Access, excess, and overdiagnosis: the case for thyroid cancer

Abstract

The incidence of thyroid cancer in women is increasing at an epidemic rate. Numerous studies have proposed that the cause is increasing detection due to availability and use of medical diagnostic ultrasound. Our objective was to compare rates of diagnosis across different health-care regions to rates of diagnostic tests and to features of both health and access of the regional populations. This is a population-based retrospective ecological observational study of 12,959 patients with thyroid cancer between January 1, 2000 and December 31, 2008 in Ontario Canada based on the health-care utilization regions (Local Health Integration Networks) of the province of Ontario Canada. We found that some regions of Ontario had four times the rates of diagnosis of thyroid cancer compared to other regions. The regions with the highest use of discretionary medical tests (pelvic ultrasound, abdominal ultrasound, neck ultrasound, echocardiogram, resting electrocardiogram, cardiac nuclear perfusion tests, and bone scan), highest population density, and better education had the highest rates of thyroid cancer diagnoses. Differences in the rates of the ordering of discretionary diagnostic medical tests, such as diagnostic ultrasound, in different geographic regions of Ontario lead to differences in the rates of diagnosis of thyroid cancer.

Thyroid cancer incidence in Canada: a national cancer registry analysis

“…However, between 1992 and 2012, incidence rates varied dramatically between provinces and even between regions within a province, as reported in Ontario. 15 In 2012, the highest incidence rates were in Ontario; BC had the lowest rates, at about half those in Ontario. The age-specific incidence curve had also dramatically changed, especially for women, and its shape differed among provinces.…”

“…25 This increasing use of imaging is mirrored by the increasing rates of thyroid cancer diagnosis, with the fourfold variation in diagnostic rates between regions correlating with patterns in the use of ultrasound, especially of the neck. 15 Kent and colleagues 22 found that the increase of thyroid cancer in Ontario is mainly due to small differentiated tumours, with the greatest increase in tumours less than 2 cm, considered nonpalpable and subclinical. These findings support the hypothesis that the increased incidence rates of thyroid cancer are due to overdiagnosis, with cases discovered incidentally in small tumours.…”

Temporal Trends in Thyroid Cancer Incidence in California—Letter

“…TC incidence is also increasing in Ontario, with significant regional variability (2). National Canadian data have suggested increased TC incidence in regions with the highest prevalence of foreign-born individuals (3).…”

Thyroid Cancer ? South American Experience

“…However, claiming that one or other trend totally accounts for the rise in the incidence of cancer would be to neglect the importance of the counterpart; so the most feasible explanation is that both trends are additive and complementary [51][52][53]. Other reasons may explain the marked increase in the frequency of papillary carcinoma, including:…”