The Rising Incidence of Thyroid Cancer Reconsidered
“The history of screening and the available evidence underscore the need for rigorous trials to ensure that screening interventions [benefit patients].”
— C. Seth Landefeld, MD
Despite a significant rise in the incidence of thyroid cancer, the U.S. Preventive Services Task Force (USPSTF), a panel of independent experts in primary care and screening, has given thyroid cancer screening a D recommendation, which is a recommendation against screening. To shed light on this and other issues that the USPSTF addresses, The ASCO Post recently spoke with USPSTF member C. Seth Landefeld, MD. Dr. Landefeld is Chairman of the Department of Medicine and the Spencer Chair in Medical Science Leadership at the University of Alabama School of Medicine, Birmingham.
USPSTF Operations
Please tell the readers a bit about the USPSTF structure and procedures.
The Task Force works to improve the health of all Americans by making evidence-based recommendations about clinical preventive services such as screenings, counseling services, and preventive medications. The Task Force includes about 16 members who are expert in primary and preventive care and in evaluation of clinical information. Recommendations are reached by a process that involves presentation and discussion of relevant data, formulation of recommendations, and voting on final recommendations. With each topic we look at, there are usually four or five members from the Task Force who are identified as leads, and then we have spokespersons for those leading the discussion. In the case of thyroid screening, I am one of the spokespersons. The final decision is reached by a majority vote, and by and large, most of the decisions are arrived at without controversy within the group.
Trends and Causes
The incidence of thyroid cancer has more than doubled since the 1970s, and in women, it is the cancer with the fastest-growing number of new cases. What are your thoughts on this trend?
Yes, the incidence of thyroid cancer in the developed world has increased. In the United States, the incidence has gone up about 3 times over the past 15 years, and in other developed countries, it has grown about 2 to 4 times. In South Korea, the incidence has increased about 15-fold over the past 15 years or so. That said, we did not study the cause of this dramatic increase in the incidence of thyroid cancer.
It is a great topic for study. There has been suspicion that there is a relationship between increased screening and increased incidence, and there was a nice discussion in The New England Journal of Medicine on that topic led by Ahn et al.1 These authors found the increase was due to discovering small papillary cancers, which led them to conclude that increased screening caused the rise in incidence. Another important finding from those data was that the actual death rate from thyroid cancer had not changed over that same period.
Influence on Task Force Recommendations
Has the increased incidence in thyroid cancer affected the Task Force’s decision-making process?
No. For the past 20 years or so, the Task Force has given thyroid cancer screening a D recommendation, which recommends against the use of screening in asymptomatic people in this setting. Then, as now, the Task Force determined that the potential harms associated with population-based screening far outweigh the benefits. Many of the cancers detected on screening are small nodules that would not affect long-term survival, and treatment can have adverse effects without benefits for patients.
Prevention Efforts
The USPSTF has been at the forefront of many public and political debates about the value of certain cancer screening tests. From your perspective as an active member of the Task Force, where do we stand in our efforts to prevent cancer?
We believe that screening and other prevention modalities have tremendous potential to improve health outcomes in the country. The history of screening and the available evidence underscore the need for rigorous trials to ensure that screening interventions actually have value in the health-care system. One of the great successes along these lines is in cervical cancer, where screening and human papillomavirus (HPV) vaccination programs have greatly decreased morbidity and mortality from this one very deadly disease in the United States. There are other areas such as lung cancer screening, where we have only recently determined the benefits of screening.
Preventing cancer is a huge challenge. We saw a major success in cancer prevention with the war on tobacco, which led to a drop in smoking rates in this country from about 50% in the 1950s to about 15% currently. We’ve also seen the introduction of HPV vaccinations, which are having a great effect on cervical cancer prevention. But for many cancers, we still do not have reliable prevention maneuvers, so there’s a lot of work needed to be able to identify the underlying causes of these malignancies before we can develop methods of prevention. ■