Cancer Survivors May Be at Increased Risk for Secondary Primary Thyroid Cancer

Following their initial diagnosis, cancer survivors, compared with the overall population, are at a 90% increased risk for developing a secondary primary thyroid cancer, according to a poster presented at the 91st Annual Meeting of the American Thyroid Association.

“Our latency period model identifying risk according to each type of primary cancer may aid clinicians in identifying patients at risk of developing [a secondary primary thyroid cancer],” Lauren Mueller, BA, Department of Surgery, Tulane University School of Medicine, said in a presentation of the data. “The first 3 years after primary cancer diagnosis are the most critical to screen for [thyroid cancer] as over half of [secondary primary thyroid cancer] cases are diagnosed within this period.”

In the study, investigators found that cancer survivors were at a significant increased risk (90%) of a secondary primary thyroid cancer compared to the standard population. In particular, this elevated risk was observed in soft tissue sarcomas (standardized incidence ratio [SIR], 4.51; 95% CI, 3.79-5.33), head and neck tumors (SIR, 3.1; 95% CI, 2.77-3.46), and hematologic malignancies (SIR, 4.25; 95% CI, 1.16-10.88), as well as in those who were treated with chemotherapy for their initial malignancy (P < .001).

Moreover, investigators observed that a quarter of secondary primary thyroid cancer cases developed in the first year after their initial malignancy diagnosis (SIR, 4.06; 95% CI, 3.91-4.22; P < .05). Mueller noted that these cases are the most aggressive with the most advanced stage.

“A latency trend analysis identified persistent high risk for development of [secondary primary thyroid cancer] 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 a high 5-year risk after cancers such as larynx, oral, orbit, bone, small intestine, and liver,” the investigators wrote in the abstract, adding that additional indicators for risk of a secondary primary thyroid cancer included male sex, Asian/Pacific Islander ethnicity, and young age.

Study Rationale

According to Mueller, the incidence of mortality of thyroid cancer has increased significantly in the United States in recent years. “The American the Cancer Society estimates there to be 44,000 new cases and 2,200 deaths from thyroid cancer in 2022,” she said, adding that there are various proposed causes for this increase, including overdiagnosis due to recently available advanced diagnostic tools and radiation cancer treatments; however, radiation treatment as risk factor is inconclusive.

Therefore, investigators aimed to identify risk factors for developing a secondary primary thyroid cancer and to develop a risk model that predicts the latency period of a secondary primary thyroid cancer by each primary malignancy.

Investigators used the Surveillance, Epidemiology, and End Results (SEER) database (SEER 18 Registry) to identify cancer survivors diagnosed with a secondary primary thyroid cancer from 1975 to 2016, collecting data for 15,620 individuals who were enrolled in the final analysis.

“A high index of suspicion for second primary cancers is warranted,” the investigators concluded. “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. The results of our study may enhance clinical guidelines to optimize thyroid cancer care.”

_Reference:

_{Mueller L, Hussein MH, Trinh L, Haidari M, Toraih E, Kandil E. Predicting the Risk of a Second Primary Thyroid Cancer after Surviving a Malignancy: A Latency Trend Analysis Over Four Decades. Thyroid. 2022;32(1):P-1-A-135. doi:10.1089/thy.2022.29137.abstracts.}