Lung cancer is divided into two main categories: small cell lung cancer and non-small cell lung cancer.
For small cell lung cancer, systemic chemotherapy is the primary treatment. If a patient is clinically staged at limited stage at the time of diagnosis of small cell lung cancer, the 5-year survival rate after treatment is around 20%, whereas for patients who are staged at extensive stage at the time of diagnosis, the 5-year survival rate after treatment is less than 5%. Non-small cell lung cancer encompasses a variety of pathological types, mainly squamous, adenocarcinoma, and large cell carcinoma.
For non-small cell lung cancer, surgery is the preferred treatment for patients with clinical stage I-IIIA. In contrast, for patients with stage IIIB and IV at diagnosis, systemic chemotherapy is the mainstay. There are also some targeted drugs, which also fall under the category of systemic therapy, but are different from conventional chemotherapy. Patients with stages IIIB and IV are clinically referred to as advanced patients, and the 5-year survival rate for these patients is less than 5%. In recent years, thanks to the introduction of new drugs into the clinic, the prognosis for some specific populations has improved greatly. For example, before the introduction of targeted drugs, the median survival of patients with advanced non-small cell lung cancer was only about 10 months.
The median survival of patients with advanced non-small cell lung cancer with EGFR-sensitive mutations has now surpassed 3 years after treatment with targeted agents. Therefore to determine the survival time of a lung cancer patient after treatment, several other aspects need to be evaluated.