Modified POSSUM to predict postoperative morbidity following gastrectomy

In order to predict morbidity after gastrectomy for gastric cancer in aged patients, the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) scoring system was applied.A total of 123 patients who had gastrectomies for gastric cancer at the age of 75 or above, between 1994 and 2002, were enrolled in this study. Postoperative morbidities and mortalities were analyzed and POSSUM scores were calculated.The predicted mortality and morbidity rates according to the POSSUM scores in this series were 47.9% and 14.1% respectively. The observed morbidity and mortality rates were 39.8% and 1.6% respectively. Using these results, we created a modified POSSUM equation to predict the morbidity in this population, expressed as ln[R/(1-R)] = -2.59 + (0.087 x PS) + (0.013 x OS), where PS: Physiological Severity, OS: Operative Severity, R=predicted morbidity rate. We applied this equation prospectively to 26 patients who underwent gastrectomies in 2003. The figures for predicted morbidity and observed morbidity were 37.3% and 38.5% respectively, indicating that our modified equation predicted morbidity more accurately than the POSSUM.The POSSUM over-predicted the morbidity of patients who underwent gastrectomy. However, after creating a modified equation using data from retrospective analysis, a modified POSSUM was found to predict the prospective morbidity rate accurately.