Randomization to screening for prostate, lung, colorectal and ovarian cancers and thyroid cancer incidence in two large cancer screening trials

Risk of thyroid cancer in a lung cancer screening population of the National Lung Screening Trial according to the presence of incidental thyroid nodules detected on low-dose chest CT

PURPOSE

This study evaluated thyroid cancer risk in a lung cancer screening population according to the presence of an incidental thyroid nodule (ITN) detected on low-dose chest computed tomography (LDCT).

METHODS

Of 47,837 subjects who underwent LDCT, a lung cancer screening population according to the National Lung Screening Trial results was retrospectively enrolled. The prevalence of ITN on LDCT was calculated, and the ultrasonography (US)/fine-needle aspiration (FNA)-based risk of thyroid cancer according to the presence of ITN on LDCT was compared using the Fisher exact or Student t-test as appropriate.

RESULTS

Of the 2,329 subjects (female:male=44:2,285; mean age, 60.9±4.9 years), the prevalence of ITN on LDCT was 4.8% (111/2,329). The incidence of thyroid cancer was 0.8% (18/2,329, papillary thyroid microcarcinomas [PTMCs]) and was higher in the ITN-positive group than in the ITN-negative group (3.6% [4/111] vs. 0.6% [14/2,218], P=0.009). Among the 2,011 subjects who underwent both LDCT and thyroid US, all risks were higher (P<0.001) in the ITNpositive group than in the ITN-negative group: presence of thyroid nodule on US, 94.1% (95/101) vs. 48.6% (928/1,910); recommendation of FNA according to the American Thyroid Association guideline and Korean Thyroid Imaging Reporting and Data System guideline, 41.2% (42/101) vs. 2.4% (46/1,910) and 39.6% (40/101) vs. 1.9% (37/1,910), respectively.

CONCLUSION

Despite a higher risk of thyroid cancer in the LDCT ITN-positive group than in the ITN-negative group in a lung cancer screening population, all cancers were PTMCs. A heavy smoking history may not necessitate thorough screening US for thyroid incidentalomas.

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

The incidence of thyroid carcinoma has been increasing worldwide. This is interpreted as an increase in the incidental detection of papillary thyroid microcarcinomas (PTMCs). However, mortality has not changed, suggesting overdiagnosis and overtreatment. Prospective clinical trials of active surveillance for low-risk PTMC (T1aN0M0) have been conducted in two Japanese institutions since the 1990s. Based on the favorable outcomes of these trials, active surveillance has been gradually adopted worldwide. A task force on the management of PTMC in adults organized by the Japan Thyroid Association therefore conducted a systematic review and has produced the present position paper based on the scientific evidence concerning active surveillance. This paper indicates evidence for the increased incidence of PTMC, favorable surgical outcomes for low-risk PTMC, recommended criteria for diagnosis using fine needle aspiration cytology, and evaluation of lymph node metastasis (LNM), extrathyroidal extension (ETE) and distant metastasis. Active surveillance has also been reported with a low incidence of disease progression and no subsequent recurrence or adverse events on survival if conversion surgery was performed at a slightly advanced stage. Active surveillance is a safe and valid strategy for PTMC, because it might preserve physical quality of life and reduce 10-year medical costs. However, some points should be noted when performing active surveillance. Immediate surgery is needed for PTMC showing high-risk features, such as clinical LNM, ETE or distant metastasis. Active surveillance should be performed under an appropriate medical team and should be continued for life.

Selenium in colorectal and differentiated thyroid cancer

The current review aims to provide a brief overview of developments in the research field of selenium and cancer. The focus is on two tissues that show a rising incidence of cancer cases each year, namely the colon and the thyroid. Effects of adequate selenium concentrations on tumor development are most probably mediated by selenoproteins. However, the role of selenoproteins changes during the carcinogenic process as well as in a tissue-specific manner. During the initiation phase, selenoproteins protect cells from oxidative DNA damage and thus appear to inhibit tumor development, whereas, in already existing tumor cells, selenoproteins might, on the contrary, support their growth and thus reduce the survival probability of patients.

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

Rates of thyroid cancer in women with a history of breast cancer are higher than expected. Similarly, rates of breast cancer in those with a history of thyroid cancer are increased. Explanations for these associations include detection bias, shared hormonal risk factors, treatment effect, and genetic susceptibility. With increasing numbers of breast and thyroid cancer survivors, clinicians should be particularly cognizant of this association. Here, we perform a systematic review and meta-analysis of the literature utilizing PubMed and Scopus search engines to identify all publications studying the incidence of breast cancer as a secondary malignancy following a diagnosis of thyroid cancer or thyroid cancer following a diagnosis of breast cancer. This demonstrated an increased risk of thyroid cancer as a secondary malignancy following breast cancer [OR = 1.55; 95% confidence interval (CI), 1.44-1.67] and an increased risk of breast cancer as a secondary malignancy following thyroid cancer (OR = 1.18; 95% CI, 1.09-1.26). There is a clear increase in the odds of developing either thyroid or breast cancer as a secondary malignancy after diagnosis with the other. Here, we review this association and current hypothesis as to the cause of this correlation.

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

PURPOSE

Thyroid nodules incidentally identified on imaging are thought to contribute to the increasing incidence of thyroid cancer. We aim to determine the true rate of incidental thyroid nodule reporting, malignancy rates of these nodules, and to compare these findings with rates of detection by dedicated radiology review.

METHODS

A cross-sectional analysis was done to determine the prevalence of thyroid nodules in radiologist reports by analyzing all reports for CT, PET, and MRI scans of the head, neck, and chest as well as neck ultrasounds performed at a tertiary care center from 2007 to 2012. Retrospective chart review was performed on patients with a reported thyroid nodule to determine clinical outcomes of these nodules. Radiology reports were compared with dedicated radiology review of 500 randomly selected CT scans from the study group to determine the difference between clinical reporting and actual prevalence of thyroid nodules.

RESULTS

97,908 imaging studies met inclusion criteria, and 387 (0.4%) thyroid incidentalomas were identified on radiology report. One hundred and sixty three (42.1%) of these nodules were worked up with fine-needle aspiration, diagnosing 27 thyroid cancers (0.03% of all studies, 7.0% of reported incidentalomas). The prevalence of incidentalomas clinically reported was 142/100,000 CT scans, 638/100,000 MRIs, 358/100,000 PET scans, and 6,594/100,000 ultrasounds. In contrast, review of CT scans screening for thyroid nodules had a prevalence of 10%.

CONCLUSION

Routine clinical reporting of incidental thyroid nodules is far less common than on dedicated review.

IMPACT

These data contradict the notion that incidentalomas contribute significantly to rising thyroid cancer rates.