ISSN OS48-944X DEPARTMENT OF HEALTH SPECIAL REPORT SERIES A CANCER MORTALITY ATLAS OF' NEW ZEALAND Issued by the National Health Statistics Centre Department ofHealth, Wellington New Zealand p 2 1982 , , I I OJe to difficulties in the reproductive stage of printing, the shading for some maps does not precisely cover the areas for which they apply. I ISSN 0548-944X . DEPARTMENT OFHEALTH , . -A CANCER MORTALITYATLAS:OF NEW ZEALAND , I / by BARR Y BORltdAN MA .National Health Statistics Centre Department ofHealth· SPECIAL REPORT No. 63 096369' Issued by the National Health Statistics Centre . Department of Health, Wellington . ., New Zealand . 1982 ,. CONTENTS ACKNOWLEDGMENTS DISCLAIMER AND COPYRIGHT FOREWORD INTRODUCTI ON 1 METHODOLOGY 3 CANCER OF THE BUCCAL CAVITY AND PHARYNX 11 CANCER OF THE OESOPHAGUS 15 CANCER OF THE STOMACH 19 CANCER OF THE LARGE INTESTINE 25 CANCER OF THE RECTUM 31 CANCER OF THE LARGE BOWEL 37 CANCER OF THE LIVER, GALLBLADDER AND BILE DUCTS 43 CANCER OF THE PANCREAS 49 CANCER OF THE LARYNX 53 CANCER OF THE TRACHEA, BRONCHUS AND LUNG, PLEURA AND MEDIASTINUM 57 MELANOMA OF THE SKIN 63 CANCER OF THE BREAST 67 CANCER OF THE CERVIX UTERI 71 CANCER OF THE UTERUS 75 CANCER OF THE OVARY, FALLOPIAN TUBE AND BROAD LIGAMENT 79 CANCER OF THE PROSTATE 83 CANCER OF THE BLADDER 87 CANCER OF THE BRAIN 91 LYMPHOSARCOMA 95 HODGKIN'S DISEASE 99 MULTIPLE MYELOMA 103 LEUKAEMIA 107 APPENDIX 111 ACKNOWLEDGMENTS· . The co-operation and assistance of th~ following people is gratefu.lly acknowledged: * . DrNMcGlashan, Department of Geography, University of Tasmani.a, .who introduced the author to.the field of medical geography and . made constructive criticisms on the development of this project. *·DrA Smith and Mr N· Pearce, Department of·Community. Health, Wellington' Clinical School of Medicine,. who made available the computer program'to' conduct the temporal analysis,and willingly offered advice and suggestions. * Mr J Findlay and Mr J Fraser, National Health Statistics Centre, ,for their, continued encouragement and support throughout this, .. study. Also Mr F Foster, for allowing access to the data and permission to publish. * Mr HFleming, Mr C Mooney, Miss K Carson, MsA Johnston, Mrs S Leiataua, and Miss S McKenna, for programming, clerical, and typing assistance. * Ms G·Simmonds, and the staff of the General Draughting Section, . Department of Lands and Survey, who accommodated every demand .; n -the production of the maps and graphs. - - /' DISCLAIMER The views expressed in this report are those of the author and do not necessarily represent the views of the Department of Health. COPYRIGHT Provided the source is acknowledged information contained in this report may be freely used by any person. FOREWORD Whereas atlases of diseases, especially those of infectious and epidemic nature, started to appear at international scale in the nineteenth century, it has not been until comparatively recently that national atlases portraying death from cancer on a geographic basis have been produced. This apparent delay has been necessitated by the time taken to determine standard methods of dealing with problems of differential diagnosis, of recording and of presenting these generally unfamiliar data. Since Melvyn Howe's national atlas of mortality for the United Kingdom in 1963, atlases specialising in cancer deaths have been produced from as far afield as the United States and Japan, West Germany and mainland China. Each adopts its own system of geographic units and statistical classes to cope with large population numbers. In New Zealand Mr Borman has had the rather different problems stemming from the small numbers of deaths in individual geographic divisions of a nation of only 3 million people. The major questions, of course, are of selecting small enough units of space to retain realistic accuracy of locality and yet to have large enough populations for confidence in the findings. The time span selected relates to these twin aims: a longer period of years will increase the gross numbers in each unit but tend to disguise temporal shifts of incidence and become more subject to unrealities from the mobility of individuals. Barry Borman has steered a rational and explicable course through these professional problems in a way that presents the facts clearly and establishes for his readers both where significance in his geographic patterns may be placed and where less confidence lies. There can be few of us in the developed countries today whose families have not been touched by one of the many forms of cancer. Any advance in knowledge of these conditions is therefore to be welcomed and the underlying implication of defining cancer variations over space must be, in the long run, to explain those variations either in terms of environmental or other factors. This is a peculiarly geographic task and an approach to cancer elucidation validly complementary to those of medical and other researchers in the field. I am happy to commend Barry Borman's work to a readership which I would like to hope will extend beyond medicine, geography and kindred sciences to all those lay people who still have wonder about their world and can question the mechanisms behind the mysterious, even apparently quixotic, cancer distribution patterns of New Zealand. Neil McGlashan Department of Geography University of Tasmania Tasmania INTRODUCTION Cancer is the second leading cause of death in New Zealand, accounting for 20 percent of the total annual mortality. The national death rate for some sites (eg, large bowel and melanoma of the skin) are among the highest in the world. Although the aetiology of most human neoplasms remains elusive, the majority are believed to be attributable, directly or indirectly, to environmental factors. One initial approach to identifying these carcinogens, and hence facilitate primary prevention, is to describe the demographic, geographic, and temporal distributions of cancer in populations. Often this will provide clues to the underlying disease causative processes. This report presents the results of a study designed to define the spatial patterns and secular trends of cancer martality in the total New Zealand population. The principal objective in the cartographic and graphic portrayal of these data is to generate aetiological hypotheses for testing in subsequent research. 1 METHODOLOGY SPATIAL ANALYSIS The age, sex, and domicile of persons registered [1] as dying from cancer in various sites (Table 1) between 1974-1978 (inclusive) were extracted from the computer tapes held by the ~lational Health Statistics Centre. The de jure population [2] of each areal unit at the time of the 1976 Census (held on 23 March 1976) was used as the denominator. This was supplied by the Department of Statistics. The following caveat must be applied to these data. Although both the numerator and denominator take as a person's domicile [3] their 'usual place of residence' there are no stipulated criteria as to what constitutes 'usual'. This may produce anomalous situations. For . example, two people will be coded as living (or dying) in the same area even if the former had resided there for 20 years and the latter only one year. A hierarchy of spatial divisions were employed, which permitted both regional and small-scale local patterns to be defined (Fig. 2): a) The 24 main urban areas. In addition to the central city or borough, these non-administrative units include neighbouring boroughs, town districts and parts of counties which are regarded. as suburban and thus belonging to that centre of population irrespective of their being under different local body administration [4J. Urban areas were used, in preference to cities, as their boundaries at the 1976 Census were, generally, unchanged from those at the 1971 Census [5J. b) Geographic counties (counties) excluding the main urban areas. These cover the county and any borough, or town district which may be geographically ""/ithin, or adjacent to, that county [6]. By the 1976 Census date the Thames and Coromandel Counties and Thames borough had been amalgamated under a single controlling authority - the Thames-Coromande1 District Council. However, in this report the Thames-Coromandel District, as it is officially titled, has been designated the Coromandel ..Thames County to avoid confusion with the Thames hospital board district. c) Hospital board districts (districts) which are amalgams of various counties. It should be noted that the Waiapu, Taumarunui, Mar"lborough, Vincent, and r~aniototo Counties and districts are synonymous. Accordingly, reference to these units implies the same mortality experience at both scales. The need to incorporate some form of stochastic test in spatial studies of morbidity or mortality has been previously emphasised [7J. It is crucial to distinguish between those areas in which disease or death results from random influences and those in which the occurrence is beyond being merely a chance event. A statistically significant variation implies that there is an underlying cause for which an explanation should be sought. 3 4 The indirect method of standardisation [8] was used to adjust for differences in the local population age structures. This permits the calculation, for each area, of a standardised mortality ratio (SMR) which expresses, as a percentage, the ratio of the observed number of deaths to those theoretically expected if the national age-specific death rates had been in operation. An SMR of 100, therefore, indicates a mortality level equal to that of the total New Zealand population; an SMR of less than 100 signifies a more favourable experience; and an SMR of over 100 represents an unfavourable experience. The actual confidence level, based on the Poisson distribution, of each local deviation of the observed from the expected number of deaths was determined [9J. As a probability value could, therefore, be placed on each area it became feasible to identify gradients of morta1i ty by compari ng the. experi ence of conti guous areas.