Chemotherapy is most appropriate for this patient with stage II non–small cell lung cancer (NSCLC). Although several combination chemotherapeutic regimens have been studied, so far only a cisplatin-based regimen has been shown to be effective in selected patients with NSCLC. Currently available studies indicate that adjuvant cisplatin-based chemotherapy, given for a total of four cycles, improves survival in patients who have undergone successful resection of stage II or stage III NSCLC, regardless of histologic type.

Erlotinib is a tyrosine kinase inhibitor with activity against tumors expressing mutations in the epidermal growth factor receptor (EGFR). Although erlotinib is effective in the treatment of EGFR mutation–positive patients with metastatic NSCLC, its effectiveness in the adjuvant treatment setting has not been established.

Although radiation therapy may decrease locoregional recurrence, it has not been shown to improve survival in patients with stage II lung cancer with clear margins after resection and therefore is not given to such patients as adjuvant treatment.

Observation alone is inappropriate because of the survival advantage associated with adjuvant chemotherapy and because this patient has no apparent contraindications to administration of chemotherapy. Potential contraindications to chemotherapy include poor performance status following surgery and the presence of medical comorbidities that predict for an increase in toxicity associated with chemotherapy treatment.