Molecular Testing: Tailoring Treatment by Targeting Pathways

Phillip D. Reid, MD


What is molecular testing? How it is used in cancer care?

A.  As we learn how to treat specific subtypes of cancer more accurately, molecular testing, molecular medicine and molecular diagnostics are becoming more prominent in oncology.

In the past, once a cancer was diagnosed, we determined the organ where it started, how much cancer was in the body and where it was. We have since discovered many pathways through which a cancer develops. We now need to know not only the stage, type and origin of cancer, but also the pathway through which it developed and then target that pathway.


How does the pathway concept affect therapy selection?

A.  It enhances our ability to treat the cancer, but we now need extra testing on a patient’s particular cancer cells. The great thing about molecular testing is we get an answer specific for the individual, not just for everyone, for example, with lung cancer. But it does require more time for us to find the pathway. From the patient’s standpoint, diagnosis and stage are obtained, and then sometimes we have to send off the cancer cells for extra testing, which increases the time between diagnosis and treatment. But ultimately, a better sense is provided of what drug to use and when to use it, and there’s a much greater likelihood of devising specific, effective treatment.


For which types of cancer should molecular testing be used?

A.  Molecular testing has revolutionized every major cancer diagnosis. Patients with lung and breast cancer are the best candidates, but molecular testing also is useful in colon cancer, head-and-neck and bladder cancer, and some leukemias and myelomas.


What have been the main developments over the last two to three years with molecular testing?

A.  It’s becoming easier and more standardized to get molecular testing done. A patient receives a diagnosis and his or her cancer is sent off to a lab, which evaluates all known pathways for that cancer. A specific result is received. As the patient receives therapy, sometimes the cancer changes and he or she may need a second or third biopsy one to three years after the initial diagnosis to see what’s changed in the cancer, and then the treatment changes based on that result. We now see cancer as a moving target as it progresses, and we have to recalibrate every few years so that we’re shooting that target correctly.


What should patients know about molecular testing before proceeding?

A.  After a patient receives his or her staging diagnosis, the next question is, “What subtype of lung cancer do I have and what pathway did the cancer use to develop?” The patient needs to have patience, as that extra information may not arrive for two to four weeks, but that information can increase the chances of treatment success.

Also ask about clinical trials of cancer medications before beginning therapy, because we often know about upcoming medications that are effective and possibly better than what we have right now.