Diagnostic Patterns of Non-Small-Cell Lung Cancer at Princess Margaret Cancer Centre

: Accurate classification of lung cancer subtypes has become critical in tailoring lung cancer treatment. Our study aimed to evaluate changes in diagnostic testing and pathologic subtyping of advanced non-small-cell lung cancer (NSCLC) over time at a major cancer centre. : In a review of patients diagnosed with advanced NSCLC at Princess Margaret Cancer Centre between 2007-2009 and 2013-2015, diagnostic method, sample type and site, pathologic subtype, and use of immunohistochemistry (IHC) staining and molecular testing were abstracted. : The review identified 238 patients in 2007-2009 and 283 patients in 2013-2015. Over time, the proportion of patients diagnosed with adenocarcinoma increased to 73.1% from 60.9%, and diagnoses of NSCLC not otherwise specified (NOS) decreased to 6.4% from 18.9%, < 0.0001. Use of diagnostic bronchoscopy decreased (26.9% vs. 18.4%), and mediastinal sampling procedures, including endobronchial ultrasonography, increased (9.2% vs. 20.5%, = 0.0001). Use of IHC increased over time to 76.3% from 41.6% ( < 0.0001). Larger surgical or core biopsy samples and those for which IHC was performed were more likely to undergo biomarker testing (both < 0.01). : Customizing treatment based on pathologic subtype and molecular genotype has become key in treating patients with advanced lung cancer. Greater accuracy of pathology diagnosis is being achieved, including through the routine use of IHC.