Ovarian stimulation and risk of breast cancer in Swedish women

Fertility drugs and cancer: a guideline

Methodological limitations in studying the association between the use of fertility drugs and cancer include the inherent increased risk of cancer in women who never conceive, the increased risk of cancer because of factors (endometriosis and unopposed estrogen) associated with infertility, the low incidence of most of these cancers, and that the diagnosis of cancer is typically several years after fertility drug use. On the basis of available data, there does not appear to be an association between fertility drugs and breast, colon, or cervical cancer. There is no conclusive evidence that fertility drugs increase the risk of uterine cancer, although women with infertility are at higher risk of uterine cancer. There are insufficient data to comment on the risk of melanoma and non-Hodgkin lymphoma associated with fertility drug use. Women should be informed that there may be an increased risk of invasive and borderline ovarian cancers and thyroid cancer associated with fertility treatment. It is difficult to determine whether this risk is related to underlying endometriosis, female infertility, or nulliparity.

The risk of breast cancer and gynecologic malignancies after ovarian stimulation: Meta-analysis of cohort study

The effects of ovarian stimulation on breast and gynecological tumor incidence remain controversial. Therefore, the aim of this meta-analysis was to study the risk of cancer in ovarian stimulation. Of the 22713 studies initially identified, 28 were eligible for inclusion. The results revealed that the impact of ovarian cancer (RR = 1.33, [1.05; 1.69]) and cervical cancer (RR = 0.67, [0.46; 0.97]) is significant among the overall effects. In subgroup analysis, in the nulliparous population (RR = 0.81 [0.68; 0.96]) was the protective factor for the breast cancer. In the Caucasians subgroup (RR = 1.45, [1.12; 1.88]), the ovarian cancer incidence was statistically significant. In the Asian subgroup (RR = 1.51, [1.00; 2.28]), the endometrial cancer incidence was statistically significant. In the subgroup of Asians (RR = 0.55 [0.44; 0.68]) and the multiparous population (RR = 0.31, [0.21; 0.46]), them can be the statistically protective factor for the cervical cancer.

Published registry-based pharmacoepidemiologic associations show limited concordance with agnostic medication-wide analyses

OBJECTIVES

To assess how the results of published national registry-based pharmacoepidemiology studies (where select associations are of interest) compare with an agnostic medication-wide approach (where all possible drug associations are tested).

STUDY DESIGN AND SETTING

We systematically searched for publications that reported drug associations with any, breast, colon/colorectal, or prostate cancer in the Swedish Prescribed Drug Registry. Results were compared against a previously performed agnostic medication-wide study on the same registry.

PROTOCOL

https://osf.io/kqj8n.

RESULTS

Most published studies (25/32) investigated previously reported associations. 421/913 (46%) associations had statistically significant results. 134 of the 162 unique drug-cancer associations could be paired with 70 associations in the agnostic study (corresponding drug categories and cancer types). Published studies reported smaller effect sizes and absolute effect sizes than the agnostic study, and generally used more adjustments. Agnostic analyses were less likely to report statistically significant protective associations (based on a multiplicity-corrected threshold) than their paired associations in published studies (McNemar odds ratio 0.13, P = 0.0022). Among 162 published associations, 36 (22%) showed increased risk signal and 25 (15%) protective signal at P < 0.05, while for agnostic associations, 237 (11%) showed increased risk signal and 108 (5%) protective signal at a multiplicity-corrected threshold. Associations belonging to drug categories targeted by individual published studies vs. nontargeted had smaller average effect sizes; smaller P values; and more frequent risk signals.

CONCLUSION

Published pharmacoepidemiology studies using a national registry addressed mostly previously proposed associations, were mostly "negative", and showed only modest concordance with their respective agnostic analyses in the same registry.

Assisted reproductive technology treatment and risk of breast cancer: a population-based cohort study

STUDY QUESTION

Is there an increased risk of breast cancer among women after ART treatment including ovarian hormone stimulation?

SUMMARY ANSWER

The risk of breast cancer was slightly increased among women after ART treatment compared to age-matched, untreated women in the background population, and the risk was further increased among women initiating ART treatment when aged 40+ years.

WHAT IS KNOWN ALREADY

The majority of breast cancer cases are sensitive to oestrogen, and ovarian hormone stimulation has been suggested to increase the risk of breast cancer by influencing endogenous oestrogen levels. Previous studies on ART treatment and breast cancer have varied in their findings, but several studies have small sample sizes or lack follow-up time and/or confounder adjustment. Recent childbirth, nulliparity and higher socio-economic status are breast cancer risk factors and the latter two are also associated with initiating ART treatment.

STUDY DESIGN, SIZE, DURATION

The Danish National ART-Couple II (DANAC II) cohort includes women treated with ART at public and private fertility clinics in 1994-2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women with no cancer prior to ART treatment were included (n = 61 579). Women from the background population with similar age and no prior history of ART treatment were randomly selected as comparisons (n = 579 760). The baseline mean age was 33.1 years (range 18-46 years). Results are presented as hazard ratios (HRs) with corresponding CIs.

MAIN RESULTS AND THE ROLE OF CHANCE

During follow-up (median 9.69 years among ART-treated and 9.28 years among untreated), 5861 women were diagnosed with breast cancer, 695 among ART-treated and 5166 among untreated women (1.1% versus 0.9%, P < 0.0001). Using Cox regression analyses adjusted for nulliparity, educational level, partnership status, year, maternal breast cancer and age, the risk of breast cancer was slightly increased among women treated with ART (HR 1.14, 95% CI 1.12-1.16). All causes of infertility were slightly associated with breast cancer risk after ART treatment. The risk of breast cancer increased with higher age at ART treatment initiation and was highest among women initiating treatment at age 40+ years (HR 1.37, 95% CI 1.29-1.45). When comparing women with a first birth at age 40+ years with or without ART treatment, the increased risk among women treated with ART persisted (HR 1.51, 95% CI 1.09-2.08).

LIMITATIONS, REASONS FOR CAUTION

Although this study is based on a large, national cohort of women, more research with sufficient power and confounder adjustment is needed, particularly in cohorts with a broad age representation.

WIDER IMPLICATIONS OF THE FINDINGS

An increased risk of breast cancer associated with a higher age at ART treatment initiation has been shown. Ovarian stimulation may increase the risk of breast cancer among women initiating ART treatment when aged 40+ years. Age-related vulnerability to hormone exposure or higher hormone doses during ART treatment may explain the increased risk.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by a PhD grant to D.V. from the Faculty of Health and Medical Sciences, University of Copenhagen, Denmark. Funding for establishing the DANAC II cohort was received from the Ebba Rosa Hansen Foundation. The authors report no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Fertility treatment and cancers-the eternal conundrum: a systematic review and meta-analysis

STUDY QUESTION

Does fertility treatment (FT) significantly increase the incidence of breast, ovarian, endometrial or cervical cancer?

SUMMARY ANSWER

Overall, FT does not significantly increase the incidence of breast, ovarian or endometrial cancer and may even reduce the incidence of cervical cancer.

WHAT IS KNOWN ALREADY

Infertility affects more than 14% of couples. Infertility and nulliparity are established risk factors for endometrial, ovarian and breast cancer, yet the association with FT is more contentious.

STUDY DESIGN, SIZE, DURATION

A literature search was carried out using Cochrane Library, EMBASE, Medline and Google Scholar up to December 2019. Peer-reviewed studies stating cancer incidence (breast, ovarian, endometrial or cervical) in FT and no-FT groups were identified. Out of 128 studies identified, 29 retrospective studies fulfilled the criteria and were included (n = 21 070 337).

PARTICIPANTS/MATERIALS, SETTING, METHODS

In the final meta-analysis, 29 studies were included: breast (n = 19), ovarian (n = 19), endometrial (n = 15) and cervical (n = 13), 17 studies involved multiple cancer types and so were included in each individual cancer meta-analysis. Primary outcome of interest was cancer incidence (breast, ovarian, endometrial and cervical) in FT and no-FT groups. Secondary outcome was cancer incidence according to specific fertility drug exposure. Odds ratio (OR) and random effects model were used to demonstrate treatment effect and calculate pooled treatment effect, respectively. A meta-regression and eight sub-group analyses were performed to assess the impact of the following variables, maternal age, infertility, study size, outliers and specific FT sub-types, on cancer incidence.

MAIN RESULTS AND THE ROLE OF CHANCE

Cervical cancer incidence was significantly lower in the FT group compared with the no-FT group: OR 0.68 (95% CI 0.46-0.99). The incidences of breast (OR 0.86; 95% CI 0.73-1.01) and endometrial (OR 1.28; 95% CI 0.92-1.79) cancers were not found to be significantly different between the FT and no-FT groups. Whilst overall ovarian cancer incidence was not significantly different between the FT and no-FT groups (OR 1.19; 95% CI 0.98-1.46), separate analysis of borderline ovarian tumours (BOT) revealed a significant association (OR 1.69; 95% CI 1.27-2.25). In further sub-group analyses, ovarian cancer incidence was shown to be significantly higher in the IVF (OR 1.32; 95% CI 1.03-1.69) and clomiphene citrate (CC) treatment group (OR 1.40; 95% CI 1.10-1.77), respectively when compared with the no-FT group. Conversely, the incidences of breast (OR 0.75; 95% CI 0.61-0.92) and cervical cancer (OR 0.58; 95% CI 0.38-0.89) were significantly lower in the IVF treatment sub-group compared to the no-FT group.

LIMITATIONS, REASONS FOR CAUTION

The large, varied dataset spanning a wide study period introduced significant clinical heterogeneity. Thus, results have to be interpreted with an element of caution. Exclusion of non-English citations, unpublished work and abstracts, in order to ensure data accuracy and reliability was maintained, may have introduced a degree of selection bias.

WIDER IMPLICATIONS OF THE FINDINGS

The results for breast, ovarian, endometrial and cervical cancer are reassuring, in line with previously published meta-analyses for individual cancers but the association between IVF and CC treatment and an increase in ovarian cancer incidence requires additional work to understand the potential mechanism driving this association. In particular, focusing on (i) discriminating specific treatments effects from an inherent risk of malignancy; (ii) differential risk profiles among specific patient sub-groups (refractory treatment and obesity); and (iii) understanding the impact of FT outcomes on cancer incidence.

STUDY FUNDING/COMPETING INTEREST(S)

This study did not receive any funding. The authors have no financial, personal, intellectual and professional conflicts of interest to declare.

PROSPERO REGISTRATION NUMBER

CRD42019153404.

Gonadotrophin stimulation and risk of relapse in breast cancer

STUDY QUESTION

Is gonadotrophin stimulation as part of IVF associated with an increased risk of relapse in breast cancer?

SUMMARY ANSWER

Controlled ovarian stimulation (COS) in connection with IVF in women with previous breast cancer was not associated with an increased risk of breast cancer relapse.

WHAT IS KNOWN ALREADY

Breast cancer is the most common malignancy among women worldwide and the leading cause of cancer death among females. The use of COS with gonadotrophins with subsequent cryopreservation of oocytes or embryos in order to enhance the chances of pregnancy after cancer treatment is the current most established fertility preservation method for women with breast cancer. To date, there are only a few small retrospective hospital-based controlled studies evaluating the risk of breast cancer relapse in patients undergoing fertility preservation with or without COS, showing no evident risk of relapse in breast cancer after the use of gonadotoxic agents.

STUDY DESIGN, SIZE, DURATION

This was a retrospective, population-based cohort study comprising 5857 women with previous breast cancer of whom 337 were exposed to COS. Exposure (COS) and outcomes (relapse and death) were identified for all patients from 2005 to 2014 by assessing the National Quality Register for Assisted Reproduction, the Swedish Medical Birth Register, the National Patient Register, the Swedish Prescribed Drug Register, the Swedish Cause of Death Register, the National Breast Cancer Register and the Swedish Cancer Register. Matching according to set criteria was possible for 334 women, who constituted the control group. A total of 274 women had undergone IVF after completing breast cancer treatment and 63 women had undergone COS for fertility preservation at the time of breast cancer diagnosis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women aged 20–44 years previously diagnosed with breast cancer and exposed to COS were matched for age at breast cancer diagnosis ±5 years, tumour size and lymph node involvement with a non-exposed control group, including women with known T- and N-stages. In a subsequent analysis, the matched cohort was assessed by also including women with unknown T- and N-stages. A secondary analysis comprised the entire non-matched cohort, including all women with known T- and N-stages. Also here, a subsequent analysis included women with missing data for T- and N-stages. The risk of relapse in breast cancer was estimated as crude hazard ratios (HRs) and 95% CI using Cox proportional hazards models in the primary and secondary analyses where T- and N-stages were known: otherwise the risks of relapse were only given descriptively.

MAIN RESULTS AND THE ROLE OF CHANCE

In the primary matched analysis, relapse occurred in 20 of 126 women exposed to COS (15.9%) compared with 39 of 126 (31.0%) in the control cohort (HR = 0.70; 95% CI 0.39–1.45; P = 0.22). In the subsequent analysis, also including women with unknown T- and N-stages, relapse occurred in 27 of 337 (8.0%) women having undergone COS compared with 71/334 (21.3%) among the non-exposed. In the secondary adjusted analysis, relapse occurred in 20 of 126 (15.9%) exposed women and in 918 of 3729 (24.6%) non-exposed women (HR = 0.81; 95% CI 0.49–1.33; P = 0.70). In the subsequent analysis, including unknown T- and N-stages, relapse occurred in 27 of 337 (8.0%) women in the exposed group and 1176 of 5520 (21.3%) in the non-exposed cohort.

LIMITATIONS, REASONS FOR CAUTION

A substantial degree of missing data on important prognostic variables was a limitation, particularly when analysing the total cohort. Furthermore, data on confounding factors, such as BMI, were not completely covered. Another limitation was that a pre-specified variable for relapse was not in use for the majority of the National Breast Cancer Register. Furthermore, the follow-up time from available register data (2005–2014) is rather short. Finally, we cannot be sure whether the prognostic information from receptor status, showing a lower incidence in the exposed group, is representative. Information on T- and N-stages was missing in more than half of the patients.

WIDER IMPLICATIONS OF THE FINDINGS

In this large, retrospective, matched cohort study, we found no increased risk of relapse in breast cancer among women who had been exposed to gonadotrophins as part of IVF. This is reassuring but might be confounded by the selection of a group of women with a more favourable prognosis than those not undergoing IVF. The present study strengthens previous findings by being large, national and register based. Its results are applicable to women undergoing fertility preservation as well as to those undergoing regular IVF treatment.

STUDY FUNDING/COMPETING INTEREST(S)

Supported in part by grants from the Swedish state under the agreement between the Swedish government and the county councils the ALF-agreement (ALFGBG-720291), The Assar Gabrielsson Fund (FB 15-20), The Breast Cancer Fund and the Swedish Association of Local authorities and Regions, SKR. There are no conflicts of interest to declare.

TRIAL REGISTRATION

N/A

Cancer in IVF patients treated at age 40 years and older: long term follow-up

RESEARCH QUESTION

Current knowledge of cancer risk among women who undergo IVF is based mainly on studies of women treated in their thirties, frequently with short follow-up periods. Therefore, information about cancer risk among infertile menopausal women is limited. We aimed to evaluate the risk of cancer among IVF patients treated at age 40 years and older, followed up for an extended period.

DESIGN

Historical cohort study of all IVF patients treated at the age of 40 years or older at two university-affiliated IVF units in Jerusalem, Israel, between 1994 and 2002. Data were cross-linked with the Israel National Cancer Registry to 2016. Standardized incidence ratios (SIR) and 95% confidence intervals were computed by comparing the observed number of cancer cases with the expected cancer rate in the general Israeli population adjusted for age and year of birth. In addition, Kaplan-Meier analysis was conducted to account for the length of follow-up.

RESULTS

A total of 501 patients were included in the analysis, with mean follow-up of 16.7 ± 3.7 years (range 2-22 years). Mean age at first IVF cycle was 42.3 years (±2.1). Mean number of IVF cycles was 3.2 ± 2.6 (range 1-15). Thirty-six women (7.2%) developed invasive cancer, compared with 47.2 expected cases; SIR 0.76 (95% CI 0.53 to 1.06); 22 women were diagnosed with invasive breast cancer, compared with 19.84 expected; SIR 1.11 (95% CI 0.69 to 1.68).

CONCLUSIONS

Older women undergoing IVF treatment were not significantly associated with an excess risk of cancer at long-term follow up. Further studies, however, are needed to confirm these findings.

A Cohort Study of Breast Cancer Risk after 20 Years of Follow-Up of Women Treated with Fertility Drugs

BACKGROUND

Using a nationwide cohort of Danish women, we investigated the association between use of fertility drugs and risk of breast cancer.

METHODS

The study cohort included women ages 20 to 44 years and living in Denmark between January 1, 1995 and December 31, 2011. Information on fertility status, use of fertility drugs, breast cancer, covariates, and vital status was obtained from the Danish Infertility Cohort and various Danish national registers. Cox proportional hazard regression models were applied to estimate hazard ratios (HR) and 95% confidence intervals (CI), adjusted for potential confounders.

RESULTS

Of the 1,330,852 women included, 96,782 (7.3%) were infertile, and 20,567 (1.5%) were diagnosed with breast cancer during a median follow-up of 20.9 years. Compared with fertile women, infertile women who had used any fertility drugs did not have an increased hazard for breast cancer overall (HR = 1.02; 95% CI, 0.95-1.10), or for any of the histologic types (ductal, lobular, or mucinous) of breast cancer. Furthermore, no associations were observed between use of specific types of fertility drugs and breast cancer.

CONCLUSIONS

No convincing associations between use of fertility drugs and breast cancer were observed after two decades of follow-up.

IMPACT

Our results do not support a marked association between fertility drugs and breast cancer and are therefore reassuring for infertile women treated with fertility drugs.

The risk of breast and gynecological cancer in women with a diagnosis of infertility: a nationwide population-based study

Some studies have suggested that infertility is a risk factor for endometrial, ovarian and breast cancer. The study aimed to create a comprehensive picture of the association between infertility and the risk of ovarian, endometrial and breast cancer, and whether any association could be explained by ovulatory disturbances, endometriosis or nulliparity. In a population-based cohort of 2,882,847 women, cox regression analysis was used to investigate cancer incidence among infertile women. Overall, infertility was associated with a higher incidence rate of ovarian (adjusted hazard ratio [aHR] 1.53, 95% confidence interval [CI] 1.38-1.71) and endometrial cancer (aHR 1.25, 95% CI 1.11-1.40), but not of breast cancer (aHR 0.96, 95% CI 0.92-1.01). Ovarian cancer incidence was higher in women diagnosed with endometriosis, and in nulliparous women with ovulatory disturbances, compared to women with none of the diagnoses. Endometrial cancer incidence was higher in women with ovulatory disturbances, but not in women with endometriosis. These findings suggest that infertility could have long-term consequences of importance to physicians and public health workers.

Do the Fertility Drugs Increase the Risk of Cancer? A Review Study

Aim: All over the world, many couples cannot conceive a child and have problems with pregnancy. Ovulation-inducing drugs are among the most important drugs used for the treatment of infertility. In recent years, there have been many debates about the relationship between fertility medication and cancer. Due to the lack of comprehensive study of this matter, and as understanding the relationship between the use of fertility drugs and cancer is of importance, the present study was conducted to investigate the relationship between infertility drugs and cancer in women. Materials and Methods: To determine the relationship between infertility treatment and cancer, a comprehensive search was carried out in databases such as; Medline, Web of Science Core Collection, and Scopus using keywords words; "infertility," "ovulation induction," "cancer," "infertility treatment," "ART," "tumor," "controlled ovarian stimulation," "fertility agents," and "neoplasms." Full-text, English language, and original articles were included in this study. Results: In total, 81 articles were entered into the study. The relationship between fertility medications and breast, ovary, endometrial, uterus, colon, thyroid, skin, cervical, and non-Hodgkin's lymphoma cancers were studied. Although the relationship between fertility medications and cancer is theoretically justifiable, most studies have shown that risk of cancer will not increase after fertility treatment. Conclusion: The results of this study did not show that fertility medications increase the risk of cancer among users. In summary, the relationship between infertility treatment and cancer incidence remains an open question.

Identification of Differentially Expressed Genes between Original Breast Cancer and Xenograft Using Machine Learning Algorithms

Breast cancer is one of the most common malignancies in women. Patient-derived tumor xenograft (PDX) model is a cutting-edge approach for drug research on breast cancer. However, PDX still exhibits differences from original human tumors, thereby challenging the molecular understanding of tumorigenesis. In particular, gene expression changes after tissues are transplanted from human to mouse model. In this study, we propose a novel computational method by incorporating several machine learning algorithms, including Monte Carlo feature selection (MCFS), random forest (RF), and rough set-based rule learning, to identify genes with significant expression differences between PDX and original human tumors. First, 831 breast tumors, including 657 PDX and 174 human tumors, were collected. Based on MCFS and RF, 32 genes were then identified to be informative for the prediction of PDX and human tumors and can be used to construct a prediction model. The prediction model exhibits a Matthews coefficient correlation value of 0.777. Seven interpretable interactions within the informative gene were detected based on the rough set-based rule learning. Furthermore, the seven interpretable interactions can be well supported by previous experimental studies. Our study not only presents a method for identifying informative genes with differential expression but also provides insights into the mechanism through which gene expression changes after being transplanted from human tumor into mouse model. This work would be helpful for research and drug development for breast cancer.