Obesity is a major public health problem, in Mexico there is a high prevalence of obesity. However, there have been few studies that have reported association between obesity and rectal cancer outcomes in the Mexican population. Many studies have recently revealed the relationship between obesity and cancer. Controversy remains as to whether obesity has a harmful prognostic effect in advanced stage rectal cancer patients. There is a report that obesity was associated with lower pathologic complete response rates in rectal cancer patients after neoadjuvant chemoradiotherapy. In their study, complete response was associated with better disease-free survival. Therefore, we hypothesized that obesity influenced the local treatment outcomes in patients with rectal cancer after surgery and RT.
A total of 312 eligible patients were retrospectively analyzed; from 1999 to 2014 at National Cancer Institute Mexico, they received chemo-radiotherapy concomitant before surgery for rectal cancer.
The patients were categorized as obese, overweight, normal weight, or underweight based on BMI according to World Health Organization (WHO) criteria. Pathological complete response (pCR) was defined as no invasive cancer in the rectal or lymph tissue. Chi-squared tests were used for detecting the predictors of pCR and determining the relationship between BMI category and pCR rate in the subgroup analysis with respect to other variables.
Median age was 54 years (18-82), 24% of patients were obese, 31% were overweight, and 45% normal or underweight. 22% (n = 68) of patients were pCR. In multivariate analysis, there was statistical trend in pCR between treatment groups: pCR for obese 16/75 patients, overweight 21/97 and normal or underweight was 31/140 patients (p = 0.057). Nevertheless, obese patients compared with normal weight patients (OR = 0.81; 95% CI, 0.69 to 1.33 p = 0.039) were significantly less likely to have a pCR.
These results show an association between obesity and a poor pathological response in rectal cancer patients. This analysis suggests that higher BMI should be considered, and the mechanism of influence of BMI and obesity, on treatment response in patients with rectal cancer.
Clinical trial identification
Legal entity responsible for the study
Diaz Romero Maria del Consuelo.
Has not received any funding.
All authors have declared no conflicts of interest.