Small Cell Lung Cancer

There are two main types of lung cancer: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). While this document will address some common issues with both types, the focus will be on small cell lung cancer. Non-small cell lung cancer will be addressed separately.

Most lung cancers, whether SCLC or NSCLC, tend to start in the bronchi but lung cancer can originate from other locations such as trachea (wind pipe), bronchioles, or alveoli. Lung cancers are thought to start as pre-cancerous changes within the lungs and then develop into lung cancer over many years. The pre-cancerous changes occur at the cellular level so they cannot be seen by x-rays, magnetic resonance imaging (MRI), or computed tomography (CT or CAT) scans, nor will they cause symptoms.

The pre-cancerous changes may progress to cancer over time. As lung cancer develops and grows, new blood vessels form to nourish and feed the lung tumor. Eventually the tumor will grow large enough to be seen by imaging scans. The problem is that lung cancers tend to break off and move to distant organs (metastasize) and may have already done so by the time they are discovered on imaging scans. Both blood supply and even more frequently, the lymphatic system may carry tumor cells to distant organs which result in the formation of new tumors at these sites.

Small cell lung cancer, named for the size of the cells that form these lung cancers, comprise about 10-15% of all lung cancers. While only a small percentage of lung cancers are small cell lung cancer, the overwhelming majority of these cancers are caused by smoking. Smoking is almost always the primary cause of SCLC and is sometimes called “smoker’s cancer”. It is very rare for someone who has never smoked or never had prolonged exposure to second hand smoke to have small cell lung cancer.
Small cell lung cancer usually starts in the bronchi near the center of the chest and SCLC is one of the most aggressive types of cancer and spreads rapidly & widely forming additional large tumors in lymph nodes, bones, adrenal glands, liver & brain. In the United States, there are over 200,000 new cases of small cell lung cancer diagnosed and greater than 150,000 deaths annually from SCLC. Without treatment, the lack of symptoms until larger tumors are established and the aggressive course of metastases of SCLC provides only a 2 – 4 month average survival period from the time of diagnosis for small cell lung cancer patients.

At diagnosis, about 30% of small cell lung cancer patients have their SCLC confined to their lung origin, chest cavity (mediastinum), or supraclavicular lymph nodes (between the shoulder & neck). These lung cancer patients are designated with limited-stage disease and most 2-year survivors will be from this group. Some small cell lung cancer patients with limited-stage disease may benefit from surgical resection of a localized tumor and if so, may have a better prognosis. SCLC patients with disseminated tumor(s) are designated with extensive-stage disease and will have a worse prognosis than those with limited-stage disease. Average survival with therapy may be 6-12 months, but long-term survival is rare.

As with most cancers, prognosis of patients with small cell lung cancer is based upon multiple factors. Favorable indicators include otherwise good health and able to walk and move about, female and limited-stage disease. Patients who have additional tumor involvement of the central nervous system (brain & spinal cord) or liver have a worse prognosis than those SCLC patients with tumor involvement elsewhere.

 Due to the very quick spread of small cell lung cancer, localized treatment such as surgery or radiation therapy is rarely a singular treatment option. However, when chemotherapy is added to the treatment program, survival is prolonged with a 4 to 5-fold improvement when compared to small cell lung cancer patients who do not receive any therapy. While the survival times with chemotherapy do noticeably improve, there is still no cure. Approximately 10% of SCLC patients receiving treatment will remain free of disease symptoms for up to 2 years from the start of therapy. The aggressive nature of small cell lung cancer, however, usually leads to relapse and the overall survival at 5 years is only 5-10%.
Despite many improvements in both diagnosis & therapy for small cell lung cancer, current prognosis for any patient with SCLC is not usually good. All patients are eligible for clinical trials and should consider these as a treatment option in conjunction with current regimens.

TREATMENT
North Central Cancer Treatment Group is currently enrolling patients in a randomized, placebo controlled Phase II study for NTX-010 in the treatment of extensive-stage small cell lung cancer. Treatment is administered as a single 100mL intravenous infusion over 1 hour. NTX-010 is a naturally occurring virus that has shown to be very effective in treating SCLC tumors in pre-clinical studies. Patients previously treated with NTX-010 have only had minimal flu-like symptoms lasting 2-3 days and no typical chemotherapy side effects.