La aplicaci´ on de las TIC en la Salud: teor´ıa y realidad

Background

Breast cancer is the most common cancer among women in Scotland, accounting for 25% of all cancers, with a total o f 3 374 new cases o f invasive disease diagnosed in 1997. Incidence has been increasing over time since the 1970s, and has increased at an even greater rate in the 1990s, partly due to the introduction o f the Scottish National Breast Screening Programme (SNBSP). Mortality from breast cancer had also been increasing until the late 1980s, since when there has been a 28% reduction (Figure 5.1). A similar reduction has also been observed in England125,126 and the United States127. In 1999, 1 129 women died of breast cancer in Scotland.

Figure 5.1: Breast cancer in Scodand: trends in incidence (1979-1997) and mortality (1979-1999), all ages (European age-standardised rates)

As for many cancers, age is the most important known influence on incidence (Figure 5.2), with the highest risk in the elderly. Risk in women of screening age (50-64 years) has increased faster than expected from the underlying trend, whereas incidence in women aged

65-69 years appears to have levelled off in the 1990s. Risk varies markedly between countries (Figure 5.3) with slighdy higher rates in Scotland than in England and Wales.

Figure 5.2: Breast cancer in Scotland: trends in incidence (1975-1997), by age band

1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 Year of diagnosis

The SNBSP was introduced in 1988 for women aged 50-64 and the first (prevalent) round completed in 1994. The first time that women are screened (prevalent round), breast screening picks up many small and slow-growing tumours, some of which might not have presented clinically until later, if at all. The detection at screening o f a large number of cancers with relatively good prognosis, which might never present symptomatically in a woman’s life-time, is known as length bias12*. It may explain why incidence is still higher than would be expected from a projection of the underlying historical trends. Length bias would affect both incidence and survival.

In the trial setting a reduction in mortality due to screening was seen seven years after the introduction of screening129, however, compliance to attend screening is lower in the routine setting so a longer interval may be expected before a reduction in mortality is seen. Therefore, screening has probably played a relatively small part in the large (16%) mortality reduction observed since 1990 in Scodand. Around 30% of the corresponding reduction in England has been attributed to the direct effects of screening, with the remainder due to improved adjuvant treatments and earlier presentation outside the screening programme114. Other researchers believe the screening effect may be lower130.

Figure 5.3: International comparison o f breast cancer incidence, around 1988-1992 (world age-standardised rates per 100,000)

J a p a n .O a a k a S m g apo ra C h in a a a S pain. Z a ra g o ta ( 1 I M - I 0 ) N o r « ay Qarm a ny. S aarland Finland (1 S S 7 -1 M 2 ) Auatralla. Victoria E n g la n d and W alaa ( 1 I M - I 0 ) S co tland D a n m a rk S w itza rla n d . V a u d Now Zaaland: N o n -M a o ri Franca. B a a -R h ln Nadiarlanda <1 # • # -• !) U S . 8 E E R : W hita 0 2 0 4 0 6 0 8 0 1 0 0 I n c i d e n c e c i t e p e c 1 0 0 ,0 0 0

Source: Cancer Incidence in Five Continents, Volume VII"

A by-product o f the screening programme has been raised diagnostic standards and improved organisation o f services across all age groups, which would also be expected to have had an impact on mortality rates.

Even before the introduction o f screening, breast cancer survival in Scodand was improving steadily over time, due to improvements in stage at diagnosis, and to the increasing use of radiotherapy and chemotherapy22,151. For women diagnosed in 1971, the five-year relative survival rate was 53%, and for women diagnosed in 1993 this had increased to 73%. However, survival has been increasing more quickly in the age group which encompasses those invited for screening (ages 50-69; Figure 5.4).

The introduction o f the screening programme complicates interpretation of the survival trends in the age range 50-69 because o f length bias (very slow growing tumours) and lead- time bias (where the time o f diagnosis is advanced but death is not delayed). The prevalent round of screening was completed in Scotland by the end of 1994, and survival might be expected to improve for women diagnosed during this round. However, it is sustained for women diagnosed after 1994, when most women had incident (second and subsequent) screens and is more pronounced at five years after diagnosis than at one year after diagnosis.

Figure 5.4: Women diagnosed with breast cancer in Scodand during 1971-1995: trends in relative survival by age band

This is not typical of lead-time bias. The sustained improvement in survival could be due to the enhanced effectiveness o f treatment being given at an earlier stage, in other words, the desired effect o f screening, or it could be caused by length bias.

Length bias could play a role because incidence o f breast cancer is higher in more affluent women, and compliance with screening was initially higher in these women, who also have better than average underlying mortality rates. If a large number o f affluent women were diagnosed with tumours that would not have presented clinically for a long time, then we would see survival increasing with time since diagnosis. The data analysed in detail in this chapter relate to 1997, 10 years after the introduction of screening, so the effects o f lead time and length bias should be small.

Survival from breast cancer in Scotland is lower than in other countries in Europe6 and the USA (Figure 5.5). Several factors have been linked to poor breast cancer survival. These include co-morbidity132; tumour type, with invasive lobular carcinoma conferring better prognosis than invasive ductal carcinoma133; patient delay but not GP delay134; long-term oral contraceptive use135; treatment by a non-specialist surgeon27; low clinician workload26, and differences in the use o f systemic adjuvant therapy136. One study found survival was poorer during the holiday months o f the year when medical teams may be under-represented137. A study in Yorkshire found that hospitals with a special interest in breast cancer used more up-

to-date methods and made more treatment options available1“ . In East Anglia, being treated at a specialist hospital was significantly beneficial in women aged under 75 years at diagnosis51, even after accounting for tumour stage. There is strong evidence that women managed by a multidisciplinary team do better22,26,27.

Figure 5.5: Breast cancer international comparison o f five-year relative survival (with 95% confidence intervals), selected countries, women diagnosed around 1985-1989, all ages

1 Women diagnosed 1986-90, aged 15-99 2 Women aged 15-99

Sources: Bemno it al.*, Gatta u a/.'*9, Coleman it aL*

Breast cancer is more common among affluent women, but survival is also better in these w om en4,15,16140. Geographic and socio-economic differences in investigation and treatment have been reported in the UK and Europe1,,1,,U1,142. There is conflicting evidence on w hether these differences remain after adjustment for stage at diagnosis, with differences remaining for studies in south-east England15,16, Finland54 and Glasgow15 and conflicting evidence from a different Glasgow study145, and studies from The Netherlands144 and Australia145. Tumour stage is a very significant prognostic indicator for breast cancer survival15,16,144,146 and is linked to delay at diagnosis147, however, within each category o f tum our stage, delay was not found to be an important prognostic factor in an Argentinean study14*. In south-east England it was found that the low social classes were more likely to present as an emergency admission and less likely to have surgical interventions149. Tumour morphology does not appear to account for social class differences in Scotland15. Oestrogen receptor negative tumours have been linked both to poor survival and to social class150, but

in an audit o f Scottish women diagnosed in 1987, only a third of the effect of deprivation on survival could be accounted for by differences in oestrogen receptor status22-151.

Projections o f recent trends in incidence and mortality in Scotland152 suggest a further large increase in breast cancer incidence in the decade up to 2010, and a continuing decline in mortality rates (Figure 5.6). There could be as many as 4 775 cases diagnosed per year in 2010. These trends underline the public health importance of breast cancer and the continuing need to understand and further improve survival from breast cancer.

Figure 5.6: Projections of breast cancer incidence and mortality in Scotland (numbers of cases and deaths, and European age-standardised rates)

1 9 8 0 -8 4 1 9 8 5 -8 9 1 9 9 0 - 9 4 1 9 9 5 -9 9 2 0 0 0 -0 4 2 0 0 5 -0 9 2 0 1 0 - 1 4

In this chapter, the survival of 3 309 women diagnosed with breast cancer in Scotland in 1997 is investigated to identify reasons for differences in survival by deprivation category. For definitions o f the variables included in the analyses, please refer to Chapter 2.

Results and commentary

For women diagnosed in Scotland in 1997, incidence was 25% higher in women from the most affluent areas (37.8 per 100 000; herein referred to as the affluent group or affluent women) compared to women from the most deprived areas (30.3; the deprived group or deprived women). The mortality rates (for women dying in 1999) show very little variation across deprivation groups. The deprivation-specific trend in incidence is not matched by a

similar trend in mortality because of differentials in survival, with two-year survival 8% higher in the affluent (85.3%) than the deprived (77.5%) group (Figure 5.7).

Figure 5.7: Women diagnosed with breast cancer in Scotland in 1997: incidence1 and two-year relative survival2, and mortality1 in 1999, by deprivation category

1 2 3 4 5

Affluent

Carstairs deprivation quintile

Deprived

1 Age-standardised rates per 100 000 person-years at risk (European standard population)

2 Using deprivation-specific life tables; age-standardised using the world standard cancer patient population

O f the 3 309 women diagnosed with breast cancer in 1997, 1 418 (43%) were from deprivation groups 1 and 2 and 1 240 (37%) from deprivation groups 4 and 5 (Table 5.1). The median age o f diagnosis was 61 years with inter-quartile range from 51 to 74 years, with no significant difference in age at presentation between the deprivation groups. Breast cancer was the first primary malignancy for 3 104 (94%) women, with 3% having had a previous breast cancer and a further 3%, a previous primary at another site. These proportions were similar between the deprivation groups, so the fact o f a previous primary was not included in the multivariate analyses.

Deprived women mainly came from urban areas (81% compared to 41% for affluent women). Almost 80% o f the most deprived women were resident in only three o f the fifteen health boards: Greater Glasgow Health Board (GGHB; 50%), Lanarkshire (17%) and

Argyll and Clyde (12%). Within health board the mix of deprivation categories amongst women with breast cancer varied very widely (for example, GGHB: 50% deprived and 19% affluent; Lothian and Borders: 7% deprived and 28% affluent; Grampian: 3% deprived and 54% affluent).

Table 5.1: Women diagnosed with breast cancer in Scotland in 1997: demographic data by deprivation category (number and percentage of cases)

Deprivation

category Number (%) of casca

Median age (inter­ quartile

range)

Cases for which: Urban

resident1 First primary Previous breast primary Previous prim ary elsewhere Affluent 734 (22%) 61 (51-73) 697 (95%) 20 (3%) 17 (2%) 302 (41%) 2 684 (21%) 60 (51-73) 642 (94%) 19 (3%) 23 (3%) 153 (.22%) 3 651 (20%) 61 (51-73) 615 (94%) 20 (3%) 16 (2%) 161 (25%) 4 644

_(19%)

62 (51-74) 593 (92%) 22 (3%) 29 (5%) 291 (45%) Deprived 5% (18%) 63 (53-75) 557 (93%) 19 (3%) 20 (3%) 485 (81%) Total 3,309 (100% ) 61 J5U 74L 3404 100

_J3%L

10S 1,392 (42% )

1 Chi-square test for association between urban residence and deprivation: p<0.001

In document Guía de la Cooperación Española para la incorporación de las TIC en las intervenciones de Salud en la Cooperación para el Desarrollo (página 53-56)