Elsevier

Cancer Epidemiology

Volume 42, June 2016, Pages 32-38
Cancer Epidemiology

Population-level cure of colorectal cancer in Malta: An analysis of patients diagnosed between 1995 and 2004

https://doi.org/10.1016/j.canep.2016.03.001Get rights and content

Highlights

  • We analyse short and long term survival of colorectal cancer in Malta.

  • We use mixture model with Weibull survival distribution to model ‘cure’.

  • We see an improvement in long and short term survival over 15 years.

  • Age at diagnosis associated with both short and long term survival.

Abstract

Aim

The aim of this study was to estimate the population-level ‘cure’ of Maltese colorectal cancer patients diagnosed between 1995 and 2004, and to estimate the median survival time for the ‘uncured’ patients.

Methods and study population

Analysis was conducted on 1470 cases registered by the Malta National Cancer Register between 1995 and 2004 and followed up to end of 2010. The mean age of the patients was 66.4 (95%CI 65.8–67.1), and the number of men and women were equal. Background mortality for 1995–2010 was extracted from publicly available life tables. A mixture model with Weibull survival distribution and identity link was used to model ‘cure’.

Results

The overall ‘cured’ proportion for the patients diagnosed in 1995–1999 was 45.3% (95%CI 40.2–50.5) while the ‘cured’ proportion for the patients diagnosed in 2000–2004 was 52.3% (95%CI 47.2–57.5). Median survival time for the ‘uncured’ patients increased in the second calendar period from 1.25 years (95%CI 1.04–1.45) to 1.42 years (95%CI 1.15–1.76).

Conclusion

In Malta, as in the rest of Europe, improvements have been made in short- and long-term survival over the 15-year period under study. To continue this improvement, differences by age that still persist must be investigated and efforts focused to reduce any gaps between Malta and other European countries.

Introduction

Cancer is one of the leading causes of death worldwide and colorectal cancer is the fourth most common cause of cancer death. It is estimated that in Europe there were 214,700 deaths from colorectal cancer (12.3% of all cancer deaths) in 2012 [1]. In Malta, in 2013, colorectal cancer was the second leading cause of cancer death amongst both men and women [2].

Relative survival analysis presents survival estimates adjusted for the background risk of death at particular time points after diagnosis. An extension of the relative survival concept is the notion of ‘statistical cure’ or ‘population cure’. This is defined at a group level and is different from the concept of individual cure where patients can be considered medically free of cancer [3]. ‘Population cure’ relates to the tendency for some cancer relative survival curves to reach a plateau after a period of follow-up. This indicates that the excess mortality attributed to the cancer of the patient is equal to their background mortality, and thus these cancer patients are no more likely to die than their counterparts in the general population. The analysis of ‘cure’ can expand our understanding of the pattern of cancer survival.

The EUROCARE project estimated the ‘cured’ proportion of patients diagnosed between 1978 and 1999 in Europe [4], [5] and found a 12% improvement in long-term survival for the ‘cured’ proportion from 36% in 1978–1985 to 48.5% in 1997–1999. The study also showed a strong negative association between age and ‘cure’. Studies conducted in Sweden, Finland and North West England have also made use of ‘cure’ models to assess survival trends for colorectal cancer and have found similar results [6], [7], [8].

The aim of this study was to estimate the proportion of Maltese colorectal patients diagnosed between 1995 and 2004 who were statistically ‘cured’, and to estimate the median survival time for the uncured. This study is the first to apply ‘cure’ models on data from the Malta National Cancer Register.

Section snippets

Data sources

The data used in this study were taken from the Malta National Cancer Register which collects data for all incident cancers in the population resident in Malta and Gozo [9]. Cancer notification is compulsory by the Notification of Cancer Act of 1957 [10]. Data were collected for all patients diagnosed with colorectal cancer from 1995 to 2004 and followed up to the end of 2010. Colorectal cancers are coded by the registry using the International Classification of Diseases for Oncology (ICD-O-2)

Results

The mean age of the patients was 66.4 (95%CI 65.8–67.1). The proportion of men and women was similar in the two periods. Distribution of patients across the six regions reflects the relative population sizes of the regions (Table 1).

Five-year relative survival for the whole study population (1995–2004) was 53.3% (95%CI 50.3–56.3). Survival estimates were similar for men and women and by period of diagnosis. The curves by age group indicated lower survival in the older age groups. Five-year

Discussion

This is the first study on population ‘cure’ for colorectal cancer in Malta. Comparable European level ‘cure’ estimates are available only for the period 1994–1999 [5]. The proportion of ‘cured’ patients in Malta for this same period was 45.3% (95%CI 40.2–50.5). The median survival time for the ‘uncured’ group was 1.25 years (95%CI 1.04–1.45). The proportion of ‘cured’ patients in our study is slightly lower than the European estimate from the EUROCARE data for 1994–1999: 46.8% for patients in

Conflict of interest

The authors declare no potential conflict of interest.

Role of the funding source

The funding source did not have any role in the design of the study, in the collection, analysis or interpretation of the data, in the writing of the report, or in the decision to submit the paper.

Ethical approvals

Local ethical approval to conduct this study was obtained from the Malta University Research Ethics Committee in December 2011 (reference number 91/2011), and subsequent ethical approval was acquired on the 9th April 2012 from the London School of Hygiene and Tropical Medicine Ethics Committee (reference number 011/36).

Acknowledgements

Ms Dorothy Gauci was partially funded by the Strategic Educational Pathways Scholarship (Malta). The scholarship is part-financed by the European Union-European Social Fund (ESF) under Operational Programme II − Cohesion Policy 2007–2013, ‘Empowering People for More Jobs and a Better Quality of Life’.

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