The co-occurrence of both breast- and differentiated thyroid cancer: incidence, association and clinical implications for daily practice

Abstract

Background Breast cancer (BC) and differentiated thyroid cancer (TC) are two common cancer types with the highest incidence in women. BC and TC can develop synchronous or metachronous and the occurrence of both is higher than expected by chance. This study aimed to examine the association between BC and TC in the Netherlands. Methods This is a retrospective cohort study during the period of 1989–2020 retrieved from the Netherlands Cancer Registry (NCR). Patients diagnosed with BC-TC and BC alone as control group and TC-BC and TC alone as control group were included. The primary outcome was the standardized incidence ratio (SIR) of BC-TC and TC-BC. Secondary outcomes included data on the demographics, type of malignancy, treatment and overall survival (OS). Results The incidence of TC among 318.002 women with BC (BC-TC) was 0.1% (423 patients) (SIR = 1.86 (95% CI: 1.40–2.32)) and the incidence of BC among 12,370 patients with TC (TC-BC) was 2.9% (355 patients) (SIR = 1.46 (95% CI: 1.09–1.83)). BC-TC patients were younger compared to the BC alone group at BC diagnosis (55 vs 60 years, p < 0.001). The age-adjusted odds ratio to develop TC was not significantly increased for patients who received chemotherapy and radiotherapy. Most TC cases were synchronous tumors after BC diagnosis (19%) with a TNM stage 1. Only 6% of the BC tumors after TC occurred synchronous with a TNM stage 1 in most cases. The OS of all groups was the most favorable in patients with both BC and TC compared to BC- and TC alone. Conclusion and relevance The SIR of TC after BC diagnosis and BC after TC diagnosis was higher than predicted based on the rates of the general population. TC and BC as second primary tumors were diagnosed in an early stage and did not affect overall survival. Therefore, Dutch women who have been treated for BC or TC require no special surveillance for their thyroid- and breast gland.

Clinical implications of non-breast cancer related findings on FDG-PET/CT scan prior to neoadjuvant chemotherapy in patients with breast cancer

“…[21]Notably, 10 patients in this study were diagnosed with thyroid cancer, which is a frequently reported incidental finding on FDG-PET/CT scans [ 23 ]. A correlation between BC and thyroid cancer has been reported; thyroid cancer occurs at an incidence of 0.1% among patients with BC [ 24 ]. In our study, we observed thyroid cancer in 0.74% of the patients, consistent with the existing literature.…”

Association between breast cancer and thyroid cancer risk: a two-sample Mendelian randomization study

“…studied the risk of cancer among first-degree relatives of cancer probands, and they found that first-degree relatives of breast cancer patients had an increased risk of thyroid cancer ( 43 ). Previous research has identified probable causal factors in both cancers, such as the thyroid gland, estrogen signaling, lifestyle, and environmental factors ( 14 ). However, the causal link between breast cancer and thyroid cancer remains uncertain, and new preventative measures, diagnostic tests, and therapies cannot be developed until the underlying causes of the secondary primary tumors are understood ( 44 ).…”

“…So far, the epidemiological and clinical trial investigations have not established a causal relationship between breast cancer and thyroid cancer ( 13 , 14 ). A retrospective case-control study that compared the genetic profiles of hereditary cancer risk genes between breast cancer and co-occurring breast-thyroid cancer patients found a genetic tendency for co-occurrence ( 15 ).…”

Risk of cancer survivors with second primary thyroid cancer: an analysis of data from the SEER database

“…For this reason, we did not compare the OS for the two groups. Interestingly, Piek et al [5] showed that patients with BC-TC had better OS than patients with BC alone, and the underlying mechanism needs to be further investigated. There was no statistical difference in TCSS between the two groups, suggesting that for SPTC patients, both over-and undertreatment should be avoided.…”

“…The incidence of thyroid cancer has been reported to be rising among cancer survivors across the United States [4] . Data from a large cohort study showed an increased risk of TC in patients with primary BC and vice versa [5,6] . The meta-analysis further con rmed that the ratio of secondary TC after BC was 1.55 (95% CI: 1.44-1.67) [7] .…”