Preoperative PET and the reduction of unnecessary surgery among newly diagnosed lung cancer patients in a community setting

The goals of this study were to examine the real-world effectiveness of PET in avoiding unnecessary surgery for newly diagnosed patients with non-small cell lung cancer. Methods: A cohort of 2,977 veterans with non-small cell lung cancer between 1997 and 2009 were assessed for use of PET during staging and treatment planning. The subgroup of 976 patients who underwent resection was assessed for several outcomes, including pathologic evidence of mediastinal lymph node involvement, distant metastasis, and 12-mo mortality. We anticipated that PET may have been performed selectively on the basis of unobserved characteristics (e.g., providers ordered PET when they suspected disseminated disease). Therefore, we conducted an instrumental variable analysis, in addition to conventional multivariate logistic regression, to reduce the influence of this potential bias. This type of analysis attempts to identify an additional variable that is related to receipt of treatment but not causally associated with the outcome of interest, similar to randomized assignment. The instrument here was calendar time. This analysis can be informative when patients do not receive the treatment that the instrument suggests they "should" have received. Results: Overall, 30.3% of patients who went to surgery were found to have evidence of metastasis uncovered during the procedure or within 12 mo, indicating that nearly one third of patients underwent surgery unnecessarily. The use of preoperative PET increased substantially over the study period, from 9% to 91%. In conventional multivariate analyses, PET use was not associated with a decrease in unnecessary surgery (odds ratio, 0.87; 95% confidence interval, 0.66-1.16; P = 0.351). However, a reduction in unnecessary surgery (odds ratio, 0.53; 95% confidence interval, 0.34-0.82; P = 0.004) was identified in the instrumental variable analyses, which attempted to account for potentially unobserved confounding. Conclusion: PET has now become routine in preoperative staging and treatment planning in the community and appears to be beneficial in avoiding unnecessary surgery. Evaluating the effectiveness of PET appears to be influenced by potentially unmeasured adverse selection of patients, especially when PET first began to be disseminated in the community.