Key prognostic factors for EGFR-mutated non-adenocarcinoma lung cancer patients in the Japanese Joint Committee of Lung Cancer Registry Database

Introduction: The efficacy of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) for EGFR-mutated non-adenocarcinoma (ADC) non-small cell lung cancer patients is not well established. Herein, we investigated key prognostic factors influencing the efficacy of EGFR-TKIs in these patients. Methods: A total of 12,320 lung cancer patients pathologically diagnosed in 2012 at teaching hospitals in Japan were retrospectively selected. The follow-up survey was closed in 2016. Results: EGFR-mutated non-ADC patients were more prone to malignant pleural effusion (MPE) and distant metastasis than ADC patients (P = 0.071 and 0.022, respectively). EGFR-mutated ADC patients were likely to have a longer median overall survival (OS) than non-ADC patients [hazard ratio (HR) 1.3 (95 % CI, 0.97-1.8, P = 0.072)-29.5 months (95 % CI, 27.9-31.1 months) versus 19.5 months (95 % CI, 10.8-28.2 months) (P = 0.068)]. There was no significant difference in median OS between EGFR-positive ADC and non-ADC patients receiving treatment with first-generation EGFR-TKI. Among EGFR-positive non-ADC patients, the median OS was significantly longer for patients receiving EGFR-TKI treatment than for those who did not [HR 4.5 (95 % CI, 2.1-9.8, P < 0.001)-25.5 months (95 % CI, 8.1-42.9 months) versus 7.5 months (95 % CI, 3.4-11.6 months) (P< 0.001)]. While there was no significant difference in the median OS for ADC patients with either 19 del or L858R mutations, the median OS was significantly longer for EGFR-mutated non-ADC patients with 19 del than for those with L858R mutation (HR 3.2 [95 % CI, 1.5-6.9, P= 0.004]; it was not reached for 19 del and was 15.5 months for L858R [95 % CI, 6.6-24.4 months], P = 0.002). Discussion: EGFR-mutated non-ADC patients were more prone to MPE and distant metastasis. Both ADC and EGFR del19-positive non-ADC patients can benefit from EGFR-TKI treatment, whereas EGFR L858R-positive non-ADC patients might require different therapeutic options.