Will Afirma Put an End to Diagnostic Thyroid Surgery?

A new patented genetic test seeks to reduce the number of unnecessary thyroid surgeries. Veracyte is a company that has a patent on Afirma, a genetic testing tool that extracts genetic information from thyroid needle biopsies and compares it to a database of known thyroid cancer-associated genetic mutations. Statistical rigor is applied and the specimen is then labelled either “Benign” or “Suspicious”. The company reports that a “Benign” result has a 95% negative predictive value (meaning up to 5% of these will actually be cancer still).

The first question this raises is just who will benefit? A fine needle biopsy is performed in the office based on some degree of initial suspicion of a nodule (like its size being greater than 1.5cm). Then that material is looked at under a microscope by a cytopathologist. Ideally the result comes back “benign” or “highly suspicious” (likely a cancer). However about 30% will come back with an in-between “indeterminate” result. What to do with that result depends on the preferences of the doctor, the patient, and characteristics of how the nodule looks. Still 80% of these indeterminates will turn out to be not cancer anyway.

Long story short, it results in about 75% of thyroid surgeries really serving no benefit whatsoever. And only carrying costs and risk.

Afirma takes these 30% indeterminate samples and tries to see if their gene profile is at high risk for cancer. From their studies they are able to label about half of these “benign”/low risk and half of these high risk. This in theory eliminates half of the “diagnostic” thyroid surgeries.

In the long run tests like these are likely the wave and standard of the future, for not only initial cancer diagnosis but identifying treatment options for known cancers and monitoring a cancer’s responsiveness. In the short run though we are still left with a test that says “benign” but may in fact be a cancer (up to 5% are). Not only that, but thyroid nodules are very very common, meaning that there can be expected hundreds or thousands that would be labelled “benign” but in fact be cancerous. (The unspoken good news is that thyroid cancer is usually very slow growing so waiting a few months or even a year for diagnosis usually still has a good outcome).

So we are still left making decisions based on doctor preference, patient preference/comfort level, and the overall look of the lump. And in fact, even with a benign genetic study, everyone still recommends a follow up ultrasound to look for changes in the lump.

I give a cautious thumbs up to Afirma and have started using it in selected cases.