Variation in case-mix between hospitals treating colorectal cancer patients in the Netherlands

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Abstract

Aims

The purpose of this study was to determine how expected mortality based on case-mix varies between colorectal cancer patients treated in non-teaching, teaching and university hospitals, or high, intermediate and low-volume hospitals in the Netherlands.

Material and methods

We used the database of the Dutch Surgical Colorectal Audit 2010. Factors predicting mortality after colon and rectum carcinoma resections were identified using logistic regression models. Using these models, expected mortality was calculated for each patient.

Results

8580 patients treated in 90 hospitals were included in the analysis. For colon carcinoma, hospitals’ expected mortality ranged from 1.5 to 14%. Average expected mortality was lower in patients treated in high-volume hospitals than in low-volume hospitals (5.0 vs. 4.3%, p < 0.05). For rectum carcinoma, hospitals expected mortality varied from 0.5 to 7.5%. Average expected mortality was higher in patients treated in non-teaching and teaching hospitals than in university hospitals (2.7 and 2.3 vs. 1.3%, p < 0.01). Furthermore, rectum carcinoma patients treated in high-volume hospitals had a higher expected mortality than patients treated in low-volume hospitals (2.6 vs. 2.2% p < 0.05). We found no differences in risk-adjusted mortality.

Conclusions

High-risk patients are not evenly distributed between hospitals. Using the expected mortality as an integrated measure for case-mix can help to gain insight in where high-risk patients go. The large variation in expected mortality between individual hospitals, hospital types and volume groups underlines the need for risk-adjustment when comparing hospital performances.

Introduction

Colorectal carcinoma is the second most common cancer related cause of death in western countries, and incidence is rising. Surgical resection is still the cornerstone of treatment, though associated with a considerable peri-operative risk. It is also known that outcome after colorectal resections, especially postoperative mortality varies between hospitals.1 Although differences in mortality rates are often studied with a focus on the inverse relationship with procedural volume2, 3 similar variations have been reported between different types of hospitals, such as teaching and non-teaching hospitals.4, 5, 6

Part of these variations can be explained by differences in case-mix (patient and tumor characteristics). Therefore case-mix correction is considered to be essential for reliable and valid outcome comparisons.7 In the last decade, several countries have started nation-wide colorectal audit programs, which are coordinated on a European level by the EURECCA project of the European Society of Surgical Oncology. Considering this increasing interest in outcome measurements, information on differences in case-mix between (different types of) hospitals becomes more and more important.

A commonly used method for case-mix correction is the Observed/Expected mortality rate,8, 9 in which the observed mortality is the number of deaths in a hospital or group of hospitals, and the expected mortality is the sum of the patients’ estimated probabilities for mortality, based on their case-mix factors. Previous studies have described variation in the distribution of specific case-mix factors between teaching and non-teaching hospitals, and high- and low-volume hospitals, with varying results.4, 5, 6 However, to date, variations in expected mortality rates between different types of hospitals have not been studied in detail. More insight in the distribution of expected mortality can assist healthcare providers in recognizing high-risk patients treated in their hospital and focus quality improvement efforts on these patients.

Following the initiatives in Scandinavian countries and in the United Kingdom, the Dutch Surgical Colorectal Audit (DSCA) was initiated in 2009.10 The DSCA is a nation wide, web based, interactive database in which detailed patient, tumor, diagnostic, procedural and outcome data are registered of patients who undergo a resection of a primary colorectal carcinoma in the Netherlands. This database gave us the opportunity to further investigate differences in expected mortality based on differences in case-mix between patients treated in different types of hospitals in the Netherlands.

The purpose of this study was to determine

  • 1)

    Which case-mix factors are predictors for postoperative mortality after the resection of colon and rectum carcinomas in the Netherlands;

  • 2)

    How expected mortality based on case-mix factors differs between individual as well as different types of hospitals: non-teaching, teaching and university hospitals and high-, intermediate and low-volume hospitals;

  • 3)

    Which patient and tumor characteristics are responsible for these differences in expected mortality.

Section snippets

Patients

About 93% of all patients who underwent a resection of a primary colorectal carcinoma in the Netherlands from 1st of January 2010 until 31st of December 2010 were included in the DSCA [www.dsca.nl] on March 15th 2011. All Dutch hospitals participated. Data entry was web-based in a highly secured database. All participating hospitals appointed a surgeon who was responsible for the data-entry. Weekly feedback information on number of patients entered, number of registered patient files, and

Patients

At March 15th 2011, 90 hospitals (8 university hospitals, 45 teaching hospitals and 37 non-teaching hospitals) registered a total of 8835 eligible patients with a date of surgery between January 1 and December 31 2010 in the DSCA. After exclusion of patients with multiple synchronous tumors (253 patients) a total of 8580 patients were included in the analysis, 6161 patients with colon cancer and 2419 with rectum cancer. Average procedural volume was 95 patients per hospital (range 14–231). The

Discussion

This study confirms the essential role of case-mix adjustments in clinical auditing for colorectal cancer. For individual hospitals, expected mortalities varied between 1.5 and 14% for colon cancer and from 0.5 to 7.5% for rectum cancer resections. Patients treated colon cancer in low-volume hospitals had a higher expected mortality than patients treated in high-volume hospitals, due to an unfavorable case-mix. These differences in expected mortality were mostly explained by low-volume

Conclusion

The present study shows that high-risk colorectal cancer patients in the Netherlands are mostly characterized by an older age, comorbidity and an indication for non-elective resection. High-risk patients are not evenly distributed between individual and groups of hospitals. Using expected mortality as an integrated measure for their case-mix gives insight in the hospitals where high-risk patients go, which is important for the targeting of quality improvement programs. The large variation in

Conflicts of interest

The authors declare no conflicts of interest.

Acknowledgments

The authors would like to thank all surgeons, registrars, physician assistants and administrative nurses that registered all the patients in the DSCA, as well as the Dutch Surgical Colorectal Audit group and the methodological board for their advice.

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Collaborators: the Dutch Surgical Colorectal Audit group: W.A. Bemelman, O.R.C. Busch, R.M. van Dam, E. van der Harst, M.L.E.A. Jansen-Landheer, Th.M. Karsten, J.H.J.M. van Krieken, W.G.T. Kuijpers, V.E. Lemmens, E.R. Manusama, W.J.H.J Meijerink, H.J.T. Rutten, T. Wiggers, C.J.H. van de Velde.

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