Breast tumor characteristics in hormone replacement therapy users

Levonorgestrel-releasing intrauterine system and the risk of breast cancer: A nationwide cohort study

BACKGROUND

Prolonged steroid hormone therapy increases the risk of breast cancer, especially the risk of lobular cancer, but the effect of the levonorgestrel-releasing intrauterine system (LNG-IUS) use is controversial. In this study we aimed to test the hypothesis that risk for lobular breast cancer is elevated among LNG-IUS users.

MATERIAL AND METHODS

We identified from the national Medical Reimbursement Registry of Finland the women aged 30-49 who had used LNG-IUS for the treatment or prevention of menorrhagia in 1994-2007, and from the Finnish Cancer Registry breast cancers diagnosed before the age of 55 and by the end of 2012.

RESULTS

A total of 2015 women had breast cancer diagnosed in a cohort of 93 843 LNG-IUS users during follow-up consisting of 1 032 767 women-years. The LNG-IUS users had an increased risk for both ductal breast cancer [standardized incidence ratio (SIR) 1.20, 95% confidence interval (CI) 1.14-1.25] and for lobular breast cancer (SIR 1.33, 95% CI 1.20-1.46), as compared with the general female population. The highest risk was found in LNG-IUS users who purchased the device at least twice, whose SIR for lobular cancer was 1.73 (95% CI 1.37-2.15).

CONCLUSIONS

The results imply that intrauterine administration of levonorgestrel is not only related to an excess risk of lobular breast cancer but also, in contrary to previous assumptions, to an excess risk of ductal breast cancer.

KRAS rs61764370 is associated with HER2-overexpressed and poorly-differentiated breast cancer in hormone replacement therapy users: a case control study

Background

A single nucleotide polymorphism located in the 3'-untranslated region of the KRAS oncogene (KRAS variant; rs61764370) disrupts a let-7 miRNA binding and was recently reported to act as a genetic marker for increased risk of developing human cancers. We aimed to investigate an association of the KRAS variant with sporadic and familial breast cancer and breast tumor characteristics.

Methods

Genotyping was accomplished in 530 sporadic postmenopausal breast cancer cases, 165 familial breast cancer cases (including N = 29, who test positive for BRCA1/2 mutations) and 270 postmenopausal control women using the flurogenic 5' nuclease assay. Information on hormone replacement therapy (HRT) use and tumor characteristics in sporadic breast cancer cases was ascertained from a postal questionnaire and pathology reports, respectively. Associations between the KRAS genotype and breast cancer or breast tumor characteristics were assessed using chi-square test and logistic regression models.

Results

No evidence of association was observed between the KRAS variant and risk of sporadic and familial breast cancer - either among BRCA carriers or non-BRCA carriers. The KRAS variant was statistically significantly more often associated with human epidermal growth factor receptor 2 (HER2) - positive tumors and tumors of higher histopathologic grade. However, both associations were detected only in HRT users.

Conclusion

Our data do not support the hypothesis that the KRAS variant rs61764370 is implicated in the aetiology of sporadic or of familial breast cancer. In postmenopausal women using HRT, the KRAS variant might lead to HER2 overexpressed and poorly-differentiated breast tumors, both indicators of a worse prognosis.