A comparison of the risk prediction models PERSARC and Sarculator in patients with localized soft tissue sarcoma of the extremities and trunk wall

Background: Different risk classification criteria are used to select patients with localized soft tissue sarcoma of the extremities and trunk wall for neoadjuvant/adjuvant chemotherapy. The two most frequently used risk classification methods are PERSARC and Sarculator prediction models. The main aim was to evaluate and compare these two methods. Materials and methods: The study cohort consisted of 664 patients treated at Oslo University Hospital from 1998 to 2017. Predicted probabilities of distant metastasis (DM) and overall survival (OS) were calculated, and risk classification was carried out according to previously defined thresholds. Hazard ratios were estimated using Cox proportional hazards regression models. Interaction between neoadjuvant/adjuvant chemotherapy and risk groups was included in the models to investigate the effect of chemotherapy according to risk group. Results: A high degree of correlation was found between PERSARC and Sarculator in predicted 5-year probability of DM and 5-year OS. A total of 215 of 664 (32%) and 221 of 569 (39%) patients were classified as high-risk according to Sarculator and PERSARC, respectively, with agreement found in 511 of 569 patients (90%). Patients classified as high-risk by only one method had similar disease-free survival and OS as patients who were high-risk using both methods. Based on this, patients classified as high-risk by at least one method were grouped as ‘combined high-risk’ and compared with previously established risk classification criteria. Neoadjuvant/adjuvant chemotherapy was associated with improved OS and disease-free survival in all high-risk groups. Conclusions: A high degree of agreement between PERSARC and Sarculator predictions was observed. Patients classified as high-risk by only one method had similar outcomes to those who were high-risk using both. Chemotherapy was associated with improved outcome in the PERSARC, Sarculator, and combined high-risk group. Patients classified as high-risk by one of these methods could be considered for neoadjuvant/adjuvant chemotherapy.