Have the recent advancements in cancer therapy and survival benefitted patients of all age groups across the Nordic countries? NORDCAN survival analyses 2002-2021.

BACKGROUND: Since the early 2000s, overall and site-specific cancer survival have improved substantially in the Nordic countries. We evaluated whether the improvements have been similar across countries, major cancer types, and age groups. MATERIAL AND METHODS: Using population-based data from the five Nordic cancer registries recorded in the NORDCAN database, we included a cohort of 1,525,854 men and 1,378,470 women diagnosed with cancer (except non-melanoma skin cancer) during 2002-2021, and followed for death until 2021. We estimated 5-year relative survival (RS) in 5-year calendar periods, and percentage points (pp) differences in 5-year RS from 2002-2006 until 2017-2021. Separate analyses were performed for eight cancer sites (i.e. colorectum, pancreas, lung, breast, cervix uteri, kidney, prostate, and melanoma of skin). RESULTS: Five-year RS improved across nearly all cancer sites in all countries (except Iceland), with absolute differences across age groups ranging from 1 to 21 pp (all cancer sites), 2 to 20 pp (colorectum), -1 to 36 pp (pancreas), 2 to 28 pp (lung), 0 to 9 pp (breast), -11 to 26 pp (cervix uteri), 2 to 44 pp (kidney), -2 to 23 pp (prostate) and -3 to 30 pp (skin melanoma). The oldest patients (80-89 years) exhibited lower survival across all countries and sites, although with varying improvements over time. INTERPRETATION: Nordic cancer patients have generally experienced substantial improvements in cancer survival during the last two decades, including major cancer sites and age groups. Although survival has improved over time, older patients remain at a lower cancer survival compared to younger patients.

Do investments in cancer registry databases and tools bring added value? NORDCAN as an example.

BACKGROUND: In the 1990s, the large-scale collaboration Kreftbildet i Norden (KIN) drew attention to the need for timely cancer statistics for cancer control planning in the Nordic countries. Supported by the Nordic Cancer Union (NCU), a web-based version of NORDCAN was continually developed by the Association of Nordic Cancer Registries (ANCR) from 2003, with website support and hosting by the International Agency for Research on Cancer (IARC). Despite empirical evidence of its global reach, the question of whether recurrent investment in NORDCAN brings added value was raised; we sought to formally assess this. METHODS: Scientific value was determined by extracting publications citing NORDCAN from PubMed. We compared the funds allocated to the KIN project and later Nordic studies on cancer predictions and survival, with those allocated to NORDCAN. RESULTS: 96 publications in 43 journals were retrieved. Two publication peaks, in 2010 and in 2016 relate to Nordic cancer survival and Danish age care projects, respectively. Papers citing NORDCAN increased substantially from 4 published in 2017 to the 24 papers in 2022. The integration of survival and prediction projects into NORDCAN reduced the costs of investment to one-quarter of the those required in earlier years, in real terms. DISCUSSION: User statistics and scientific output clearly points to NORDCAN bringing added value given resources expended, even with the additional costs imposed to ensure GDPR compliance. Research funding indicates that the databases and interactive tools are critical as both research and education resources. Nonetheless, a sustainable funding model is needed if NORDCAN is to continue to fulfill its utility in cancer control, health care planning and cancer research.

The acceptance and applicability of a patient-reported experience measurement tool in oncological care: a descriptive feasibility study in northern Germany.

BACKGROUND: Patient-reported outcome measures (PROMs) and patient-reported experience measures (PREMs) are tools for assessing outcomes of and experiences with health care from the patient's perspective. In Germany, PROMs are widely used in research for evaluating patient outcomes and quality of care. However, the application of PREMs is rather scant, especially in oncology. The study aimed to assess the feasibility of patient-centred quality evaluation in oncological care in Germany using the German adaptation of the Danish National Cancer Patient Questionnaire. This questionnaire is a PREM/PROM-tool addressing patients of all cancer sites and covering the entire cancer patient pathway. METHODS: The Danish National Cancer Patient Questionnaire was translated into German via forward-backward translation. Face-validity was tested among three cancer patients in a conventional pre-test. The German adaptation contains 99 questions. A pilot test was carried out among 245 newly diagnosed breast and colorectal cancer patients in the German federal state Schleswig-Holstein. Patients were recruited via clinics participating in the Oncological Care Registry (12 specialised units in seven hospitals) and contacted six to nine months after diagnosis. Response behaviour and response patterns were compared to the Danish study population (n = 1964). RESULTS: The willingness among clinicians to support patient recruitment as well as the response rate of patients to the questionnaire was high (65%). Moreover, response behaviour and response patterns of German and Danish patients were consistent. Despite the generally good response behaviour of patients to the single items, the authors observed that questions assessing the diagnostic process did not fully capture German pathways. Only 19.3% of the German patients stated that their diagnostic process was initiated by a visit to a general practitioner (GP) in contrast to 52% in Denmark. The assessment of patient experiences in the diagnostic phase heavily focuses on experiences in general practice, which does not seem appropriate in the German health care setting. CONCLUSION: The translation was successful, and the feasibility of a future large-scale study within existing structures is given. However, some modifications of questions heavily related to the Danish health care system, especially referring to the diagnostic phase, are necessary.

Cancer After Liver Transplantation in Children and Young Adults: A Population-Based Study From 4 Nordic Countries.

Cancer after liver transplantation (LT) constitutes a threat also for young recipients, but cancer risk factors are usually absent in children and large studies on the cancer risk profile in young LT recipients are scarce. Data of patients younger than 30 years who underwent LT during the period 1982-2013 in the Nordic countries were linked with respective national cancer registries to calculate standardized incidence ratios (SIRs). A total of 37 cancer cases were observed in 923 patients with 7846 person-years of follow-up. The SIR for all cancer types, compared with the matched general population, was 9.8 (12.4 for males and 7.8 for females). Cumulative incidence of cancer adjusted for the competing risk of death was 2% at 10 years, 6% at 20 years, and 22% at 25 years after LT. Non-Hodgkin lymphoma was the most common cancer type (n = 14) followed by colorectal (n = 4) and hepatocellular cancer (n = 4). Age was a significant risk factor for cancer, and the absolute risk of most cancers (except for lymphoma) increased considerably in young adults older than 20 years. The cancer risk pattern is different in pediatric and young LT patients compared with adult recipients. The striking increase in cancer incidence in young adulthood after the second decade of life deserves further consideration in transition programs.

Nordic Cancer Registries - an overview of their procedures and data comparability.

BACKGROUND: The Nordic Cancer Registries are among the oldest population-based registries in the world, with more than 60 years of complete coverage of what is now a combined population of 26 million. However, despite being the source of a substantial number of studies, there is no published paper comparing the different registries. Therefore, we did a systematic review to identify similarities and dissimilarities of the Nordic Cancer Registries, which could possibly explain some of the differences in cancer incidence rates across these countries. METHODS: We describe and compare here the core characteristics of each of the Nordic Cancer Registries: (i) data sources; (ii) registered disease entities and deviations from IARC multiple cancer coding rules; (iii) variables and related coding systems. Major changes over time are described and discussed. RESULTS: All Nordic Cancer Registries represent a high quality standard in terms of completeness and accuracy of the registered data. CONCLUSIONS: Even though the information in the Nordic Cancer Registries in general can be considered more similar than any other collection of data from five different countries, there are numerous differences in registration routines, classification systems and inclusion of some tumors. These differences are important to be aware of when comparing time trends in the Nordic countries.

Cancer risks after solid organ transplantation and after long-term dialysis.

Immunosuppression involves an inability to control virus infections and increased incidence of virus-associated cancers. Some cancers without known viral etiology are also increased, but data on exactly which cancer forms are increased has been inconsistent. To provide a reliable and generalizable estimate, with high statistical power and long follow-up time, we assessed cancer risks using comprehensive, population-based registries in two different countries and from two different immunosuppressed patient groups (solid organ transplant recipients (OTRs) and long-term dialysis patients (LDPs)). National registries in Denmark and Sweden identified 20,804 OTRs and 31,140 LDPs that were followed up using national cancer registries. Standardized incidence ratios (SIR) compared to the general population were estimated. We found highly similar results, both for the two different countries and for the two different immunosuppressed cohorts, namely an increased incidence for the following specific cancer forms: Non-melanoma skin cancer (NMSC), non-Hodgkin's lymphoma and cancers of the lip, kidney, larynx and thyroid. The SIR for overall cancer among OTRs was 3.5 [n = 2,142, 95% CI, 3.4-3.7] in Sweden, 2.9 [n = 1,110, 95% CI, 2.8-3.1] in Denmark and 1.6 [n = 1,713, 95% CI, 1.5-1.6] among LDP. The SIR for NMSC among OTRs was 44.7 [n = 994, 95% CI, 42-47.5] in Sweden and 41.5 [n = 445, 95% CI, 37.8-45.5] in Denmark. The increased SIR for NMSC among LDPs was 5.3 [n = 304, 95% CI, 4.7-5.9]). In summary, an increased SIR for a specific, similar set of cancer forms is consistently found among the immunosuppressed. Conceivable explanations include surveillance bias and immunosuppression-related susceptibility to viral infections.

Increased pancreatic cancer risk following radiotherapy for testicular cancer.

BACKGROUND: Pancreatic cancer risk is elevated among testicular cancer (TC) survivors. However, the roles of specific treatments are unclear. METHODS: Among 23 982 5-year TC survivors diagnosed during 1947-1991, doses from radiotherapy to the pancreas were estimated for 80 pancreatic cancer patients and 145 matched controls. Chemotherapy details were recorded. Logistic regression was used to estimate odds ratios (ORs). RESULTS: Cumulative incidence of second primary pancreatic cancer was 1.1% at 30 years after TC diagnosis. Radiotherapy (72 (90%) cases and 115 (80%) controls) was associated with a 2.9-fold (95% confidence interval (CI) 1.0-7.8) increased risk. The OR increased linearly by 0.12 per Gy to the pancreas (P-trend<0.001), with an OR of 4.6 (95% CI 1.9-11.0) for ⩾25 Gy vs <25 Gy. Radiation-related risks remained elevated ⩾20 years after TC diagnosis (P=0.020). The risk increased with the number of cycles of chemotherapy with alkylating or platinum agents (P=0.057), although only one case was exposed to platinum. CONCLUSIONS: A dose-response relationship exists between radiation to the pancreas and subsequent cancer risk, and persists for over 20 years. These excesses, although small, should be considered when radiotherapy with exposure to the pancreas is considered for newly diagnosed patients. Additional data are needed on the role of chemotherapy.

Global surveillance of cancer survival 1995-2009: analysis of individual data for 25,676,887 patients from 279 population-based registries in 67 countries (CONCORD-2).

BACKGROUND: Worldwide data for cancer survival are scarce. We aimed to initiate worldwide surveillance of cancer survival by central analysis of population-based registry data, as a metric of the effectiveness of health systems, and to inform global policy on cancer control. METHODS: Individual tumour records were submitted by 279 population-based cancer registries in 67 countries for 25·7 million adults (age 15-99 years) and 75,000 children (age 0-14 years) diagnosed with cancer during 1995-2009 and followed up to Dec 31, 2009, or later. We looked at cancers of the stomach, colon, rectum, liver, lung, breast (women), cervix, ovary, and prostate in adults, and adult and childhood leukaemia. Standardised quality control procedures were applied; errors were corrected by the registry concerned. We estimated 5-year net survival, adjusted for background mortality in every country or region by age (single year), sex, and calendar year, and by race or ethnic origin in some countries. Estimates were age-standardised with the International Cancer Survival Standard weights. FINDINGS: 5-year survival from colon, rectal, and breast cancers has increased steadily in most developed countries. For patients diagnosed during 2005-09, survival for colon and rectal cancer reached 60% or more in 22 countries around the world; for breast cancer, 5-year survival rose to 85% or higher in 17 countries worldwide. Liver and lung cancer remain lethal in all nations: for both cancers, 5-year survival is below 20% everywhere in Europe, in the range 15-19% in North America, and as low as 7-9% in Mongolia and Thailand. Striking rises in 5-year survival from prostate cancer have occurred in many countries: survival rose by 10-20% between 1995-99 and 2005-09 in 22 countries in South America, Asia, and Europe, but survival still varies widely around the world, from less than 60% in Bulgaria and Thailand to 95% or more in Brazil, Puerto Rico, and the USA. For cervical cancer, national estimates of 5-year survival range from less than 50% to more than 70%; regional variations are much wider, and improvements between 1995-99 and 2005-09 have generally been slight. For women diagnosed with ovarian cancer in 2005-09, 5-year survival was 40% or higher only in Ecuador, the USA, and 17 countries in Asia and Europe. 5-year survival for stomach cancer in 2005-09 was high (54-58%) in Japan and South Korea, compared with less than 40% in other countries. By contrast, 5-year survival from adult leukaemia in Japan and South Korea (18-23%) is lower than in most other countries. 5-year survival from childhood acute lymphoblastic leukaemia is less than 60% in several countries, but as high as 90% in Canada and four European countries, which suggests major deficiencies in the management of a largely curable disease. INTERPRETATION: International comparison of survival trends reveals very wide differences that are likely to be attributable to differences in access to early diagnosis and optimum treatment. Continuous worldwide surveillance of cancer survival should become an indispensable source of information for cancer patients and researchers and a stimulus for politicians to improve health policy and health-care systems. FUNDING: Canadian Partnership Against Cancer (Toronto, Canada), Cancer Focus Northern Ireland (Belfast, UK), Cancer Institute New South Wales (Sydney, Australia), Cancer Research UK (London, UK), Centers for Disease Control and Prevention (Atlanta, GA, USA), Swiss Re (London, UK), Swiss Cancer Research foundation (Bern, Switzerland), Swiss Cancer League (Bern, Switzerland), and University of Kentucky (Lexington, KY, USA).

Quality assessment of prostate cancer reports to the Danish Cancer Registry.

BACKGROUND: The Danish Cancer Registry (DCR) is the oldest nationwide population-based cancer registry in the Nordic countries. At the time of the study the DCR recorded date of diagnosis, tumor stage and initial treatment. The validity of the clinical information reported to the DCR has never been analyzed. MATERIAL AND METHODS: Patients diagnosed with prostate cancer from 1 May to 31 December 1997 and living in eight Danish counties were identified through the DCR. Clinical data was retrieved from hospital records where date of diagnosis, stage at diagnosis and treatment received were registered. RESULTS: The mean age at diagnosis was 74.6 years (s.d. 8.6 years). Diagnosis was verified histologically for 87% of cases. Overall 95% of the patients had a difference less than three months between the reported date of diagnosis and the date found in hospital records. Correction of dates of diagnosis had no impact on survival. Hospital records identified 86 patients with T1-2 disease without distant metastases (M0), but only 56 of these patients (65%) were reported to the DCR as having localized disease. According to hospital records a total of 242 patients were confirmed having distant metastases (M1) at diagnosis but only 139 of these cases (57%) were reported to the DCR as such. Considerable "over reporting" of curative treatment was observed. CONCLUSION: The DCR has been shown to be reliable in terms of new cases being reported. For the majority of cases there were insignificant differences concerning the date of diagnosis. However, the DCR information on stage and treatment was found to be inaccurate. Since 2004 the DCR registration process, including staging according to the TNM classification, has been carried out electronically from several registers. Future comparison between cohorts of different time intervals or international comparison should be interpreted with caution when clinical information is included.

Trends in cancer in the elderly population in Denmark, 1980-2012.

BACKGROUND: Age is the strongest risk factor for developing cancer. The aim of the present analysis is to give an overview of the trends in cancer incidence, mortality, prevalence, and relative survival in Denmark from 1980 to 2012 focusing on age, comparing persons aged 70 years or more with those aged less than 70 years. MATERIAL AND METHODS: Data derived from the NORDCAN database with comparable data on cancer incidence, mortality, prevalence and relative survival in the Nordic countries. The Danish data originate from the Danish Cancer Registry and the Danish Cause of Death Registry with follow-up for death or emigration until the end of 2013. RESULTS: Incidence and mortality rates of all sites, but non-melanoma skin cancer, were higher and relative survival was lower among persons aged 70 years or more than those aged less than 70 years. The age distribution (age group-specific percentages of total number of incident cases) remained constant over time while the percentage of persons dying from cancer decreased with time up to the age of 79 years but increased for those aged 80 years or more, in whom about a third of all cancer deaths occurred in 2012. In 2003-2007, the five-year relative survival was 48% for men aged 70-79 years, 38% for men aged 80-89 years, and 29% for men aged 90 years or more and the corresponding figures for women were 46%, 39%, and 36%, respectively. There was a substantial increase in the number of prevalent cancer cases aged 70 years or older, especially among those aged 90 years or more. CONCLUSION: An increase in elderly cancer patients is expected over the coming 20 years due to an increasing elderly population. Healthcare providers need to focus on developing specific strategies for treatment of elderly cancer patients in the future.

Mortality from cancer and other causes in commercial airline crews: a joint analysis of cohorts from 10 countries.

BACKGROUND: Commercial airline crew is one of the occupational groups with the highest exposures to ionising radiation. Crew members are also exposed to other physical risk factors and subject to potential disruption of circadian rhythms. METHODS: This study analyses mortality in a pooled cohort of 93 771 crew members from 10 countries. The cohort was followed for a mean of 21.7 years (2.0 million person-years), during which 5508 deaths occurred. RESULTS: The overall mortality was strongly reduced in male cockpit (SMR 0.56) and female cabin crews (SMR 0.73). The mortality from radiation-related cancers was also reduced in male cockpit crew (SMR 0.73), but not in female or male cabin crews (SMR 1.01 and 1.00, respectively). The mortality from female breast cancer (SMR 1.06), leukaemia and brain cancer was similar to that of the general population. The mortality from malignant melanoma was elevated, and significantly so in male cockpit crew (SMR 1.57). The mortality from cardiovascular diseases was strongly reduced (SMR 0.46). On the other hand, the mortality from aircraft accidents was exceedingly high (SMR 33.9), as was that from AIDS in male cabin crew (SMR 14.0). CONCLUSIONS: This large study with highly complete follow-up shows a reduced overall mortality in male cockpit and female cabin crews, an increased mortality of aircraft accidents and an increased mortality in malignant skin melanoma in cockpit crew. Further analysis after longer follow-up is recommended.

Non-preventable cases of breast, prostate, lung, and colorectal cancer in 2050 in an elimination scenario of modifiable risk factors.

Most Western countries have increasing number of new cancer cases per year. Cancer incidence is primarily influenced by basically avoidable risk factors and an aging population. Through hypothetical elimination scenarios of multiple major risk factors for cancer, we estimated the number of new cancer cases that are non-preventable in 2050. We compare numbers of new postmenopausal breast, prostate, lung, and colorectal cancer cases in 2021 to projected numbers of new cases in 2050 under prevention scenarios regarding smoking, overweight and obesity, and alcohol consumption: no intervention, 50%, and 100% instant reduction. Cancer incidence data were derived from NORDCAN, and risk factor prevalence data from the Danish National Health Survey. Cancer projections were calculated with the Prevent program. Hypothetical 100% instant elimination of major risk factors for cancer in Denmark in 2022 will result in unchanged numbers of new breast and colorectal cancers in 2050. The number of new prostate cancers will increase by 25% compared to 2021. Unchanged risk factor levels will result in noticeable increase in cancer burden. Increase in life expectancy and age will entail an increase in cancer incidence, despite maximum effect of preventive actions in the population. Our results are important when planning future health care.

Breast cancer survival in the US and Europe: a CONCORD high-resolution study.

Breast cancer survival is reportedly higher in the US than in Europe. The first worldwide study (CONCORD) found wide international differences in age-standardized survival. The aim of this study is to explain these survival differences. Population-based data on stage at diagnosis, diagnostic procedures, treatment and follow-up were collected for about 20,000 women diagnosed with breast cancer aged 15-99 years during 1996-98 in 7 US states and 12 European countries. Age-standardized net survival and the excess hazard of death up to 5 years after diagnosis were estimated by jurisdiction (registry, country, European region), age and stage with flexible parametric models. Breast cancers were generally less advanced in the US than in Europe. Stage also varied less between US states than between European jurisdictions. Early, node-negative tumors were more frequent in the US (39%) than in Europe (32%), while locally advanced tumors were twice as frequent in Europe (8%), and metastatic tumors of similar frequency (5-6%). Net survival in Northern, Western and Southern Europe (81-84%) was similar to that in the US (84%), but lower in Eastern Europe (69%). For the first 3 years after diagnosis the mean excess hazard was higher in Eastern Europe than elsewhere: the difference was most marked for women aged 70-99 years, and mainly confined to women with locally advanced or metastatic tumors. Differences in breast cancer survival between Europe and the US in the late 1990s were mainly explained by lower survival in Eastern Europe, where low healthcare expenditure may have constrained the quality of treatment.

Colorectal Cancer Survival in German-Danish Border Regions-A Registry-Based Cohort Study.

The aim of this study was (i) to update the reporting of colorectal cancer survival differences over time in the German-Danish border region (Schleswig-Holstein, Southern Denmark, and Zealand) and (ii) to assess the extent to which it can be explained by stage and primary treatment. Incident invasive colorectal cancer cases diagnosed from 2004 to 2016 with a follow-up of vital status through 31 December 2017 were extracted from cancer registries. Analyses were conducted by anatomical subsite and for four consecutive periods. Kaplan-Meier curves and log-rank tests were computed. Cox regression models using data from Schleswig-Holstein from 2004 to 2007 as the reference category were run while controlling for age, sex, stage, and treatment. The cox regression models showed decreasing hazard ratios of death for all three regions over time for both anatomical subsites. The improvement was stronger in the Danish regions, and adjustment for age, sex, stage, and treatment attenuated the results only slightly. In 2014-2016, colon cancer survival was similar across regions, while rectal cancer survival was significantly superior in the Danish regions. Regional survival differences can only partially be explained by differing stage distribution and treatment and may be linked additionally to healthcare system reforms and screening efforts.

Nordcan.R: a new tool for federated analysis and quality assurance of cancer registry data.

Aim of the article: We present our new GDPR-compliant federated analysis programme (nordcan.R), how it is used to compute statistics for the Nordic cancer statistics web platform NORDCAN, and demonstrate that it works also with non-Nordic data. Materials and methods: We chose R and Stata programming languages for writing nordcan.R. Additionally, the internationally used CRG Tools programme by International Agency for Research on Cancer (IARC/WHO) was employed. A formal assessment of (GDPR-compliant) anonymity of all nordcan.R outputs was performed. In order to demonstrate that nordcan.R also works with non-Nordic data, we used data from the Netherlands Cancer Registry. Results: nordcan.R, publicly available on Github, takes as input cancer and general population data and produces tables of statistics. Each NORDCAN participant runs nordcan.R locally and delivers its results to IARC for publication. According to our anonymity assessment the data can be shared with international organizations, including IARC. nordcan.R incidence results on Norwegian and Dutch data are highly similar to those produced by two other independent methods. Conclusion: nordcan.R produces accurate cancer statistics where all personal and sensitive data are kept within each cancer registry. In the age of strict data protection policies, we have shown that international collaboration in cancer registry research and statistics reporting is achievable with the federated analysis approach. Undertakings similar to NORDCAN should consider using nordcan.R.

Improved survival of Danish cancer patients 2007-2009 compared with earlier periods.

INTRODUCTION: For the majority of cancers, improved long-term survival may be accessed from survival during the first year after diagnosis. A steady improvement in survival was seen both before and after the introduction of cancer control plans in 2000 and 2005. On the basis of data from 2007-2009, we studied the trend in 1-year survival after the introduction of the 2005 plan. MATERIAL AND METHODS: All cancers from 1995-2009 were studied in five 3-year cohorts of incident cases which were followed-up for death to the end of 2010. Age-standardised 1-, 3- and 5-year relative survival was calculated and 1-year survival presented for 2004-2006 and 2007-2009 to allow comparison with our previous publication. RESULTS: The improvement over time in overall 1-year age-standardised relative survival was maintained with a three percentage point increase to 72% for men and 75% for women. Exclusion of prostate and breast cancer from calculations lowered relative survival to 65% and 67%, respectively; but improvement was maintained. Cancer sites which previously enjoyed a high survival saw the least or no improvement as was the case for haematological cancers, except for non-Hodgkin lymphoma in men. The differences in survival between men and women are diminishing, especially for cancers of the digestive tract. CONCLUSION: The improvements over time in survival after introduction of the cancer plans were maintained for non-haematological cancers. The fast-track system for diagnosis and treatment introduced gradually by cancer sites until the end of 2008 along with some centralisation of elective surgery may have narrowed the gap in cancer survival between men and women for digestive tract cancers and may also have improved survival for other cancers, e.g. the sex-specific types and kidney and brain cancers. FUNDING: not relevant. TRIAL REGISTRATION: not relevant.

Survival of breast cancer patients in German-Danish border regions - A registry-based cohort study.

BACKGROUND AND AIM: Denmark reports slightly lower breast cancer survival before 2010 than its neighbouring country Germany. Previous research is limited by lacking stage and treatment information. This study aims to investigate differences in breast cancer survival between the bordering regions Schleswig-Holstein (Germany), Southern Denmark and Zealand (Denmark) using registry data including stage and treatment information. METHOD: Invasive female breast cancer cases diagnosed during 2004-2013 with follow up through 31st December 2014 were extracted from cancer registries. Cases notified by death certificates only and those aged 90+ years were excluded. Kaplan-Meier curves and log-rank tests were computed. Cox regression analysis was conducted with adjustment for year of diagnosis, age, stage, and treatment. RESULTS: The analytical sample included 42,966 cases. Kaplan-Meier curves and log-rank tests show significant survival differences between the regions. The Cox regression model adjusted for year of diagnosis and age shows significantly worse overall survival of breast cancer patients in both Danish regions compared to Schleswig-Holstein with hazard ratios (HR) of 1.09 (95 % CI: 1.04; 1.15) for patients from Southern Denmark (SD) and 1.25 (95 % CI: 1.18; 1.32) for residents of Zealand (ZL). This effect diminished after adjustment for stage and treatment (HR: 1.05 (SD), 1.09 (ZL) 95 % CI: 0.99; 1.10 (SD), 1.03; 1.15 (ZL)). CONCLUSION: Survival differences can be explained by differing stage distribution and treatment administration, which formerly were more favourable in Schleswig-Holstein. The survival gap will probably close due to Denmark's national screening program and increased use of adjuvant cancer therapy.