There were substantial changes over time in the management of over 14,000 oesophageal and stomach cancer patients diagnosed over a 12-year period in the East of England. During the study period, curative surgery use decreased substantially (by over a quarter) and chemotherapy use increased dramatically (by more then three-fold). Adjusting for other variables, more deprived patients were less likely to be treated by curative surgery and by chemotherapy, however this association was much stronger for chemotherapy. Chemotherapy use was also less likely in women.
Deprivation differences in use of curative surgery, although statistically significant, were relatively limited in both absolute and proportional terms (e.g. 26% compared with 23% use, in least and most deprived patients respectively). In contrast, socioeconomic treatment patterning was much stronger for chemotherapy use (e.g. 23% compared with 17% use, in least and most deprived patients respectively). Moreover, although the apparent effect of deprivation status on frequency of chemotherapy use was linear, no such consistent effect was observed for curative surgery use. These observations mean that data limitations (described below) could at least in theory be responsible for the observed socioeconomic difference in use of curative surgery. However, given the substantial effect size of deprivation status on use of chemotherapy, as well as its apparent linear effect, this is less likely to be the case for the observed socioeconomic variation in chemotherapy use, which is more likely to be genuine.
The main strengths of our study are its population-based basis and the fact that it covers a substantial time period and very large number of patients.
The main and most important limitation of our analysis is the lack of information on stage at diagnosis for the great majority of the patients. Population-based survival estimates for oesophageal and stomach cancers have remained poor and changed very little during the study period[6–9]. This would strongly suggest a stable over time distribution of stage among incident cases, that could not account for the observed substantial reduction over time in use of surgery and the dramatic increase in use of chemotherapy. However, lack of stage information poses certain interpretation challenges in relation to the observed socioeconomic differences in use. Several non-UK studies suggest that lower socioeconomic status individuals may have more advanced diagnosis stage[28, 29]. This limitation has to be seen in the context of the population-based nature and size of the dataset, and the study period: There is very limited availability of stage information for upper gastrointestinal cancers in population-based datasets covering the same period in England, although this weakness in cancer registration systems is now being rapidly addressed. No significant association between deprivation and stage at presentation was observed among the subgroup of OAC patients for whom stage information was available, but this finding may simply reflect lack of power to detect a significant association, and is best considered as inconclusive. Nevertheless, if more deprived patients in this dataset were presenting at relatively more advanced stage, one could have expected an association between increasing deprivation and increasing use of palliative surgery. No such significant trend was observed, in fact, there was an apparent trend in the opposite direction, which however did not reach significance. Therefore, even if they existed, potential deprivation group differences in stage at presentation are unlikely to fully explain the observed socioeconomic gradients in use of curative surgery and chemotherapy. Previous research also indicates that survival inequalities cannot be fully explained by socioeconomic differences in stage[13, 14]. These interpretation challenges should be addressed by further research.
Another limitation is the lack of information on patients' co-morbidity status, which may vary between different oesophago-gastric cancers, and deprivation groups. However, if more deprived patients had a greater co-morbidity burden, one could again expect this to have mainly influenced surgical treatment use (because of the greater anaesthetic risk of patients with higher co-morbidity burden). In contrast, socioeconomic inequalities in both the use of surgery and the use of chemotherapy were observed (and as noted above, socioeconomic variation in use was greater for chemotherapy). These observations would indicate that potential socioeconomic differences in co-morbidity status are unlikely to fully explain the observed deprivation differences in treatment use.
Furthermore, we could not examine whether chemotherapy or radiotherapy were used with a palliative or curative intent. However, the observed increase in combined use of curative surgery and chemotherapy suggests that most of the increase over time in chemotherapy use could be expected to have been in an adjuvant context - although pre-operative chemotherapy will not have actually been followed up by actual surgery in all patients, because of inadequate response.
Treatment status information might have been incomplete (or inaccurate) for some patients - particularly in relation to palliative interventions. However, this would have only introduced non-differential error, and should have not therefore biased the observed findings in relation to socioeconomic or gender variation (or its lack). Such an assumption is both logical and supported by empirical evidence from other 'routine data' sources. Similarly, it is possible that changes during the study period in data quality (including in the degree of treatment status ascertainment) may at least in part be responsible for some of the observed findings. However, there has been a high degree of consistency over time in cancer registration systems used in the UK, where cancer registration has been established over a number of decades. In addition, potential improvements in capturing treatment status could have perhaps explained the observed increase in chemotherapy use but are very unlikely to be responsible for the observed decrease in use of curative surgery. Furthermore, any changes over time in treatment status ascertainment would have been non-differential between patients of different gender and socioeconomic groups,  and cannot therefore be responsible for the observed gender and socioeconomic differences in use. For these three reasons, we believe that potential secular changes in data quality are unlikely to be responsible for the observed findings.
We could not examine treatment use beyond six months from diagnosis - however, given the poor prognosis of oesophagogastric cancer, for most patients, treatments that would have been administered beyond that period are likely to have been palliative. Information about whether patients were treated in private hospitals (for all or part of their care) would have been useful. We had no information about other aspects of treatment quality (for example: chemotherapy or radiotherapy dose and regime; treatment timeliness after diagnosis; and adequacy of surgical excision). Information about other quality of care aspects would have made the analysis more informative.
The observed decrease over time in use of curative surgery is consistent with similar trends reported in two recent national studies (which however also included OSCC in analysis)[2, 32]. More specifically, an England and Wales audit including information about over 105,000 patients indicated that 'cancer surgery' use in oesophagogastric cancer decreased by nearly a third (from 28% to 20%) between 1998 and 2005, similar to our own findings. Comparing our findings with this study, although we defined tumour categories differently, we also found curative surgery rates being highest for patients with junctional and stomach adenocarcinomas, and relatively lower for OAC patients. Similarly, in Ireland, there was a nearly two-fold reduction in curative surgery use between patients diagnosed in 2000-1 compared with 1994-6. These findings may reflect improved patient selection because of better staging, either by endoscopic ultrasound, and/or CT and PET scanning[2, 29].
Previous reports indicate a near doubling in use of 'either chemotherapy or radiotherapy' between 1998 and 2005, from 18% to 34%, without further dis-aggregation of this figure into chemotherapy and radiotherapy. Our findings strongly indicate that the greatest rise in use of non-surgical treatments for (non-OSCC) gastro-oesophageal tumours relates to chemotherapy, probably reflecting increasing peri-operative use in patients judged suitable for curative surgery,[3, 4] as also directly observed in our study, with increasing trends in the combined use of chemotherapy and curative surgery.
The findings would support the hypothesis that socioeconomic differences in treatment use may be at least partly responsible for survival inequalities among men with oesophageal and stomach cancer, and, in relation to curative surgery, they are consistent with those from a population-based study in The Netherlands.
Deprivation differences in curative surgery and in chemotherapy use were present in both men and women. This provides no insights into reasons for the previously reported better survival in most deprived women with gastric cancer, although potential differences in stage at presentation between the two genders may be responsible. Most of the observed gender differences in treatment use did not persist once the effect of other variables was adjusted for in multivariable analysis, most likely reflecting the fact that women patients were on average older than men. Nevertheless, the observed lower chemotherapy use in women, which persisted even in multivariable analysis adjusting, among other variables, for age, is surprising. As there were no significant gender differences in use of both chemotherapy and curative surgery, the observed differences might principally relate to use of chemotherapy with a palliative intent, however, this hypothesis would require further research.