Validity assessment of the POLARS score tool in the prediction of post rectal cancer surgery LARS score in a population-based Swedish cohort

Objective Low anterior resection syndrome (LARS) is one of the most common functional impairments after rectal cancer surgery with a high impact on quality of life. The Pre-Operative LARS score (POLARS) nomogram and its online tool has been developed to predict the degree of postoperative LARS. The aim of this study was to analyse how accurately the POLARS score could predict LARS scores when compared with actual patient-reported LARS (PR-LARS) scores in a population-based Swedish cohort. Design This retrospective cohort study included patients who underwent curative rectal cancer surgery between 2007 and 2013 in Stockholm County and were identified using the Swedish Colorectal Cancer Registry (SCRCR). Information regarding preoperative risk factors, patient and treatment characteristics, and presence of LARS postoperatively were collected from patient charts, SCRCR and patient questionnaires. The POLARS model formula was used to predict LARS scores, which then were compared with the actual PR-LARS scores. Individual LARS score differences between the two estimates were shown with a modified Bland-Altman plot of difference. Results The cohort included 477 patients, of whom 359 (75%) of patients were categorised as having no/minor LARS based on the POLARS score. The correctly identified patients by the POLARS score were 80/255 (31%) in the major LARS group and 184/222 (83%) no/minor LARS group. The sensitivity was 31% for major LARS and the positive predictive value was 68%. Conclusion The POLARS score has a low sensitivity for major LARS in this Swedish cohort. Other methods to predict the risk of LARS need to be developed.