Relevance of the novel IASLC/ATS/ERS classification of lung adenocarcinoma in advanced disease

Since the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS) and European Respiratory Society (ERS) reported a new lung adenocarcinoma (ADC) classification, several groups have validated its association with prognosis in early stage disease. To our knowledge, there are no studies in advanced disease. We reviewed 313 patients with invasive lung ADC who were re-classified using the new IASLC/ATS/ERS criteria. Patients received platinum-based chemotherapy. Clinical characteristics, EGFR mutations, response and progression-free survival (PFS) after chemotherapy and overall survival were analysed. ADCs were classified as lepidic 7.4%, acinar 44.7%, papillary 10.1%, micropapillary 3.5% and solid 34.2%. When patterns were lumped into groups, response rates and PFS to platinum-based chemotherapy were better in high-grade ADC (micropapillary, papillary and solid-predominant) versus intermediate-grade ADC (lepidic and acinar-predominant) (36.9% versus 25.4% p=0.034 and 6.4 versus 5.5 months p=0.009, respectively). Overall survival was better in high-grade ADC (25 versus 16.8; p=0.023). Factors associated with better overall survival were Eastern Cooperative Oncology Group (0-1), EGFR mutations and high-grade ADC. Prognostic differences found with the new classification in early disease may not apply to patients with advanced disease. Unlike in early stages, patients with high-grade ADC have longer overall survival compared with intermediate-grade ADC, probably due to a better response to chemotherapy.