Development and external validation of a nomogram and online tool to predict bowel dysfunction following restorative rectal cancer resection: the POLARS score

OBJECTIVE: Bowel dysfunction is common following a restorative rectal cancer resection, but symptom severity and the degree of quality of life impairment is highly variable. An internationally validated patient-reported outcome measure, Low Anterior Resection Syndrome (LARS) score, now enables these symptoms to be measured. The study purpose was: (1) to develop a model that predicts postoperative bowel function; (2) externally validate the model and (3) incorporate these findings into a nomogram and online tool in order to individualise patient counselling and aid preoperative consent. DESIGN: Patients more than 1 year after curative restorative anterior resection (UK, median 54 months; Denmark (DK), 56 months since surgery) were invited to complete The European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire - Core 30 version3 (EORTC QLQ-C30 v3), LARS and Wexner incontinence scores. Demographics, tumour characteristics, preoperative/postoperative treatment and surgical procedures were recorded. Using transparent reporting of a multivariable prediction model for individual prognosis or diagnosis (TRIPOD) guidelines, risk factors for bowel dysfunction were independently assessed by advanced linear regression shrinkage techniques for each dataset (UK:DK). RESULTS: Patients in the development (UK, n=463) and validation (DK, n=938) datasets reported mean (SD) LARS scores of 26 (11) and 24 (11), respectively. Key predictive factors for LARS were: age (at surgery); tumour height, total versus partial mesorectal excision, stoma and preoperative radiotherapy, with satisfactory model calibration and a Mallow's Cp of 7.5 and 5.5, respectively. CONCLUSIONS: The Pre-Operative LARS score (POLARS) is the first nomogram and online tool to predict bowel dysfunction severity prior to anterior resection. Colorectal surgeons, gastroenterologist and nurse specialists may use POLARS to help patients understand their risk of bowel dysfunction and to preoperatively highlight patients who may require additional postoperative support.