Defining the impact of prognostic factors at the time of relapse for nonmetastatic rhabdomyosarcoma

Background: The prognosis for patients with relapsed rhabdomyosarcoma (RMS) depends on a number of variables, including tumor characteristics, type of relapse, and treatment received. All published studies have considered tumor characteristics at initial diagnosis, but not at the time of recurrence. In this study, we compared tumor characteristics at diagnosis and at the moment of local relapse to better define the chance of cure in this group of patients. Methods: We first analyzed 92 children with localized RMS treated according to the RMS96 and RMS2005 protocols who developed relapse after achieving complete remission at the end of treatment. Then we restricted our analysis to 51 patients with local recurrence to compare their initial tumor characteristics with those at relapse. All characteristics were studied using univariate and multivariate analyses. Results: The 10-year progression-free survival (PFS) and overall survival (OS) rates for the whole group were 23.5% (15.4-32.6) and 34.4% (24.8-44.1), respectively. On multivariate analysis, only primary tumor site appeared to have a strong impact on prognosis (P =.0010). The 10-year PFS and OS rates of patients with locoregional recurrences were 22.7% (12.3-35.0) and 34.9% (22.1-47.9), respectively. Multivariate analysis showed that tumors at unfavorable sites (P =.0044), and tumor size > 5 cm at recurrence (P =.0088) were associated with the poorest prognosis. Conclusion: Our study demonstrates that to estimate the chance of cure in patients with relapsed RMS, we should also consider tumor characteristics at the time of relapse, and tumor size in particular.