2011/04 LEUKAEMIA IN WALES Welsh Cancer Intelligence and Surveillance Unit

Transcription

1 2011/04 LEUKAEMIA IN WALES Welsh Cancer Intelligence and Surveillance Unit

2 Table of Contents 1 Definitions and Statistical Methods Results Leukaemia Acute Lymphoblastic Leukaemia Chronic Lymphocytic Leukaemia Acute Myeloid Leukaemia Chronic Myeloid Leukaemia Contact Details.. 32 Page 1

3 Definitions and Statistical Methods For incidence and mortality data the period of diagnosis has been examined. Tables are presented showing the number of cases by sex, 5 year age band and year of diagnosis, along with crude and age standardised rates. Figures are also presented by sex at Local Authority (LA) level with Wales Age Standardised Rates and European Age Standardised Rates. Mortality data for Wales is sourced from the ONS. For survival analysis the period of diagnosis considered is , split into two periods (Period 1) and (Period 2) to allow comparison. All cases have been followed up until 31st December 2008, thus allowing a minimum follow up period of 5 years after diagnosis for all patients included in the analysis. For each cancer site 1, 3 and 5 year observed and relative survival estimates are presented for both diagnosis periods and overall ten year period. Although relative survival estimates take into account age and sex-specific differences in background mortality, cancer survival is also dependent on age at diagnosis and is in general likely to be lower in older patients. Therefore if the age distribution of the general population at risk and cancer patients varies between different populations, comparing relative survival across these populations can be misleading. Age standardised relative survival is often presented to overcome this. In these analyses however, numbers were frequently too small to calculate reliable age-sex specific rates. Life tables for Wales were obtained from the London School of Hygiene and Tropical Medicine1 1. These tables are by sex and single year of age up to 100 and based on single year from 1981 to Each of the tables is based on the latest revised mid-year population estimates and deaths data for a specific year. Relative survival was computed using a STATA algorithm 2 based on the maximum likelihood method of Esteve et al 3. As zero survival times are not accepted by STATA, a follow up duration of 1 day is imputed where necessary strel command for estimation of relative survival written by Slogett A, Hills M, de Stavola B, Mander A. (1999). 3 Estève J, Benhamou E, Croasdale M, Raymond L. Relative survival and the estimation of net survival: elements for further discussion. Stat Med 1990; 9: Page 2

4 The following time intervals were generally used: 6 months for the first 3 years, then intervals of 1 year up to 5 years. However, occasionally regrouping of time intervals was necessary for analysis to enable at least 10 deaths in a calculation. Cumulative Rate This can be interpreted as the chance of developing a disease during a particular life span. Thus a cumulative rate (0-64) for acute myeloid leukaemia in men of 0.2% means that a man in Wales has an approximate 1 in 500 chance of developing acute myeloid leukaemia before he is 65. Calculation of Incidence Rates and Age Standardisation Crude Rate This is the total number of cases registered per year as a proportion of the total population. It is usually quoted per 100,000 population. For example, the crude incidence rate of acute lymphoblastic leukaemia for men in Wales in 2004 was 1.67 per 100,000 population: that is calculated from 24 cases out of a population of approximately 1,434,000. Rates for older age groups are in general, much higher than those for younger people, so the crude rate for an area is very much influenced by the age structure of the population of that area. This means that comparisons of the crude rates between populations with different age structures can be misleading. For this reason, methods have been developed to age-standardise cancer incidence rates. Direct Standardisation There are two standard hypothetical populations in general use the "European Standard Population" and the "World Standard Population", as shown below: Page 3

5 Standard Populations Age Group European World Under and over , ,000 The European Age Standardised Rate (EASR) for Wales per 100,000 population is calculated by applying age specific rates for Wales to the relevant standard European population shown above. These are then summed across all age groups to obtain the overall EASR. The age structure of the Welsh population differs from that of the European standard population, and as such the standardised rate for Wales, for any particular type of cancer will differ from the crude rate. In general, because the Welsh population is slightly older than the European standard, the effect will be to lower the crude rate. For example, for chronic lymphocytic leukaemia in 2002, the crude rate for women in Wales is 4.84 per 100,000 population, whereas the EASR is 2.92 per 100,000 population. The World standard population is even younger than the European standard, so that the World Age Standardised Rate for female chronic lymphocytic leukaemia in Wales in 2002 is lower at 1.87 per 100,000 population. Page 4

6 Percentage Change in E.A.S.R The percentage change in the European age-standardised rates (E.A.S.R.) for a cancer site is estimated by fitting a linear regression line to the annual age standardised rates for the period in question. The statistical significance of the fitted regression lines are indicated by the 'p' values. No geographical variation within Wales is presented here due to the very small numbers at Wales level. Prevalence Prevalence is defined as the number of people still alive at 31st December 2008 that were diagnosed with cancer previously. The column shown with Number is the number of people still alive at 31st December 2008 and diagnosed up to 1 year ago, between 1 and 5 years ago, between 5 and 10 years ago and between 10 and 20 years ago. The rate per 100,000 population represents the prevalence rate using population figures from The percentage of population in 2008 that were still alive and diagnosed earlier is also given along with the percentage of prevalence in each of the time intervals. Survival Analysis Life Tables A life table provides a summary description of mortality, survivorship and life expectancy for a specified population. In demography a complete life table is a mortality schedule showing detail for each single year of age and continuing until the last member of the synthetic cohort dies. An abridged table usually shows detail for grouped ages, usually 5 year groups, and typically ends with an open ended age group such as 85+. Complete life tables were used for the analysis presented in this report. Observed and Relative Survival Survival analysis is concerned with the analysis of times to the occurrence of an event. In cancer studies this is frequently the time period between diagnosis and death for each patient. Cancer registries in the UK hold population based databases and follow up the patients held on this from diagnosis until death. Observational studies therefore, can provide the actual survival rates being achieved in the entire population and are a very important public health tool. Page 5

7 There are several approaches to estimating cancer survival in population studies. We consider observed (crude) survival and relative survival. Estimates of median survival time are also estimated. Observed (crude) survival is simply the probability of survival at a given time since diagnosis, irrespective of cause of death. It is usually expressed as the percentage alive at the given time point, e.g. 1 year, 5 years etc. since diagnosis. Problems with this method arise if comparisons are to be made between populations with different age distributions. Observed survival is likely to be lower in an older population as they are more likely to die not just of the cancer, but also of other causes. Relative survival is the most widely used method in population studies. It is the ratio of the survival observed in the group of cancer patients to the survival that would be expected if they were subject to the same overall mortality rates by age, sex and calendar period as the general population. The expected probabilities are obtained from life tables for Wales that provide the life expectancy of persons for a given year by age and sex. The problems arising with crude survival are therefore overcome. It enables one to measure variations in cancer survival (or its complement, mortality) independently of variations in expected (background) mortality associated with age, geographic region, deprivation and calendar time. Although relative survival estimates take into account age and sex-specific differences in background mortality, cancer survival is also dependent on age at diagnosis and is in general likely to be lower in older patients. Therefore if the age distribution of the general population at risk and cancer patients varies between different populations, comparing relative survival across these populations can be misleading. Age standardised relative survival needs to be presented to overcome this. To do this, age and sex-specific survival rates are multiplied by the corresponding sex and group weight for a standard, reference population. These are summed to obtain a standardised rate. Median observed survival time is defined as the length of time after diagnosis until half the patients have died, regardless of their cause of death. Thus by definition, it is usually highest in cancers that have a good prognosis and those that are diagnosed in younger people. Page 6

8 C91-C95: Leukaemia Summary Male Female Av registrations per annum ( ) Mean age at diagnosis (in years) Cumulative Rate (0-64 years) 0.5% 0.4% Cumulative Rate (0-74 years) 1.1% 0.6% Percentage Annual Change in EASR (incidence) -0.1% -0.2% Percentage Annual Change in EASR (mortality) 0.0% -1.5% Percentage Death Certificate Only 3.3% 5.1% Av deaths per annum ( ) Mortality:Incidence Ratio ( ) 48.1% 50.7% * Significant at 5% level, ** Significant at 1% level There are around 265 male leukaemia cases and 192 female leukaemia cases diagnosed each year with the mean age at diagnosis at 64.9 years and 66.5 years respectively. Both sexes show very similar incidence trends with very small increases and decreases from year to year. The EASR per 100,000 population is very similar throughout the periods for both sexes. The cumulative rate for males is nearly twice that of females for ages 0-74 years. A large number of registrations for leukaemia were registered via the death certificate compared with other cancer sites. Around half of those diagnosed die each year in Wales. For mortality, the number of deaths has slightly increased for males but the EASR has stayed stable throughout. Females show slight increases and decreases in numbers over the period with a slight decrease in the EASR. 0.08% of the population in Wales as of the 31 st December 2008 was living with leukaemia who had been diagnosed in the past 20 years. Survival trends for males and females have both increased by four percentage points for one year relative survival at 63% and 59% respectively in Five year relative survival rates were 43% for both sexes in Page 7

9 Incidence Males Under All ages Crude Rate EASR WASR Females Under All ages Crude Rate EASR WASR Page 8

10 Persons Under All ages Crude Rate EASR WASR Mortality Males Under All ages Crude Rate EASR WASR Page 9

11 Females Under All ages Crude Rate EASR WASR Persons Under All ages Crude Rate EASR WASR Page 10

12 Prevalence Sex Period Number Rate per 100,000 % prev in pop % in each time interval Up to 1 year >1 to 5 years Males >5 to 10 years >10 to 20 years Unique Patients Up to 1 year >1 to 5 years Females >5 to 10 years >10 to 20 years Unique Patients Up to 1 year >1 to 5 years Persons >5 to 10 years >10 to 20 years Unique Patients Survival in Wales, followed up to 31 st December 2008 Period Sex 1 Year Survival 5 Year Survival Obs Rel Obs Rel Males Males Males Females Females Females Persons Persons Persons Page 11

13 C910: Acute Lymphoblastic Leukaemia Summary Male Female Av registrations per annum ( ) Mean age at diagnosis (in years) Cumulative Rate (0-64 years) 0.1% 0.1% Cumulative Rate (0-74 years) 0.1% 0.1% Percentage Annual Change in EASR (incidence) -0.2% -0.4% Percentage Annual Change in EASR (mortality) -3.5% -10.7%* Percentage Death Certificate Only 1.5% 0.9% Av deaths per annum ( ) 9 5 Mortality:Incidence Ratio ( ) 39.9% 35.9% * Significant at 5% level, ** Significant at 1% level Incidence of acute lymphoblastic leukaemia is rare in Wales with around 20 male and 15 female cases diagnosed each year in Wales. It is predominantly diagnosed in the younger ages with the mean age at diagnosis around 26 years of age. Incidence rates for males in Wales have generally remained stable over the fifteen year period and are similar in 2008 as they were in For females, the trend has been a very small decrease over the period. It is very difficult to summarise the mortality rates due to the very small numbers an increase of just one or two cases from one year to the next can dramatically affect the resulting rates. In the second diagnosis period, one year relative survival rates are much higher in males than females and with five year relative survival also higher in males at 35% compared with females at 29%. Page 12

14 Incidence Males Under All ages Crude Rate EASR WASR Females Under All ages Crude Rate EASR WASR Page 13

15 Persons Under All ages Crude Rate EASR WASR Mortality Males Under All ages Crude Rate EASR WASR Page 14

16 Females Under All ages Crude Rate EASR WASR Persons Under All ages Crude Rate EASR WASR Page 15

17 Prevalence Sex Period Number Rate per 100,000 % in each time interval Up to 1 year >1 to 5 years Males >5 to 10 years >10 to 20 years Unique Patients Up to 1 year >1 to 5 years Females >5 to 10 years >10 to 20 years Unique Patients Up to 1 year >1 to 5 years Persons >5 to 10 years >10 to 20 years Unique Patients Survival in Wales, followed up to 31 st December 2008 Period Sex 1 Year Survival 5 Year Survival Obs Rel Obs Rel Males Males Males Females Females Females Persons Persons Persons Page 16

18 C911: Chronic Lymphocytic Leukaemia Summary Male Female Av registrations per annum ( ) Mean age at diagnosis (in years) Cumulative Rate (0-64 years) 0.2% 0.1% Cumulative Rate (0-74 years) 0.4% 0.2% Percentage Annual Change in EASR (incidence) -0.7% 0.2% Percentage Annual Change in EASR (mortality) 1.3% -0.9% Percentage Death Certificate Only 2.6% 4.5% Av deaths per annum ( ) Mortality:Incidence Ratio ( ) 31.6% 31.0% * Significant at 5% level, ** Significant at 1% level Chronic lymphocytic leukaemia is a leukaemia diagnosed later in life compared with acute lymphoblastic leukaemia with a mean age at diagnosis of 71 years for males and 75 years for females. Approximately 100 cases are diagnosed each year for males and 70 for females. The trend for males is a slightly decreasing one over the period while females has marginally increased over the period. Just over 30 males die of this type of leukaemia each year in Wales while the number is just over 20 for females. There has been a large increase in one year relative survival for males from 78% in to 88% in Females, however have only marginally increased from 81% to 83%. Five year relative survival shows a similar pattern with males increasing from 58% to 68% while females have only increased from 67% to 69%. However, males were much lower than females in Page 17

19 Incidence Males Under All ages Crude Rate EASR WASR Females Under All ages Crude Rate EASR WASR Page 18

20 Persons Under All ages Crude Rate EASR WASR Mortality Males Under All ages Crude Rate EASR WASR Page 19

21 Females Under All ages Crude Rate EASR WASR Persons Under All ages Crude Rate EASR WASR Page 20

22 Prevalence Sex Period Number Rate per 100,000 % in each time interval Up to 1 year >1 to 5 years Males >5 to 10 years >10 to 20 years Unique Patients Up to 1 year >1 to 5 years Females >5 to 10 years >10 to 20 years Unique Patients Up to 1 year >1 to 5 years Persons >5 to 10 years >10 to 20 years Unique Patients Survival in Wales, followed up to 31 st December 2008 Period Sex 1 Year Survival 5 Year Survival Obs Rel Obs Rel Males Males Males Females Females Females Persons Persons Persons Page 21

23 C920: Acute Myeloid Leukaemia Summary Male Female Av registrations per annum ( ) Mean age at diagnosis (in years) Cumulative Rate (0-64 years) 0.2% 0.1% Cumulative Rate (0-74 years) 0.3% 0.2% Percentage Annual Change in EASR (incidence) 2.2%** -0.5% Percentage Annual Change in EASR (mortality) 2.1%* -0.2% Percentage Death Certificate Only 3.5% 5.8% Av deaths per annum ( ) Mortality:Incidence Ratio ( ) 76.9% 77.7% * Significant at 5% level, ** Significant at 1% level Incidence of acute myeloid leukaemia in Wales averages around 75 cases per year for males and 61 for females. Incidence has increased over the period for males and this rise is significant. The trend for females is a slight decrease over the period. Mortality trends are very similar to the incidence rates. Survival of this type of leukaemia is poor. One year relative survival rates have increased from and for both sexes; 29% to 34% for males and 24% to 30% for females. However, five year relative survival rates have remained the same for both periods at 10% for males and 14% for females. Page 22

24 Males Under All ages Crude Rate EASR WASR Females Under All ages Crude Rate EASR WASR Page 23

25 Persons Under All ages Crude Rate EASR WASR Mortality Males Under All ages Crude Rate EASR WASR Page 24

26 Females Under All ages Crude Rate EASR WASR Persons Under All ages Crude Rate EASR WASR Page 25

27 Prevalence Sex Period Number Rate per 100,000 % in each time interval Up to 1 year >1 to 5 years Males >5 to 10 years >10 to 20 years Unique Patients Up to 1 year >1 to 5 years Females >5 to 10 years >10 to 20 years Unique Patients Up to 1 year >1 to 5 years Persons >5 to 10 years >10 to 20 years Unique Patients Survival in Wales, followed up to 31 st December 2008 Period Sex 1 Year Survival 5 Year Survival Obs Rel Obs Rel Males Males Males Females Females Females Persons Persons Persons Page 26

28 C921: Chronic Myeloid Leukaemia Summary Male Female Av registrations per annum ( ) Mean age at diagnosis (in years) Cumulative Rate (0-64 years) 0.1% 0.0% Cumulative Rate (0-74 years) 0.1% 0.1% Percentage Annual Change in EASR (incidence) -2.7% 0.3% Percentage Annual Change in EASR (mortality) -14.6%** -6.0%** Percentage Death Certificate Only 3.7% 4.7% Av deaths per annum ( ) Mortality:Incidence Ratio ( ) 46.3% 51.9% * Significant at 5% level, ** Significant at 1% level Incidence of chronic myeloid leukaemia is rare in Wales with approximately 23 new males diagnoses each year and 20 females each year. A decreasing trend for males is apparent with females showing slight increases and decreases throughout the period. Around half of those people die of this type of leukaemia with approximately 11 deaths for males and 10 deaths for females each year. There is a significant decrease in mortality over the fifteen year period, however, like acute lymphoblastic leukaemia the number of deaths per year are very small. One year relative survival rates have not changed much from to at around 68% for males and 69% for females. There has been a 10 percentage point increase in survival for five year relative survival for both sexes with relative survival at 48% for males and 42% for females in Page 27

29 Males Under All ages Crude Rate EASR WASR Females Under All ages Crude Rate EASR WASR Page 28

30 Persons Under All ages Crude Rate EASR WASR Mortality Males Under All ages Crude Rate EASR WASR Page 29

31 Females Under All ages Crude Rate EASR WASR Persons Under All ages Crude Rate EASR WASR Page 30