Analysis of Differentiation Changes and Outcomes at Time of First Recurrence of Retroperitoneal Liposarcoma by Transatlantic Australasian Retroperitoneal Sarcoma Working Group (TARPSWG)

Background: Local recurrence following resection of retroperitoneal liposarcoma (RLPS) is common. Well-differentiated (WD) and dedifferentiated (DD) RLPS are distinct entities with differing outcomes. A few reports suggest that WDLPS can recur as DDLPS and that DDLPS can recur as WDLPS. This study evaluates whether this change in differentiation from the primary tumor to the first local recurrence impacts long-term outcomes. Methods: Retrospective review from 22 sarcoma centers identified consecutive patients who underwent resection for a first locally recurrent RLPS from January 2002 to December 2011. Outcomes measured included overall survival, local recurrence, and distant metastasis. Results: A total of 421 RPLS patients were identified. Of the 230 patients with primary DDLPS, 34 (15%) presented WDLPS upon recurrence (DD → WD); and of the 191 patients with primary WDLPS, 54 (28%) presented DDLPS upon recurrence (WD → DD). The 6-year overall survival probabilities (95% CI) for DD → DD, DD → WD, WD → WD, and WD → DD were 40% (32–48%), 73% (58–92%), 76% (68–85%), and 56% (43–73%) (p < 0.001), respectively. The 6-year second local recurrence incidence was 66% (59–73%), 63% (48–82%), 66% (57–76%), and 77% (66–90%), respectively. The 6-year distant metastasis incidence was 13% (9–19%), 3% (0.4–22%), 5% (2–11%), and 4% (1–16%), respectively. On multivariable analysis, DD → WD was associated with improved overall survival when compared with DD → DD (p < 0.001). Moreover, WD → DD was associated with a higher risk of LR (p = 0.025) Conclusion: A change in RLPS differentiation from primary tumor to first local recurrence appears to impact survival. These findings may be useful in counseling patients on their prognosis and subsequent management.