Diagnosing Lung Cancer

If lung cancer is suspected as a result of a screening procedure (CT, MRI or PET scan), a small piece of tissue from the lung must be examined under a microscope to look for cancer cells. Called a biopsy, this procedure can be performed in different ways. In some cases, the doctor passes a needle through the skin into the lungs to remove a small piece of tissue; this procedure is often called a needle biopsy.

In other cases, a biopsy may be done during a bronchoscopy. With the patient under sedation, the doctor inserts a small tube through the mouth or nose and into the lungs. The tube, which has a light, small camera and a surgical instrument on the end, allows the doctor to see inside the lung and remove a small tissue sample.

Recently, the FDA approved the first liquid biopsy for lung cancer which utilizes free floating DNA in the bloodstream for analysis. Tumors shed this DNA material into the blood as the cells within them die. The DNA is collected and analyzed allowing doctors to get a “snapshot” of the genetic mutations and other irregularities that drive a tumor’s growth. Liquid biopsies offer some important advantages, in that they are non-invasive, inexpensive, provide timely results and are easily repeatable.

If cancer cells are found in the tissue sample, a genetic test may be performed. Genetic testing, which may also be referred to as “molecular profiling or mutation profiling,” allows doctors to look inside tumor cells for gene mutations or changes that may have caused them to be cancerous. This testing helps a doctor develop a treatment plan for the patient.

Pathologists (doctors who identify diseases by studying cells and tissues under a microscope) and geneticists (scientists with special training in the study of genes) can give your doctor the information he or she needs to tailor a treatment that will be most effective. These specialists can determine the distinct characteristics of each lung cancer: the tumor type (NSCLC or SCLC, for example); how far it has advanced (its stage); and the mutations (gene changes) that cause or “drive” the cancer.

As the importance of understanding the genetic characteristics of a lung tumor cell has increased, pathologists and pulmonologists are encouraging that reflex testing be carried out. Reflex testing involves performing testing for currently known lung cancer mutations or drivers at the same time that the diagnostic testing is carried out, irrespective of the patient’s tumor staging.