Validity of using immunohistochemistry to predict treatment outcome in patients with non-small cell lung cancer not otherwise specified.

purposeHistology samples are important for the appropriate administration of tumor type-specific cytotoxic and molecular-targeted therapies for the treatment of non-small cell lung cancer (NSCLC). When biopsy samples lack a definite morphology, a diagnosis can be selected from three subtypes based on immunohistochemistry (IHC) results, as follows: favor adenocarcinoma (ADC), favor squamous cell carcinoma (SQC), or not otherwise specified (NOS)-null. In terms of patient outcome, however, the validity of IHC-based classifications remains unknown.

methodsA large series of 152 patients with advanced NSCLC whose diagnoses had been made based on morphological findings and who had been homogeneously treated were enrolled. We used IHC staining (TTF-1, SP-A, p40, and CK5/6) to examine tumor samples and refined the diagnoses. We then analyzed the pathological subgroups according to the IHC staining results.

resultsIHC profiling resulted in 50% of the cases being classified as favor ADC, 31% being classified as favor SQC, and 19% being classified as NOS-null groups. Compared with the favor ADC and favor SQC groups, the NOS-null group had a significantly poorer outcome. Pemetrexed-containing platinum regimens produced a response rate similar to that of other platinum doublet regimens in the favor ADC group (44% vs. 46%), whereas it produced a poorer response in the favor SQC group (0% vs. 52%) and the NOS-null group (0% vs. 24%). The favor ADC group tended to have a higher percentage of EGFR positivity and ALK positivity than the favor SQC group (25% vs. 11% and 7% vs. 0%, respectively).

conclusionsThese findings support the use of immunohistological subtyping of NSCLC biopsy specimens to select patient-appropriate treatments.