Malignant pleural mesothelioma, a rare and deadly cancer that attacks the lining of the lungs, presents a poor chance of recovery and currently has no cure. As such, treatment options are limited and often difficult, depending on the severity of the condition.
Most patients’ only hope is to improve prognosis and reduce symptoms through first-line avenues including surgery (such as pleurectomy), radiation therapy, and chemotherapy. When these options don’t work, patients may need to pursue experimental therapies by participating in clinical trials. One such promising alternative currently in testing is immunotherapy.
In a new study, researchers looked at the potential of an existing immunotherapy drug, pembrolizumab, as a second-line treatment for mesothelioma. Dr. Evan Alley, the study’s lead author, and colleagues assessed data from an international clinical trial testing the drug’s effectiveness on advanced-stage tumors.
Possible Evidence of Long-Term Disease Control
Of the 25 patients assessed – who were given a dose of pembrolizumab every 2 weeks – 14 patients’ tumors decreased in size. As a result, the average overall survival was 18 months, 6 of which were progression-free. Sadly, 14 of the 25 patients have died since the trial began 2 years ago – but 4 are still receiving treatment.
These results show positive developments around what may be an approved second-line therapy in the future. Alley, along with researchers at the University of Pennsylvania’s Penn Presbyterian Medical Center, concluded that pembrolizumab is well-tolerated, involves few adverse reactions, and has encouraging anti-tumor effects. “Most patients who receive a second-line therapy have a life expectancy of about 6 or 7 months,” said Dr. Alley. “So to have four patients still ongoing at 2 years is very encouraging."
The road to a cure, however, is a long one requiring much more investigation – and isn’t certain to have an end.
The Sheer Destructiveness of Mesothelioma
Mesothelioma is an aggressive cancer that afflicts the mesothelium, or lining of the organs, in most areas of the body. The disease is found in the lungs in 90 percent of cases, but also commonly found in the heart and abdomen.
The disease’s only known cause is asbestos, a fibrous, carcinogenic mineral. When asbestos is inhaled or ingested into the body, its microscopic fibers build up within mesothelium and, over several decades, begin to form tumors. In fact, the symptoms of mesothelioma don’t appear until up to 50 years after first exposure to asbestos. By the time the cancer is diagnosed, its stage is such that patients rarely survive longer than one year.
Today, around 3,200 Americans are diagnosed with mesothelioma annually – and asbestos exposure is nothing new. For most of the 20th century, the mineral was widely used to construct buildings and manufacture products, as it was known back then to have useful properties. Most importantly for industry, asbestos was cheap. Although manufacturers were well aware of its dangers, they opted to keep them hidden in exchange for generous profits.
The Environmental Protection Agency (EPA) has since exposed asbestos-related disease risks to the public and introduced partial bans of its use in the U.S. Despite all the evidence pointing toward the need for a complete ban, however, it still hasn’t happened. Asbestos remains concealed within countless products, structures, and homes built before the 1990s.
With so much risk of exposure and so many people already dying from asbestos-related disease, prevention is not yet possible thanks to slow-moving regulatory efforts. Medical treatment, and seeking compensatory damages to cover costs, is the only solution.
How Does Immunotherapy Work?
As opposed to more conventional methods, immunotherapy is an emerging treatment designed to build the body’s own natural defenses against cancer and other chronic diseases. The antibody drug works by either stimulating the immune system to react more effectively to cancer cells or by providing man-made immune system components.
In the last few decades, immunotherapy has become recognized has an important, and generally very safe, part of cancer therapy. Immunotherapy drugs have already succeeded in making previously-thought “incurable” cancers curable, and new drugs are persistently tested.
Of course, the treatment works better on some types of cancer than others. Its effectiveness for mesothelioma is very much still under question. Thus, clinical trials are not just an important treatment option for the individual – they are an invaluable form of research for the thousands of people who will be diagnosed with mesothelioma in the future.
More studies are needed to support the Penn Presbyterian Medical Center’s findings, and many other clinical trials remain ongoing. Dr. Alley noted that he hadn’t seen any potential for long-term management of mesothelioma before this pembrolizumab study, which shows a move in the right direction. But, he said, “we need to better understand what we can do next to make immunotherapy more effective for more patients.”
