Is cigarette smoke associated with increased catabolism of gemcitabine in patients with advanced solid tumors?

Abstract

2602 Background: Cigarette smoking can accelerate chemotherapy metabolism and result in lower plasma concentrations of the chemotherapeutic agent. Reduced drug levels may lead to undertreatment in smokers and, conversely, increased treatment-related neutropenia in nonsmokers. Methods: An IRB-approved retrospective chart review was performed on 151 patients with solid tumor malignancies who received gemcitabine alone or in combination with oral chemotherapy agents from July 1, 2009 to June 30, 2011 at the University of Michigan. Using logistic regression, we compared toxicity, including neutropenia, and smoking history measured in pack-years in smokers vs. nonsmokers to ascertain whether cigarette smoking is an independent factor predictive of toxicity to gemcitabine. Results: Tumor types included breast (9.3%), lung (4.6%), pancreatobiliary (70.9%), or other/unknown primary (15.2%). Most patients had advanced disease (stage III-IV; 78.1%); specifically, of the pancreatobiliary cohort (PB; n=107), 77.6% patients had stage III-IV disease. Within the PB cohort, most patients were “ever” smokers as compared to “never” smokers (60.7% vs. 39.3%). Logistic regression of this cohort showed that current smokers had decreased CTC-AE grade 3-4 neutropenia vs. never smokers (OR 0.667; 95% CI [0.156-2.859]). This effect was more pronounced with higher pack-year history: smokers with >50 pack-years had even less neutropenia as compared to never smokers (OR 0.333; 95% CI [0.065-1.699]). Further statistical analysis of subgroups was not performed due to small sample size. Conclusions: Smokers with pancreatobiliary malignancies receiving gemcitabine had less treatment-related neutropenia as compared to never smokers, a finding that was more pronounced as pack-years increased. Decreased toxicity, including neutropenia, may be due to increased metabolism and drug clearance as a result of smoking. This may lead to potential undertreatment of smokers and, conversely, increased treatment-related toxicity in never smokers. A prospective clinical trial is needed to further elucidate this correlation, and is currently being designed.