This is a stage IV by definition , if the pleural effusion is symptomatic then drainage for symptomatic fast relieve is indicated , if not symptomatic then will start systemic therapy with any EGFR TKI ( erlotinib, gefitinib, and afatinib ) all have efficacy in EGFR-mutant lung cancer and are generally well tolerated.
The choice will depend on the availability , cost , toxicity profile , physician comfort with the chosen agent , some reports indicates that afatinib may yield the strongest disease outcomes but may also cause the most side effects. Some reports also indicates gefitinib may be the best tolerated agents.