Small Cell Lung Cancer: A Review

Importance: Small cell lung cancer (SCLC) is a high-grade neuroendocrine carcinoma with an incidence of 4.7 cases per 100 000 individuals in 2021 in the US and a 5-year overall survival of 12% to 30%.

Observations: Cigarette smoking is the primary risk factor for development of SCLC, as 95% of patients diagnosed with SCLC have a history of tobacco use. Patients with SCLC may present with respiratory symptoms such as cough (40%), shortness of breath (34%), hemoptysis (10%), or metastases with corresponding local symptoms (30%) such as pleuritis or bone pain; approximately 60% of patients with SCLC may be asymptomatic at diagnosis. Chest imaging may demonstrate central hilar (85%) or mediastinal lymphadenopathy (75%). At diagnosis, approximately 15% of patients have brain metastases, which may present as headache or focal weakness. Diagnosis is confirmed by biopsy of a primary lung mass, thoracic lymph node, or metastatic lesion. Small cell lung cancer is classified into limited stage (LS-SCLC; 30%) vs extensive stage (ES-SCLC; 70%) based on whether the disease can be treated within a radiation field that is typically confined to 1 hemithorax but may include contralateral mediastinal and supraclavicular nodes. For patients with LS-SCLC, surgery or concurrent chemotherapy with platinum-etoposide and radiotherapy is potentially curative in 30% of patients. More recently, median survival for LS-SCLC has reached up to 55.9 months with the addition of durvalumab, an immunotherapy. First-line treatment for ES-SCLC is combined treatment with platinum-etoposide chemotherapy and immunotherapy with the programmed cell death 1 ligand 1 (PD-L1) inhibitors durvalumab or atezolizumab followed by maintenance immunotherapy until disease progression or toxicity. Although initial rates of tumor shrinkage are 60% to 70% with platinum-etoposide and immunotherapy treatment, the median overall survival of patients treated for ES-SCLC is approximately 12 to 13 months, with 60% of patients relapsing within 3 months. Second-line therapy for patients with ES-SCLC includes the DNA-alkylating agent lurbinectedin (35% overall response rate; median progression-free survival, 3.7 months) and a bispecific T-cell engager against delta-like ligand 3, tarlatamab (40% overall response rate; median progression-free survival, 4.9 months).

Conclusions and relevance: Small cell lung cancer is a smoking-related malignancy that presents at an advanced stage in 70% of patients. Three-year overall survival is approximately 56.5% for LS-SCLC and 17.6% for ES-SCLC. First-line treatment for LS-SCLC is radiation targeting the tumor given concurrently with chemotherapy and followed by consolidation immunotherapy. For ES-SCLC, first-line treatment is chemotherapy and immunotherapy followed by maintenance immunotherapy.