Small cell carcinoma of the lung overview

Overview
Small cell carcinoma of the lung is an anaplastic, highly malignant, and usually bronchogenic carcinoma composed of small ovoid cells with scanty neoplasm. It is characterized by a dominant, deeply basophilic nucleus, and absent or indistinct nucleoli. There are admixtures of small cell lung carcinoma with other types of lung cancer. Small cell carcinomas are distinguished by their distinctive biological features, response to chemotherapy and radiotherapy, and by their nearly universal tendency to develop overt or subclinical metastases, which frequently eliminates surgery in most patients.

Without treatment, small cell lung cancer (SCLC) has the most aggressive clinical course of any type of pulmonary tumor, with median survival from diagnosis of only 2 to 4 months. Compared with other cell types of lung cancer, SCLC has a greater tendency to be widely disseminated by the time of diagnosis but is much more responsive to chemotherapy and radiation therapy.

Because patients with small cell lung cancer tend to develop distant metastases, localized forms of treatment, such as surgical resection or radiation therapy, rarely produce long-term survival. With incorporation of current chemotherapy regimens into the treatment program, however, survival is unequivocally prolonged, with at least a 4- to 5-fold improvement in median survival compared with patients who are given no therapy. Furthermore, about 10% of the total population of patients remains free of disease during 2 years from the start of therapy, the time period during which most relapses occur. Even these patients, however, are at risk of dying from lung cancer (both small- and non-small cell types). The overall survival at 5 years is 5% to 10%.

Limited-stage disease
At the time of diagnosis, approximately 30% of patients with SCLC will have tumor confined to the hemithorax of origin, the mediastinum, or the supraclavicular lymph nodes. These patients are designated as having limited-stage disease, and most 2-year disease-free survivors come from this group. In limited-stage disease, median survival of 16 to 24 months with current forms of treatment can reasonably be expected. A small proportion of patients with limited-stage disease may benefit from surgery with or without adjuvant chemotherapy; these patients have an even better prognosis.

Extensive-stage disease
Patients with tumors that have spread beyond the supraclavicular areas are said to have extensive-stage disease and have a worse prognosis than patients with limited-stage disease. Median survival of 6 to 12 months is reported with currently available therapy, but long-term disease-free survival is rare.