Factors Associated with Referral to Medical Oncology and Subsequent Use of Adjuvant Chemotherapy for Non-Small-Cell Lung Cancer: A Population-Based Study

Background: Adjuvant chemotherapy (act) for non-small-cell lung cancer (nsclc) is associated with improved survival in the general population, but may be underutilized. We explored the factors associated with referral to medical oncology and subsequent use of act among all patients with resected nsclc in Ontario, Canada. Methods: The Ontario Cancer Registry was used to identify all incident cases of nsclc diagnosed in Ontario during 2004–2006. We linked electronic records of treatment and of physician billing to identify surgery, act, and medical oncology consultation. A multivariate logistic regression model was used to evaluate factors associated with referral to medical oncology and subsequent use of act. Results: Among 3354 cases of nsclc resected in Ontario during 2004–2006, 1830 (55%) were seen postoperatively by medical oncology, and 1032 (31%) were treated with act. Patients more than 70 years of age were less likely than younger patients to have a consultation [odds ratio (or): 0.4; p < 0.001]. A higher proportion of cases with stage ii or iii nsclc than with stage i disease were referred (ors: 2.7, 2.0 respectively; p < 0.005). We observed substantial geographic variation in the proportion of surgical cases referred (range: 32%–88%) that was not explained by differences in case mix. Among cases referred to medical oncology, older patients (age 60–69 years, or: 0.4; age 70+ years, or: 0.1; p < 0.001) with greater comorbidity (Charlson comorbidity index: 3+; or: 0.5; p < 0.05) and a longer postoperative stay (median length of stay: 7+ days; or: 0.7; p = 0.001) were less likely to receive act. Use of act was greater in patients with stage ii or iii than with stage i disease (ors: 3.0, 2.7 respectively; p < 0.001); use also varied with geographic location (range: 46%–63%). Conclusions: The initial decision to refer to medical oncology is associated with age and stage of disease, and those factors have an even greater effect on the decision to offer act. Comorbidity and postoperative length of stay were not associated with initial referral, but were associated with use of act in patients seen by medical oncology.