The standardised mortality ratio is unreliable for assessing quality of care in rectal cancer

Background: The standardised mortality ratio (SMR) for rectal or anal cancer was above average in a large tertiary referral centre for locally advanced rectal cancer in the Netherlands. The aim of this study was to investigate whether the increased SMR was indeed related to poor quality of care or whether it could be explained by inadequate adjustment for case-mix factors. Methods: Between 2006 and 2008, 381 patients were admitted for rectal or anal cancer. The SMR score of this diagnostic group was 230 (95% CI 140 to 355), corresponding with 20 in-hospital deaths. The hospital dataset was merged with data from the Eindhoven Cancer Registry to obtain more detailed information. Results: Patients admitted for palliative care only accounted for 45% (9/20) of the in-hospital mortality. In contrast to the high SMR, postoperative mortality was low, i.e. 2.6%. The majority of the rectal or anal cancer patients were diagnosed in and referred from another hospital. Referred patients more often had an advanced tumour stage, more often underwent resection and were more frequently treated with chemotherapy and/or radiotherapy than non-referred patients (p<0.01). Postoperative mortality rates for referred and non-referred patients were 2.9% and 1.9%, respectively. Conclusions: The increased SMR appeared to be caused by the admission of patients who received palliative care only. Consequently, the SMR is unreliable for the assessment of quality of care in patients with rectal or anal cancer.

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