Morphology, grading may determine treatment approach in synovial sarcoma

WAILEA, Hawaii — Not all cases of synovial sarcoma of the extremities result in severe outcomes, according to study results presented at Connective Tissue Oncology Society Annual Meeting.

“High-risk patients identified on the basis of morphology and grading may qualify for an aggressive treatment approach,” Marco Gambarotti, MD, of the department of pathology at Istituto Ortopedico Rizzoli in Italy, and colleagues wrote.

Synovial sarcoma — which accounts for 5% to 10% of soft tissue sarcomas — typically occurs in the extremities of young adults. Diagnosis is based on clinical, morphological, immunohistochemical and genetic data, specifically the identification of X;18 (SS18-SSX1 or SS18-SSX2) translocations.

Several factors have been proposed as prognostic variables, including morphology (monophasic vs. biphasic), grading, type of translocation and loss of INI1 expression, according to study background.

Gambarotti and colleagues retrospectively analyzed 196 patients with synovial sarcoma of the extremities treated at Istituto Ortopedico Rizzoli from January 1976 to April 2016.

Investigators assessed tumor grade based on the French Federation of Cancer Centers Sarcoma Group system. They also retrospectively evaluated tissue specimens for SS18-SSX fusion type, as well as immunohistochemical expression of INI1.

The majority of patients had monophasic morphology (78%) rather than biphasic (22%); 59% had grade 2 disease and 41% had grade 3 disease. Sixty percent had SSX1 translocation and 40% had SSX2 translocation. Similar percentages had maintained INI1 expression (51%) or lost it (49%).

Researchers reported OS rates of 56% at 5 years and 46.9% at 10 years. Results revealed significantly poorer survival among patients with monophasic morphology (P = 0.11), as well as a trend toward poorer survival among those with grade 3 tumors.

Neither SSX fusion types nor INI1 expression correlated with survival.

Gambarotti and colleagues reported local RFS rates of 78.9% at 5 years and 75.9% at 10 years. Patients whose tumors had SSX2 translocation (P = .049) and those who had grade 3 disease (P = 0.028) had significantly higher local recurrence rates. – by Mark Leiser

For more information:

Gambarotti M, et al. Poster 207. Presented at: Connective Tissue Oncology Society Annual Meeting; Nov. 8-11, 2017; Maui.

Di sclosure: The researchers report no relevant financial disclosures.