Register-based studies of cancer screening effects

Manifest diabetes after gestational diabetes: a double-cohort, long-term follow-up in a Danish population

PURPOSE

The aim was to follow-up two cohorts of women with GDM to investigate the incidence and time of diagnosis of manifest diabetes mellitus (DM) postpartum and identify the risk factors for diabetes in our population.

METHODS

A follow-up study on two independent cohorts having oral glucose tolerance test (OGTT) in 1991/1992 and 2011-2016: Cohort 1 consisted of 406 women including 54 with GDM and 352 with a non-GDM OGTT-test and cohort 2 had 433 women diagnosed with GDM. The first cohort had nearly 25 years of follow-up and gave information on magnitude, conversion rate and type of diabetes manifestation. The second cohort was started recently to evaluate whether newer diagnostic criteria and baseline information on the old cohort are still valid for prediction of diabetes risk.

RESULTS

The risk of manifest diabetes in cohort 1 at the end of follow-up was six times higher in women with previous GDM compared with non-GDM (RR = 6; 95% CI 4-11). We observed a 70% diabetes rate 25 years after pregnancy. Only family history of diabetes in cohort 2 was associated with conversion to manifest diabetes (p = 0.002), also after adjustment for age, BMI, non-Danish origin and smoking during pregnancy (p < 0.001) CONCLUSION: The incidence of diabetes after GDM is higher than that previously reported in Scandinavian populations and the rate of manifest diabetes rises steeply 15 years after pregnancy and after 40 years of age. The women of cohort 2 with recent GDM are at risk of DM at a higher rate. On this background our results are useful in identifying the time where GDM women may benefit from the effective implementation of evidence-based treatment to postpone and advert manifest DM.

Final analysis of a 14-year long-term follow-up study of the effectiveness and immunogenicity of the quadrivalent human papillomavirus vaccine in women from four nordic countries

BACKGROUND

The quadrivalent human papillomavirus (qHPV) vaccine prevented vaccine HPV type-related infection and disease in young women in the 4-year FUTURE II efficacy study (NCT00092534). We report long-term effectiveness and immunogenicity at the end of 14 years of follow-up after enrollment in FUTURE II.

METHODS

Young women (16-23 years of age) from Denmark, Iceland, Norway, and Sweden who received three qHPV vaccine doses during the randomized, double-blind, placebo-controlled FUTURE II base study were followed for effectiveness for an additional ≥10 years through national registries. Tissue samples including but not limited to those collected during organized cervical cancer screening programs were obtained from regional biobanks to be adjudicated for histopathology diagnosis and tested for HPV DNA. The observed incidence of HPV16/18-related high-grade cervical dysplasia (primary outcome) was compared with recent historical background incidence rates in an unvaccinated population. Serum was collected at years 9 and 14 to assess antibody responses.

FINDINGS

No cases of HPV16/18-related high-grade cervical dysplasia were observed in the per-protocol effectiveness population (N = 2121; 24,099·0 person-years of follow-up) during the entire study. Vaccine effectiveness of 100% (95% CI 94·7-100) was demonstrated for ≥12 years, with a trend toward continued protection through 14 years post-vaccination. Seropositivity rates at study conclusion were >90% (HPV6/11/16) and 52% (HPV18) using competitive Luminex immunoassay, and >90% (all four HPV types) using the more sensitive IgG Luminex immunoassay.

INTERPRETATION

Vaccination of young women with qHPV vaccine offers durable protection against HPV16/18-related high-grade cervical dysplasia for ≥12 years, with a trend toward continued protection through 14 years post-vaccination, and induces sustained HPV6/11/16/18 antibody responses for up to 14 years post-vaccination. There was no evidence of waning immunity, suggesting no need for a booster dose during that period.

FUNDING

Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

Negative controls to detect uncontrolled confounding in observational studies of mammographic screening comparing participants and non-participants

BACKGROUND

When comparing mammography-screening participants and non-participants, estimates of reduction in breast-cancer mortality may be biased by poor baseline comparability. We used negative controls to detect uncontrolled confounding.

METHODS

We designed a closed cohort of Danish women invited to a mammography-screening programme at age 50-52 years in Copenhagen or Funen from 1991 through 2001. We included women with a normal screening result in their first-invitation round. Based on their second-invitation round, women were divided into participants and non-participants and followed until death, emigration or 31 December 2014, whichever came first. We estimated hazard ratios (HRs) of death from breast cancer, causes other than breast cancer and external causes. We added dental-care participation as an exposure to test for an independent association with breast-cancer mortality. We adjusted for civil status, parity, age at first birth, educational attainment, income and hormone use.

RESULTS

Screening participants had a lower hazard of breast-cancer death [HR 0.47, 95% confidence interval (CI) 0.32, 0.69] compared with non-participants. Participants also had a lower hazard of death from other causes (HR 0.43, 95% CI 0.39, 0.46) and external causes (HR 0.35, 95% CI 0.23, 0.54). Reductions persisted after covariate adjustment. Dental-care participants had a lower hazard of breast-cancer death (HR 0.75, 95% CI 0.56, 1.01), irrespective of screening participation.

CONCLUSIONS

Negative-control associations indicated residual uncontrolled confounding when comparing breast-cancer mortality among screening participants and non-participants.

Cervical Cancer Screening Programs in Europe: The Transition Towards HPV Vaccination and Population-Based HPV Testing

Cervical cancer is the fourth most frequently occurring cancer in women around the world and can affect them during their reproductive years. Since the development of the Papanicolaou (Pap) test, screening has been essential in identifying cervical cancer at a treatable stage. With the identification of the human papillomavirus (HPV) as the causative agent of essentially all cervical cancer cases, HPV molecular screening tests and HPV vaccines for primary prevention against the virus have been developed. Accordingly, comparative studies were designed to assess the performance of cervical cancer screening methods in order to devise the best screening strategy possible. This review critically assesses the current cervical cancer screening methods as well as the implementation of HPV vaccination in Europe. The most recent European Guidelines and recommendations for organized population-based programs with HPV testing as the primary screening method are also presented. Lastly, the current landscape of cervical cancer screening programs is assessed for both European Union member states and some associated countries, in regard to the transition towards population-based screening programs with primary HPV testing.

When Life Got in the Way: How Danish and Norwegian Immigrant Women in Sweden Reason about Cervical Screening and Why They Postpone Attendance

Introduction

Danish and Norwegian immigrant women in Sweden have an increased risk of cervical cancer compared to Swedish-born women. In addition, Danish and Norwegian immigrant women follow the national recommendations for attendance at cervical screening to much lesser extent than Swedish-born women. The aim of this study was to explore how Danish and Norwegian immigrant women in Sweden reason about attending cervical screening, focusing on women’s perceptions as to why they and their compatriots do not attend.

Methods

Eight focus group discussions (FGDs) were conducted with Danish and Norwegian immigrant women living in Stockholm. The women were between 26 and 66 years of age at the time of the FGDs, and were aged between <1 and 48 years old when they immigrated to Sweden. A FGD guide was used, which included questions related to cervical screening, and obstacles and motivators to attend cervical screening. The FGDs were tape recorded and transcribed, and the results analysed according to the principles of qualitative content analysis.

Results

The main theme was “Women have a comprehensive rationale for postponing cervical screening, yet do not view themselves as non-attenders”. Investigation of women’s rationale for non-attendance after being invited to cervical screening revealed some complex reasons related to immigration itself, including competing needs, organisational and structural factors and differences in mentality, but also reasons stemming from other factors. Postponing attendance at cervical screening was the category that linked all these factors as the reasons to why women did not attend to cervical screening according to the recommendations of the authorities.

Conclusions

The rationale used to postpone cervical screening, in combination with the fact that women do not consider themselves to be non-attenders, indicates that they have not actively taken a stance against cervical screening, and reveals an opportunity to motivate these women to attend.

Effect of treatment and mammography detection on breast cancer survival over time: 1990-2007

BACKGROUND

The extent to which improvements over time in breast cancer survival are related to earlier detection by mammography or to more effective treatments is not known.

METHODS

At a comprehensive cancer care center, the authors conducted a retrospective cohort study of women ages 50 to 69 years who were diagnosed with invasive breast cancer (stages I through III) and were followed over 3 periods (1990-1994, 1995-1999, and 2000-2007). Data were abstracted from patient charts and included detection method, diagnosis, treatment, and follow-up for vital status in the institutional breast cancer registry (n = 2998). The method of detection was categorized as patient or physician detected or mammography detected. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for 5-year disease-specific survival in relation to detection method and treatment factors, and differences in survival were analyzed using the Kaplan-Meier method.

RESULTS

Fifty-eight percent of breast cancers were mammography detected, and 42% were patient or physician detected; 56% of tumors were stage I, 31% were stage II, and 13% were stage III. The average length of follow-up was 10.71 years. The combined 5-year disease-specific survival rate was 89% from 1990 to 1994, 94% from 1995 to 1999, and 96% from 2000 to 2007 (P < .001). In an adjusted model, mammography detection (HR, 0.43; 95% CI, 0.27-0.70), hormone therapy (HR, 0.47; 95% CI, 0.30-0.75), and taxane-containing chemotherapy (HR, 0.61; 95% CI, 0.37-0.99) were significantly associated with a decreased risk of disease-specific mortality.

CONCLUSIONS

Better breast cancer survival over time was related to mammography detection, hormone therapy, and taxane-containing chemotherapy. Treatment improvements alone are not sufficient to explain the observed survival improvements over time.

Measuring the burden of interval cancers in long-standing screening mammography programmes

Objectives

Mammography screening programme sensitivity is evaluated by comparing the interval cancer rate (ICR) with the expected breast cancer incidence without screening, ie. the proportional interval cancer rate (PICR). The PICR is usually found by extrapolating pre-screening incidence rates, whereas ICR is calculated from data available in the screening programmes. As there is no consensus regarding estimation of background incidence, we seek to validate the ICR measure against the PICR.

Methods

Screening data from the three mammography screening programmes of Stockholm, Copenhagen, and Funen in the period 1989-2011 provided data to calculate the ICR. The most commonly described methods of extrapolating pre-screening incidence rates to calculate the PICR were illustrated and PICRs were calculated by year and programme using these different methods and compared with the ICRs.

Results

PICRs varied greatly, reaching a difference of 32–34% in Stockholm, 79% in Copenhagen, and 100–106% in Funen between the highest and the lowest value, depending on which method was applied. PICRs exhibited large variations yearly and from programme to programme. ICRs did not vary to the same extent, ranging on average from 0.100 to 0.136 in the first 12-months and between 0.201 and 0.225 in the last 12-months of the two-year period after a negative screen across the three programmes.

Conclusion

The value of the PICR is hugely influenced by which method is applied, whereas the ICR is calculated purely on data available within programmes. We find that the PICR, the establishing indicator for sensitivity, could preferably be replaced by the ICR.

Is mammography screening history a predictor of future breast cancer risk?

Inspired by the model by Walter and Day for risk of cervical cancer following negative screens, one might hypothesize that women in a mammography screening programme with a certain number of negative screens had a lower remaining breast cancer risk than that of women in general. We studied whether number of negative screens was a predictor for a low remaining breast cancer risk in women participating in the mammography screening programmes in Stockholm, Copenhagen and Funen. Data were collected from the mammography screening programmes in Stockholm, Sweden (1989-2012), Copenhagen, Denmark (1991-2009) and Funen, Denmark (1993-2009), and linked to the respective cancer registries. We calculated cumulative hazard rates for breast cancer in women in cohorts defined by age at entry and number of negative screens for the maximum follow-up period in each screening centre. For all centres and cohorts, the cumulative hazard were parallel for all number of negative screens, from after the time, when the women were scheduled to be invited for the next screen. This means that the remaining breast cancer risk is similar no matter how many negative screens a woman have had. Number of negative screens was not a predictor of a low remaining breast cancer risk in women participating in the mammography screening programmes in Stockholm, Sweden, Copenhagen and Funen, Denmark. The history of previous negative screens is therefore not suitable for personalisation of mammography screening.

Healthcare spending in the case of a HPV16/18 population-wide vaccination programme

BACKGROUND

The policy of population-wide human papillomavirus (HPV) vaccination has been debated as the introduction of such a programme in a low-resource country faces the risk of insufficient cost-effectiveness.

OBJECTIVES

To assess the potential healthcare spending changes after the introduction of a HPV16/18 population-wide vaccination programme in Lithuania.

STUDY DESIGN

For a cost-effectiveness analysis, we used mathematical simulation and epidemiological data modelling based on a Lithuanian female population. We performed comparative analysis of an annual 12-year-old girls population-wide vaccination programme combined with cervical cancer screening programme compared to the screening programme strategy only.

RESULTS

HPV vaccination would gain an average of 35.6 life years per death avoided or up to 284.8 thousand life years would be gained over 90 years in total. The programme costs would be 2932.58 EUR per life year gained. All costs associated with the introduction of the vaccination programme could be recovered in 48 years. The HPV vaccination programme in Lithuania has the potential to generate up to 40.07 million EUR of economic returns annually compared with the current practice of the cervical screening alone.

CONCLUSIONS

In Lithuania the HPV16/18 vaccination programme would be economically effective only in the long term. The investment costs of HPV16/18 vaccination have the potential to be recovered.