External validation of a rectal cancer outcome prediction model with a cohort of patients treated with preoperative radiochemotherapy and deep regional hyperthermia

Abstract

Purpose: To validate a nomogram for the prediction of treatment outcomes after preoperative radiochemotherapy and surgery for locally advanced rectal cancer with a cohort of patients treated with additional deep regional hyperthermia. Patients and methods: A total of 86 patients were treated with preoperative radiochemotherapy and deep regional hyperthermia at our institution. For every patient, the 5-year probability for death, distant metastases and local failure based on a previously published nomogram were calculated and patients were divided into three risk groups. Results: Low-lying and clinically lymph node positive tumours were more frequent in the validation cohort. Five-year Kaplan–Meier estimates for overall survival (OS), distant metastases-free survival (DMFS) and local control (LC) were 87.3%, 79.9%, 95.8% (observed) and 75.5%, 71%, 90% (predicted), respectively. Discrimination between low- and high-risk groups was at a significant level for all endpoints. The c-index was 0.81 (OS), 0.67 (DMFS) and 0.92 (LC), respectively. Conclusions: The nomogram showed reasonable performance when deep regional hyperthermia is incorporated into preoperative therapy. The higher than predicted rates seen for OS and DMFS in particular in the high-risk groups warrant further prospective validation and subsequent investigation of the underlying mechanisms.