Lymph nodes act as a filtering system outside the lung, collecting cancer cells that are beginning to migrate out of the lung. Distant: the cancer has spread (or metastasized) to other parts of the body (aka: extensive stage SCLC).At the time of diagnosis, 60–70% of people already have metastases.Small-cell carcinoma is an undifferentiated neoplasm composed of primitive-appearing cells. As the name implies, the cells in small-cell carcinomas are smaller than normal cells, and barely have room for any cytoplasm. Some researchers identify this as a failure in the mechanism that controls the size of the cells. Treatment
Small-cell lung cancer is most commonly treated with a combination of two drugs, which is more effective than one drug alone. Chemotherapy
Cisplatin and etoposide,
Carboplatin and etoposide. Cisplatin-resistance
The drug paclitaxel may be useful in the treatment of cisplatin-resistant cancer. About 68.1% of cisplatin-resistant cells
appear to be sensitive to paclitaxel and 66.7% of paclitaxel-resistant cells to
cisplatin. The mechanism for this activity is unknown. Paclitaxel-based chemotherapy showed modest activity in SCLC patients refractory to both etoposide- and camptothecin-based chemotherapy. The newer agent lurbinectedin is active in relapsed SCLC and was approved for medical use in the United States in June 2020. Immunotherapy
In 2018, the FDA approved two immunotherapies for small cell lung cancer:
1. Nivolumab (Opdivo), and
2. Atezolizumab (Tecentriq)

Funding controversy
Tecentriq treatment costs on average $13,200 per month, depending on the dosage schedule.
Despite updated data showing 30% more people with extensive stage small cell lung cancer are alive at 24 months compared to those who received chemotherapy alone, Canadian regulator had rejected to fund Tecentriq for extensive stage small-cell lung cancer "as too costly" followed by United Kingdom also citing "drug’s cost-effectiveness." Radiation therapy
Chest radiation helps SCLC patients live longer by killing cancer cells and helping prevention of cancer recurrence. Another type of radiation, prophylactic cranial radiation, prevents central nervous system recurrence and can improve survival in patients with good performance status who have had a complete response or a very good partial response to chemoradiation in LD or chemotherapy in ED. In case of relapse
If small cell lung cancer comes back after treatment, the following combination of drugs may be used as a salvage therapy:
Cyclophosphamide (Cytoxan, Procytox),
Doxorubicin (Adriamycin) and
Vincristine (Oncovin)
Paclitaxel (Taxol)
Irinotecan (Camptosar) Current guidelines recommend that patients who relapse > 6 months from initial therapy should be retreated with the original chemotherapy regimen. For patients who relapse in < 6 months, single-agent chemotherapy either topotecan second-line therapy, or paclitaxel can be used. Novel agents
Several newer agents, including temozolomide and bendamustine, have activity in relapsed SCLC.