Retroperitoneal dedifferentiated liposarcomas: semi-quantitative assessment of the dedifferentiated component and prognosis

Abstract

To evaluate the impact of malignancy grade and the proportion of the dedifferentiated component (DC) in retroperitoneal dedifferentiated liposarcomas (DDLS) on the course and prognosis of the disease. The retrospective study enrolled 74 patients with primary retroperitoneal DDLS who underwent radical surgical treatment in the N.N. Blokhin National Medical Research Center of Oncology, Ministry of Health of Russia. Histological surgery specimens from all cases of DDLS were reexamined and reclassified. According to malignancy grades and the proportion of the dedifferentiated component in the tumor, the patients were divided into the comparison groups included in the intergroup analysis of overall and relapse-free survival (OS and RFS) rates. The authors also analyzed the relationship between the proportion of the dedifferentiated component in DDLS and the frequency of adjacent organ invasion. Patients with a more than 15% dedifferentiated component had significantly lower OS rates than those with a less than 15% one (p=0.0001; log-rank test). The median OS in the DDLS group with a less than 15% dedifferentiated component was 91 months (95% CI, 82-100); that in the DDLS group with a more than 15% dedifferentiated component was 29 months (95% CI 17-41). The 5-year overall survival rates in the groups with less than 15% and more than 15% dedifferentiated components were 69% and 2%, respectively. The group with a more than 15% dedifferentiated component had significantly lower RFS rates than that with a less than 15% one (p=0.0001; log-rank test). In the DDLS groups with less than 15% and more than 15% dedifferentiated components, the median RFS rates were 25 months (95% CI 23-27) and 13 months (95% CI 8-18), respectively. In these groups, the 2-year RFS rates were equal to 50% and 9%, respectively. In the DDLS groups with less than 15% and more than 15% dedifferentiated components, pathologically confirmed invasion into the adjacent organs was observed in 32% and 63% of cases, respectively. There were no statistically significant differences in the OS and RFS of patients with DDLS according to tumor grade (p=0.069; p=0.102). This investigation suggests that DDLS have a more aggressive course with an increasing proportion of the dedifferentiated component in the tumor. Considering the histological variability in the dedifferentiated component, which is demonstrated in the research and scientific literature, as well as lack of a prognostic impact of histological grade, the authors believe that semi-quantitative assessment of the proportion of the dedifferentiated component in DDLS is able to serve as a simple and efficient morphological marker for the course of the disease and prognosis in retroperitoneal DDLS.