active/ physical-activity-guidelines-for-americans/index.html. Updated February 1, 2019. Accessed September 30, 2019.

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