Data quality at the Cancer Registry of Norway: An overview of comparability, completeness, validity and timeliness

Prospective study on metabolic factors and risk of prostate cancer

BACKGROUND

There are inconsistent data regarding the association between metabolic factors, separately and combined, and the risk of prostate cancer and death from prostate cancer.

METHODS

In the Metabolic Syndrome and Cancer Project (Me-Can), data on body mass index (BMI); blood pressure; and blood levels of glucose, cholesterol, and triglycerides were collected for 289,866 men. Cox proportional hazard models were used to calculate relative risks (RRs) by exposures in quintiles as well as for z scores (with a mean of 0 and a standard deviation of 1) together with a composite sum of scores to assess the combined effect of metabolic factors. RRs were corrected for random errors in measurement.

RESULTS

During a mean follow-up of 12 years, 6673 men were diagnosed with prostate cancer and 961 died of the disease. Men with high levels of glucose and triglycerides were found to have a decreased risk of prostate cancer: top versus bottom quintile of glucose: RR, 0.82 (95% confidence interval [95% CI], 0.62-1.08; P value for trend = .03) and top versus bottom quintile of triglycerides: RR, 0.88 (95% CI, 0.74-1.04; P value for trend = .001). High BMI, elevated blood pressure, and a high composite z score were found to be associated with an increased risk of death from prostate cancer: top versus bottom quintile of BMI: RR, 1.36 (95% CI, 1.08-1.71); systolic blood pressure: RR, 1.62 (95% CI, 1.07-2.45); and per 1-unit increase of the composite z score: RR, 1.13 (95% CI, 1.03-1.25).

CONCLUSIONS

The authors found no evidence of an association between high levels of metabolic factors and the risk of prostate cancer, but high BMI, elevated blood pressure, and a composite score of all metabolic factors were associated with an increased risk of death from prostate cancer.

Breast cancer and ductal carcinoma in situ among women with prior squamous or glandular precancer in the cervix: a register-based study

Background:

Human papillomavirus and hormonal contraceptives may be risk factors for cervical precancer and malignant breast tumours.

Methods:

Standardised incidence ratios (SIRs) of malignant breast tumours during 1970–2008 were estimated separately for women with prior squamous and glandular cervical precancer.

Results:

Women with squamous precancer and women with glandular precancer in the cervix had a significantly higher risk of malignant breast tumours than the general female population (SIR, 95% confidence interval: 1.10, 1.05–1.14 and 1.52, 1.11–2.08, respectively).

Interpretation:

Shared risk factors or screening attendance may explain the excess risk of malignant breast tumours among women with a history of cervical precancer.

Data quality at the Icelandic Cancer Registry: comparability, validity, timeliness and completeness

INTRODUCTION

The nationwide Icelandic Cancer Registry (ICR) was established in 1954 and has been extensively used for research from the outset although formal quality assessment of the registry database has not previously been undertaken. In this paper we report the first formal evaluation of the comparability, validity, timeliness and completeness of the ICR.

MATERIAL AND METHODS

Data from the ICR for the period 1955-2009 (41 994 cancer diagnoses) were used, applying established quantitative and semi-quantitative methods. In order to evaluate the completeness of the ICR, record linkage was performed between the ICR and the population-based Hospital Discharge Registry to identify potential missing cases for tumour diagnoses in 2000 and 2001.

RESULTS

The registration is in accordance with internationally accepted standards. It has high validity, but random variation in rates is prominent in this small population. Record linkage with the Hospital Discharge Registry revealed that in addition to the 2459 cancers registered in 2000-2001, 21 cases were missing, indicating 99.15% completeness. Tumours of the central nervous system constituted 71%, and haematological malignancies 19% of these missing entries.

DISCUSSION

The ICR has high completeness, validity and timeliness and is comparable to the cancer registries of the other Nordic Countries. As cancer registries have many important roles, it is of great importance that their data are at all times as complete and valid as possible. Thus the ICR aims to constantly improve and update the data gathering process.

A population-based study on the effect of temozolomide in the treatment of glioblastoma multiforme

The effect of temozolomide (TMZ) and radiotherapy (RT) in the treatment of glioblastoma multiforme (GBM) has been well documented in randomized controlled trials. Here we present our findings on the effect of TMZ added to RT at a population level. The Cancer Registry of Norway was searched for patients with a GBM diagnosis from January 1, 2000 to December 31, 2007. Subsequently, the prescriptions registered to these patients were obtained from the Norwegian Prescription Database. The data were analyzed according to era (pre-TMZ introduction or post-TMZ introduction) and according to treatment received. Furthermore, a matching procedure was utilized to reduce the bias between the RT + TMZ and RT alone treatments so that the effect of TMZ could be better scrutinized. We identified 1157 GBM patients. The median overall survival (OS), in months, was 8.3 (95% confidence interval: 7.6-9.0) and 10.1 (95% confidence interval: 9.1-11.0) in the pre-TMZ and TMZ eras, respectively (P < .001). By treatment, we found median OS for the control, RT alone, and RT + TMZ groups to be 2.5, 9.0, and 16.2 months, respectively (P < .001). Two-year survival was 0%, 4%, and 25%, respectively. The effect of age on TMZ effect was insignificant. In the matched group analysis, TMZ provided a 7.6-month OS benefit. Our population data reproduce the beneficial effect of TMZ from randomized controlled trials with a median OS of 16.2 months and 25% 2-year survival.

Characteristics, therapy and outcome in an unselected and prospectively registered cohort of pancreatic cancer patients

PURPOSE

Pancreatic cancer (PC) is associated with a dismal prognosis. Few studies have examined characteristics and outcome in an unselected population-based cohort of PC patients. Therefore, we investigated patient baseline characteristics, therapy choices and survival in a complete cohort of patients with PC.

METHODS

All cases diagnosed with PC between 2007 and 2009 in the Region of Southern Denmark (pop: 1,200,000) were prospectively registered. Patient characteristics including performance status, information about haematology, liver function and therapy were retrieved from patient charts, and used to compare differently treated and untreated groups.

RESULTS

Six-hundred-eighteen cases were registered as PC; 25 of which did not have adenocarcinomas. Patients were divided in 3 clinical groups based on initial therapy; group 1: resection (n=64), group 2: chemotherapy or chemo-radiotherapy (n=191), group 3: no tumour directed therapy (n=324). Median survival (mOS) (95% confidence interval (CI)) in the three groups was 25.7 months (18-30), 8.1 months (7.0-9.5) and 1.1 months (1.0-1.3) respectively. Three percent of patients participated in clinical trials. An evaluation of baseline factors prognostic value suggested that treated patients differed significantly from non-treated patients.

CONCLUSION

This study reports survival in treated groups comparable to results obtained from clinical trials with highly selected patients. However the majority of patients with PC do not receive cancer directed therapy. This group was significantly different in several baseline factors, which could suggest a different biology. Improving the outcome of PC patients calls for research into the large group of untreated patients, as only a minority of patients receive cancer directed therapy.

Stage-specific breast cancer incidence rates among participants and non-participants of a population-based mammographic screening program

The Norwegian Breast Cancer Screening Program was rolled out county by county over the course of a decade, from 1996 to 2005, and now encompasses all Norwegian women aged 50-69 years. We aim to compare DCIS and stage-specific invasive breast cancer incidence rates among participants, non-participants, and women not yet invited to the screening program over this entire implementation period. We estimate stage-specific breast tumor incidence rates for 640,347 women 50-69 years of age invited to the screening program between 1996 and 2007. We compare incidence rates and stage distribution among women diagnosed with breast cancer who were invited and participated, invited but not participated, and women not yet invited to the screening program using two-sided Chi-squared tests to determine statistical significance between groups. The incidence of ductal carcinoma in situ (DCIS) was 3.0 times higher and invasive breast cancer was 1.5 times higher for invited participants compared to invited non-participants (p < 0.001). While the incidence of Stage I cancer was two times higher among participants compared to non-participants (p < 0.001), the incidences of Stages III and IV cancer were two and three times lower, respectively, among participants compared to non-participants (p < 0.001 for both). No significant differences in stage-specific incidence or treatment utilization rates were observed between invited non-participants and not yet invited women, except for stage IV cancers, which were detected at a higher rate among women who were not yet invited (7.5 vs. 4.6 %, p = 0.001). Compared with women invited who did not participate, participants in the screening program are more likely to be diagnosed with DCIS and early stage invasive breast cancer and are less likely to be diagnosed with advanced stage breast cancer. More research is required to determine whether these differences in stage-specific incidences among invited participants and non-participants are associated with differences in mortality rates.

Cancer in childhood, adolescence, and young adults: a population-based study of changes in risk of cancer death during four decades in Norway

PURPOSE

Cancer is one of the most common causes of death among young individuals. The purpose of this study was to explore the risk of early death (the first five years after diagnosis) among children (0-14 years), adolescents (15-19 years), and young adults (20-24 years) with cancer in Norway, born during 1965-1985.

METHODS

The overall and cancer-specific early deaths were explored by linking population-based national registers (including the Cancer Registry of Norway and the Cause of Death Registry) that include the entire population of Norway (approximately 1.3 million individuals). Hazard and sub-hazard ratios were estimated using Cox regression analyses and competing risk models.

RESULTS

A total of 5,828 individuals were diagnosed with cancer (56.3 % males). During follow-up, 1,415 individuals died from cancer (60.2 % males) within five years after diagnosis. The hazard ratio (HR) of overall death of the cancer patients relative to the general population decreased from 1965 (from HR, 385.8 (95 % confidence interval (CI): 335.3, 443.4) in 1965-74 to HR, 19.7 (CI: 9.3, 41.5) in 2005-09). Over all, there were fewer cancer-related deaths among female compared with male patients (sub-hazard ratio (SHR), 0.83 (CI: 0.74, 0.92)). Except for all hematopoietic malignancies, adolescents and young adult patients had lower risk of cancer death than children.

CONCLUSION

The difference in risk of cancer and overall deaths between the cancer patients and the general population has been substantially reduced since 1965.

Breast cancer: missed interval and screening-detected cancer at full-field digital mammography and screen-film mammography-- results from a retrospective review

PURPOSE

To compare the percentages and mammographic features of cancers missed at full-field digital mammography (FFDM) and screen-film mammography (SFM) in women who participated in the Norwegian Breast Cancer Screening Program in 2002-2008.

MATERIALS AND METHODS

Social Science Data Services approval was obtained; the requirement for informed consent was waived. Cases were all the interval and screening-detected cancers from 35&emsp14;127 FFDM and 52&emsp14;444 SFM examinations in two Norwegian counties. Prior and diagnostic FFDM examinations of 49 interval and 86 screening-detected breast cancers were reviewed by four breast radiologists and compared with a review of SFM examinations of 81 interval and 123 screening-detected cancers. Cancers were classified as missed or true, mammographic features were described, percentages were compared by using the χ(2) or Fisher exact test, and 95% confidence intervals (CIs) were calculated.

RESULTS

The percentages of interval and screening-detected cancers missed at FFDM and SFM did not differ significantly. (interval cancers missed: 33% [16 of 49] at FFDM vs 30% [24 of 81] at SFM [P = .868]; screening-detected cancers missed: 20% [17 of 86] at FFDM vs 21% [26 of 123] at SFM [P = .946]). Asymmetry was present in 27% (95% CI: 13.3%, 45.5%) of prior mammograms of cancers missed at FFDM and 10% (95% CI: 3.3%, 21.8%) of those missed at SFM (P = .070). Calcifications were observed in 18% (95% CI: 7.0%, 35.5%) of the cancers missed at FFDM and 34% (95% CI: 21.2%, 48.8%) of those missed at SFM (P = .185). Average mammographic tumor size of missed cancers manifesting as masses was 10.4 mm at FFDM and 13.6 mm at SFM (P = .036).

CONCLUSION

The use of FFDM has not reduced the challenge of missed cancers. Cancers missed at FFDM tend to have different mammographic features than those missed at SFM.

Association of time since last birth, age at first birth and parity with breast cancer survival among parous women: a register-based study from Norway

Reproductive factors that have a well-documented effect on breast cancer risk may also influence the prognosis of the disease, but previous studies on breast cancer survival have yielded conflicting results. We combined information from two population-based registries and obtained information on 16,970 parous women with invasive breast cancer. Cox regression analysis was used to assess breast cancer survival in relation to age at diagnosis, age at first birth, time since last birth and parity. We stratified the analyses by age at diagnosis (<50 and ≥ 50 years) as an approximation for menopausal age. In women diagnosed before 50 years of age, breast cancer survival was reduced with younger age at diagnosis (p for trend <0.001), whereas in women diagnosed at 50 years or later, survival was reduced with older age at diagnosis (p for trend 0.011). For breast cancer diagnosed before 50 years, survival was poorer in women with four or more births compared to women with one or two births (hazard ratio 1.3, 95% confidence interval 1.1-1.6). A short time since last birth was associated with reduced survival (p for trend 0.05), but adjustment for stage and grade attenuated the association. Among women diagnosed at 50 years or later, we found no association with survival for any of the reproductive factors. In summary, reproductive factors were associated with survival from breast cancer diagnosed before but not after age 50 years. Young women had a particularly poor prognosis throughout the study period.

Metabolic risk factors and skin cancer in the Metabolic Syndrome and Cancer Project (Me-Can)

BACKGROUND

Little is known about the associations of metabolic aberrations with malignant melanoma (MM) and nonmelanoma skin cancer (NMSC).

OBJECTIVES

To assess the associations between metabolic factors (both individually and combined) and the risk of skin cancer in the large prospective Metabolic Syndrome and Cancer Project (Me-Can).

METHODS

During a mean follow-up of 12 years of the Me-Can cohort, 1728 (41% women) incident MM, 230 (23% women) fatal MM and 1145 (33% women) NMSC were identified. Most NMSC cases (76%) were squamous cell carcinoma (SCC) (873, 33% women). Hazard ratios (HRs) were estimated by Cox proportional hazards regression for quintiles and standardized z-scores (with a mean of 0 and SD of 1) of body mass index (BMI), blood pressure, glucose, cholesterol, triglycerides and for a combined metabolic syndrome score. Risk estimates were corrected for random error in the measurements.

RESULTS

Blood pressure per unit increase of z-score was associated with an increased risk of incident MM cases in men and women [HR 1·17, 95% confidence interval (CI) 1·04-1·31 and HR 1·18, 95% CI 1·03-1·36, respectively] and fatal MM cases among women (HR 2·39, 95% CI 1·58-3·64). In men, all quintiles for BMI above the reference were associated with a higher risk of incident MM. In women, SCC NMSC risk increased across quintiles for glucose levels (P-trend 0·02) and there was a trend with triglyceride concentration (P-trend 0·09).

CONCLUSION

These findings suggest that mechanisms linked to blood pressure may be involved in the pathogenesis of MM. SCC NMSC in women could be related to glucose and lipid metabolism.

Cytology and human papillomavirus testing 6 to 12 months after ASCUS or LSIL cytology in organized screening to predict high-grade cervical neoplasia between screening rounds

We carried out a prospective study comparing the performance of human papillomavirus (HPV) E6/E7 mRNA (PreTect HPV-Proofer; NorChip, Klokkarstua, Norway) and DNA (Amplicor HPV test; Roche Diagnostics, Basel, Switzerland) triage testing of women 6 to 12 months after atypical-squamous-cells-of-undetermined-significance (ASCUS) or low-grade-squamous-intraepithelial-lesion (LSIL) cytology in organized screening to predict high-grade cervical intraepithelial neoplasia of grade 2 or worse (CIN2+) between screening rounds. Between January 2005 and April 2008, 692 study women with screening-detected ASCUS/LSIL cytology 6 to 12 months earlier returned for HPV mRNA and DNA testing and repeat cytology. The median follow-up time was 3 years, using existing health care facilities. Follow-up test results were available for 625 women. Of the 145 CIN2+ cases detected during the study period, 95 (65.5%) were HPV mRNA positive 6 to 12 months after screening-detected ASCUS/LSIL, 44 (30.4%) were HPV mRNA negative, and 6 (4.1%) were invalid. The corresponding HPV DNA results were 139 (95.9%), 5 (3.4%), and 1 (0.7%), respectively. The cumulative incidences of CIN2+ 3 years after a negative HPV mRNA and DNA test were 10.3% (95% confidence interval [CI], 7.2 to 13.3%) and 1.8% (95% CI, 0.0 to 3.6%), respectively. The cumulative incidences of CIN2+ 3 years after positive HPV mRNA and DNA tests were 52.8% (95% CI, 40.1 to 60.1%) and 41.3% (95% CI, 35.5 to 46.6%), respectively. In conclusion, both positive HPV mRNA and DNA test results have a high enough long-term prediction of CIN2+ risk to consider referral to colposcopy as good practice when performed in delayed triage of women with ASCUS/LSIL cytology. In addition, the low CIN2+ risk among women with a negative Amplicor HPV test in our study confirms its safe use in a clinical setting.

Prospective study of human papillomavirus seropositivity and risk of nonmelanoma skin cancer

Cutaneous human papillomaviruses (HPVs) have been associated with squamous cell carcinoma (SCC) in case-control studies, but there are limited data from prospective studies assessing whether virus exposure predicts risk of future cancer development. Two major biobanks, the Southern Sweden Microbiology Biobank (1971-2003) and the Janus Biobank (1973-2003) in Norway, containing samples from 850,000 donors, were searched for incident skin cancer for up to 30 years using registry linkages. Altogether, 2,623 donors with samples taken before diagnosis of SCC or basal cell carcinoma (BCC) of the skin were identified. Prediagnostic samples and samples from 2,623 matched controls were tested for antibodies against 33 types of HPV. Baseline seropositivity to HPV types in genus β species 2 was associated with SCC risk (odds ratio = 1.3, 95% confidence interval: 1.1, 1.7); this was also the case for samples taken more than 18 years before diagnosis (odds ratio = 1.8, 95% confidence interval: 1.1, 2.8). Type-specific persistent seropositivity entailed elevated point estimates for SCC risk for 29 HPV types and decreased point estimates for only 3 types. After multiple hypothesis adjustment, HPV 76 was significantly associated with SCC risk and HPV 9 with BCC risk. In summary, seropositivity for certain HPV types was associated with an increased risk for future development of SCC and BCC.

Cancer's unequal impact on incomes in Norway

BACKGROUND

At a group level, cancer results in reduced labor earnings. Public benefits common to welfare states may, however, compensate for all or parts of the decline in earnings. Norwegian cancer survivors' incomes, including both labor earnings and compensatory welfare benefits, were compared to those of the cancer-free population to assess potential welfare consequences of cancer. Possible modifying effects of parental and marital status, education, prior earnings and age were assessed in depth.

MATERIAL AND METHODS

Log-linear regression models were used to estimate incomes across different sociodemographic variables using register data covering the entire Norwegian population 40-59 years old with any income in 2008, 536 600 men and 502 500 women, of whom more than 17,000 were diagnosed with cancer in 2000-2007.

RESULTS

Compared to the cancer-free general population, cancer was associated with a modest 7% decline in incomes overall. The decline was, however, significantly associated with sociodemographic factors, marital status exempted. Childless men with low education and low prior earnings were most adversely affected. Lymphomas and lung cancer accounted largely for these unfavorable effects.

CONCLUSIONS

Declines in earnings after cancer are to a large degree compensated by the Norwegian welfare state, and incomes overall are only modestly decreased among cancer survivors compared to the general population. Persons with multiple unfavorable sociodemographic characteristics experience particularly low incomes after cancer. This is of concern in a supposedly egalitarian society with public health care and antidiscrimination acts in place. Welfare state interventions, i.e. work reintegration efforts and/or compensations for labor earning drops, directed specifically towards these subgroups might be warranted.

A cohort study of permanently reduced work ability in breast cancer patients

PURPOSE

The aims of this cohort study were to explore various longitudinal aspects of employment and disability pension due to permanently reduced work ability among women with breast cancer and to investigate the impact of breast cancer on income.

PATIENTS AND METHODS

In a national register-based controlled cohort study from Norway, 1,548 women diagnosed with breast cancer (all stages) between 1992 and 1996 at the age 45-54 years and 1,548 cancer-free women matched for age, municipality and civil status were followed for up to 14 years. Medical data from the Cancer Registry of Norway were linked with longitudinal data on employment, social security benefits and socio-demography collected from other national official registries.

RESULTS

Compared to cancer-free controls, breast cancer patients were significantly more likely to receive disability pension (hazard ratio (HR) 2.7, 95% CI 2.3-3.2) after adjustment for unmatched socio-demographic variables (education, income and children <18 years in the household). Adjusted HR in breast cancer stage I patients was 1.8 (95% CI 1.5-2.3) and 3.0 (95% CI 2.4-3.8) in stage II/III patients compared to controls. The risk increased with mastectomy compared to breast-conserving surgery (HR 1.5, 95% CI 1.2-1.9). At the end of the observation period, employment rates were higher in non-disabled patients than in non-disabled controls (82% vs. 77%, p = 0.008). Working breast cancer patients experienced a temporary negative effect on employment income.

CONCLUSION

A considerable proportion of women with breast cancer will over time experience permanently reduced work ability and become disability pension holders. In case of reduced work ability in breast cancer survivors, medical personel caring for them should consider and discuss with them rehabilitation and workplace adjustment in order to prevent early disability pension.

Children and young adults with parents with cancer: a population-based study

Background

Today many people are choosing to have children later in life. Additionally, the use of sophisticated diagnostic tools and screening modalities has increased over recent years. Because of these factors, cancer is being diagnosed more frequently during the child-rearing years. Sociodemographic and cancer-related information on families and minor (0–18 years) and young adult (YA) (19–25 years) children experiencing parental cancer is scarce, but this information is vital for healthcare initiatives aimed toward those potentially adversely affected. Therefore, the aim of this study was to describe features of families and minor and YA children affected by parental cancer in a nationwide population.

Methods

Complete Norwegian birth cohort data were obtained from national registries. Descriptive prevalence and incidence statistics were collected for parents and minor and YA children. Logistic regression models were used to assess factors likely to influence parental death.

Results

Every year around 0.3% of all families with children under the age of 18 years encounter parental cancer, and 3.1% of minors and 8.4% of YAs have a parent who has been diagnosed with cancer. This study found skin, breast, testicular, and colorectal cancers were the most common forms of cancer diagnosed. The sociodemographic features of those affected were fairly similar to those of the general population. One in five children experienced parental death from cancer; parental death was more often paternal than maternal and was most common in parents diagnosed with leukemia or brain, colorectal, and lung tumors. Deaths are uncommon among parents without cancer.

Conclusion

Adequate assistance for minor and YA children affected by parental cancer requires knowledge of their number and characteristics. Parental cancer is more common than previously suggested: the annual incidence of parental cancer for children under 18 years of age is 0.3%, whereas approximately 4% of children aged 0–25 years have or have had parents diagnosed with cancer, corresponding to a population prevalence of 1.4%. Around 20% of these children experience parental death, and surveys of live respondents should account for this.

Metabolic risk factors and cervical cancer in the metabolic syndrome and cancer project (Me-Can)

BACKGROUND

Little is known about the association between metabolic risk factors and cervical cancer carcinogenesis.

MATERIAL AND METHODS

During mean follow-up of 11 years of the Me-Can cohort (N=288,834) 425 invasive cervical cancer cases were diagnosed. Hazard ratios (HRs) were estimated by the use of Cox proportional hazards regression models for quintiles and standardized z-scores (with a mean of 0 and a SD of 1) of BMI, blood pressure, glucose, cholesterol, triglycerides and MetS score. Risk estimates were corrected for random error in the measurements.

RESULTS

BMI (per 1SD increment) was associated with 12%, increase of cervical cancer risk, blood pressure with 25% and triglycerides with 39%, respectively. In models including all metabolic factors, the associations for blood pressure and triglycerides persisted. The metabolic syndrome (MetS) score was associated with 26% increased corrected risk of cervical cancer. Triglycerides were stronger associated with squamous cell carcinoma (HR 1.48; 95% CI, 1.20-1.83) than with adenocarcinoma (0.92, 0.54-1.56). Among older women cholesterol (50-70 years 1.34; 1.00-1.81), triglycerides (50-70 years 1.49, 1.03-2.16 and ≥70 years 1.54, 1.09-2.19) and glucose (≥ 70 years 1.87, 1.13-3.11) were associated with increased cervical cancer risk.

CONCLUSION

The presence of obesity, elevated blood pressure and triglycerides were associated with increased risk of cervical cancer.

Understanding recent trends in incidence of invasive breast cancer in Norway: age-period-cohort analysis based on registry data on mammography screening and hormone treatment use

OBJECTIVE

To quantify the separate contributions of menopausal hormone treatment and mammography screening activities on trends in incidence of invasive breast cancer between 1987 and 2008.

DESIGN

Population study using aggregated data analysed by an extended age-period-cohort model.

SETTING

Norway. Population Norwegian women aged 30-90 between 1987 and 2008, including 50,102 newly diagnosed cases of invasive breast cancer. Main outcomes measures Attributable proportions of mammography screening and hormone treatment to recent incidence of invasive breast cancer, and the remaining variation in incidence after adjustment for mammography screening and hormone treatment.

RESULTS

The incidence of invasive breast cancer in Norway increased steadily until 2002, levelled off, and then declined from 2006. All non-linear changes in incidence were explained by use of hormone treatment and mammography screening activities, with about similar contributions of each factor. In 2002, when the incidence among women aged 50-69 was highest, an estimated 23% of the cases in that age group could be attributed to mammography screening and 27% to use of hormone treatment.

CONCLUSIONS

Changes in incidence trends of invasive breast cancer since the early 1990s may be fully attributed to mammography screening and hormone treatment, with about similar contributions of each factor.

Incidence and causes of perioperative mortality after primary surgery for intracranial tumors: a national, population-based study

OBJECT

Surgical mortality is a frequent outcome measure in studies of volume-outcome relationships, and the Agency for Healthcare Research and Quality has endorsed surgical mortality after craniotomies as an Inpatient Quality Indicator. Still, the frequency and causes of 30-day mortality after neurosurgical procedures have not been much explored. The authors sought to study the frequency and possible causes of death following primary intracranial tumor operations. They also sought to explore a possible predictive value of perioperative mortality rates from neurosurgical centers in relation to long-term survival.

METHODS

Using population-based data from the Norwegian cancer registry, the authors identified 15,918 primary operations for primary CNS tumors treated in Norway in the period from August 1955 through December 2008. Patients were followed up until death, emigration, or September 2009. Causes of mortality as indicated on death certificates were studied. Factors associated with an increased risk of perioperative death were identified.

RESULTS

The overall risk of perioperative death after first-time surgery for primary intracranial tumors is currently 2.2% and has decreased over the last decades. An age ≥ 70 years and histopathological entities with poor long-term prognoses are risk factors. Overlapping lesions are also associated with excess risk, indicating that lesion size or multifocality may matter. The overall risk of perioperative death is also higher in biopsy cases than in resection cases. Perioperative mortality rates of the 4 Norwegian neurosurgical centers were not predictive of their respective long-term survival rates.

CONCLUSIONS

Although considered surgically related if they occur within the first 30 days of surgery, most early postoperative deaths can happen independent of the handiwork of the operating surgeon or anesthesiologist. Overall prognosis of the disease seems to be a strong predictor of perioperative death-perhaps not surprisingly since the 30-day mortality rate is merely the intonation of the Kaplan-Meier curve. Both referral and treatment policies at a neurosurgical center will therefore markedly affect such early outcomes, but early deaths may not necessarily reflect overall quality of care or long-term results. The low incidence of perioperative death in intracranial tumor surgery also greatly limits the statistical power in comparative analyses, such as between published patient series or between centers and certainly between surgeons. Therefore the authors question the value of perioperative mortality rates as a quality indicator in modern neurosurgery for tumors.

Quality assessment of the registration of vulvar and vaginal premalignant lesions at the Cancer Registry of Norway

Background

A crucial factor concerning the utility of Cancer Registries is the data quality with respect to comparability, completeness, validity and timeliness. However, the data quality of the registration of premalignant lesions has rarely been addressed. High grade vulvar intraepithelial neoplasia (VIN) and vaginal intraepithelial neoplasia (VaIN) are premalignant lesions which may develop into cancer, and are often associated with infection with the human papillomarvirus (HPV). The aim was to evaluate the quality of registration of VIN and VaIN at the Cancer Registry of Norway (CRN).

Material and methods

We re-collected all notifications with high grade VIN and VaIN diagnoses during 2002 to 2007 from pathology laboratories, and compared these to the data in the CRN database so as to quantitatively measure the completeness, validity and timeliness of the data.

Results

Over the period 2002 to 2007 we estimated the completeness of the 1556 VIN and 297 VaIN notifications to be 95.0% and 92.9%, respectively. The original and reabstracted topography codes showed major discrepancies for 12 of 642 (1.9%) VIN and 7 of 128 (5.5%) VaIN notifications. The original and reabstracted morphology codes for VIN and VaIN were identical for 724 out of 814 notifications. Sixteen notifications had a major discrepancy. For the period 2002 to 2007 the median time elapsed between date of diagnosis and date of registration were 436 and 441 days for VTN and VaIN cases, respectively.

Discussion

Based on the present analysis of the comparability, completeness, validity and timeliness of premalignant lesions of vulva and vagina, we conclude that the Cancer Registry of Norway is able to monitor such premalignant lesions satisfactorily.

Serum levels of 25-hydroxyvitamin D and survival in Norwegian patients with cancer of breast, colon, lung, and lymphoma: a population-based study

PURPOSE

We investigated the association between serum levels of 25-hydroxyvitamin D (25-OHD) and risk of death in Norwegian cancer patients.

METHODS

The study population was 658 patients with cancers of the breast (n = 251), colon (n = 52), lung (n = 210), and lymphoma (n = 145), obtained from JANUS, a population-based serum bank in Norway. Serum samples were collected within 90 days of cancer diagnosis and were analyzed for 25-OHD. Patients were diagnosed during 1984-2004 and were followed for death throughout 2008. We used Cox regression models to assess the relationship between serum 25-OHD and risk of death.

RESULTS

Three hundred and ninety-nine patients died during follow-up, of whom 343 (86%) died from cancer. Adjusted for sex, age at diagnosis, and season of blood sampling, patients with 25-OHD levels below 46 nmol/L at diagnosis experienced shorter survival. Compared to patients in the lowest quartile of serum 25-OHD, the risk of cancer death among patients in the highest quartile was significantly reduced (HR 0.36 95% CI 0.27, 0.51). The estimated change in risk of cancer death was most pronounced between the first and the second quartile. The associations between 25-OHD levels and survival were observed for all four cancers.

CONCLUSIONS

Higher circulating serum levels of 25-OHD were positively associated with the survival for cancers of the breast, colon, lung, and lymphoma.

Survival and treatment patterns of glioblastoma in the elderly: a population-based study

BACKGROUND

As the older segment of the population grows faster than any other age group, the number of elderly diagnosed with glioblastoma is expected to increase. The aim of this study was to explore survival and the treatment provided to elderly patients diagnosed with glioblastoma in a population-based setting. We further studied whether increased treatment aggressiveness may have contributed to a clinically important survival benefit in the elderly population.

METHODS

From the Norwegian Cancer Registry, we included 2882 patients who were diagnosed with glioblastoma between 1988 and 2008.

RESULTS

The proportion of patients ≥66 years was 42.5% (n = 1224), and 15.9% of patients (n = 459) were ≥75 years at diagnosis. Treatment patterns varied significantly between age groups (P < 0.001). Elderly patients (66 years) were less likely to receive multimodal treatment with resection combined with radiotherapy and/or chemotherapy. Elderly patients were more likely to receive a diagnosis of glioblastoma without histopathologic verification (P < 0.001). Among patients receiving multimodal treatment with surgical resection, radiotherapy, and chemotherapy, shorter survival was seen in the elderly (P < 0.001). Belonging to the age group ≥75 years was the strongest predictor of decreased survival (P < 0.001), thus seemingly of higher prognostic impact than the patterns of care. Increasing age, no tumor resection, no radiotherapy, and no chemotherapy were identified as independent predictors of reduced survival. There was a statistically significant, albeit debatable, clinically relevant survival advantage for the oldest patients (≥75 years) diagnosed in the last 5 years of the study.

CONCLUSIONS

Advancing age remains a very strong and independent negative prognostic factor in glioblastoma. Although there has been an increase in the aggressiveness of treatment provided to elderly with glioblastoma, the gain for the oldest age group seems at best very modest. The prognosis of the oldest age group remains very poor, despite multimodal treatment.

Incidence and Outcome of Male Breast Cancer: An International Population-Based Study

Purpose

Male breast cancer is a rare disease with an incidence rate less than 1% of that of female breast cancer. Given its low incidence, few studies have assessed risk and prognosis.

Methods

This population-based study, including 459,846 women and 2,665 men diagnosed with breast cancer in Denmark, Finland, Geneva, Norway, Singapore, and Sweden over the last 40 years, compares trends in incidence, relative survival, and relative excess mortality between the sexes.

Results

World standardized incidence rates of breast cancer were 66.7 per 105 person-years in women and 0.40 per 105 person-years in men. Women were diagnosed at a younger median age (61.7 years) than men (69.6 years). Male patients had a poorer 5-year relative survival ratio than women (0.72 [95% CI, 0.70 to 0.75] v 0.78 [95% CI, 0.78 to 0.78], respectively), corresponding to a relative excess risk (RER) of 1.27 (95% CI, 1.13 to 1.42). However, after adjustment for age and year of diagnosis, stage, and treatment, male patients had a significantly better relative survival from breast cancer than female patients (RER, 0.78; 95% CI, 0.62 to 0.97).

Conclusion

Male patients with breast cancer have later onset of disease and more advanced disease than female patients. Male patients with breast cancer have lower risk of death from breast cancer than comparable female patients.

Changes over time in the effect of marital status on cancer survival

Background

Rates of all-cause and cause-specific mortality are higher among unmarried than married individuals. Cancer survival is also poorer in the unmarried population. Recently, some studies have found that the excess all-cause mortality of the unmarried has increased over time, and the same pattern has been shown for some specific causes of death. The objective of this study was to investigate whether there has been a similar change over time in marital status differences in cancer survival.

Methods

Discrete-time hazard regression models for cancer deaths among more than 440 000 women and men diagnosed with cancer 1970-2007 at age 30-89 were estimated, using register data encompassing the entire Norwegian population. More than 200 000 cancer deaths during over 2 million person-years of exposure were analyzed.

Results

The excess mortality of the never-married compared to the married has increased steadily for men, in particular the elderly. Among elderly women, the excess mortality of the never-married compared to the married has increased, and there are indications of an increasing excess mortality of the widowed. The excess mortality of divorced men and women, however, has been stable.

Conclusions

There is no obvious explanation for the increasing disadvantage among the never-married. It could be due to a relatively poorer general health at time of diagnosis, either because of a more protective effect of partnership in a society that may have become less cohesive or because of more positive selection into marriage. Alternatively, it could be related to increasing differentials with respect to treatment. Today's complex cancer therapy regimens may be more difficult for never-married to follow, and health care interventions directed and adapted more specifically to the broad subgroup of never-married patients might be warranted.

Metabolic risk factors and ovarian cancer in the Metabolic Syndrome and Cancer project

BACKGROUND

No studies have so far evaluated the impact of the metabolic syndrome (MetS) as an entity on ovarian cancer risk. The authors aimed to examine the association between factors in the MetS, individually and combined, and risk of ovarian cancer incidence and mortality.

METHODS

Altogether, 290,000 women from Austria, Norway and Sweden were enrolled during 1974-2005, with measurements taken of height, weight, blood pressure and levels of glucose, cholesterol and triglycerides. Relative risks (RRs) of ovarian cancer were estimated using Cox regression for each MetS factor in quintiles and for standardized levels (z-scores), and for a composite z-score for the MetS. RRs were corrected for random error in measurements.

RESULTS

During follow-up, 644 epithelial ovarian cancers and 388 deaths from ovarian cancer were identified. There was no overall association between MetS and ovarian cancer risk. Increasing levels of cholesterol [RR 1.52, 95% confidence interval (95% CI) 1.01-2.29, per 1-U increment of z-score] and blood pressure (RR 1.79, 95% CI 1.12-2.86) conferred, however, increased risks of mucinous and endometrioid tumours, respectively. In women below the age of 50 years, there was increased risk of ovarian cancer mortality for MetS (RR 1.52, 95% CI 1.00-2.30). Increasing levels of BMI (RR 1.17, 95% CI 1.01-1.37) conferred increased risk of ovarian cancer mortality in women above the age of 50 years.

CONCLUSION

There was no overall association between MetS and ovarian cancer risk. However, increasing levels of cholesterol and blood pressure increased the risks of mucinous and endometrioid tumours, respectively. Increasing levels of BMI conferred an increased risk of ovarian cancer mortality in women above the age of 50 years.

Breast cancer incidence trends in Norway--explained by hormone therapy or mammographic screening?

A decline in breast cancer incidence has been observed in several countries after 2002. Reduced use of menopausal hormonal therapy (HT), as a consequence of the publication of results from the Women's Health Initiative, has been argued to be the main reason. In Norway, the governmentally funded Norwegian Breast Cancer Screening Program (NBCSP) was implemented during the same time period as the increased use of HT. This study investigated trends in breast cancer incidence by use of HT and introduction of the screening program. We obtained rates of breast cancer from the Cancer Registry of Norway and sales data of HT preparations from the Norwegian Institute of Public Health. Mammography rates were estimated from published reports. Breast cancer incidence rates increased steadily from 1956 to the end of the 20th century, particularly in women aged 55-69 during 1996-2002 residing in the counties where the NBCSP was first introduced. The rates declined after 2002-2003. HT use increased in 1987-2001, peaking around year 2000. In particular, sales of combined estrogen and progestogen preparations declined after 2002. Among women aged 55-59, rates of hormone receptor positive breast cancers peaked in 2000-2003. No such trend was seen in other age groups. In conclusion, the interpretation of breast cancer incidence trends in Norway from 1987 to 2009 is complicated because the NBCSP was introduced during a period with increasing HT use. Both factors likely contributed to the observed trends, and the role of each may vary across age groups.

Occupation and risk of primary fallopian tube carcinoma in Nordic countries

The aetiology of primary Fallopian tube carcinoma (PFTC) is poorly understood. Occupational exposures may contribute to PFTC risk. We studied incidence of PFTC in occupational categories in the Nordic female population aged 30-64 years during the 1960, 1970, 1980/1981 and/or 1990 censuses in Denmark, Finland, Iceland, Norway and Sweden. Standardized incidence ratios (SIRs) for the years following inclusion in the study up to 2005 were calculated for 53 occupations; the expected numbers of cases were based on PFTC incidence in the national populations. Altogether 2,206 PFTC cases were detected during follow up via data linkages with the Nordic cancer registries. Significantly increased risks of PFTC were observed for smelting workers (SIR 3.99, 95% confidence interval 1.46-8.68, Obs = 6), artistic workers (2.64, 1.44-4.43, Obs = 14), hairdressers (2.18, 1.41-3.22, Obs = 25), packers (1.62, 1.11-2.29, Obs = 32), nurses (1.49, 1.14-1.92, Obs = 60), shop workers (1.25, 1.07-1.46, Obs = 159) and clerical workers (1.20, 1.07-1.35, Obs = 271) and these sustained over times and different Nordic countries. There was a nonsignificant increased risk for PFTC among welders, printers, painters and chemical process workers. The risk was significantly and consistently low for women working in farming (0.68, 0.47-0.95, Obs = 34) and among economically inactive women (0.88, 0.82-0.94, Obs = 833). The possible role of occupational exposures to the PFTC risks found in this study must be further evaluated in studies with a possibility to adjust for possible confounding factors, such as reproductive and life-style factors, which was not possible in our study.

Investigating the completeness of a histopathological cancer registry: estimation by capture-recapture analysis in a French geographical unit Alpes-Maritimes, 2008

INTRODUCTION

Cancer population studies require reliable and complete baseline data, which should theoretically be available by collecting histopathology records. The completeness of such a collection was evaluated using capture-recapture analysis based on three data sources concerning breast and colorectal cancers over an identical period and within the same geographical area.

METHOD

The total number of breast and colon cancer cases was estimated using capture-recapture analysis based on the number of cases which were common or not between sources recording screened, diagnosed and treated cancers in the French Alpes Maritimes district.

RESULT

The estimated total number of new cases of breast cancer diagnosed among Alpes Maritimes residents women aged 50-75 was 791 (95% CI: 784-797) in 2008. Of these 791 cases, 729 were identified through histopathology records, thus amounting to 92.2% completeness (95% CI: 91.5-93.0%). The total estimated number of new cases of colorectal cancer diagnosed among Alpes Maritimes residents aged 50-75 was 527 (95% CI: 517-536). Of these 527 cases, 481 were identified through histopathology records, thus amounting to 91.3% completeness (95% CI: 89.7-93.0%).

CONCLUSION

The estimated completeness of cancer records collected from histopathology laboratories was higher than 90% for new cases of breast and colorectal cancer within the age range concerned by the screening programme. A verified and validated histopathology data collection may be useful for cancer population studies.

Record linkage for pharmacoepidemiological studies in cancer patients

BACKGROUND

An increasing need has developed for the post-approval surveillance of (new) anti-cancer drugs by means of pharmacoepidemiology and outcomes research in the area of oncology.

OBJECTIVES

To create an overview that makes researchers aware of the available database linkages in Northern America and Europe which facilitate pharmacoepidemiology and outcomes research in cancer patients.

METHODS

In addition to our own database, i.e. the Eindhoven Cancer Registry (ECR) linked to the PHARMO Record Linkage System, we considered database linkages between a population-based cancer registry and an administrative healthcare database that at least contains information on drug use and offers a longitudinal perspective on healthcare utilization. Eligible database linkages were limited to those that had been used in multiple published articles in English language included in Pubmed. The HMO Cancer Research Network (CRN) in the US was excluded from this review, as an overview of the linked databases participating in the CRN is already provided elsewhere. Researchers who had worked with the data resources included in our review were contacted for additional information and verification of the data presented in the overview.

RESULTS

The following database linkages were included: the Surveillance, Epidemiology, and End-Results-Medicare; cancer registry data linked to Medicaid; Canadian cancer registries linked to population-based drug databases; the Scottish cancer registry linked to the Tayside drug dispensing data; linked databases in the Nordic Countries of Europe: Norway, Sweden, Finland and Denmark; and the ECR-PHARMO linkage in the Netherlands. Descriptives of the included database linkages comprise population size, generalizability of the population, year of first data availability, contents of the cancer registry, contents of the administrative healthcare database, the possibility to select a cancer-free control cohort, and linkage to other healthcare databases.

CONCLUSIONS

The linked databases offer a longitudinal perspective, allowing for observations of health care utilization before, during, and after cancer diagnosis. They create new powerful data resources for the monitoring of post-approval drug utilization, as well as a framework to explore the (cost-)effectiveness of new, often expensive, anti-cancer drugs as used in everyday practice.

Completeness of case ascertainment and survival time error in English cancer registries: impact on 1-year survival estimates

BACKGROUND

It has been suggested that cancer registries in England are too dependent on processing of information from death certificates, and consequently that cancer survival statistics reported for England are systematically biased and too low.

METHODS

We have linked routine cancer registration records for colorectal, lung, and breast cancer patients with information from the Hospital Episode Statistics (HES) database for the period 2001-2007. Based on record linkage with the HES database, records missing in the cancer register were identified, and dates of diagnosis were revised. The effects of those revisions on the estimated survival time and proportion of patients surviving for 1 year or more were studied. Cases that were absent in the cancer register and present in the HES data with a relevant diagnosis code and a relevant surgery code were used to estimate (a) the completeness of the cancer register. Differences in survival times calculated from the two data sources were used to estimate (b) the possible extent of error in the recorded survival time in the cancer register. Finally, we combined (a) and (b) to estimate (c) the resulting differences in 1-year cumulative survival estimates.

RESULTS

Completeness of case ascertainment in English cancer registries is high, around 98-99%. Using HES data added 1.9%, 0.4% and 2.0% to the number of colorectal, lung, and breast cancer registrations, respectively. Around 5-6% of rapidly fatal cancer registrations had survival time extended by more than a month, and almost 3% of rapidly fatal breast cancer records were extended by more than a year. The resulting impact on estimates of 1-year survival was small, amounting to 1.0, 0.8, and 0.4 percentage points for colorectal, lung, and breast cancer, respectively.

INTERPRETATION

English cancer registration data cannot be dismissed as unfit for the purpose of cancer survival analysis. However, investigators should retain a critical attitude to data quality and sources of error in international cancer survival studies.

The impact of provider surgical volumes on survival in children with primary tumors of the central nervous system--a population-based study

BACKGROUND

Provider volume is often a central topic in debates about centralization of procedures. In Norway, there is considerable variation in provider volumes of the neurosurgical centers treating children. We sought to explore long-term survival after surgery for central nervous system tumors in children in relation to regional provider volumes.

METHOD

Based on data from the Norwegian Cancer Registry we analyzed survival in all reported central nervous system tumors in children under the age of 16 treated over two decades, between March 1988 and April 2008; a total of 816 patients with histologically confirmed disease.

RESULTS

There was no overall difference in survival between regions. In the subgroup of PNET/medulloblastomas, both living in the high-provider volume health region and receiving treatment in the high-volume region was significantly associated with inferior survival.

CONCLUSIONS

In this population-based study of children operated over a period of two decades, we found no evidence of improved long-term survival in the high-provider volume region. Surprisingly, a subgroup analysis indicated that survival in PNET/medulloblastomas was significantly better if living outside the most populated health region with the highest provider volumes. One should, however, be careful of interpreting this directly as a symptom of quality of care, as there may be unseen confounders. Our study demonstrates that provider case volume may serve as an axiom in debates about centralization of cancer surgery while perhaps much more reliable and valid but less quantifiable factors are important for the final results.

Night work and breast cancer risk among Norwegian nurses: assessment by different exposure metrics

Associations between night work and breast cancer risk were investigated in a nested case-control study within a cohort of 49,402 Norwegian nurses. A total of 699 (74%) of the live cases diagnosed in 1990-2007 and 895 (65%) controls, cancer free at the time of sampling, were interviewed about work history and potential risk factors. The odds ratios for risk of breast cancer in relation to different exposure metrics were estimated by multivariate unconditional logistic regression models. No increase of risk was found after long duration of work by nurses working ≥3 night shifts per month. Small, nonsignificantly increased risks were observed for exposure to ≥30 years in hospitals or other institutions (odds ratio (OR) = 1.1), ≥12 years in schedules including night work (OR = 1.3), ≥1,007 night shifts during the lifetime (OR = 1.2), and lifetime average number of ≥4 night shifts per month (OR = 1.2). Nonsignificantly increased risks of breast cancer were observed in nurses who worked ≥5 years with ≥4 (OR = 1.4) and ≥5 (OR = 1.6) consecutive night shifts. Significantly increased risks were seen in nurses who worked ≥5 years with ≥6 consecutive night shifts (OR = 1.8, 95% confidence interval: 1.1, 2.8). The results suggest that risk may be related to number of consecutive night shifts.

Quantifying differences in breast cancer survival between England and Norway

BACKGROUND

Survival from breast cancer is lower in the UK than in some other European countries. We compared survival in England and Norway by age and time from diagnosis.

METHODS

We included 303,648 English and 24,919 Norwegian cases of breast cancer diagnosed 1996-2004 using flexible parametric relative survival models, enabling improved quantification of differences in survival. Crude probabilities were estimated to partition the probability of death due to all causes into that due to cancer and other causes and to estimate the number of "avoidable" deaths.

RESULTS

England had lower relative survival for all ages with the difference increasing with age. Much of the difference was due to higher excess mortality in England in the first few months after diagnosis. Older patients had a higher proportion of deaths due to other causes. At 5 years post diagnosis, a woman aged 85 in England had probabilities of 0.35 of dying of cancer and 0.32 of dying of other causes, whilst in Norway they were 0.26 and 0.35. By eight years the number of "avoidable" all-cause deaths in England was 1020 with the number of "avoidable" breast cancer related deaths 1488.

CONCLUSION

Lower breast cancer survival in England is mainly due to higher mortality in the first year after diagnosis. Crude probabilities aid our understanding of the impact of disease on individual patients and help assess different treatment options.

Metabolic syndrome and risk of bladder cancer: prospective cohort study in the metabolic syndrome and cancer project (Me-Can)

There are little data on the putative association between factors in the metabolic syndrome (MetS) and risk of bladder cancer. In the Metabolic Syndrome and Cancer project (Me-Can), measurements of height, weight, blood pressure and circulating levels of glucose, cholesterol, and triglycerides had been collected from 578,700 subjects in cohorts in Norway, Austria, and Sweden. We used Cox proportional hazard models to calculate relative risks (RRs) of bladder cancer by exposures divided into quintiles, in categories according to the World Health Organisation (WHO) and as a continuous standardized variable (z-score with mean = 0 and standard deviation = 1) for each separate component and its standardized sum, a composite MetS score. RRs were corrected for random error in measurements. During a mean follow-up of 11.7 years (SD = 7.6), 1,587 men and 327 women were diagnosed with bladder cancer. Significant associations with risk were found among men per one unit increment of z-score for blood pressure, RR = 1.13 (95% CI 1.03-1.25), and the composite MetS score, RR = 1.10 (95% CI 1.01-1.18). Among women, glucose was nonsignificantly associated with risk, RR = 1.41 (95% CI 0.97-2.06). No statistically significant interactions were found between the components in the MetS in relation to bladder cancer risk. Hypertension and a composite MetS score were significantly but modestly associated with an increased risk of bladder cancer among men and elevated glucose was associated with a nonsignificant increase in risk among women.

Use of combined search criteria improved validity of rare disease (craniopharyngioma) diagnosis in a national registry

OBJECTIVE

To evaluate sensitivity and validity of the Danish National Patient Registry (NPR) including relevant International Classification of Diseases, Eighth Revision (ICD-8) and International Classification of Diseases, Tenth Revision (ICD-10) codes and explore potential benefits of combining diagnosis and department codes in composite search strategies.

STUDY DESIGN AND SETTING

The study period was 1985-2004. Medical records of patients identified with one or more of seven ICD-8 or ICD-10 codes from a number of registries were reviewed to confirm or reject the craniopharyngioma diagnosis. NPR sensitivity was evaluated in North Jutland County through comparison with hospital registries, the county registry, and the Danish Cancer Registry. Codes and search strategies were studied using NPR data from Denmark (population 5.2 million).

RESULTS

In the North Jutland County study, the NPR identified 95% of new patients with histologically verified or probable craniopharyngioma. In the code and search strategy studies, the NPR search identified 684 patients. Records were retrieved in 607 (89%), of whom 185 (30%) had verified or probable craniopharyngioma. Searches combining "best code" and "highly specialized department" or "neurosurgery procedure" registrations improved validity considerably, whereas reducing sensitivity only modestly.

CONCLUSION

The NPR identified 95% of new craniopharyngioma patients, but only 30% of cases were correct. Validity was improved by applying a modified composite search strategy.