The impact of excluding or including Death Certificate Initiated (DCI) cases on estimated cancer survival: A simulation study

Trends in lung cancer survival in the Nordic countries 1990-2016: The NORDCAN survival studies

OBJECTIVES

The aim of this study was to evaluate if the previously reported improvements in lung cancer survival were consistent across age at diagnosis and by lung cancer subtypes.

MATERIALS AND METHODS

Data on lung cancers diagnosed between 1990 and 2016 in Denmark, Finland, Iceland, Norway and Sweden were obtained from the NORDCAN database. Flexible parametric models were used to estimate age-standardized and age-specific relative survival by sex, as well as reference-adjusted crude probabilities of death and life-years lost. Age-standardised survival was also estimated by the three major subtypes; adenocarcincoma, squamous cell and small-cell carcinoma.

RESULTS

Both 1- and 5-year relative survival improved continuously in all countries. The pattern of improvement was similar across age groups and by subtype. The largest improvements in survival were seen in Denmark, while improvements were comparatively smaller in Finland. In the most recent period, age-standardised estimates of 5-year relative survival ranged from 13% to 26% and the 5-year crude probability of death due to lung cancer ranged from 73% to 85%. Across all Nordic countries, survival decreased with age, and was lower in men and for small-cell carcinoma.

CONCLUSION

Lung cancer survival has improved substantially since 1990, in both women and men and across age. The improvements were seen in all major subtypes. However, lung cancer survival remains poor, with three out of four patients dying from their lung cancer within five years of diagnosis.

Cancer survival in sub-Saharan Africa (SURVCAN-3): a population-based study

BACKGROUND

The Cancer Survival in Africa, Asia, and South America project (SURVCAN-3) of the International Agency for Research on Cancer aims to fill gaps in the availability of population-level cancer survival estimates from countries in these regions. Here, we analysed survival for 18 cancers using data from member registries of the African Cancer Registry Network across 11 countries in sub-Saharan Africa.

METHODS

We included data on patients diagnosed with 18 cancer types between Jan 1, 2005, and Dec 31, 2014, from 13 population-based cancer registries in Cotonou (Benin), Abidjan (CÔte d'Ivoire), Addis Ababa (Ethiopia), Eldoret and Nairobi (Kenya), Bamako (Mali), Mauritius, Namibia, Seychelles, Eastern Cape (South Africa), Kampala (Uganda), and Bulawayo and Harare (Zimbabwe). Patients were followed up until Dec 31, 2018. Patient-level data including cancer topography and morphology, age and date at diagnosis, vital status, and date of death (if applicable) were collected. The follow-up (survival) time was measured from the date of incidence until the date of last contact, the date of death, or until the end of the study, whichever occurred first. We estimated the 1-year, 3-year, and 5-year survival (observed, net, and age-standardised net survival) by sex, cancer type, registry, country, and human development index (HDI). 1-year and 3-year survival data were available for all registries and all cancer sites, whereas availability of 5-year survival data was slightly more variable; thus to provide medium-term survival prospects, we have focused on 3-year survival in the Results section.

FINDINGS

10 500 individuals from 13 population-based cancer registries in 11 countries were included in the survival analyses. 9177 (87·4%) of 10 500 cases were morphologically verified. Survival from cancers with a high burden and amenable to prevention was poor: the 3-year age-standardised net survival was 52·3% (95% CI 49·4-55·0) for cervical cancer, 18·1% (11·5-25·9) for liver cancer, and 32·4% (27·5-37·3) for lung cancer. Less than half of the included patients were alive 3 years after a cancer diagnosis for eight cancer types (oral cavity, oesophagus, stomach, larynx, lung, liver, non-Hodgkin lymphoma, and leukaemia). There were differences in survival for some cancers by sex: survival was longer for females with stomach or lung cancer than males with stomach or lung cancer, and longer for males with non-Hodgkin lymphomas than females with non-Hodgkin lymphomas. Survival did not differ by country-level HDI for cancers of the oral cavity, oesophagus, liver, thyroid, and for Hodgkin lymphoma.

INTERPRETATION

For cancers for which population-level prevention strategies exist, and with relatively poor prognosis, these estimates highlight the urgent need to upscale population-level prevention activities in sub-Saharan Africa. These data are vital for providing the knowledge base for advocacy to improve access to prevention, diagnosis, and care for patients with cancers in sub-Saharan Africa.

FUNDING

Vital Strategies, the Martin-Luther-University Halle-Wittenberg, and the International Agency for Research on Cancer.

TRANSLATIONS

For the French and Portuguese translations of the abstract see Supplementary Materials section.

Contemporary validation of cT1a vs. cT1b substaging of incidental prostate cancer

OBJECTIVE

The cT1a vs. cT1b substratification was introduced in 1992 but never formally tested since. We tested the discriminative ability of cT1a vs. cT1b substaging on cancer-specific survival (CSS) in contemporary incidental prostate cancer (PCa) patients.

DESIGN, SETTING AND PARTICIPANTS

Incidental (cT1a/cT1b) PCa patients were identified within the Surveillance, Epidemiology, and End Results (SEER) database (2004-2015).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Kaplan-Meier estimates, as well as uni- and multivariable Cox regression models predicted CSS at five years. Subgroup analyses addressed CSS at five years according to active vs. no local treatment (NLT) as well as Gleason score sum (GS; 6 vs. 7 vs. ≥ 8).

RESULTS AND LIMITATION

We identified a total of 5,155 incidental prostate cancer patients of which 3,035 (59%) were stage cT1a vs. 2,120 (41%) were stage cT1b. In all incidental PCa patients, CSS at five years was 95% (95% CI 0.94-0.96). In cT1a patients, CSS at five years was 98 vs. 90% in cT1b patients (p < 0.001). In multivariable Cox regression analyses, cT1b independently predicted 2.8-fold higher CSM than cT1a (HR 2.5, 95% CI 1.8-3.6, p < 0.001) for incidental PCa patients who underwent NLT. In subgroup analyses, cT1b represented an independent predictor of higher CSM in GS ≥ 8 (HR 3.0, 95% CI 1.4-6.2, p = 0.003), and GS 7 (HR 3.9, 95% CI 1.6-9.7 p = 0.002) patients who underwent NLT. For actively treated patients, cT1b was not independently associated with worse CSM.

CONCLUSION

The historical subclassification of cT1a vs. cT1b in incidental PCa patients displayed a strong ability to discriminate CSS in contemporary GS 7 and GS ≥ 8 patients who underwent NLT. However, no statistically significant difference was recorded in actively treated patients. In consequence, the importance of the current substage stratification predominantly applies to GS ≥ 8 patients who undergo a non-active treatment approach.

Prognostic Significance of Radiographic Lymph Node Invasion in Contemporary Metastatic Renal Cell Carcinoma Patients

PURPOSE

To test the prognostic significance of radiographic cN-stage in metastatic renal cell carcinoma (mRCC) patients with low metastatic burden (1 site of metastasis), relying on the Surveillance, Epidemiology, and End Results database (SEER 2010-2020).

METHODS

Included were mRCC patients with 1 site of metastasis, treated with systemic therapy without cytoreductive nephrectomy (CN). Kaplan-Meier plots and multivariable Cox-regression models addressed cancer-specific mortality (CSM) according to radiographic cN-stage (ccN1 vs. ccN0). Separate subgroup analyses were performed, addressing radiographic N-stage in patients with distinct histology (clear-cell vs. RCC not otherwise specified [RCC NOS]).

RESULTS

Of 1756 mRCC patients, 545 (31%) were radiographic cN1. Overall, the median CSM-free survival of the cohort was 11 months. Median CSM-free survival was 8 vs. 14 months in radiographic cN1 vs. cN0 mRCC patients (HR 1.49, P < .0001). In multivariable Cox regression analyses, radiographic cN1 status was an independent predictor of higher CSM (HR 1.39; P = .01). In subgroup analyses, addressing patients with clear-cell histology and patients with RCC NOS separately, radiographic cN1 status remained independently associated with a higher CSM in both groups (clear-cell: HR 1.36; P = .03; RCC NOS: HR 2.06; P = .009).

CONCLUSION

In mRCC patients with low metastatic burden, presence or absence of radiographic lymph node invasion results in a clinically meaningful discrimination between those with poor prognosis and others. In consequence, consideration of radiographic lymph node invasion might be of great value in this specific population of mRCC patients.

Characteristics of incidental prostate cancer in the United States

BACKGROUND

Data regarding North-American incidental (cT1a/b) prostate cancer (PCa) patients is scarce. To address this, incidental PCa characteristics (age, PSA values at diagnosis, Gleason score [GS]), subsequent treatment and cancer-specific survival (CSS) rates were explored.

METHODS

Incidental PCa patients were identified within the Surveillance, Epidemiology, and End Results (SEER) database (2004-2015). Descriptive statistics, annual percentage changes (EAPC), Kaplan-Meier estimates, as well as Cox regression models were used. Bootstrapping technique was used to generate 95% confidence intervals for CSS at 6 years.

RESULTS

Of all 344,031 newly diagnosed non metastatic PCa patients, 5155 harbored incidental PCa. Annual rates of incidental PCa increased from 1.9% (2004) to 2.5 % (2015; p = 0.02). PSA values at diagnosis were 0-4 ng/ml in 48% vs. 4-10 ng/ml in 31% vs. > 10 ng/ml in 21%. Of all incidental PCa patients, 64% harbored GS 6 vs. 25% GS 7 vs. 11% GS ≥ 8. Of all incidental PCa patients, 47% were aged < 70, 35% were between 70 and 79 and 18% were ≥ 80 years. Subsequently, 71% underwent no local treatment (NLT) vs. 16% radical prostatectomy (RP) vs. 14% radiotherapy (RT). Proportions of patients with NLT increased from 65 to 81% (p = 0.0001) over the study period (2004-2015). CSS at six years ranged from 58% in GS ≥ 8 patients with NLT to 100% in patients who harbored GS 6 and underwent either RP or RT.

CONCLUSION

Incidental PCa in the United States is rare. Most incidental PCa patients are diagnosed in men aged less than 80 years of age. The majority of incidental PCa patients undergo NLT and enjoy excellent CSS.

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.

Survival trends in patients diagnosed with colon and rectal cancer in the nordic countries 1990-2016: The NORDCAN survival studies

BACKGROUND

Survival of patients with colon and rectal cancer has improved in all Nordic countries during the past decades. The aim of this study was to further assess survival trends in patients with colon and rectal cancer in the Nordic countries by age at diagnosis and to present additional survival measures.

METHODS

Data on colon and rectal cancer cases diagnosed in the Nordic countries between 1990 and 2016 were obtained from the NORDCAN database. Relative survival was estimated using flexible parametric models. Both age-standardized and age-specific measures for women and men were estimated from the models, as well as reference-adjusted crude probabilities of death and life-years lost.

RESULTS

The five-year age-standardized relative survival of colon and rectal cancer patients continued to improve for women and men in all Nordic countries, from around 50% in 1990 to about 70% at the end of the study period. In general, survival was similar across age and sex. The largest improvement was seen for Danish men and women with rectal cancer, from 41% to 69% and from 43% to 71%, respectively. The age-standardized and reference-adjusted five-year crude probability of death in colon cancer ranged from 30% to 36% across countries, and for rectal cancer from 20% to 33%. The average number of age-standardized and reference-adjusted life-years lost ranged between six and nine years.

CONCLUSION

There were substantial improvements in colon and rectal cancer survival in all Nordic countries 1990-2016. Of special note is that the previously observed survival disadvantage in Denmark is no longer present.

Five ways to improve international comparisons of cancer survival: lessons learned from ICBP SURVMARK-2

BACKGROUND

Comparisons of population-based cancer survival between countries are important to benchmark the overall effectiveness of cancer management. The International Cancer Benchmarking Partnership (ICBP) Survmark-2 study aims to compare survival in seven high-income countries across eight cancer sites and explore reasons for the observed differences. A critical aspect in ensuring comparability in the reported survival estimates are similarities in practice across cancer registries. While ICBP Survmark-2 has shown these differences are unlikely to explain the observed differences in cancer-specific survival between countries, it is important to keep in mind potential biases linked to registry practice and understand their likely impact.

METHODS

Based on experiences gained within ICBP Survmark-2, we have developed a set of recommendations that seek to optimally harmonise cancer registry datasets to improve future benchmarking exercises.

RESULTS

Our recommendations stem from considering the impact on cancer survival estimates in five key areas: (1) the completeness of the registry and the availability of registration sources; (2) the inclusion of death certification as a source of identifying cases; (3) the specification of the date of incidence; (4) the approach to handling multiple primary tumours and (5) the quality of linkage of cases to the deaths register.

CONCLUSION

These recommendations seek to improve comparability whilst maintaining the opportunity to understand and act upon international variations in outcomes among cancer patients.

Impact of the Management and Proportion of Lost to Follow-Up Cases on Cancer Survival Estimates for Small Population-Based Cancer Registries

BACKGROUND

Estimation of survival requires follow-up of patients from diagnosis until death ensuring complete and good quality data. Many population-based cancer registries in low- and middle-income countries have difficulties linking registry data with regional or national vital statistics, increasing the chances of cases lost to follow-up. The impact of lost to follow-up cases on survival estimates from small population-based cancer registries (<500 cases) has been understudied, and bias could be larger than in larger registries.

METHODS

We simulated scenarios based on idealized real data from three population-based cancer registries to assess the impact of loss to follow-up on 1-5-year overall and net survival for stomach, colon, and thyroid cancers-cancer types with very different prognosis. Multiple scenarios with varying of lost to follow-up proportions (1-20%) and sample sizes of (100-500 cases) were carried out. We investigated the impact of excluding versus censoring lost to follow-up cases; punctual and bootstrap confidence intervals for the average bias are presented.

RESULTS

Censoring of lost to follow-up cases lead to overestimation of the overall survival, this effect was strongest for cancers with a poor prognosis and increased with follow-up time and higher proportion of lost to follow-up cases; these effects were slightly larger for net survival than overall survival. Excluding cases lost to follow-up did not generate a bias on survival estimates on average, but in individual cases, there were under- and overestimating survival. For gastric, colon, and thyroid cancer, relative bias on 5-year cancer survival with 1% of lost to follow-up varied between 6% and 125%, 2% and 40%, and 0.1% and 1.0%, respectively.

CONCLUSION

Estimation of cancer survival from small population-based registries must be interpreted with caution: even small proportions of censoring, or excluding lost to follow-up cases can inflate survival, making it hard to interpret comparison across regions or countries.

The validity of cancer information on death certificates in Norway and the impact of death certificate initiated cases on cancer incidence and survival

BACKGROUND

Death certificates are an important source of information for cancer registries. The aim of this study was to validate the cancer information on death certificates, and to investigate the effect of including death certificate initiated (DCI) cases in the Cancer Registry of Norway when estimating cancer incidence and survival.

METHODS

All deaths in Norway in the period 2011-2015 with cancer mentioned on the death certificates were linked to the cancer registry. Notifications not registered from other sources were labelled death certificate notifications (DCNs), and considered as either cancer or not, based on available information in the registry or from trace-back to another source.

RESULTS

From the total of 65 091 cancers mentioned on death certificates in the period 2011-2015, 58,425 (89.8%) were already in the registry. Of the remaining 6 666 notifications, 2 636 (2 129 with cancer as underlying cause) were not regarded to be new cancers, which constitutes 4.0% of all cancers mentioned on death certificates and 39.5% of the DCNs. Inclusion of the DCI cases increased the incidence of all cancers combined by 2.6%, with largest differences for cancers with poorer prognosis and for older age groups. Without validation, including the 2 129 disregarded death certificates would over-estimate the incidence by 1.3%. Including DCI cases decreased the five-year relative survival estimate for all cancer sites combined with 0.5% points.

CONCLUSION

In this study, almost 40% of the DCNs were regarded not to be a new cancer case, indicating unreliability of death certificate information for cancers that are not already registered from other sources. The majority of the DCNs where, however, registered as new cases that would have been missed without death certificates. Both including and excluding the DCI cases will potentially bias the survival estimates, but in different directions. This biases were shown to be small in the Cancer Registry of Norway.

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.