In Cancer Medicine, Precision Is Worth the Wait

Mark G. Kris, MD


April 20, 2020

This transcript has been edited for clarity.

Editor's note: This commentary is the second in a series on the wait time between cancer being diagnosed and treatment being initiated, and its effect on both patients and physicians.

Hello. I'm Mark Kris from Memorial Sloan Kettering.

I would like to continue to discuss the wait time between a cancer diagnosis being made and precision therapy being initiated.

Just as oncologists each have their own way of taking care of patients from the initial visits through treatment, pathologists have their own way of doing their jobs. Working as a team with our pathologists is critical. We have to understand their processes and how they work.

Part of our responsibility is to ensure that the appropriate tests are ordered. A pathologist may receive a specimen but not know what tests are needed for that patient. They need to know the tests and have them ordered. When there are limited tissues, the pathologist needs to know the most critical pieces of information we have so they can prioritize its use.

Tissue- vs Blood-Based Testing

What about blood-based testing? For some patients it can be helpful, especially for those with common mutations, including EGFR and ALK mutations.

However, inherent limitations exist to this testing. First, when you compare a tissue result with a blood result, you get an answer about 75% of the time; for the other roughly 25%, if you don't get an answer from the blood, the answer could still be in the tissue. That's important to know. Second, a blood test cannot always show what we're looking for, like histologic change. Those of you who work in the EGFR space know that a morphologic transformation can happen to small cell lung cancer or squamous cell cancer that can only be gleaned from a morphologic test, not a blood test. Lastly, blood tests have tiny amounts of DNA. The tests are not created in such a way that the different aberrations needed to assay are available with the required accuracy.

Although blood tests can be helpful and are a good adjunct, they can miss histologic changes. They are only about 75% as good as testing the tissue. They are not all configured to find all of the molecular aberrations that we need to treat patients.

Our Job Is to Guide Patients

Let's also not forget the patients, who are first and foremost in our minds and the most important group we need to pay attention to. The diagnosis of cancer is overwhelming with so much information. Tissue interrogation is unexpected and is not something that patients have any personal experience with. It is our job to guide them.

We must explain the process to patients, in that we don't immediately go to a microscope with a pathology slide and say, "Yes, this is lung cancer." They should understand that after submission to the pathology department, pathologists go through their own processes and may want additional testing to make the most precise diagnosis. You need to explain to patients that it all takes time.

It is also important for patients to understand the time involved with molecular testing, particularly next-generation sequencing. After the tissue goes to the molecular lab and through the sequencer, a pathologist reviews the raw data for mutations or aberrations that are of sufficient magnitude and certainty to say whether a fusion or a mutation is present.

The bottom line is that we must meet with our patients and help manage their expectations of the wait time involved in a cancer diagnosis being made.

Mark G. Kris, MD, is chief of the thoracic oncology service and the William and Joy Ruane Chair in Thoracic Oncology at Memorial Sloan Kettering Cancer Center in New York City. His research interests include targeted therapies for lung cancer, multimodality therapy, the development of new anticancer drugs, and symptom management with a focus on preventing emesis.

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