Purpose: Comparing surgical performance across institutions may assist in identifying best practices in the interest of patients, clinicians, payers and policy makers. Although 30-day mortality is the most commonly used performance indicator, follow-up length required to capture deaths potentially due to surgical quality is debated. We aimed to determine optimal follow-up period for mortality after esophageal resection to measure surgical quality, using a decision analytical approach. We also aimed to develop a case-mix adjustment model to compare surgical performance across hospitals.
Methods: Esophageal cancer patients were included prospectively from a large university hospital. The cause of death was classified for all patients who died within one year after surgery as potentially surgery related vs. probably not surgery related (progression of disease). We calculated the numbers of false positives and false negatives for a range of follow-up periods and the ratio between these. Case-mix adjustment models were developed using logistic regression.
Results: Between 1991 and 2011 1,283 patients were operated, of whom 393 (29%) died within 1 year: 107 (29%) with a potential surgical cause, and 261 (70%) with a most likely oncological cause. For 5 deaths (1%), the cause was unknown. Within 30 days after surgery, 36 (2.9%) patients had died, all -except one unknown- with a surgical cause. Within 90 days after surgery 90 (7%) patients had died, 79 with a surgical cause and 10 with an oncological cause. With a follow-up period of 30 days, there would be 34/107 (33%) true positives (surgical deaths) against no false positives (oncological deaths), implying a ratio of infinity for the importance of misclassifying a death as potentially surgery related (figure). With 90 days follow-up, there would be 76 /107 (71%) true positives, and 8/261 (3%) false negatives, implying a ratio of 9.5. A ratio of 1:1 was only reached after 200 days. Important predictors of 90-day mortality were older age, male gender, involvement of resection margins, transthoracic surgery (vs. transhiatal surgery), weight loss prior to surgery, neoadjuvant therapy, and a history of cardiovascular disease.
Conclusions: A substantial number of surgery related deaths occurred after 30 days after surgery. The optimal length of follow-up depends on the misclassification costs attached to false-positives vs. false-negatives. Weighting both as equally important would require a follow-up up to 200 days.
