ACTIVE SURVEILLANCE FOR SMALL THYROID CANCER

Active surveillance that incorporates three-dimensional monitoring of potential tumor growth may be a better choice for patients with small, low-risk papillary thyroid cancers (PTCs) than immediate surgery.

A cohort study of close to 300 patients undergoing active surveillance found that overall, rates of tumor growth were low and serial measurements of tumor volume could signal cancers that required therapeutic intervention.

The findings are published  in JAMA-Otolaryngology–Head & Neck Surgery.

The American Thyroid Association recently endorsed active surveillance as an alternative to traditional treatment in carefully selected patients.

The findings support the use of active surveillance for low-risk PTCs as advocated by Japanese researchers, say the researchers.  

Taking a Wait-and-See Approach

"They used to say this would only work in Japan, that nobody would do it [active surveillance] over here, but we've identified a group of patients who don't have to rush to surgery," lead author, R. Michael Tuttle, MD, Memorial Sloan Kettering Cancer Center, New York City, told Medscape Medical News.

"Many won't need surgery for years, and maybe never. We are moving away from the mindset that as soon as you get a diagnosis of thyroid cancer you have to rush and do the surgery. Now, it's more of a common sense approach, and in fact there are groups of patients in the US that this should be perfectly acceptable for. There are patients in the US who don't immediately want surgery for every little, small thyroid cancer," Dr Tuttle said.

For the study, he and his group sought to determine the natural history and growth kinetics of PTCs in 291 patients undergoing active surveillance at Memorial Sloan Kettering.

Most (n = 219 [75.3%]) were women, and the mean age was 52 years (standard deviation, 15 years).

All patients had small, low-risk tumors (≤1.5 cm) that were confined to the thyroid gland

Tumor volume was measured by ultrasonography every 6 months for the first 2 years, and then every year thereafter.

During a median active surveillance of 25 months (range, 6 to 166 months), growth in tumor diameter of 3 mm or more was seen in 11 (3.8%) patients. The cumulative incidence was 2.5% at 2 years and 12.1% at 5 years.

For volume increase greater than 50%, the cumulative incidence was 11.5% at 2 years and 24.8% at 5 years.

In addition, volume increased by more than 50% in 36 patients, was stable in 229 patients, and decreased by more than 50% in 19 patients. Volume changes could not be determined in 7 patients.

No regional or distant metastases developed during active surveillance.

Three-Dimensional Measurement Is New  

Measuring all three dimensions of the tumor volume allowed for earlier identification of tumor growth.

Dr Tuttle said that three-dimensional measurement of tumor volume is a new and important concept.

"Tumors are three dimensional, they are ellipsoids or spheres,  so when you measure a tumor three dimensionally you are measuring the height, the length, and the width. In the past we just looked at the size of the tumor, not the volume. When we saw that the tumor increased by 3 mm or more, we knew it was growing because 3 mm is the minimum you can reliably measure on ultrasound. We think it's very important to measure the volume, and most ultrasound reports provide the volume now," he said.

Tumor volume measurements identified growth 8.2 months before the tumor diameter reached the threshold of 3 mm.

Younger age at diagnosis (≤50 years) and risk factors that would make active surveillance inappropriate (extrathyroidal extension or nodal or distant metastases at presentation) were independently associated with a higher likelihood of tumor growth.

"Tumors that occurred in people in their 20s, 30s, and 40s tended to grow. You hardly saw any growth in the 60, 70, 80 age group. The Japanese have showed this as well. Tumors that were deemed inappropriate to watch also grew. We had people that we thought would be inappropriate to watch and we advised them to go to surgery, but people are adults and can do whatever they want, so when they said no to surgery I asked if we could follow them anyway. And their tumors did grow," Dr Tuttle said.

Tumor growth was exponential and the rate remained constant, he added.

"Doing the ultrasound every 6 months for the first 2 years allowed us to see whether the tumor was growing and also determine what the growth rate is. If the growth rate is fast, then surgery is the best option. But in most instances, it took me a couple years just to figure out if they were growing. Most tumors didn't grow at all, so the vast majority of these cancers are either not growing or they are growing very slowly," Dr Tuttle said.

Doctors should offer their low-risk patients the option of active surveillance, he said.

Rushing to surgery may be the right thing for an individual patient, but there's no hurry if they are willing to watch. A lot of people value their thyroid and don't want to be on thyroid hormone for life, so if they have the option of watching, they see that as a valuable option," Dr Tuttle said.

The study "provides invaluable and much-needed support to implement active surveillance protocols in the United States," writes Joseph Scharpf, MD, Head and Neck Institute, Cleveland Clinic Foundation, Ohio, in an invited commentary.

Until new prognostic and predictive markers are developed to individualize care and decrease "potential overtreatment," Dr Tuttle and colleagues' study "contributes to the body of knowledge regarding thyroid cancer, and the authors are to be commended for this excellent work that will benefit so many patients diagnosed with a cancer characterized as an epidemic of diagnosis rather than an epidemic of disease," Dr Scharpf writes.

The study was funded by the National Cancer Institute. Dr Tuttle and Dr Scharpf have disclosed no relevant financial relationships. 

JAMA Otolaryngol Head Neck Surg. Published online Augst 31, 2017. Abstract, Commentary