Q&A: The Relationship Between Weight and Colorectal Cancer Outcomes

While the association between body mass index (BMI) and colorectal cancer (CRC) is unique, several factors affect this, so the association is not entirely clear. Furthermore, less is known about the relationship between obesity and CRC outcomes.

To study this, Violeta Popov, MD, PhD, from the VA New York Harbor Health System, and colleagues performed a systematic review of electronic databases for retrospective and prospective cohort studies that reported CRC outcomes at least 60 months after diagnosis.

The findings showed that among persons with CRC, obesity, overweight, and underweight were risk factors for CRC-specific mortality. Persons who were underweight had a poorer prognosis than persons who were overweight, but the prognosis was not significantly different from persons with obesity.

Gastroenterology Consultant caught up with study coauthors Dr Popov; Vita Jaspan, BA, from the New York University School of Medicine; and Kevin Lin, BA, from the New York University School of Medicine, about the research, which was presented at the American College of Gastroenterology (ACG) 2019 Annual Scientific Meeting and Postgraduate Course. 

GASTRO CON: What prompted you to conduct the study?

VP, VJ, and KL: CRC is a leading cause of cancer-related death in the United States. There is abundant evidence that obesity is linked to the pathophysiology and development of CRC. However, less is known about the relationship between obesity and CRC outcomes. Being underweight is associated with poor prognosis and advanced stages of CRC, but the role of obesity is less clear. There is a hypothesis known as the obesity paradox, where excess weight is thought to confer a survival advantage in cancer, since the weight would provide increased nutritional reserve. In our study, we compiled results from prior studies and conducted a meta-analysis to more definitively determine the association between obesity and CRC outcomes. This allowed us to analyze a larger sample size than with any individual study. Our goal was to clarify the relationship between weight and CRC prognosis. Since weight is modifiable by patients, our results could affect how patients are counseled.

GASTRO CON: What are the most important findings from your research?

VP, VJ, and KL: Our systematic review and meta-analysis of 251,347 persons with stage I to III nonmetastatic CRC—who were followed for a period of 2.5 years to more than 15 years—clearly shows that obesity is associated with poor CRC prognosis, including increased cancer-related mortality, decreased odds of disease-free survival, and increased CRC recurrence. Both obesity and being underweight were associated with poor long-term outcomes. We observed a 30% increase in CRC mortality and 20% increase in overall mortality among patients with obesity and patients who were underweight compared with persons with normal weight, as measured by BMI or high waist circumference in this analysis. Persons with obesity had similar likelihood of survival and mortality compared with persons who were underweight, who typically represent a subset with cachexia and more advanced disease. Persons who were underweight were less likely to experience CRC recurrence than persons with obesity.

GASTRO CON: Why do you think patients who were underweight had a poorer prognosis than patients who were overweight?

VP, VJ, and KL: Perhaps some amount of excess weight provides a protective effect in patients who are overweight compared with patients who are underweight. This effect is no longer seen among patients with obesity, since adiposity is thought to be involved in the underlying pathogenesis of CRC. Ultimately, patients with obesity and patients who were underweight had similar prognosis. Additionally, patients with a normal weight had better outcomes than patients with obesity, patients who were underweight, and patients who were overweight, so any “protective effect” of excess in weight is only in comparison to patients who are underweight, not patients with a normal weight.

GASTRO CON: What is important from your study that gastroenterologists should know?

VP, VJ, and KL: Weight is one of the few variables that patients can modify to decrease the risk of cancer recurrence and risk of mortality from CRC. Maintaining a healthy weight can not only prevent CRC, but is also associated with increased life expectancy and decreased chance of recurrence among cancer survivors. This is important for gastroenterologists to know so that they can adequately counsel patients prior to and following cancer diagnosis.

GASTRO CON: What lifestyle changes can a gastroenterologist recommend to patients to lower their risk of CRC-specific mortality?

VP, VJ, and KL: As our paper showed poorer long-term outcomes among persons with obesity, persons who are underweight, and persons who are overweight, gastroenterologists should recommend maintaining a normal BMI to lower the risk of CRC-specific mortality and should educate patients on the risks of excess weight especially as it relates to their cancer prognosis. For persons who are overweight and persons with obesity, gastroenterologists can recommend losing weight and help them address weight issues by encouraging participation and referring to multidisciplinary weight loss programs that utilize various modalities such as lifestyle and behavioral  interventions,  weight loss medications, minimally invasive bariatric procedures—such as gastric balloons and endoscopic gastroplasty—, and ultimately if these measures fail, bariatric surgery.

Reference:

Jaspan V. Impact of weight parameters on colorectal cancer survival: a systematic review and meta-analysis [abstract 72]. Presented at: ACG 2019 Annual Scientific Meeting and Postgraduate Course; October 25-30, 2019; San Antonio, TX.