This is the fifth annual report on cancer incidence and mortality produced by the Malta National Cancer Registry, since its transition to a population-based registry in 1991. Each report aims at producing updated and comprehensive information on the cancer burden in the Maltese Islands by using the data collected on cancer on a nation-wide scale. This report presents cancer incidence and mortality data for 1996 and 1997 separately and also for the five years 1993 to 1997 together. Due to the relatively small number of cases registered annually for each specific cancer it is useful to present information and analysis on aggregated five year data to reduce the effect of year to year fluctuations on interpretation.
The registry tries to include new items of information in each subsequent report that it produces. This report will be publishing information on the survival experience of cases diagnosed with cancer in Malta for the first time. This analysis used the data collected on the cases registered between 1993 and 1997. Relative survival was calculated by using the statistical software SURV2: Relative Survival Analysis Program (Version 2.02b, 1998) prepared by the Finnish Cancer Registry and the Cancer Epidemiology Unit of the Karolinska Institute in Sweden. This analysis also necessitated the use of the General Mortality data of the Maltese population. This data was acquired from the information on mortality published in the Demographic Reviews for 1993 to 1997 by the Central Office of Statistics, Malta.
Incidence
Cancer incidence is defined as the occurrence of new cancers in a defined population during a specified period of time. For the purposes of this report, the incidence is based on those cancers registered as first diagnosed between 1st January 1996 and 31st December 1996 for 1996 and 1st January 1997 and 31st December 1997 for 1997 in the residents of the Maltese Islands. Tourists and persons who were not living in Malta for more than six months prior to their cancer diagnosis are not included in the register.
The incidence data in this report are the 1996 and 1997 statistics as they stood at the end of September 1999. Future publications and requests for data may not correspond exactly to the figures in this report, as they will reflect subsequent improvements to the data.
The Malta National Cancer Registry (MNCR) codes the sites, types and morphology of cancers using the International Classification of Diseases for Oncology (ICD-O), Second edition, 1990. Incidence reflects the number of primary tumours rather than the number of individuals with cancer. The MNCR database records multiple primary cancers in the same person. The registration of these tumours is guided by the recommendations issued in 1995 for the coding of Multiple Primaries by the International Agency for Research on Cancer (IARC) and the International Association of Cancer Registries (IACR).
Mortality and Survival
The National Mortality Registry regularly supplies the MNCR with a copy of the coded death certificates bearing the mention of a cancer anywhere on the document. This helps to update the cancer registry database with information on the death of cases which were already registered and also to initiate registrations when the first encounter is made from the death certificate. Every effort is made by the registry to obtain additional information about the latter cases so that the registration will not remain on the basis of a death certificate only (DCO). The cases registered on the basis of a DCO were excluded from the calculation of the survival figures published in this report.
The Mortality reported in this publication is defined as the number of cases whose death was attributed to cancer on their death certificate during the years 1993 to 1997. Hence only the cases where a cancer was designated as the underlying cause of death were included in the mortality figures. This information was obtained directly from the databases of the National Mortality Registry within the Department of Health Information (DHI). On the other hand the calculation of survival took into consideration all the cases that died prior to the 31st December 1998, whether or not the cancer was the underlying cause of their death.
Confidentiality
The registry collects and stores personal information on the registered cases such as names, addresses, date of birth and identification numbers. The primary aim for the collection of this data is to prevent multiple registrations for the same primary neoplasm and to help identify individuals for follow-up and survival analysis. The registry forms part of the DHI which houses a number of other national and hospital-based databases concerned with the collection of mortality and morbidity information on the Maltese population. Information is shared between these registries and databases for the mutual benefit of all. The major links are with the National Mortality Registry which supplies information about the deaths of cancer patients.
The registry supplies information in an anonymised format for requests made from agencies and individuals outside the DHI. Confidential information bearing identification data on the registered cases is only given to ethically approved studies, or requests approved by the Director General of the Health Division or to assist doctors in reviewing their own work on their own patients.
Links with other Cancer Registries
The MNCR has been a voting member of the IACR since 1995 and is an associate member of the European Network of Cancer Registries (ENCR). Full membership in the latter organisation is only accorded to cancer registries within the nations that are members of the European Union. Information on cancer in Malta is sent regularly to the above associations and is included within their publications and databases.
In 1998, the medical officer in charge of the MNCR attended the Annual Meeting of the IACR which was held in Atlanta, Georgia, USA. The presentations and discussions at this conference were mainly concerned with Genetics in Population-based Cancer Research. The Annual Meeting of the IACR for 1999 was held in Lisbon, Portugal. The programme of this conference was very extensive and included presentations concerned with Screening related to cancer registries, Tobacco and Young people, Genetic Epidemiology and Familial Cancer, Quality control on cancer registries, Cancer Mapping and Cancer Trends.
In February 1999 the ENCR held a workshop the role of cancer registries in organised cancer screening programmes in Luxembourg. The medical officer in charge of the MNCR participated in this workshop.
The MNCR was invited to participate in a Field Test Trial on a proposed third edition of the International Classification of Diseases for Oncology by IARC in June 1999. The registry accepted this invitation and more than 200 cases of cancer and another 200 cases of leukaemias and lymphoma registered during 1998 and 1999 were recoded using the new coding system and sent over to Lyon for analysis together with our comments on this new classification.
New cases of cancers registered in 1996 and 1997
A total of 1310 and 1495 malignant cases were newly registered in 1996 and in 1997 respectively. When the non-melanoma skin cancers were excluded the total number of new cases amounted to 1118 in 1996 and to 1229 in 1997. Table 1.1 gives the number of new cancers registered by the topography codes (C-codes ) and by gender for 1996 and 1997 separately.
TABLE 1.1 Cancer in Malta: 1996 and 1997. Number
of new cancer cases by site and gender.