Characteristics and Outcomes of Locally Recurrent Retroperitoneal Sarcoma After First Relapse in a Single Tertiary Asian Centre and Applicability of the Sarculator

Abstract

ObjectiveRetroperitoneal sarcomas (RPS) comprise of 15% of soft tissue sarcomas where five-year overall survival rate is about 50%. Locoregional recurrences are observed in up to 50% of patients within the first five years following resection. Various factors have been shown to influence survival outcomes, such as histological subtype and tumour size. A nomogram for first relapse locally recurrent RPS was developed using 602 patients from 22 centres. The recurrent RPS Sarculator is available in an electronic interface and includes variables of age, size, margins of re-resection, radiotherapy, chemotherapy and histology to predict for 6-year disease-free survival (DFS) and overall survival (OS). It has not been validated externally. This study aims to validate the Sarculator recurrence nomogram in predicting the survival outcomes of recurrent RPS in an Asian population as well as examine relapse patterns.MethodsPatients diagnosed with first recurrent RPS from 1 January 2000 to 31 December 2017 with first local relapse and eligible for curative re-resection were retrospectively analysed. The type of surgery was unique for individual patients and suggestions of adjuvant therapy were based on globally recognised standards. Patients were followed up every 3 to 4 months post-operatively for the first 2 to 3 years and 6-monthly to a year thereafter. A R0 or R1 margin is deemed as complete resection, including a microscopically negative margin (R0) and microscopically positive but macroscopically clear margin (R1). R2 is classified as an incomplete resection with tumour rupture or remaining disease. Harrell’s C concordance index was used to determine the nomogram’s discriminative ability and calibration plots were used to assess accuracy. For the calibration, the patients were divided into 3 groups. Death data was retrieved from the National Birth and Death registry for accuracy.ResultsThere were 53 patients included in this study. Patient and tumour characteristics have been summarised in Table 1. All patients had their second resection at a single centre. 66.0% had their first resection at the same centre. The median age was 53 (range 21- 79) at diagnosis, median tumour size was 17cm (12cm to 28cm) and median follow-up duration was 44.1 months. The most commonly encountered subtypes were de-differentiated liposarcoma (DDLPS) (56.6%), well-differentiated liposarcoma (WDLPS) (20.8%) and leiomyosarcoma (LMS) (11.3%) with a majority being high-grade (75.5%). The median disease-free interval was 2.9 years (2- 5.3 years) from the first surgery. The median age at second surgery was 56 (21- 79) and all patients had a complete resection (R0/R1). Recurrence patterns differed with subtypes where 90.9% and 9.1% of WDLS, 76.7% and 16.7% of DDLPS and 83.3% and 16.7% of LMS had local and distant relapses respectively from the second surgery. 62.5% of distant relapses was in the lung followed by nodes (18.8%) and liver (12.5%). The 5-year OS from the second surgery was 66.2% (95% CI: 54.3%- 80.8%). The 1-year, 3 years and 6 years DFS were 50.2% (95% CI: 38.2% - 65.9%), 10.4% (4.26% - 25.5%) and 3.91% (0.684% - 22.4%) respectively. Overall, 32 patients (60.4%) had passed away from sarcoma. The concordance indices for 6-year OS and DFS were 0.7 and 0.65 (Figure 1) respectively which represents a fairly accurate prediction by Sarculator.ConclusionOur study has shown the Sarculator nomogram for primary recurrent was applicable in our cohort and its potential application in an Asian setting. The Sarculator nomogram will be a useful tool in clinical practice to improve risk stratification and facilitate prognosis-based decision-making. Moving forward, novel therapeutic strategies are required to enhance the prognosis of patients with recurrent RPS.

Prognostic Factors and Nomogram Construction for First Local Recurrent Retroperitoneal Sarcoma Following Surgical Resection: A Single Asian Cohort of 169 Cases

“…In November 2021, Hui et al. performed an external validation of the above nomogram using an Asian cohort of 53 patients; the concordance indices for the 6-year OS was 0.7, but only 0.65 for the 6-year DFS ( 12 ), which is consistent with the external validation results in our study (the concordance indices for the 6-year OS and DFS were 0.67 and 0.65, respectively). However, the study of Hui et al.…”

“…Recently, an Asian sarcoma center published a cohort of 53 patients and discovered that Asian patients with FLR-RPS were younger, had longer DFI, and had a higher tumor burden compared with Western populations. However, due to the limited sample size, it was unable to explore relevant prognostic variables in the Asian population ( 12 ).…”

“…conducted an external validation study on the TARPSWG nomogram using a 53-person Asian cohort. Given the disparities between the Asian cohort and the Western cohort, the concordance indices for 6-year DFS were only 0.65 ( 12 ). Therefore, its ability to accurately forecast outcomes in the Asian population needs improvement.…”

Effects of marital status on survival of retroperitoneal liposarcomas stratified by age and sex: A population‐based study

“…Retroperitoneal soft tissue sarcomas (RPSs), a heterogeneous group of rare malignancies, comprise 0.15% of all malignancies and approximately 15% of all soft tissue sarcomas. 32 , 37 RPLs are the most common pathological type, and their early diagnosis and efficient treatment represent considerable challenges due to the size and deep location of RPSs. As a consequence, recurrence the following surgery occurs in the majority of patients with RPLs and is the cause of death in most patients.…”