Randomization to Screening for Prostate, Lung, Colorectal and Ovarian Cancers and Thyroid Cancer Incidence in Two Large Cancer Screening Trials

Abstract

BackgroundThyroid cancer incidence has increased significantly over the past three decades due, in part, to incidental detection. We examined the association between randomization to screening for lung, prostate, colorectal and/or ovarian cancers and thyroid cancer incidence in two large prospective randomized screening trials.MethodsWe assessed the association between randomization to low-dose helical CT scan versus chest x-ray for lung cancer screening and risk of thyroid cancer in the National Lung Screening Trial (NLST). In the Prostate Lung Colorectal and Ovarian Cancer Screening Trial (PLCO), we assessed the association between randomization to regular screening for said cancers versus usual medical care and thyroid cancer risk. Over a median 6 and 11 years of follow-up in NLST and PLCO, respectively, we identified 60 incident and 234 incident thyroid cancer cases. Cox proportional hazards regression was used to calculate the cause specific hazard ratios (HR) and 95% confidence intervals (CI) for thyroid cancer.ResultsIn NLST, randomization to lung CT scan was associated with a non-significant increase in thyroid cancer risk (HR = 1.61; 95% CI: 0.96–2.71). This association was stronger during the first 3 years of follow-up, during which participants were actively screened (HR = 2.19; 95% CI: 1.07–4.47), but not subsequently (HR = 1.08; 95% CI: 0.49–2.37). In PLCO, randomization to cancer screening compared with usual care was associated with a significant decrease in thyroid cancer risk for men (HR = 0.61; 95% CI: 0.49–0.95) but not women (HR = 0.91; 95% CI: 0.66–1.26). Similar results were observed when restricting to papillary thyroid cancer in both NLST and PLCO.ConclusionOur study suggests that certain medical encounters, such as those using low-dose helical CT scan for lung cancer screening, may increase the detection of incidental thyroid cancer.

Benign and Malignant Thyroid Incidentalomas Are Rare in Routine Clinical Practice: A Review of 97,908 Imaging Studies

“…Discrepancies between rates of incidental thyroid nodules on dedicated review or ultrasound screening compared to those found in clinical practice have been previously described in a review of both the National Lung Screening Trial, and the Prostate Lung Colorectal and the Ovarian Cancer Screening Trial data (16). Additionally, we found the rate of clinically reported thyroid incidentalomas varied greatly based on imaging modality, with neck ultrasounds providing a much higher rate of detection than other cross-sectional imaging methods (Table 2).…”

The Breast–Thyroid Cancer Link: A Systematic Review and Meta-analysis

“…It should be noted, however, that while thyroid cancer-specific screening leads to increased rates of detection, the same does not appear to be true for screening for other types of malignancies and incidental thyroid nodules are only rarely reported on routine cross-sectional imaging studies (47, 48). Despite a clear correlation between non-thyroid or breast screening and increased diagnosis and lack of directed screening for breast or thyroid cancer in survivors of the other, it is possible that this increase in surveillance or improved compliance is responsible for higher rates of detection of secondary malignancies.…”

Position paper from the Japan Thyroid Association task force on the management of low-risk papillary thyroid microcarcinoma (T1aN0M0) in adults

“…A greater number of opportunities for examinations, such as thyroid US, is reportedly associated with a greater incidence of PTC, but most are small, unpalpable carcinomas [15]. In addition, computed tomography (CT), magnetic resonance imaging (MRI) and fluorodeoxyglucose (FDG)-positron emission tomography (PET)/CT carried out for the purpose of screening or evaluation of other diseases has led to the increased detection of incidental thyroid carcinoma [13,[50][51][52][53].…”