The SYT-SSX1 variant of synovial sarcoma is associated with a high rate oftumor cell proliferation and poor clinical outcome

Cytogenetically, synovial sarcoma (SS) is characterized by the translocatio n t(X;18)(p11.2;q11.2), resulting in a fusion between the SYT gene on chrom osome 18 and SSX1 or SSX2, on the X chromosome and the formation of new chi meric genes, SYT-SSX1 or SYT-SSX2, We examined the potential clinical relev ance of SYT-SSX1 and SYT-SSX2 fusion transcripts together with tumor prolif eration. In a series of 33 patients with primary SS, the type of fusion tra nscript was assessed by reverse transcription-PCR and sequence analysis. Th e proliferation rate was analyzed using anti-Ki-67 antibodies. One case car rying an atypical transcript with a 57-bp insert was excluded, leaving 13 S YT-SSX1 and 19 SYT-SSX2 cases for analysis. The hazard ratio (with respect to metastasis-free survival for patients with SYT-SSX1 versus patients with SYT-SSX2 fusion transcripts was 7.4 (95% confidence interval, 1.5-36; log- rank P = 0.004), There was also an association with reduced overall surviva l for patients with SYT-SSX1 compared to patients with SYT-SSX2 (hazard rat io, 8.5; 95% confidence interval, 1.0-73; log-rank P = 0.02), The 5-year me tastasis-free survival for patients with SYT-SSX1 was 42% versus 89% for pa tients with SYT-SSX2. There was a significant association between SYT-SSX1 and a high tumor proliferation rate (P = 0.02), We conclude that the findin gs suggest that the type of SYT-SSX2 fusion transcript determines the proli feration rate and is an important predictor of clinical outcome In patients with SS.