Obesity May Be Associated with Increased Cancer Mortality in Most Cancers; Lower in Others

Obesity was associated with higher rates of mortality and relapse in patients with cancer, except among those with lung cancer, renal cell carcinoma and melanoma, according to an observational study published in JAMA Oncology.

Obesity, which is defined as having a body mass index (BMI) higher than 30, is considered a chronic disease that has become increasingly prevalent worldwide. Past studies have found that obesity and being overweight were associated with an increased risk of all-cause mortality. A higher BMI has also been associated with an increased risk of multiple cancer types, as well as cancer mortality.

“During (the) last decades, we have observed a more rapid increase in obesity among adult cancer survivors compared with the general population,” the researchers wrote. “The mechanisms contributing to higher cancer incidence and mortality may include alterations in sex hormone metabolism, insulin and insulin-like growth factor levels and adipokine pathways.”

There have also been studies suggesting patients with cancer and a normal BMI (20-25) have worse outcomes than patients with obesity and some cancer types, such as lung cancer and melanoma. The phenomenon is referred to as “the obesity paradox,” and is not well-understood, according to the authors.

In the meta-analysis, researchers evaluated a total of 203 studies with 6,320,365 participants, examining the association of overall survival (OS), cancer-specific survival (CSS) and progression-free survival (PFS; the time between trial assignment and disease progression or death) or disease-free survival (DFS; the length of time after treatment ends and the patient survives without any signs or symptoms of disease) in patients with cancer with a BMI of at least 30 compared with patients with cancer with a BMI of less than 30. There were no restrictions placed on study setting, size, race or country. Exploratory analyses were done on predefined subgroups of disease type, study type, duration of follow-up and race.

Out of the 203 studies, 170 (84%) were eligible for inclusion in reviewing the association of obesity with OS, which was found to be significantly worse among patients with obesity than for patients without. Additionally, when evaluating CSS, PFS, or DFS, all three were found to be reduced in patients with obesity.

After a subgroup analysis for OS based on disease type, it was found that patients with breast, colorectal or uterine cancers and obesity had higher overall mortality than those without. Contrastingly, patients with obesity who had lung cancer, renal cell carcinoma or melanoma had better survival outcomes than patients without.

“Lung cancers are indeed known to be aggressive, and patients with advanced disease usually have poorer performance statuses and experience significant weight loss at the time of diagnosis, which underlies a systemic inflammatory response,” the authors wrote.

The researchers noted that accurate measures of self-reported height and weight can be a challenge in observational studies, making their inclusion in this analysis a limitation. Additionally, in some studies, the timing of the obesity diagnosis was not described. Obesity can also increase costs for treatment and complications, causing patients with lower socioeconomic status to have reduced access to medical facilities and therefore experience worse outcomes.

The study authors noted that the findings support the suggestion that obesity is a risk factor for OS, CSS and PFS among patients with cancer, except for patients with lung cancer, renal cell carcinoma and melanoma.

“These results suggest that oncologists should increase their efforts to manage patients in multidisciplinary teams for care and cure of both cancer and obesity,” they concluded. “Improving lifestyle factors (e.g., physical activity, caloric intake, care and prevention of cardiovascular complications), more intensive follow-ups of cancer in patients with obesity and adequate dose of medical therapies are all proven measures that may improve prognosis for patients with cancer and obesity.”

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