Latency Trend Analysis as a Guide to Screening Malignancy Survivors for Second Primary Thyroid Cancer

Abstract

Primary cancer survivors have a higher risk of developing second primary thyroid cancer (SPTC). Patients with SPTC who survived primary malignancies, diagnosed from 1975 to 2016, were identified from the Surveillance, Epidemiology, and End Results (SEER) database (SEER 18 Registry). A total of 33,551 cancer cases were enrolled in the final analysis. Individuals with a primary malignancy were at a significant 90% increased risk of developing SPTC (SIR = 1.90, 95%CI = 1.86−1.93, p < 0.05) compared to the general population. More than half (54.7%) of SPTC diagnoses were made in the first three years after primary cancer diagnosis, and the most aggressive presentations of SPTC occurred within the first year following malignancy. A latency trend analysis identified persistent high risk for development of SPTC after diagnosis of lymphoma, leukemia, soft tissue tumors, kidney, breast, and uterine cancer; elevated 10-year risk for most cancers such as salivary gland, melanoma, stomach, lung, colon, ovarian, pancreas, prostate, and bladder; and high 5-year risk after cancers such as larynx, oral, orbit, bone, small intestine, and liver. Our latency period model identifying risk according to each type of primary cancer may aid clinicians in identifying at-risk patients to be screened for thyroid cancer and guide them in developing a surveillance plan according to the latency period attributed to a patient’s primary cancer.

Keywords: SEER; screening; second primary thyroid cancer; thyroid latency.

Figure 1

The annual increase in diagnosed cases of thyroid cancer. SPTC: Second primary thyroid cancer.

Figure 2

Type of primary cancer as a percentage of patients with primary malignancy developing subsequent thyroid cancer. UB: Urinary and bladder cancer, CRC: Colorectal cancer.

Figure 3

Overall incidence and risk of SPTC overtime after a primary cancer diagnosis. First-year does not include the first two months. SPTC: Second primary thyroid cancer. SIR: standardized incidence ratio (observed/expected). (A) Annual percentage of patients developing SPTC. (B) Latency course of SPTC development stratified by TC stage.

Figure 4

Latency course of elevated SIRs of developing second primary thyroid cancer risk in patients according to selected primary cancer. Primary cancers which mantained increased risk at (A) 10-years and at (B) 5-years. SIR: standardized incidence ratio (observed/expected), CI: confidence interval.

Figure 5

Risk of developing SPTC stratified by tumor differentiation status over time. SIR: standardized incidence ratio (observed/expected).

Figure 6

Geographical distribution of elevated risk developing second primary thyroid cancer (SPTC) in the United States. SIR: standardized incidence ratio (observed/expected). (A) Mapping counties with significant elevated SIR (n = 155 counties) during the first year following another primary malignancy. Color shows SIR for county, state, and zip code. (B) SIR across SEER registries during the first year and lifelong period.