Lung cancer is the number one cancer killer worldwide.
Small cell lung cancer (SCLC) is one of the two major types of lung cancer. The other is non-small cell lung cancer (NSCLC). Of the 235,760 new lung cancer cases diagnosed each year, SCLC accounts for 15% of them. Although it is less common than NSCLC, it is an aggressive form of lung cancer, and better therapies are desperately needed.
Finding Better Treatments for Small Cell Lung Cancer
Nature provides us with two lungs that work so well that we are able to live with only one. This is why it is not until the disease is in an advanced stage that symptoms present, in both Small Cell Lung Cancer (SCLC) and Non-Small Cell Lung Cancer (NSCLC). By that time, it may have spread to other organs, often to the brain, bones, liver or other lung. But there is hope – the continued research by scientists is yielding a deeper understanding of SCLC, so that better treatments can be discovered.
What is Small Cell Lung Cancer, and why is it so tough to treat?
Small cell lung cancer is one of the two major types of lung cancer – the other type being non-small cell lung cancer. SCLC is an uncontrolled proliferation of small cells in the lung. In contrast, NSCLC occurs in non-small cells like glandular cells in the case of adenocarcinoma, or squamous cells, like in squamous cell carcinoma. About 15% of all lung cancer cases are classified as SCLC, also known as oat cell cancer, and usually presents more aggressively than NSCLC.
There are a few factors that contribute to the difficulty in treating SCLC. Since lung cancer screening is generally uncommon and symptoms usually don’t present themselves until the later stages, patients don’t know that they have SCLC until it’s more difficult to treat. And once the diagnosis is known, the disease is particularly problematic because the particular mutations in SCLC suppress the natural mechanism our cells have to stop uncontrolled cell growth.
Although SCLC initially responds well to standard treatment protocol, aggressive chemotherapy, it usually has only short-term effects. It is not long before the disease returns and is even faster growing than before treatment. The life expectancy for a patient diagnosed with SCLC is under one year.
What Are The Risk Factors For Small Cell Lung Cancer?
Several risk factors increase a person’s chance of developing small cell lung cancer. Having a risk factor does not necessarily determine if a person will be affected, and even those without any risk factors may still develop the disease.
Smoking and Second-Hand Smoke
The number one risk factor for SCLC is smoking. 95% of individuals affected are current or former smokers. Heavy smokers are at particular risk for SCLC. Cigar smoke is almost as likely as cigarette smoke to cause SCLC. Chronic exposure to second-hand smoke can also increase a person’s likelihood of developing SCLC.
Radon is the leading cause of lung cancer among non-smokers. It is a radioactive gas that occurs naturally when uranium in rocks and soil breaks apart. It is not concentrated enough outdoor to present a danger but can become concentrated indoors, particularly in basements.
People who work with asbestos are much more likely to die of lung cancer. Fortunately, government regulation has greatly reduced the amount of asbestos used for commercial and industrial purposes. It may still be present in older buildings, though it is not considered harmful unless it’s released into the air.
Other Environmental Factors
Other environmental risk factors are less common but still present a risk. These include exposure to chloromethyl esters, which are used in chemical manufacturing, diesel exhaust, or air pollution.
The genetic determinants of SCLC have not received much attention because most cases are attributed to smoking. But a new study from the Center for Cancer Research has identified specific inherited mutations that increase an individual’s risk of developing SCLC.
Doctors divide SCLC into two stages, limited-stage and extensive-stage. Limited-stage disease means the cancer is contained in one part of the chest. Extensive-stage disease means that the cancer has metastasized.
Chemotherapy is used for both limited-stage and extensive-stage SCLC. Typically, this is a regimen of a platinum-based drug, like cisplatin or carboplatin, and etoposide.
Limited-stage SCLC patients will also receive radiation treatment during their first or second round of chemotherapy. Although the tumor is in one place during this stage, surgery is rarely an option.
Radiation therapy may be used to mitigate tumors before treatment for advanced SCLC.
The standard treatment for extensive-stage SCLC incorporates chemotherapy and immunotherapy. Immunotherapy encourages the body’s own immune system to recognize and attack the cancer cells.
Combination therapy, also known as multimodal therapy, is commonly used to treat small cell lung cancer. Chemotherapy, radiation, and other therapies are used in combination to increase overall survival (OS), progression free survival (PSF), and other factors in SCLC patients.
Targeted therapy is a type of personalize medicine that targets genetic mutations in cancer cells and offers treatments specific to their disease. These treatments are not widely available for SCLC patients, but recent gains have been made. Tyrosine kinase inhibitors (TKIs), like apatinib (Rivoceranib), inhibit tumor growth in SCLC patients.
Research already underway aims to give us a further understanding of SCLC subtypes and genetic factors. These discoveries will allow patients to work with doctors to find the most effective treatment for their SCLC.
Learn about the SCLC research underway
These are grim and frightening statistics. The good news is that the scientific world is giving more attention to SCLC now than ever before. Research, both in the lab and clinical trials, has led to the most significant strides in treatment in the past 30 years. Scientists are gaining a deeper understanding of the disease which can result in discovering new treatment options.
Christine M. Lovly, M.D., Ph.D. at Vanderbilt-Ingram Cancer Center notes:
“Thanks to a huge amount of preclinical work happening now and in the pipeline, we are finding better and different ways to study small cell lung cancer.”
We now know, for example, that while there is no known genetic component to the disease, new research reveals that two gene mutations – RB1 and TP53 – are always present. Other research, which has focused on immunotherapy protocols, shows promise toward successful long-term treatment. It is discoveries such as these that are bringing us closer than ever to understanding the root cause of SCLC.
According to Dr. Charles M. Rudin, MD, PhD at Memorial Sloan Kettering Cancer Center,
“We have a much better understanding of the biology of small cell lung cancer thanks to lab studies demonstrating the biological part of the disease. This translates into “therapeutic hope.”