Applicability of the Sarculator and MSKCC nomograms to retroperitoneal sarcoma prognostication in an Asian tertiary center.

Aim: To study the applicability of 2 common nomograms in retroperitoneal sarcoma patients treated in an Asian tertiary hospital, and to study relapse patterns.

Methods: Patients from 1st January 2000 to 31st December 2017 were retrospectively analysed. R2 resection from an external institution were ineligible. Harrel's C concordance index and calibration plots were used to assess nomograms' accuracy.

Results: 109 patients were eligible, with a median age of 56, median tumour size of 16 cm and median follow up of 44.1 months. Most common subtypes were DDLPS (46.8%), LMS (19.3%) and WDLPS (13.8%). Overall, 81.1% had passed away from sarcoma. Recurrence patterns differed with subtypes; 6.7% of WDLPS and 66.7% of LMS had distant relapses. WDLPS patients had a median sarcoma specific survival of 139 months (122-NA), while the rest had a median SSS of 72.3 months (59.7-NA). The 5-years and 7-year OS were 63.0% (95% CI: 53.6%-74.0%) and 51.6% (41.1%-64.8%) respectively. The 5-years and 7-year DFS were 22.4% (15.5%-32.3%) and 17.5% (11%-27.8%) respectively. The 4-years, 8-years and 12-year SSS were 71.3% (62.7%-81.0%), 51.8% (40.8%-65.8%) and 32.2% (19.7%-52.6%) respectively. The concordance indices for 7-year DFS and OS (Sarculator) were 0.63 and 0.73. The concordance indices for 4-, 8- and 12-year SSS (MSKCC) were 0.64, 0.72 and 0.72.

Conclusion: Both nomograms were effective in our cohort. Both nomograms can be further improved by specifying the type of relapse and including a longer-term endpoint for the Sarculator.