Lung cancer – two diseases

Lung cancer is often thought of as one type of cancer, however there are different types of lung cancer: small cell lung carcinomas (SCLCs) and non-small cell lung carcinomas (NSCLCs).

15% of lung cancer patients have SCLCs, most of whom are smokers.  This type of cancer is highly malignant and often spreads to other areas of the body before the patient is diagnosed with the cancer.  This can lead to the diagnosis of cancer without finding the source of the cancer.  Because all the blood passes through the lungs, part of the SCLC can easily break away and be spread anywhere in the body, usually the lymph nodes or the liver.

SCLCs grow quickly and are almost always inoperable because the cancer is so advanced.  Patients with SCLCs have a poor prognosis, but often respond well to chemotherapy, which can extend their lives by several months.  Generally patients with SCLCs live for only a few months because by the time they are diagnosed the cancer has metastasised (spread to other parts of the body).  The two-year survival rate for patients with advanced SCLCs is less than 5%, but if caught early it is 20%.  Taraceva, a targeted drug normally used to treat NSCLCs has been seen to extend life expectancy by several months, and drug trials are underway for patients with SCLCs.

The other 85% of lung cancer sufferers have NSCLCs, which can then be subdivided into 5 different types of cancer: Squamous (42% of NSCLCs); Adenocarcinoma (39% of NSCLCs); Large cell (8% of NSCLCs); Carcinoid tumours (7% of NSCLCs) and Bronchoalveolar cell (4% of NSCLCs).

Patients with NSCLCs tend to have a better prognosis than SCLCs with 5 year survival rates of 11-15% for squamous NSCLC and Large cell NSCLC; and 17% for Adenocarcinoma NSCLC.  This compares to less than 10% for SCLCs with a median life expectancy of 6-12 months with treatment.  Without treatment this rapidly declines to 2-3 month median life expectancies.