That is the conclusion of a new retrospective analysis presented during a poster session given at the annual meeting of the European Society for Medical Oncology. The study sought to better understand ICI outcomes. “These are complex new treatments and, because they harness the immune system, no two patients are likely to respond in the same way. BMI has previously been associated with improved survival in patients with advanced lung cancer treated with immunotherapy. However, the reasons behind this observation, and the implications for treatment are unknown, as is whether this observation is specific for patients with only certain types of cancers,” study author Dwight Owen, MD, said in an email.
He pointed out that the retrospective nature of the findings means that they have no immediate clinical implications. “The reason for the discrepancy in males remains unclear. Although our study included a relatively large number of patients, it is a heterogenous cohort and there may be confounding factors that we haven’t recognized, so these findings need to be replicated in larger cohorts,” said Dr. Owen, a medical oncologist with The Ohio State University Comprehensive Cancer Center, Columbus.
Asked if there is a potential biological explanation for a difference between males and females, Dr. Owen said that this is an area of intense research. One recent study examined whether androgen could help explain why men are more likely than women to both develop and have more aggressive nonreproductive cancers. They concluded that androgen receptor signaling may be leading to loss of effector and proliferative potential of CD8+ T cells in the tumor microenvironment. Once exhausted, these cells do not respond well to stimulation that can occur after ICI treatment.
On the opposite end of the spectrum, cancer cachexia is also a key subject of study. It is characterized by weight loss and is associated with worse clinical outcomes. A cachexia mouse model found that weight loss can lead to more clearance of immune checkpoint antibodies.
Still, much more work needs to be done. “For now, how BMI, obesity, and cachexia relate to other factors, for instance the microbiome and tumor immunogenicity, are still not fully understood,” Dr. Owen said.
The study data
The researchers analyzed data from 688 patients with metastatic cancer treated at their center between 2011 and 2017. 94% were White and 5% were Black. 41% were female and the mean age was 61.9 years. The mean BMI was 28.8 kg/m2; 40% of patients had melanoma, 23% had non–small cell lung cancer, 10% had renal cancer, and 27% had another form of cancer.
For every unit decrease in BMI, the researchers observed a 1.8% decrease in mortality (hazard ratio, 0.982; P = .007). Patients with a BMI of 40 or above had better survival than all other patients grouped by 5 BMI increments (that is, 35-40, 30-35, etc.). When separated by sex, males had a significant decrease in mortality for every increase in BMI unit (HR, 0.964; P = .004), but there was no significant difference among women (HR, 1.003; P = .706). The relationship in men held up after adjustment for Eastern Cooperative Oncology Group score, line of therapy, and cancer type (HR, 0.979; P = .0308). The researchers also looked at a separate cohort of 185 normal weight and 15 obese (BMI ≥ 40) NSCLC patients. Median survival was 27.5 months in the obese group and 9.1 months in the normal weight group (HR, 0.474; 95% CI, 0.232-0.969).
Dr. Owen has received research funding through his institution from Bristol-Myers Squibb, Genentech, Pfizer, Palobiofarma, and Onc.AI.