When faced with the possibility of cancer, one of the steps in a lengthy diagnostic process is typically a biopsy. This often painful procedure requires retrieving a piece of the tumor for study to determine its origin and characteristics. There two primary ways to obtain this tissue:
- Needle biopsy: Collects a small piece of the tumor by extracting it through a needle.
- Endoscopic biopsy: Uses an instrument with a small camera and a device for retrieving tissue into the patient, usually via small cuts near the area being examined.
Unfortunately, these techniques may not always obtain enough of the tissue necessary to make a diagnosis. As a result, more invasive procedures may be needed to collect a larger sample. In such cases, doctors may have to perform surgery and open the abdomen or chest in order to access the tumor and retrieve tissue for study.
Once the tissue has been retrieved, a pathologist (doctor who studies tissue samples to diagnose illnesses) examines it under the microscope and performs tests on it to determine what type of cancer or other disease is in the tissue and what might treat it. Biopsies may also be done during treatment to track the success or lack thereof. However, the more invasive the biopsy, the less likely it is to be repeated.
The Need for a Less Invasive Procedure
Mesothelioma is almost always caused by asbestos exposure, and it has a long “latency” period – the time between the asbestos exposure and the first appearance of the symptoms of mesothelioma. By the time mesothelioma is found, it is often advanced and difficult, if not impossible, to treat, resulting in a generally poor prognosis for the disease. The best way to improve that prognosis is to find a way to detect mesothelioma earlier.
In addition to using biopsies as a diagnostic test, biopsies can also be used during treatment to tell doctors whether the therapy is working and, if it is, at what point it quits working. This allows doctors to adjust the treatments being administered and provides an opportunity to try different treatments – or possibly switch to palliative care.
Unfortunately, given the invasiveness of biopsies, it is not always possible or advisable to perform a biopsy until it’s deemed necessary. Also, most patients are unable or unwilling to undergo the numerous invasive biopsies that may be required to monitor ongoing treatment.
Therefore, researchers have been looking for other techniques to diagnose and monitor cancer. Recently, they have developed what is generically called the “liquid biopsy,” that is, a new blood test for cancer. Results for a recent study looking at liquid biopsy as an effective diagnostic tool for cancer were presented at the Chicago meeting of the American Society of Clinical Oncology (ASCO) in June.
How Does a “Liquid Biopsy” Work?
With a liquid biopsy, blood is drawn as it is for any blood test, meaning that the discomfort and inconvenience to the patient is relatively minimal – certainly less so than endoscopic biopsies or exploratory surgeries. The blood is then analyzed for DNA mutations or changes that could indicate cancer.
Cancer occurs when the DNA in a cell is changed such that the signals inside the cell that regulate cell division and cell death fail to work, and as a result, cells division runs rampant. Researchers have found that cancer patients have DNA from the tumors in their bloodstream, and that mutations in that DNA are almost always the same as the mutations found at the tumor site.
Thus, by analyzing the blood for mutated cells, it may be possible to determine not only whether someone has cancer, but what type of cancer they have.
What Liquid Biopsy Means for Mesothelioma
While many doctors believe that, at least for the near future, biopsies of the actual tumors will still be the most accurate way of getting an initial diagnosis, liquid biopsies can be done on people who are unable to have surgery due to the cancer or other health conditions. This includes many mesothelioma patients, who are generally older individuals and may have poor overall health simply due to aging.
Also, cancer cells have a habit of continuing to change, or mutate, such that a treatment that is initially successful quits working. Many cancer treatments today are targeted, meaning that pathologists study the tumor tissue to pick the best treatment such that one person’s lung cancer could be treated differently than another person’s because of the DNA in the tumor. The liquid biopsy makes it possible to regularly monitor the tumor’s DNA and see if the treatment is successful or if the cancer is changing in a way that makes another treatment more likely to be successful.
While liquid biopsies are not currently in regular use, the possibility is there that they could become a screening method for those at high risk of developing mesothelioma. If mesothelioma was caught earlier, the hope is that new, more effective treatments could be developed.