Nevi Number Linked to Breast Cancer Risk

A woman’s moles may give a non-invasive way of assessing breast cancer risk

medwireNews: Cutaneous nevi may indicate a woman’s risk of developing breast cancer, suggest the results of two intriguing studies published in PLOS Medicine.

In an accompanying editorial, Barbara Fuhrman and Victor Cardenas, from the University of Arkansas for Medical Sciences in Little Rock, USA, say that any relationship between moles and breast cancer is unlikely to be causal but would instead “reflect a shared cause or causes”.

Welcoming the possibility of an easy, non-invasive way of identifying women who may especially benefit from breast cancer screening, they recommend: “Additional studies should be carried out to investigate melanocytic nevi and other cutaneous features in association with the risks of breast cancer and other estrogen-related proliferative diseases.”

The first study, using data from the E3N study of 89,902 French women, found that women reporting having “very many” nevi had a significantly increased risk of developing breast cancer (hazard ratio [HR]=1.13) than those with none, after adjusting for age, education, hormone use and age at menopause.

The significance of the increased risk was lost after further adjusting for a history of benign breast disease (BBD) and a family history of breast cancer.

Nevertheless, Marina Kvaskoff, from the Centre for Research in Epidemiology and Population Health in Villejuif, France, and co-authors found dose–response relationships between the number of nevi and both cases of biopsy-confirmed BBD and cases of breast cancer in first-degree family members.

The 10-year absolute risk of invasive breast cancer increased from 3,749 cases per 100,000 women for those without nevi to 4,124 cases per 100,000 women with very many nevi, but the risk was only significantly increased for postmenopausal women, giving a HR of 1.40.

“More research is warranted to elucidate these relationships and to understand their underlying mechanisms,” the researchers say.

The second study, reported by Jiali Han, from Brigham and Women’s Hospital and Harvard Medical School in Boston, Massachusetts, USA, and co-authors used data for 74,523 participants of the Nurses’ Health Study.

Compared with women without nevi, those with one to five nevi, six to 14 nevi, and 15 or more nevi were a significant 1.04, 1.15 and 1.35 times more likely to develop breast cancer after adjusting for confounders.

And the absolute risk of breast cancer over 24 years of follow-up was 8.48% for women without nevi, rising to 11.4% for those with at least 15 nevi.

However, further analysis found the nevi number was only significantly related to the risk of Oestrogen receptor-positive breast cancer.

There was a positive and significant relationship between number of nevi and levels of estradiol and testosterone. Analysis of a subgroup of 362 breast cancer patients and 611 controls matched for levels of five different hormones showed that the increased risk of breast cancer per five nevi fell from an odds ratio of 1.25 to 1.16 after adjusting for plasma hormones.

But, contrary to the report by Barbara Fuhrman and Victor Cardenas, the relationship between nevi and breast cancer risk was not confirmed in a further analysis of postmenopausal women who did not use hormone therapy.

“These data suggest that the association between nevus count and breast cancer risk was at least partially mediated through hormone levels,” Jiali Han et al write.

References

Kvaskoff M, Bijon A, Mesrine S, et al. Association between melanocytic nevi and risk of breast diseases: The French E3N Prospective Cohort. PLOS 2014; 10 June. DOI: 10.1371/journal.pmed.1001660

Zhang M, Zhang X, Qureshi A, et al. Association between cutaneous nevi and breast cancer in the Nurses’ Health Study: A prospective cohort study. PLOS 2014; 10 June. DOI: 10.1371/journal.pmed.1001659

Fuhrman B, Cardenas V. Melanocytic nevi as biomarkers of breast cancer risk. PLOS 2014; 10 June. DOI: 10.1371/journal.pmed.1001661

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