Original Research published: 08 June 2018 doi: 10.3389/fonc.2018.00209
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Sara Bønløkke1*, Jan Blaakær 2, Torben Steiniche1, Estrid Høgdall3, Steffen Grann Jensen3, Anne Hammer4,5, Eva Balslev 3, Mikael Lenz Strube 6, Helle Knakkergaard1 and Suzan Lenz7 1 Department of Pathology, Aarhus University Hospital, Aarhus, Denmark, 2 Department of Obstetrics and Gynecology, Odense University Hospital, Odense, Denmark, 3 Department of Pathology, Copenhagen University Hospital, Herlev, Denmark, 4 Department of Clinical Medicine, Aarhus University, Aarhus, Denmark, 5 Department of Obstetrics and Gynecology, Herning Hospital, Herning, Denmark, 6 DTU Bioengineering, Technical University of Denmark, Kongens Lyngby, Denmark, 7 Private Gynecological Clinic “Suzan Lenz Gynækolog”, Copenhagen, Denmark
Edited by: Charles A. Kunos, National Cancer Institute (NIH), United States Reviewed by: Jennifer M. Giltnane, Genentech, Inc., United States Stephanie Wethington, Johns Hopkins University, United States *Correspondence: Sara Bønløkke
[email protected] Specialty section: This article was submitted to Women’s Cancer, a section of the journal Frontiers in Oncology Received: 20 March 2018 Accepted: 23 May 2018 Published: 08 June 2018 Citation: Bønløkke S, Blaakær J, Steiniche T, Høgdall E, Jensen SG, Hammer A, Balslev E, Strube ML, Knakkergaard H and Lenz S (2018) Evidence of No Association Between Human Papillomavirus and Breast Cancer. Front. Oncol. 8:209. doi: 10.3389/fonc.2018.00209
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Background: Globally, breast cancer is the most frequent cancer among women. Studies reported an increased risk of breast cancer among women with prior cervical dysplasia. This study aimed to describe the prevalence of human papillomavirus (HPV) in breast cancer and explore if women with prior cervical neoplasia carry an increased risk of HPV-positive breast cancer compared to women without. Methods: This case–control study identified 193 Danish women diagnosed with breast cancer (1998–2012) at Aarhus University Hospital or Copenhagen University Hospital Herlev. Cases were 93 women with cervical intraepithelial neoplasia grade 3 or worse (CIN3+) prior to breast cancer. Controls were 100 women without prior cervical dysplasia. HPV testing and genotyping were done using SPF10 PCR-DEIA-LiPA25 and an in-house semi-Q-PCR assay. results: Overall HPV prevalence in breast cancer for the assays was 1.55% (95% CI 0.32–4.48) and 0.52% (95% CI 0.01–2.85). There was no difference in HPV prevalence between cases and controls (2.15 vs. 1.00%, p = 0.61 and 1.08 vs. 0.00%, p = 0.48). HPV prevalence in CIN3+ was 94.62% (95% CI 0.88–0.98). Concordance between the assays was 98.60%. conclusion: HPV prevalence in breast cancer is very low suggesting no etiological correlation between HPV and breast cancer. Keywords: breast cancer, HPV, cervical cancer, polymerase chain reaction, Denmark, pathology, human papillomavirus
INTRODUCTION Human papillomavirus (HPV) has been established as the leading cause of cervical cancer (1), and the virus is known to also play a causative role in anal, penile, vulvar, and presumably also head and neck cancer (2). In the past decades, an increase in the incidence of HPV-related cancers has been observed (3–5). HPV is a double-stranded circular DNA virus that replicates in the nucleus of mucosal or cutaneous keratinocytes (6) and so far, over 170 HPV genotypes have been identified.
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MATERIALS AND METHODS
Based on carcinogenic risk, these can be classified as high-risk (HR), probably HR, or low-risk (LR) HPV genotypes (7). Breast cancer accounts for 25% of cancer cases and 15% of cancer-related deaths among women worldwide (8). As a result of the increasing incidence of HPV-related cancers over time and the 30% increase in breast cancer incidence in western countries between 1980 and the late 1990s (8), recent studies have suggested a possible association between HPV and breast cancer. Hansen et al. (9) found that the standardized incidence ratios (SIRs) of breast cancer during 1970–2008 were significantly higher in women with a previous diagnosis of squamous or glandular cervical dysplasia compared to the general female population (SIR, 95% CI for squamous 1.10, 1.05–1.14, for glandular 1.52, 1.11–2.08). Data from Søgaard et al. (10) are less convincing. By using conization as a marker of persistent HPV infection, they showed that conization was associated with a slightly increased breast cancer incidence (SIR, 95% CI 1.10, 1.0–1.1). Nevertheless, several studies suggest that breast cancer in some cases may be initiated by HPV (11–17), whereas other studies disagree (18–20). Due to this discrepancy in the results, we found it is important to explore a possible association between HPV and breast cancer. Thus, in the present study, we aimed to describe the overall prevalence of HPV in breast cancer in Denmark and to explore if women with a previous history of cervical intraepithelial neoplasia grade 3 or worse (CIN3+) carry an increased risk of subsequent HPV-positive breast cancer compared to women with no history.
Setting
We conducted a hospital-based case–control study in Denmark, where all patients have access to the health care system at no cost. Upon birth or immigration, each Danish citizen is assigned a CPR-number, which is a unique code that reflects the person’s age, sex, and the date of birth. Estimates in this study are based upon women who were diagnosed with breast cancer during 1998–2012 at Aarhus University Hospital and Copenhagen University Hospital Herlev.
Data Collection
The Danish Pathology Data Bank (DPDB) is a national databank storing results on all patho-anatomical tests conducted in Denmark, and it used the Systematized Nomenclature of Medicine (SNOMED) as nomenclature and classification system. The study population was identified through two SNOMED searches in the DPDB (Figure 1). A complete list of topography and morphology codes used in these searches is provided in the supplementary material (Supplementary Data S1 in Supplementary Material). The first search was used to define an overall study group of women who had been diagnosed with breast cancer during 1998–2012 at the two above-mentioned Danish hospitals. Women were eligible if they had a histologically verified diagnosis of breast cancer (i.e., ductal carcinoma, lobular
Figure 1 | Flowchart of included women.
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carcinoma, combined ductal/lobular carcinoma, or metaplastic carcinoma), regardless of stage. Women were ineligible if they had a known family history of breast and/or ovarian cancer suggesting BRCA1/BRCA2 mutation, or if they had been diagnosed with triple-negative breast cancer as this type is known to account for at least one-third of BRCA1 mutated tumors (21). Controls were selected randomly from the overall study group. The second search was used to identify an applicable group of women who had a previous diagnosis of CIN3+ in addition to their breast diagnosis (i.e., case group). For the purpose of this study, CIN3+ refers to cases of cervical intraepithelial neoplasia grade 3 or worse (i.e., CIN3, adenocarcinoma in situ, squamous cell carcinoma in situ, squamous cell carcinoma, or adenocarcinoma).
Table 1 | Characteristics of the study population (N = 193). Patients
Breast cancer Age (years) 30–39 40–49 50–59 60–69 70+ Histologic type Ductal carcinoma Lobular carcinoma Combined ductal/ lobular carcinoma Metaplastic carcinoma
Controls
Year at diagnosis 1998–2000 2001–2003 2004–2006 2007–2009 2010–2012
Women in the control group were eligible if they had a record of at least two normal cervical cytology results within 5 years of their breast cancer diagnosis. Women were excluded if they had a previous record of cervical dysplasia or cervical cancer. Overall, 100 women with a diagnosis of breast cancer were included in the control group (Table 1).
CIN3+ Age (years)
