Nov 23, 2015
By Shira Klapper, Senior Writer/Editor
For years, researchers have suspected that external sources of estrogen, such as menopausal hormone therapy (MHT), increase photosensitivity. The more photosensitive a person is, the lower the dose of ultraviolet radiation needed to redden the skin. Because ultraviolet radiation is strongly related to skin cancer, photosensitivity may also play an important role in the development of the disease. This connection between external sources of estrogen (called exogenous estrogen) and skin cancer led researchers to study whether oral contraceptives and MHT—which increase circulating levels of estrogen—also increase the risk of basal cell carcinoma (BCC).
A recent study in the Journal of Clinical Oncology (JCO) explores how the risk of BCC, the most common skin cancer, is affected not only by external sources of estrogen, but also by reproductive factors, such as age of first period and age at menopause, which affect the levels of estrogen in a woman’s body.
The study, “Female Estrogen-Related Factors and Incidence of Basal Cell Carcinoma in a Nationwide United States Cohort,” published online ahead of print on November 2, 2015, looked at data from 46,100 white women who were part of the United States Radiologic Technologists Study, a large prospective cohort with participants from across the country. The study found that a higher risk of developing BCC was associated with a later age of natural menopause and having ever used MHT.The highest risk of BCC was among women who had gone through menopause and took MHT for 10 or more years, compared to postmenopausal women who never used MHT.
Commenting on these findings, first author Elizabeth K. Cahoon, PhD, said, “Other studies have reported the relationship of estrogen-related factors with basal cell carcinoma. This is the first study that looks at a whole group of different types of exogenous and endogenous estrogen exposures in the same population.”
A higher risk of BCC was not associated with use of oral contraceptives, age at first period, age at first birth, infertility, number of full-term pregnancies, age at hysterectomy, or use of diethylstilbestrol by the participant’s mother (diethylstilbestrol is a synthetic estrogen used by pregnant women from 1938-1971).
For women with hysterectomy-induced menopause, menopausal hormone therapy not associated with increased risk for basal cell carcinoma
Whereas the study found that women who took MHT after natural menopause did have an increased risk of BCC, women who took MHT after a hysterectomy did not have a notably increased risk. In addition, the investigators found that among women who went into natural menopause, the longer one took MHT, the greater her risk of BCC. This association between duration of MHT and BCC was not as strong among women who took MHT after a hysterectomy.
More frequent skin checks for women who take MHT
Dr. Cahoon said the study’s findings might indicate that women who take MHT should be more vigilant about skin cancer screening. “Basal cell carcinoma is rarely fatal, but it does contribute substantial morbidity and cost."
Looking ahead, Dr. Cahoon said her study should be replicated and future studies might also assess whether women taking MHT who show visible skin photosensitivity, such as reddening of the skin, are at higher risk than women who don’t have these reactions while taking MHT.
Dr. Cahoon is a Fellow in the Radiation Epidemiology Branch of the National Cancer Institute.
Abstract of the original JOP article.
PDF of the original JOP article.
Cahoon EK, Kitahara CM, Ntowe E, et al. Female estrogen-related factors and incidence of basal cell carcinoma in a nationwide United States cohort. J Clin Oncol. Epub 2015 Nov 2.
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@ 2015 American Society of Clinical Oncology