Completeness of case ascertainment and survival time error in English cancer registries: impact on 1-year survival estimates.

BACKGROUND: It has been suggested that cancer registries in England are too dependent on processing of information from death certificates, and consequently that cancer survival statistics reported for England are systematically biased and too low. METHODS: We have linked routine cancer registration records for colorectal, lung, and breast cancer patients with information from the Hospital Episode Statistics (HES) database for the period 2001-2007. Based on record linkage with the HES database, records missing in the cancer register were identified, and dates of diagnosis were revised. The effects of those revisions on the estimated survival time and proportion of patients surviving for 1 year or more were studied. Cases that were absent in the cancer register and present in the HES data with a relevant diagnosis code and a relevant surgery code were used to estimate (a) the completeness of the cancer register. Differences in survival times calculated from the two data sources were used to estimate (b) the possible extent of error in the recorded survival time in the cancer register. Finally, we combined (a) and (b) to estimate (c) the resulting differences in 1-year cumulative survival estimates. RESULTS: Completeness of case ascertainment in English cancer registries is high, around 98-99%. Using HES data added 1.9%, 0.4% and 2.0% to the number of colorectal, lung, and breast cancer registrations, respectively. Around 5-6% of rapidly fatal cancer registrations had survival time extended by more than a month, and almost 3% of rapidly fatal breast cancer records were extended by more than a year. The resulting impact on estimates of 1-year survival was small, amounting to 1.0, 0.8, and 0.4 percentage points for colorectal, lung, and breast cancer, respectively. INTERPRETATION: English cancer registration data cannot be dismissed as unfit for the purpose of cancer survival analysis. However, investigators should retain a critical attitude to data quality and sources of error in international cancer survival studies.

Resection rate, hospital procedure volume and survival in pancreatic cancer patients in England: Population-based study, 2005-2009.

OBJECTIVE: We assessed the association between population resection rates, hospital procedure volume and death rates in pancreatic cancer patients in England. DESIGN: Patients diagnosed with pancreatic cancer were identified from a linked cancer registration and Hospital Episode Statistics dataset. Cox regression analyses were used to assess all-cause mortality according to resection quintile and hospital volume, adjusting for sex, age, deprivation and comorbidity. RESULTS: There were 31,973 pancreatic cancer patients studied, 2580 had surgery. Increasing resection rates were associated with lower mortality among all patients (χ(2)(1df) = 176.18, ptrend < 0.001), with an unadjusted hazard ratio (HR) of 0.78 95%CI [0.75 to 0.81] in the highest versus the lowest resection quintile. Adjustment changed the estimate slightly (HR 0.82, 95%CI [0.79 to 0.85], (χ(2)(1df) = 99.44, ptrend < 0.001)). Among patients that underwent surgery, higher procedure volume was associated with lower mortality (HR = 0.88 95%CI [0.75-1.03] in hospitals carrying out 30+ versus <15 operations a year, shared frailty model, χ(2)(1df) = 1.82, ptrend = 0.177). CONCLUSION: Higher population resection rates were associated with lower mortality. The association with hospital procedure volume was less clear possibly due to small number of patients who underwent surgery. Nevertheless these results suggest survival is higher in hospitals that carry out a greater number of operations a year, particularly those doing 30+ operations, supporting the benefit of centralising perioperative expertise in specialist centres. Ensuring people are increasingly diagnosed when they are suitable candidates for surgery, and have access to these specialist centres may lead to an increase in the proportion of patients that undergo surgical resection which could plausibly increase survival of pancreatic cancer patients.