PIK3CA mutations associated with a poor postoperative prognosis in patients with pulmonary pleomorphic carcinoma: a retrospective cohort study

BACKGROUND: Pulmonary pleomorphic carcinoma (PPC) is a rare type of non-small cell lung cancer characterized by high malignancy and a poor prognosis. PPC is associated with a high frequency of postoperative relapse, and shows resistance to chemotherapy. The high malignancy of cancers is associated with genomic instability, which is related to mutations of tumor suppressor genes, such as tumor protein p53 (TP53) and ataxia-telangiectasia mutated (ATM). In addition, signaling pathways involving the oncogenes such as phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) and epidermal growth factor receptor (EGFR) are associated with resistance to chemotherapy. However, the association of PPC with these gene mutations remains unknown. We investigated the impact of TP53, ATM, PIK3CA, and EGFR mutations on the postoperative prognosis of PPC. METHODS: Fifty-five patients with PPC who underwent complete resection were studied. A gene mutation analysis was performed using next-generation sequencing. Postoperative overall survival of patients with gene mutations was evaluated using a multivariable Cox proportional hazards model in which the explanatory variables were the presence of each gene mutation, and the confounding factors were pathological stage and age. The robustness of the results was evaluated by a sensitivity analysis. RESULTS: The frequencies of pathogenic mutations in TP53, ATM, PIK3CA, and EGFR were 47, 0, 7, and 9%, respectively. A multivariable analysis adjusted for pathological stage and age showed a significant difference for only PIK3CA mutations. The hazard ratio (HR) for overall survival in cases with pathogenic mutations of PIK3CA for wild type or non-pathogenic mutations was 4.5 (95% confidence interval [CI] 1.1–18.8). Likewise, sensitivity analyses adjusted for pathological stage and sex (HR, 7.5; 95% CI 1.7–32.4) and for age and sex (HR, 5.4; 95% CI 1.4–21.7) resulted in similar findings. Although three patients with pathogenic mutations of PIK3CA that recurred postoperatively were treated by chemotherapy or immunotherapy, they survived for less than 2 years. CONCLUSIONS: The postoperative prognosis of PPC with PIK3CA pathogenic mutations is particularly poor. Pathogenic mutations of PIK3CA may be a postoperative prognostic marker. Inhibition of signaling pathways associated with PIK3CA mutations may also be a target for chemotherapy after relapse of PPC. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12885-022-10176-4.