Introduction

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Associations between social deprivation and cancer survival have been reported for many cancers.^1-4 For most cancers, stage at presentation remains the single most important source of variation in outcome, and early diagnosis offers the greatest reduction in mortality. Evidence has been reported of variation by deprivation status in the use of primary care services and in hospital admission patterns. The fourth national study of morbidity statistics from general practice found that patients from deprived areas were more likely to consult a general practitioner with a complaint subsequently diagnosed as cancer.⁵ Patients from deprived areas, however, have also been shown to have lower uptake rates for preventive services in general practice, such as screening for cancers of the breast and cervix. ^{6 7}

A major reorganisation of cancer services is under way in England and Wales in response to the policy framework for commissioning cancer services by the Expert Advisory Group on Cancer (EAGC), commonly known as the Calman-Hine report.⁸ The report was commissioned because of concerns about apparent variations in the outcomes of treatment. Acute hospital sector care is the main focus of change: cancer units "of a size to support clinical teams with sufficient skill and facilities to manage the commoner cancers" will be set up in many district general hospitals; cancer centres, based largely in specialist units, will provide skill in the management of all cancers with specialist diagnostic and therapeutic care. For breast cancer, providers will have to admit 100 or more patients a year to apply for unit status. But primary care will also play a part in the new system. Cancer units and cancer centres are to undertake detailed discussions with general practitioners to clarify patterns of referral and diagnosis on the basis of nationally agreed and rigorously evaluated standards.

This paper considers the relation between social deprivation and hospital admissions for the three most common cancers (colorectal, female breast, and lung) in south east England. It was commissioned by South Thames Research and Development Directorate to assist with the implementation of the Calman-Hine report in the Thames regions. To that end we focus on mode of presentation (emergency or elective), type of admission (ordinary inpatient or day case), the caseload of hospitals making the admission, and, as a crude measure of treatment variation, the proportions of patients to receive surgery.

	Methods

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Census data
Data from the 1991 census were extracted from the University of Manchester's computer centre on all enumeration districts in the Thames regions. The data comprised the number of people living in each census enumeration district broken down by age (in bands of 5 years) and sex and the variables required to calculate a Townsend material deprivation score.⁹ The enumeration districts were then divided into tenths, on the basis of their Townsend score, with the first tenth containing those enumeration districts with the lowest 10% of Townsend scores (that is, the most affluent enumeration districts) and the last tenth containing those enumeration districts with the highest 10% of Townsend scores (that is, the most deprived enumeration districts).

NHS data
Hospital activity in England and Wales is measured in "finished consultant episodes" and not admissions or patients. These episodes are defined as those "where a patient has completed a period of care under a consultant and is either transferred to another consultant or is discharged."¹⁰ We requested data from the Office for National Statistics and the Department of Health on all ordinary inpatient finished consultant episodes completed by residents of the Thames regions for the financial years 1992-3 to 1994-5 with a primary diagnosis of any of three cancers of interest (ICD-9 (international classification of diseases, ninth revision) codes 153, 154, 162, 174) for patients aged <100 years at diagnosis. The information extracted is shown in the box.

Data on finished consultant episodes retrieved from the Office for National Statistics   Mode of admission (elective, emergency, other)   Type of admission (day case, ordinary)   Age at start of finished consultant episode   Date of admission   Date of discharge   Date of start of episode   District health authority of residence   District health authority of treatment   Diagnosisfirst to fifth secondary   Diagnosisprimary   Diagnosissecondary   Date of birth   Home postcode   Length of finished consultant episode (days)   NHS provider code   NHS purchaser code   NHS or private   Procedurefirst to fourth   Sex

	Results

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Census data
Townsend data were retrieved on 29 999/31 470 (95%) census enumeration districts with a median population of 462. Data on the requisite variables were not available for 1143 "special enumeration districts" (communal establishments with populations of at least 100 people) or for 101 "shipping enumeration districts" (enumeration districts covering people resident on ships at the time of the 1991 census). A further 227 enumeration districts were subject to "data suppression" because there were fewer than 50 residents or 16 households.

NHS data
We retrieved data on 153 582 finished consultant episodes for inpatient admissions completed between 1 April 1992 and 31 March 1995 by patients with a primary diagnosis of any of the designated cancers from the Department of Health and the Office for National Statistics. Of these, 150 749 (98%) had home postcodes that could be matched to Townsend tenths.

	Discussion

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Our results suggest that social deprivation strongly influences mode of admission, type of admission, and odds of surgical treatment for breast, lung, and colorectal cancer. Patients from deprived areas were more likely to be admitted as emergencies and ordinary inpatient (that is, overnight) admissions and less likely to be admitted as day cases. Patients from deprived areas were also less likely to receive therapeutic or palliative surgery (irrespective of the number of admissions experienced). Patients with colorectal cancer from deprived areas were less likely to be admitted to hospitals that admit 100 or more new cases a year whereas women with breast cancer from deprived areas were more likely to be seen at such a hospital. No deprivation gradient was found for the relation between admissions for lung cancer and hospital caseload.

The gradients reported in this study may be true or artefacts. Artefacts could arise from incomplete or inaccurate data from the hospital episode statistics or from differences by deprivation status in the use of the private sector. We will consider these in turn.

Possible artefacts of gradients
Studies of the completeness and accuracy of hospital episode statistics show mixed results (D Hewitt, Department of Health, personal communication; J Dixon, personal communication). Although we were unable to estimate the validity of the data with which we were supplied, there is no obvious reason why validity should be correlated with deprivation status of patients.

True sources of gradients

Deprivation gradients in elective admissions
The most intuitively attractive explanation for the observed deprivation gradients in elective admissions and day case admissions is stage at presentation.¹⁹ Many studies have reported an association between deprivation and screening services for breast cancer. A recent study in the United States found that low income was a strong predictor of underuse of mammography.²⁰ Similar findings have been reported in the United Kingdom for screening for both cervical and breast cancer. In two recent studies Majeed et al found significant negative correlations between rates of breast and cervical cancer screening in a South Thames health commission and variables used in the calculation of the Townsend index, such as overcrowding, not owning a car, and unemployment. ^{6 7} They also found that some general practice factors were associated with higher uptake rates. All of these findings are consistent with deprivation gradients in stage at presentation. For colorectal cancer and lung cancer no comparable programme of mass screening exists, so precise data for primary care are not available.

The cancers under review vary greatly in 5 year survival. Cancers with poor survival have less time for differences in stage at presentation to arise. For this reason we might expect the difference in the proportions of elective admissions between the most affluent and the most deprived tenth to be greatest among admissions for breast cancer (with 65% relative survival rate at 5 years) and smallest among admissions for lung cancer (with 7%), with admissions for colorectal cancer coming somewhere in between (35%). But in fact, for all three tumour sites, patients from affluent areas were consistently advantaged with regard to elective admission (and to a roughly similar extent). This strongly suggests that factors unrelated to the tumour are also at work.

It may be that patients from deprived areas do not report symptoms at the primary care stage, contributing to the relatively higher proportions of emergency admissions given to patients from deprived areas. Alternatively, general practitioners may be more alert to symptoms among affluent patients, regardless of risk. Chaturvedi and Ben-Shlomo, in a study of the relation between consultation rates in general practice and surgical provision for six common conditions in the London area, found that people from the most deprived areas were generally least likely to receive surgery despite being most likely to consult a general practitioner with symptoms.²¹ In a study based in New York, Billings et al reported a lack of timely and effective outpatient care for patients from low income areas, leading to higher rates of emergency admissions to hospital.²² The only study to consider deprivation gradients in consultation rates for cancer in general practice not confined to screening was the fourth national study (1991-2) of morbidity statistics from general practice; it found that patients of low socioeconomic status were more likely to consult a general practitioner about cancer.⁵ A prospective study is required to examine clinician bias and deprivation gradients in cancer admission rates in the United Kingdom.

The sociodemographic differences in elective inpatient and day case admissions might be explained by increased comorbidity or admissions for reasons other than the tumour. ^{23 24} To avoid confounding from admissions other than cancer we included only admissions for which at least one finished consultant episode had a primary diagnosis of one of the three cancers; finished consultant episodes with other primary diagnoses were excluded. For any given admission, the mode of admission recorded for the first finished consultant episode determines the admission status for all subsequent finished consultant episodes, even though the same primary diagnosis may vary.

Admission to hospitals admitting 100 or more new patients a year
The relation between deprivation and admission to a hospital admitting 100 or more new cases a year varied greatly according to the cancer under review (see table 3). Patients with colorectal cancer who resided in deprived areas were far less likely to be seen at such a hospital than their counterparts from affluent areas, whereas patients with lung cancer who resided in deprived areas were more likely to be seen at one. No association between these two variables was found for breast cancer.

This variation might be due in part to the degree to which treatment has been specialised and centralised in specific units. Colorectal cancer services have not been subject to the same degree of specialisation of treatment and organisation as breast cancer services or lung cancer services. Local referral mechanisms are also likely to play a part; it might be that the referral procedures at the disposal of general practitioners serving poorer populations result in more patients from those areas being seen at low volume hospitals. It is also possible that general practice referral procedures are influenced by patients' perceived deprivation status. Further work is required to investigate these hypotheses. It is unlikely that in the period under study differences in the proportion of patients in the care of general practitioner fundholders could have significantly affected this gradient.

Deprivation gradients in surgery proportions
The hospital episode statistics dataset does not include data on tumour stage. With these data it is impossible to say whether the differences in the proportion of patients who received surgery reflect real inequalities of treatment or whether they simply reflect stage at presentation. At a population level, various interventions have been shown to increase survival and reduce morbidity for each of the three cancers. But this does not necessarily hold true for the individual patient. For example, overall survival from lung cancer at 5 years has been increased by curative surgical resection (given to early stage cases); but only 10-15% of lung cancer patients would benefit from it. In the absence of detailed data on the tumour (stage, subsite, size, morphology) it is difficult to identify with certainty cases that have suffered from "inequalities of treatment." Treatment differences might simply reflect differences in patterns of presentation by deprivation status. The much lower proportion of patients with breast cancer from the most deprived tenth ever to receive surgery is worrying indeed; further study is warranted to establish its causes.

The gradients reported here are consistent with the hypothesis that patients from deprived areas present at a later stage in the course of their disease; an analysis of cancer registry data is required to assess whether this is so. Unfortunately, currently available cancer registry data are unequal to this task, partly because staging data are often incomplete but also because of the exceptionally high proportion of cases registered only from death certificates in the Thames registry (up to 25%). Such cases do not have data on stage and histology.

Conclusion
The strong deprivation gradients in mode and type of hospital admission for the three cancers under review suggest that, for whatever reason, primary care is failing patients from deprived areas. More effective diagnostic and referral procedures in primary care settings and earlier access to acute hospitals would result in significant reductions in mortality from these diseases. NHS purchasers, including primary care groups, should use the commissioning process to ensure equity in access to cancer care at both primary and secondary level. A national information strategy is required to ensure the continued availability of population based data on NHS patients and to mandate standardised datasets from the private sector. These findings have implications for resource allocation and healthcare planning. Rationalisation of acute services and plans for bed closures must take into account the increased healthcare needs and inequities in access to treatment and care of residents living in areas with high levels of deprivation. Regional outposts, health authorities, and primary care groups should re-examine their purchasing intentions, service reviews, and their monitoring arrangements in the light of these findings. Prospective studies are required to establish the mechanisms by which the deprivation gradients reported here take root.