Nulliparity enhances the risk of second primary malignancy of the breast in a cohort of women treated for thyroid cancer

Abstract

BackgroundMany studies have reported an increased risk of developing a second primary malignancy (SPM) of the breast in women treated for thyroid cancer. In this study, we investigated several potential risk factors for this association. The aim of this retrospective cohort study was to identify a subgroup of women surgically treated for papillary thyroid cancer that may benefit from more careful breast cancer screening.MethodsA total of 101 women surgically treated for papillary thyroid cancer from 1996 to 2009 with subsequent follow-up were interviewed by phone regarding personal risk factors and lifestyle habits. Only 75 questionnaires could be evaluated due to a 25.7% rate of patients not retrieved or refusing the interview. Data analysis was performed using a multivariate logistic model.ResultsThe standardised incidence ratio (SIR) for breast cancer was 3.58 (95% IC 1.14 - 8.37). Our data suggest a protective effect of multiparity on the development of a SPM of the breast (O.R. 0.15; 95% IC 0.25 - 0.86). Significant associations were not found with other known risk factors including Body Mass Index (BMI), age at first tumour, concurrent metabolic diseases, smoking, physical activity and familiarity.ConclusionsThis study confirms that a higher incidence of SPM of the breast is observed in women treated for papillary thyroid cancer. Additionally, this risk is increased by nulliparity, thus a strict breast screening program for nulliparous women treated for thyroid cancer may be advisable.

The Breast–Thyroid Cancer Link: A Systematic Review and Meta-analysis

“…Positive associations were seen between menstrual and reproductive factors and papillary thyroid cancer risk, especially for women diagnosed at a younger age (53). Additionally, evaluating breast cancer risk in a cohort of thyroid cancer patients, multi-parity was found to have a protective effect on the development of breast cancer while nulli-parity was associated with higher rates of subsequent breast cancer (42). Demonstration of this association suggests the same hormonal risk factors for the development of a primary breast cancer play a role in the development of breast cancer after thyroid cancer.…”

“…These organs include the salivary gland, stomach, small intestine, bladder and bone marrow (73). The mammary gland has the same sodium-iodine symporter as the thyroid gland thus may also be able to concentrate iodine (42). Lactating breast tissue and breast tissue with atypia or malignancy show an increase in RAI uptake (74).…”

“…This leads one to suspect a pathophysiologic reason for this increase in risk. A number of cell line and clinical studies suggest a common hormonal receptor pathway involving estrogen and/or TSH (42, 49–60). Similarly, obese women with breast cancer have higher rates of subsequent thyroid cancers.…”

Radiotherapy did not increase thyroid cancer risk among women with breast cancer: A nationwide population‐based cohort study

“…The coincidence of thyroid disorder and breast cancer has long been a subject of debate. Benign thyroid diseases are suggested to be related to breast cancer, and women treated for thyroid cancer have exhibited an increased incidence of subsequent breast cancer compared with women in the general population . Nevertheless, previous studies investigating the possible association between breast cancer and subsequent thyroid cancer have determined inconclusive results .…”

Characteristics and survival of patients with metachronous or synchronous double primary malignancies: breast and thyroid cancer

“…Some studies have reported an increased risk of TC among BC patients [2, 3], whereas others have found an increased risk of BC in TC patients [4–6]. It seems that TC and BC may have some possible associations in terms of genesis and development, such as hormonal, genetic, environmental, or therapeutic factors.…”