Small cell lung cancer is the most aggressive type of lung cancer. Unlike its far more common counterpart, non-small cell lung cancer, treatment with immunotherapy drugs hasn’t yet been approved for small cell lung cancer, but some early findings in clinical trials suggest this type of treatment may have potential.
Small cell lung cancer gets its name from its small, oval-shaped cancer cells that can be seen under a microscope. Compared with non-small cell lung cancer, small cell lung cancer – which is almost always associated with tobacco smoking – spreads earlier and often is diagnosed too late for surgery to be considered, leaving chemotherapy and radiation as the only standard option. While the disease usually responds initially to treatment, it almost always relapses, and odds of long-term survival are minimal. Unlike non-small cell disease, small cell lung cancer does not respond well to targeted drug treatments.
In the past few years, immunotherapies – treatments that use a patient’s immune system to fight cancer – have improved outcomes for some patients with advanced malignancies such as melanoma and non-small cell lung cancer, resulting in stable disease or tumor shrinkage that in some cases has lasted for more than two years in the case of non-small cell lung cancer.
Some scientists believe immunotherapy might work in this disease because the cancer cells have a lot of DNA changes called mutations, which can lead to the formation of neoantigens – molecules that can potentially trigger the body’s immune system to fight the cancer. “There is a suggestion of benefit for a sub-set of patients with small cell lung cancer,” says Jacob Sands, MD, a thoracic oncology specialist at Dana-Farber.
Data from an ongoing international clinical trial called CheckMate 032, testing two immunotherapy drugs in patients with small cell lung cancer, point to an encouraging response rate when the drugs nivolumab (Opdivo) and ipilimumab (Yervoy) were given together to patients who had a high tumor mutational burden (TMB). TMB means the patients had many mutations in their tumors, which may increase the likelihood that immunotherapy will be effective.
An October 2017 report from the trial said that 62 percent of such patients were alive at one year following the start of treatment, compared to 20 and 23 percent of patients with medium or low levels of TMB. However, the overall response rate in this trial, was 11 percent for those treated with nivolumab alone and 22 percent when treated with nivolumab and ipilimumab.
Although a small number of patients experienced significant shrinking of small cell lung cancer, the fact that some had such benefit provides some hope that researchers will be able to find more effective ways to use patients’ own immune systems to combat this deadly form of lung cancer.