STUDY OF THE PREVALENCE OF AUTOIMMUNE THYROID DISEASE IN WOMEN WITH BREAST CANCER

Case Report of Graves' Disease in a 45-Year-Old Woman Secondary to Herceptin Treatment for Breast Cancer

Graves' disease is the most common cause of thyrotoxicosis and is characterized by ophthalmopathy with proptosis, chemosis, or conjunctival injection; pretibial myxedema; and thyroid acropachy. It is an autoimmune disease that can be genetic or influenced by coexisting environmental factors such as exposure to anticancer drugs, including immune checkpoint inhibitors. The incidence rate of breast cancer is increasing due to rising awareness of risk factors and screening for breast cancer, and the mortality rate is decreasing due to recent advances in cancer treatment. However, there are side effects that are attributed to these treatment modalities, manifesting in various forms in breast cancer survivors, which are reflected in the patient in this case study.

Links between Breast and Thyroid Cancer: Hormones, Genetic Susceptibility and Medical Interventions

Breast and thyroid glands are two common sites of female malignancies. Since the late 19th century, physicians have found that the cancers in either thyroid or mammary gland might increase the risk of second primary cancers in the other site. From then on, many observational clinical studies have confirmed the hypothesis and more than one theory has been developed to explain the phenomenon. Since the two glands both have secretory functions and are regulated by the hypothalamic-pituitary axis, they may share some common oncogenic molecular pathways. However, other risks factors, including medical interventions and hormones, are also observed to play a role. This article aims to provide a comprehensive review of the associations between the two cancers. The putative mechanisms, such as hormone alteration, autoimmune attack, genetic predisposition and other life-related factors are reviewed and discussed. Medical interventions, such as chemotherapy and radiotherapy, can also increase the risk of second primary cancers. This review will provide novel insights into the research designs, clinical managements and treatments of thyroid and breast cancer patients.

Benign thyroid disease and the risk of breast cancer: An updated systematic review and meta-analysis

Background

The correlation between benign thyroid disease (BTD) and breast cancer (BC) has long been discussed. However, the definite relationship and potential mechanism between them are still disputed. The current meta-analysis aimed at performing a comprehensive assessment of the relationship between different types of benign thyroid disease and the risk of breast cancer, furthermore, assessing whether benign thyroid disease exerts an influence on the aggressiveness of breast cancer.

Method

A systematic literature search (PubMed, Web of Science, MEDLINE, and Embase databases) identified studies to evaluate the correlation between BTD and BC risk. Data were analyzed using version 16.0 STATA software, including the odds ratio (OR) and its corresponding 95% confidence intervals (CIs). Publication bias and quality assessment were conducted for the included studies.

Result

Overall, 18 studies involving 422,384 patients with BTD were incorporated. The outcome showed that autoimmune thyroiditis (OR: 2.56, 95%CI: 1.95-3.37, I2 = 0.0%, p=0.460), goiter (OR: 2.13, 95%CI: 1.19-3.79, I2 = 80.6%, p=0.000), and Graves' disease (OR: 5.01, 95%CI: 1.49-16.82, I2 = 0.0%, p=0.358) was connected with a higher risk of BC. Both hypothyroidism (OR: 0.82, 95%CI: 0.64-1.04, I2 = 85.0%, p=0.000) and hyperthyroidism (OR: 1.07, 95%CI: 0.93-1.24, I2 = 24.9%, p=0.206) had no significant association with the risk of BC. Additionally, the pooled analysis showed no apparent correlation between BTD and aggressiveness of BC. However, subgroup analysis indicated a positive relationship between BTD and aggressiveness of BC in the Europe subgroup (HR: 2.05, 95%CI: 1.32-3.17, I2 = 86.4%, p=0.000).

Conclusion

Autoimmune thyroiditis, goiter, and Graves' disease are connected with an increased risk of BC. Furthermore, subgroup analysis suggested that BTD increases the aggressiveness of BC in the European population geographically. Nevertheless, further research is needed to prove these discoveries.

Breast cancer in previously thyroidectomized patients: which thyroid disorders are a risk factor?

The aim of this study was to evaluate whether there are thyroid diseases in which breast cancer will appear later as well as the role of autoimmunity. This was a retrospective observational study. A total of 410 females (thyroid surgery and later breast cancer) and 524 females (thyroid surgery only) were compared with regard to pathological thyroid findings, thyroid hormones, thyroid autoimmunity and type of breast cancer. Thyroid autoimmunity, especially antithyroid peroxidase antibodies, significantly increased the risk of breast cancer (p < 0.01); however, this was not true for other thyroid diseases, including thyroid cancer. No variant of breast cancer was predominant, and only thyroid autoimmunity was associated with the risk of breast cancer. Further research is needed to explain the impacts of different antithyroid antibodies.

Several studies have long hypothesized a link between thyroid disease and breast cancer. The authors' study retrospectively examined a large cohort of patients who initially underwent thyroid surgery and subsequently had breast cancer compared with a control group consisting of patients with only breast cancer. This comparison showed that only autoimmune thyroid disease was a risk factor for subsequent breast cancer, whereas no significant association of thyroid cancer with breast cancer was found.

Risk of Breast Cancer in Females With Hypothyroidism: A Nationwide, Population-Based, Cohort Study

OBJECTIVES

The results of studies investigating the relationship between breast cancer and hypothyroidism vary greatly from study to study. In this study, we analyzed a large and reliable, population-based database to gain a better understanding of the correlation.

METHODS

This retrospective cohort study analyzed patients with hypothyroidism between January 1, 2000 and December 31, 2012 (hypothyroidism cohort) from the Longitudinal Health Insurance Database 2000 in Taiwan. For each woman with hypothyroidism, 1 woman without a history of breast cancer was randomly selected from the Longitudinal Health Insurance Database 2000 and frequency matched (1:4) with women without hypothyroidism by age and index year of hypothyroidism. The study outcome was the diagnosis of breast cancer during a 12-year follow-up period.

RESULTS

In this study, 6665 women with hypothyroidism and 26 660 women without hypothyroidism were identified. The hypothyroidism cohort had a significantly higher risk of breast cancer than the nonhypothyroidism cohort (adjusted hazard ratio [aHR] 1.69 [95% CI, 1.15-2.49]; P = .01), especially in the group aged 40 to 64 years (aHR 2.07 [95% CI, 1.32-3.23]; P = .01). Women in the hypothyroidism cohort taking levothyroxine for a duration ˃588 days showed a significantly decreased risk of breast cancer (aHR 0.37 [95% CI, 0.19-0.71]; P = .003).

CONCLUSION

Women with hypothyroidism are at a higher risk of breast cancer than those without hypothyroidism. Levothyroxine may reduce the risk of breast cancer in a woman with hypothyroidism.

[Hyperthyroidism and breast cancer: Is there a link?]

The objective of this review was to determine whether there is an association between hyperthyroidism and the risk of developing a breast cancer from the analysis of data in the literature.

METHOD

The analyzed articles were extracted from the PUBMED database from 2002 to 2017 using the following keywords "hyperthyroidism AND breast cancer" and "thyroid AND breast cancer".

RESULTS

A total of 22 studies were selected, including 8 cohort studies, 12 case-control studies and 2 meta-analyzes. Of these 22 studies, 15 have established a significant epidemiological or biological link between hyperthyroidism and breast cancer. Five of them were particularly interested in Graves' disease, and four demonstrated a positive association between this disease and the onset of breast cancer, especially within three years from the thyropathy diagnosis. These different studies also highlighted the increased risk of breast cancer seen in overweight or postmenopausal women. Contradictions persist over the types of mammary cancers observed and their prognosis.

CONCLUSION

This review reveals that women with hyperthyroidism appear to have a moderately high risk of breast cancer (RR<2). These data are corroborated by solid physiopathological hypotheses. Regardless of the type of thyropathy responsible for hyperthyroidism, care should be taken to ensure that these patients receive a clinical examination of the breasts on an annual basis and mammographic screening every 2 years from the age of 50 years.

HIGH PREVALENCE OF HYPOTHYROIDISM IN SYSTEMIC LUPUS ERYTHEMATOSUS PATIENTS WITHOUT AN INCREASE IN CIRCULATING ANTI-THYROID ANTIBODIES

OBJECTIVE

Because routine investigations are necessary for the early detection of thyroid disease, this study aimed to assess the prevalence of autoimmune thyroid disease (ATD) and thyroid dysfunction (TD) in patients with systemic lupus erythematosus (SLE).

METHODS

Seventy-nine SLE patients (American College of Rheumatology criteria) and 159 control patients with no diagnosis of autoimmune diseases (except for ATD) were consecutively evaluated regarding changes in laboratory assessments of thyroid function and the presence of ATD.

RESULTS

ATD was detected in 11.4% of the SLE patients and 13.8% of the control patients (P = .747), whereas TD was detected in 25.3 and 9.4% (P = .002), hypothyroidism was detected in 21.5 and 6.9% (P = .002), and hyperthyroidism was detected in 3.8 and 2.5% (P = .426) of the SLE and control patients, respectively. The mean duration of SLE was longer in patients with TD (P = .036). Mild hypothyroidism was more frequent in the SLE patients with anti-Smith antibodies (P = .029).

CONCLUSION

Because hypothyroidism was more frequent in SLE patients and the frequency of ATD was high in both groups, the authors suggest that TSH and anti-thyroid antibody levels be assessed in SLE patients.

ABBREVIATIONS

ACA = anti-cardiolipin antibodies; ANF = anti-nuclear factor; anti-CCP = anti-cyclic citrullinated peptide; anti-dsDNA = anti-double-stranded DNA; anti-RNP = anti-ribonucleoprotein; anti-Scl70 = anti-topoisomerase I antibodies; anti-SM = anti-Smith antigen antibodies; anti-SS-A/Ro = anti-Sjögren syndrome-related antigen A (Ro); anti-SS-B/La = anti-Sjögren syndrome-related antigen B (La); anti-Tg = anti-thyroglobulin; anti-TPO = anti-thyroid peroxidase; ATD = autoimmune thyroid disease; ENA = extractable nuclear antigen; fT4 = free thyroxine; OR = odds ratio; RF = rheumatoid factor; SLE = systemic lupus erythematosus; SLEDAI = SLE Disease Activity Index; TD = thyroid dysfunction; TSH = thyroid-stimulating hormone; TT3 = total triiodothyronine.

Thyroid Autoimmunity: Role of Anti-thyroid Antibodies in Thyroid and Extra-Thyroidal Diseases

Autoimmune diseases have a high prevalence in the population, and autoimmune thyroid disease (AITD) is one of the most common representatives. Thyroid autoantibodies are not only frequently detected in patients with AITD but also in subjects without manifest thyroid dysfunction. The high prevalence raises questions regarding a potential role in extra-thyroidal diseases. This review summarizes the etiology and mechanism of AITD and addresses prevalence of antibodies against thyroid peroxidase, thyroid-stimulating hormone receptor (TSHR), and anti-thyroglobulin and their action outside the thyroid. The main issues limiting the reliability of the conclusions drawn here include problems with different specificities and sensitivities of the antibody detection assays employed, as well as potential confounding effects of altered thyroid hormone levels, and lack of prospective studies. In addition to the well-known effects of TSHR antibodies on fibroblasts in Graves' disease (GD), studies speculate on a role of anti-thyroid antibodies in cancer. All antibodies may have a tumor-promoting role in breast cancer carcinogenesis despite anti-thyroid peroxidase antibodies having a positive prognostic effect in patients with overt disease. Cross-reactivity with lactoperoxidase leading to induction of chronic inflammation might promote breast cancer, while anti-thyroid antibodies in manifest breast cancer might be an indication for a more active immune system. A better general health condition in older women with anti-thyroid peroxidase antibodies might support this hypothesis. The different actions of the anti-thyroid antibodies correspond to differences in cellular location of the antigens, titers of the circulating antibodies, duration of antibody exposure, and immunological mechanisms in GD and Hashimoto's thyroiditis.

The thyroid and breast cancer

PURPOSE OF REVIEW

The female predominance of diseases of the thyroid and breast makes difficult the separation of an expected association with a causal linkage. This review will examine recent reports on associations between thyroid disease and breast cancer, comparing them with previous studies, with a view to elucidating what pointers are available to suggest either a common pathogenesis or novel thyroid-related therapeutic approach, which might arise from this association.

RECENT FINDINGS

Reports on thyroid-breast cancer associations are reviewed under the following headings: breast cancer prevalence in different thyroid disorders and their effect on risk and outcome; the possible role of thyroid autoimmunity, thyroid enlargement, effect of radioactive iodine treatment, role of stable iodine, possible joint antigens sodium iodide transporter and thyroid peroxidase and thyroid-breast cancer coincidence.

SUMMARY

Current studies on thyroid and breast cancer associations confirm earlier findings of the lack of definitive evidence of a causal relationship. The predominant relationship continues to be hypothyroidism or autoimmune thyroid disease perhaps contributing to increased breast cancer risk or outcomes. However, despite many studies and the findings of meta-analyses, elucidating the mechanisms underlying the association remains elusive. At present, there is little justification for utilizing thyroid insights as a possible therapeutic intervention in breast cancer.