Poorer prognosis of older women with breast cancer has been attributed variously to treatment received,10–17
more severe disease on presentation,13 18–21
and the presence of comorbidities.10
Stage was identified as the most important factor explaining breast cancer survival discrepancies between European countries for women given a diagnosis between 1990 and 1992,19
particularly in older age groups.
This study in more than 15 000 women diagnosed as having breast cancer in the North Thames area found that age and disease severity at diagnosis were independent predictors of early death from any cause. In the women analysed here, distant metastases on diagnosis were a strong predictor of early death, increasing the odds of dying within a year of diagnosis more than eightfold (OR 8.41, 95% CI 6.49 to 10.89). This effect was independent of age and treatment. It was also independent of patient comorbidities, although this should be interpreted with some caution, as comorbidity data were available only for the 60% of participants who could be successfully linked to the HES dataset. Surgery was strongly associated with a reduced risk of early death, and older patients were less likely to receive surgery.
Great improvements in cancer services have been made during the past decade. To investigate whether the implementation of the Cancer Plan has had any observable effect on survival, this research included a categorical variable controlling for calendar period of diagnosis in the multivariate analyses. This method was similar to that used by Rachet et al8
in their assessment of the NHS Cancer Plan for England. In our study, women given a diagnosis after 2003 had reduced odds of early death compared with women given a diagnosis before the Cancer Plan was published (OR 0.71, 95% CI 0.52 to 0.98). This suggests a survival benefit resulting from changes to cancer services after 2000.
While women of white ethnicity were at greater odds of early death in univariate analyses, this association was no longer significant when the model was adjusted for the other covariates. The white women were in general older than the non-white women, and this may explain these findings. However, in the adjusted analysis, white women were more likely to be treated surgically than those belonging to non-white ethnic groups. These results should perhaps be treated with caution, given the large proportion (26%) of cases for which ethnicity was not known.
Radiotherapy and tamoxifen treatments were independently associated with reduced likelihood of early death, while chemotherapy was associated with increased odds of dying within a year of diagnosis (OR 1.49, 95% 1.19 to 1.86). This relationship with chemotherapy is likely to be a reflection of selection bias, whereby only the most severe cases are given this form of treatment. A similar bias, but in the opposite direction, may apply to surgery—that is, with very ill patients selectively not being operated upon. However, the association between surgery and death within 1 year remained apparent in a model correcting for age and comorbidity. These findings are consistent with those in a recent study by Brewster et al22
that found age, deprivation, emergency admission, tumour stage, and grade and absence of treatment were independent factors associated with death within 30 days of diagnosis.
A recent report from the National Cancer Intelligence Network based on data from 2007 confirms that a high proportion of older women in the UK do not receive surgical treatment: 61% of women aged over 80 did not have surgery.23
This group is likely to have a particularly poor prognosis. Nearly 40% of women who died early in our study were aged 80 years or over, and 66% (252/383) of them had not had surgery.
In our study, age was strongly inversely associated with the likelihood of receiving surgery. This reflects the well-described pattern in other studies of older women being less likely to receive treatment than younger women.10 24
Women over 80 years old attending breast units in Manchester in 2002, for example, were less likely to have surgery than women aged 65–79 years even after adjustment for poorer general health, including comorbidities.11
Patient comorbidity has been shown to be a potentially important confounder in studies of treatment received,15 25
but our analyses suggest that older women are less likely to receive surgery even after adjustment for comorbidities. Comorbidity data were missing for approximately 40% of participants. Patients with missing comorbidity data were less likely to receive surgery, although there was no association between these missing data and early death after adjustment for other factors.
One potential limitation of this study is missing information. Women with missing data on ethnicity, presentation and distant metastases were more likely to die within a year of their diagnosis and were less likely to receive surgical treatment. They may represent women who were seriously ill at diagnosis and who were not scheduled for surgery. An analysis of the characteristics of patients with several missing data elements suggests that these women tend to be older, have more severe disease (as determined by a proxy of tumour size), and are more likely to die early. In addition, a failure to record important details relating to their diagnosis and treatment may be an indication that such patients are receiving worse care. With respect to this study, if women with missing information have worse disease and are generally older, then the estimates of association between these variables and early death will be biased towards underestimates of the true effects.
Retrospective analyses rely on records in which some information may be inaccurate. In this study a particular effort was made to ensure that the surgical status of women was recorded correctly, as this was considered an important marker of the quality of treatment and was expected to be strongly associated with outcome. Time and resource constraints precluded this additional effort being extended to other variables to verify database entries. However, an earlier study looking at trends in the treatment of breast cancer26
concluded that the audit database was a reasonably reliable source of such data.
The effects of deprivation on disease severity and ultimately on mortality were not explored in this study. Such analyses rely on potential patient identifiers, such as postcode data, that were not available to us. Deprivation has been linked to poorer patient outcomes for UK patients with breast cancer in several studies,22 27–29
and stated aims of the Cancer Plan and the Cancer Reform Strategy30–32
are to tackle the inequalities in cancer survival between different socioeconomic groups in England.
We suspect a complex relationship between the exposures studied here, some of which may be on the same causal pathway for early death. For example, high age and comorbidity may be rational and adequate reasons for not offering surgery. While a number of patient and treatment characteristics were strongly and independently linked with early death, these associations must be interpreted with caution and with a consideration for unmeasured confounding factors. For instance, the selection of a patient's treatment will depend on a number of factors, including some not measured here, such as their own preferences or established practices within the organisation in which they are treated.33
Furthermore, their presentation to health services depends, among other factors, on access to those services and knowledge of cancer symptoms. Many of these variables may be linked to both risk factors and outcomes and they have not been assessed in this study. However, for any underlying confounder to explain the strong statistical associations seen in our data, they would need to have a very strong correlation with death within a year of diagnosis.
Five-year relative survival in our sample (based on life tables for London during the period 1996–2001) was 84.1%. This is similar to recent estimates from the Office for National Statistics,34
which reports a value of 82% for women given a diagnosis between 2000 and 2006. Thus our cohort sample is likely to be reasonably representative of the UK population of women diagnosed as having breast cancer during this period. compares the audit data with the total registrations for female breast cancer in the North Thames region at TCR. Mean age at diagnosis was similar throughout the study period. Likewise, the proportion of patients dying within 1 year of diagnosis was broadly similar, although slightly lower in the audit database (6.5% vs 7.7% overall.) The proportion of total cases represented in the audit varied between 61% in 1997 and 13% in 2004, with an overall figure of 37%. (The decrease in the number of registered cases in 2005 is an artefact due to changes in the TCR catchment area.) In general, there was a higher representation in the earlier years, which may have implications for the applicability of the results to more recent times.
Comparison of audit cohort and registered North Thames cases