Cancer Patient Survival by Socioeconomic Status in the Netherlands: a Review for Six Common Cancer Sites
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Journal ofEpidemiology and Community Health 1994;48:441-446 441 J Epidemiol Community Health: first published as 10.1136/jech.48.5.441 on 1 October 1994. Downloaded from Cancer patient survival by socioeconomic status in The Netherlands: a review for six common cancer sites Carola T M Schrijvers, Johan P Mackenbach Abstract of common cancer sites: colon, rectum, lung Study objective - To study the size and prostate, breast, and cervix. consistency of socioeconomic differences in cancer patient survival as reported in published studies. Methods Methods - A systematic review was con- The study material was selected through Med- ducted. Several criteria were developed to line and the references of papers and books, select the study material, which resulted which resulted in 40 papers on socioeconomic in 14 reports on socioeconomic differences differences in cancer survival. To enable a use- in survival for cancers of the colon, ful comparison of the results of the reviewed rectum, lung, prostate, breast, and cervix. studies to be made some exclusion criteria were These present results on patients from the developed. United States, Japan, Australia, United Studies on patients diagnosed in the 1950s Kingdom, Sweden, Finland, and Ger- or earlier were excluded. many. The results are summarised in a Hospital based studies were excluded be- relative risk of dying or survival ratio for cause cancer patients treated in specific hos- the lowest socioeconomic status group pitals may not be representative of cancer compared with the highest. patients in the general population. In particular, Results - For cancers ofthe colon, rectum, socioeconomic contrast may be larger in the breast, and cervix, patients from higher general population than in a hospital popu- socioeconomic status groups had a better lation. survival. For lung cancer and cancer of Studies covering fewer than five years of the prostate, results were unclear. follow up were excluded, because for many Conclusion - Socioeconomic differences cancers survival differences may not yet be in cancer survival are generally small apparent shortly after diagnosis. and their contribution to socioeconomic Three measures of socioeconomic status differences in cancer mortality is probably were considered to be unfit for our purpose. small too. These findings have im- Studies using race as a measure were excluded, plications for the type of health policy because it is difficult to separate the impact of http://jech.bmj.com/ measures which should be taken to reduce socioeconomic status and other race related socioeconomic differences in cancer mor- factors on survival. Studies that used hospital tality. type or insurance status as a measure were also excluded, as we consider both variables to be (J7 Epidemiol Community Health 1994;48:441-446) intermediary in the socioeconomic status-sur- vival association. Socioeconomic differences in mortality have Studies that reported on fewer than 200 on September 24, 2021 by guest. Protected copyright. been reported for a variety of causes of death cancer deaths were excluded from this review. including cancer.'2 Cancer mortality is gen- This number of events is the minimum needed erally higher in people of low socioeconomic to indicate a relative risk (RR) of dying of 1-5 status compared with people of a high socio- when two socioeconomic groups with equal economic status. This mortality disadvantage numbers are compared (with oa= 0 05 and 1B= may be the result of differences in cancer in- 0 20).3 cidence or cancer survival. Cancer sites for which fewer than three pa- Socioeconomic differences in cancer in- pers on socioeconomic status and survival were cidence and cancer survival do not call for the available were not considered in this review. same health policy measures. Differences in Finally, 14 studies remained for inclusion in cancer incidence ask for interventions in the the review. Table 1 presents the most important Department of Public area of primary prevention, whereas socio- characteristics of the selected papers, which Health, Erasmus cancer ask are University Medical economic differences in survival ordered by country of origin of the study School, PO Box 1738, for policy measures in the area of secondary population.'9 3000 DR, Rotterdam, prevention or treatment. The country oforigin ofthe study population The Netherlands We have tried to establish the size and con- be a determinant of the strength of socio- C T M Schrijvers may cancer J P Mackenbach sistency of socioeconomic differences in economic differences in cancer survival. In gen- survival, on the basis of a systematic review of eral, these differences are expected to be smaller Correspondence to: Dr C T M Schrijvers. the available published studies on the subject. in countries like Sweden, with good access to Accepted for publication This review deals with socioeconomic differ- health care facilities for the entire population. January 1994 ences in cancer patient survival for a number The measures of socioeconomic status are 442 Schrzjvers, Mackenbach J Epidemiol Community Health: first published as 10.1136/jech.48.5.441 on 1 October 1994. Downloaded from divided into two broad categories: measures on cific cancer could be treated as censored in the the individual level such as education,8 oc- survival analysis. The resulting measure is cupation,'4 16-18 or housing tenure'3 and eco- called the corrected survival rate.4 115 17-19 The logical measures in which the place of residence relative survival rate, which is the ratio of the of cancer patients is used to assign a socio- observed and expected survival rate,16 17 is usu- economic score. These measures are either ally calculated when reliable information on based on census tract,4 block group,5 post- the exact cause of death is not available. The code,671' 15 electoral ward,'2 or community of expected survival rate is based on life tables of residence. '9 the general population. Table 1 shows that most studies cover the A few studies did not report on the exclusion 1 970s and early 80s with the exception of three of deaths from other causes.58 1214 In two other which cover an incidence period starting in the studies the distributions of deaths related and 60.4 8 16 not related to cancer were similar in the differ- From table 1 it can be seen that different ent socioeconomic categories and the authors measures of survival were used. If the survival did not therefore correct for deaths from other of cancer patients is studied, deaths due to causes. Finally, the standardised case fatality causes other than the cancer(s) of interest must ratio was employed in one study'3 - the case be excluded. In a number of studies the exact fatality rates of the entire study population for cause of death was known, and therefore the cancer in question were used as a standard. patients dying from other causes than the spe- For most studies an RR of dying for the Table 1 Study population, measure of socioeconomic status (SES) and measure of survival for 14 published reports on socioeconomic differences in cancer survival Ref Population Cancer site No of SES measure Year of Measure of no (sex) patients diagnosis survival 4 Hawaii, USA Colon 1446 Ecological: weighted score based 1960-74 Corrected Rectum 881 on: average years of education and survival rate average income per census tract; 3 categories 5 Northwestem Breast 1506 Ecological: social class, several 1973-83 Survival rate* Washington State, indicators (eg % working class) USA per block group of residence; 2 categories 6 USA Prostate 2513 Ecological: education, % of high 1977-81 Survival ratet school graduates, persons > 25 years, per postcode of residence; 4 categories 7 USA Rectum 1528 Ecological: education, % of high 1977-82 Survival ratet Colon 3617 school graduates, persons .25 years, per postcode of residence; 3 categories 8, 9 Boston, USA Breast 563 Individual: 1965-66 Survival 10 Tokyo, Japan Breast 814 education, in years of 1965-67 rate* schooling; 2 categories 11 South Lung 2934 Ecological: 1977-82 Corrected Australia Colon 2227 income, median male survival Breast 2676 income per postcode of rate residence; 3 categories 12 Sheffield, Cervix 548 Ecological: 1971-84 Survival UK occupation, % of rate* http://jech.bmj.com/ semiskilled/unskilled workers per electoral ward; 5 categories 13 England & Breast Total Individual: 1971-81 Standardised Wales Lung 17 844 housing tenure; case fatality Colon 2 categories ratio Rectum Prostate 14 South Cervix 1728 Individual: 1977-81 Survival Thames RHA social class based on rate* UK occupation; 5 categories on September 24, 2021 by guest. Protected copyright. 15 West of Scotland, Cervix 1588 Ecological: unweighed average of 1980-87 Corrected UK 4 census variables (eg semi- and survival rate unskilled manual occupation) per postcode of residence; 7 categories 16 Sweden Colon: men 3828 Individual: 1961-79 Relative women 1946 occupation; 2 categories survival Rectum: men 2659 rate women 1048 Prostate 4752 Lung: men 6587 women 953 Breast 11 531 Cervix 4087 17 Finland Breast 10 181 Individual: social class based on 1971-80 Relative occupation; 4 categories survival rate, Corrected survival rate 18 Finland Colon 2969 Individual: 1979-82 Corrected social class based on survival rate occupation; 4 categories 19 Saarland, Colon 1465 Ecological: score based on 1974-83 Corrected Germany Rectum 1162 occupation: % of blue collar survival rate workers aged 15-65y per community of residence; education: % with no more than 9 years schooling per community of residence; 3 categories * Whether a correction for other causes of death than the cancer was made is unknown. t No correction for other causes of death was made because the distributions of deaths related and not related to cancer were similar in the various socioeconomic status categories. Socioeconomic status and cancer survival 443 J Epidemiol Community Health: first published as 10.1136/jech.48.5.441 on 1 October 1994.