Low BMI associated with shorter OS in mCRC patients

Metastatic colorectal cancer patients with low BMI had shorter overall survival than obese patients, according to a pooled analysis of Avastin studies presented at the European Society for Medical Oncology 17^th World Congress on Gastrointestinal Cancer in Barcelona.

“There is good evidence that obesity increases the risk of getting colorectal cancer and that it increases the risk of colorectal cancer recurrence after curative therapy,” Yousuf Zafar, MD, associate professor of medicine at Duke Cancer Institute in Durham, North Carolina, said in a press release. “What we did not know prior to these results is whether there is a relationship between obesity and survival in patients with metastatic colorectal cancer.”

Zafar and colleagues performed a BMI-stratified pooled analysis of OS and progression-free survival using Kaplan-Meier analysis in patients with previously untreated metastatic colorectal cancer who received Avastin (bevacizumab, Genentech) with chemotherapy in one of five phase 3, prospective, observational studies performed in the U.S., Germany and France. BMI data were available for 6,128 patients (median BMI, 25.3 kg/m² [IQR: 22.6-28.7]).

“There is evidence that, at least in the U.S., obese patients may be at risk to receive lower doses of chemotherapy, so we hypothesized that obesity would be associated with worse survival in patients with colorectal cancer,” Zafar said in a separate press release. “Contrary to our hypothesis, patients who had the lowest BMI were at risk for having the shortest survival,” he said. “In this case, patients with the lowest body weight — people who had metastatic colon cancer and a BMI of less than 25 — were at the highest risk.”

Mean OS for patients with BMIs of 20 to 24.9 was 21.1 months after starting treatment compared with 23.5 months for BMIs 25 to 29, 24 months for BMIs 30 to 35 and 23.7 months for BMIs 35.1 and higher, according to a press release.

Adjusting for study, age, ECOG performance status, gender, and hypertension revealed the same result, he said. Median OS was shorter in patients with the lowest BMI, but progression-free survival was comparable between groups.

“There may be a relationship between having a lower BMI and how much treatment patients can tolerate,” Zafar said. “I would hypothesize that the lowest weight patients in our analysis received or tolerated less treatment, or received adequate treatment at first, but became too sick to receive additional therapy. That may be where we can focus more attention on improving their outcomes.”

Future research should include “a closer study of how cachexia worsens patient outcomes in [metastatic colorectal cancer],” Zafar added. “We need to understand whether it is the biology of cachexia that harms these patients more, or whether their outcome is worsened by receipt of sub-par treatment. Or it could be a combination of both.”

"This study is important because we can now consider BMI as a prognostic factor for patients with metastatic colorectal cancer. The clinical implication could be that patients with low BMI should be considered similar to patients with more aggressive cancer and probably they should be given more active treatment.,” Roberto Labianca, MD, Director of the Cancer Centre, Ospedale Giovanni XXIII in Bergamo, Italy, and ESMO spokesperson, said in a press release. “For example, polychemotherapy instead of monotherapy or a biological plus chemotherapy instead of chemotherapy alone. We need more follow up of course. The next step could be to design a prospective clinical trial using BMI to stratify patients for treatment.” – by Adam Leitenberger

Reference:

Zafar Y, et al. Abstract LBA-01. Presented at: European Society for Medical Oncology World Congress on Gastrointestinal Cancer; July 1-4, 2015; Barcelona.

Disclosure: Genentech provided funding assistance for this study.