Assessment of surveillance versus etiologic factors in the reciprocal association between papillary thyroid cancer and breast cancer.

BACKGROUND: Mutually increased risks for thyroid and breast cancer have been reported, but the contribution of etiologic factors versus increased medical surveillance to these associations is unknown. METHODS: Leveraging large-scale US population-based cancer registry data, we used standardized incidence ratios (SIRs) to investigate the reciprocal risks of thyroid and breast cancers among adult females diagnosed with a first primary invasive, non-metastatic breast cancer (N = 652,627) or papillary thyroid cancer (PTC) (N = 92,318) during 2000-2017 who survived ≥1-year. RESULTS: PTC risk was increased 1.3-fold [N = 1434; SIR = 1.32; 95 % confidence interval (CI) = 1.25-1.39] after breast cancer compared to the general population. PTC risk declined significantly with time since breast cancer (Poisson regression = Ptrend <0.001) and was evident only for tumors ≤2 cm in size. The SIRs for PTC were higher after hormone-receptor (HR)+ (versus HR-) and stage II or III (versus stage 0-I) breast tumors. Breast cancer risk was increased 1.2-fold (N = 2038; SIR = 1.21; CI = 1.16-1.26) after PTC and was constant over time since PTC but was only increased for stage 0-II and HR + breast cancers. CONCLUSION: Although some of the patterns by latency, stage and size are consistent with heightened surveillance contributing to the breast-thyroid association, we cannot exclude a role of shared etiology or treatment effects.

Life Expectancy and Treatment Patterns in Elderly Patients With Low-Risk Papillary Thyroid Cancer: A Population-Based Analysis.

OBJECTIVE: Guidelines endorse active surveillance for low-risk papillary thyroid carcinoma (PTC), but this is not commonly utilized. Those with limited life expectancy due to age and comorbidity may be best suited for active surveillance given their higher likelihood of other-cause mortality compared to disease-specific mortality. METHODS: Surveillance, epidemiology, and end results-Medicare was queried for patients >65 years with T1, N0, M0 PTC who received surgery. We evaluated the overall survival, disease-specific survival (DSS), and survival based on tumor size and extent of surgery (hemi- vs total thyroidectomy). We created a competing risk model to identify the cumulative incidence of other-cause mortality to define patient groups with life expectancies of less than 10 and 15 years. RESULTS: A total of 3280 patients were included. The 20-year overall survival and DSS were 38.2% and 98.5%, respectively. DSS was comparable between patients based on tumor size and surgery. The cancer cohort had better survival compared to matched controls (P < .001). Life expectancy was less than 15 years for any patient aged >80 years regardless of Charlson comorbidity score (CCS ≥ 0) and any patient aged >70 years with CCS ≥ 1. Life expectancy was less than 10 years for any patient a >80 years with CCS ≥ 1 and aged >70 years with CCS ≥ 3. CONCLUSION: Older patients with comorbidities have limited life expectancies but excellent DSS from low-risk PTC. Incorporating life expectancy into management decisions and guidelines would likely promote selection of less aggressive management for populations that are most suited for this approach.

Combining the American Thyroid Association's Ultrasound Classification with Cytological Subcategorization Improves the Assessment of Malignancy Risk in Indeterminate Thyroid Nodules.

Background: The risk of malignancy (RoM) of indeterminate thyroid nodules (ITNs) shows a high variability in interinstitutional cohorts. The RoM is partially associated with the cytological degree of atypia and the ultrasound (US) pattern. This study evaluated the cancer risk of ITNs by jointly considering the cytological subcategory and the American Thyroid Association (ATA)-based US risk classification. Methods: This study features a retrospective cohort from two Brazilian centers comprising 238 ITNs with confirmed outcomes. US classification, according to ATA-based guidelines, and cytological subcategorization were determined. The cytological subgroups were as follows: (1) nuclear atypia (NA) related to papillary thyroid carcinoma (PTC) but insufficient to categorize the cytology as suspicious for malignancy; (2) architectural atypia without NA (AA); (3) both architectural and nuclear atypia (ANA); (4) oncocytic pattern (OP) without NA; and (5) NA not related to PTC (NANP). NA was divided into three subgroups: nuclear size and shape, nuclear membrane appearance, and/or chromatin aspects. Results: The overall frequency of malignancy was 39.5%. Among the cytological subcategories, the highest RoM was related to the NA (43.9%) and to the ANA (43.5%), followed by AA (29.4%), and OP (9.4%). NA was positively and independently associated with cancer (odds ratio [OR]: 4.5; confidence interval [CI: 1.2-16.6]) as was the occurrence of ANA (OR 6.6 [CI 1.5-29.5]). AA and OP were not independently associated with cancer. Both ATA-based high- and intermediate-risk categories showed an independent association with cancer (OR 6.8 [CI 2.9-15.5] and OR: 2.6 [CI 1.1-5.8], respectively). ITNs with cytological findings of NA or ANA when combined with intermediate US patterns had RoM values of 47.5% and 56.7%, respectively. Both cytological subcategories, when combined with the ATA high-suspicion class reached an RoM >70%. The type of NA with the highest odds for cancer was related to the nuclear membrane (OR 11.5). Conclusions: The RoM of ITNs can reach almost 80% when both NA and ATA-based high-risk US features are present. The presence of such cytological features also increased the RoM in the ATA-based intermediate-risk US category. In addition, AA and OP were not independently related to higher cancer risk. These results strengthen the recommendations for combing cytological subcategorization and US risk classification in the workup for ITNs before the decision of a molecular testing, clinical observation, or diagnostic surgery.

Thyroid Ultrasound and the Increase in Diagnosis of Low-Risk Thyroid Cancer.

Context: Thyroid cancer incidence increased with the greatest change in adults aged ≥65 years. Objective: To determine the relationship between area-level use of imaging and thyroid cancer incidence over time. Design, Setting and Participants: Longitudinal imaging patterns in Medicare patients aged ≥65 years residing in Surveillance, Epidemiology, and End Results (SEER) regions were assessed in relationship to differentiated thyroid cancer diagnosis in patients aged ≥65 years included in SEER-Medicare. Linear mixed-effects modeling was used to determine factors associated with thyroid cancer incidence over time. Multivariable logistic regression was used to determine patient characteristics associated with receipt of thyroid ultrasound as initial imaging. Main Outcome Measure: Thyroid cancer incidence. Results: Between 2002 and 2013, thyroid ultrasound use as initial imaging increased (P < 0.001). Controlling for time and demographics, use of thyroid ultrasound was associated with thyroid cancer incidence (P < 0.001). Findings persisted when cohort was restricted to papillary thyroid cancer (P < 0.001), localized papillary thyroid cancer (P = 0.004), and localized papillary thyroid cancer with tumor size ≤1 cm (P = 0.01). Based on our model, from 2003 to 2013, at least 6594 patients aged ≥65 years were diagnosed with thyroid cancer in the United States due to increased use of thyroid ultrasound. Thyroid ultrasound as initial imaging was associated with female sex and comorbidities. Conclusion: Greater thyroid ultrasound use led to increased diagnosis of low-risk thyroid cancer, emphasizing the need to reduce harms through reduction in inappropriate ultrasound use and adoption of nodule risk stratification tools.