Axitinib in patients with advanced/metastatic soft tissue sarcoma (Axi-STS): an open-label, multicentre, phase II trial in four histological strata

BACKGROUND

Axitinib is an oral vascular endothelial growth factor receptor inhibitor with anti-tumour activity in renal, thyroid, and pancreatic cancer.

METHODS

Axi-STS was a pathologically-stratified, non-randomised, open-label, multi-centre, phase II trial of continuous axitinib treatment in patients ≥16 years, performance status ≤2, with pathologically-confirmed advanced/metastatic soft tissue sarcoma (STS). Patients were recruited within four tumour strata, each analysed separately: angiosarcoma, leiomyosarcoma, synovial sarcoma, or other eligible STSs. The primary outcome was progression-free survival at 12 weeks (PFS12). A Simon's two-stage design with activity defined as PFS12 rate of 40% determined a sample size of 33 patients per strata.

RESULTS

Between 31-August-2010 and 29-January-2016, 145 patients were recruited: 38 angiosarcoma, 37 leiomyosarcoma, 36 synovial sarcoma, and 34 other subtypes. PFS12 rate for each stratum analysed was 42% (95% lower confidence interval (LCI); 29), 45% (95% LCI; 32), 57% (95% LCI; 42), and 33% (95% LCI; 21), respectively. There were 74 serious adverse events including two treatment-related deaths of pulmonary haemorrhage and gastrointestinal bleeding. Fatigue and hypertension were the most common grade 3 adverse events.

CONCLUSIONS

Axitinib showed clinical activity in all STS strata investigated. The adverse event profile was acceptable, supporting further investigation in phase III trials.

CLINICAL TRIAL REGISTRATION

ISRCTN 60791336.

Experimentally produced synovial sarcoma in mice

BALB/c and C57 B1/6 mice which received weekly subcutaneous injections of a cannabinoid developed tumors at the points of injection. In the groin the tumors were fibrosarcomas, while in the interscapular region they were anaplastic sarcomas and synovial sarcomas. The latter developed faster and were larger in cannabinol - and cannabidiol-treated C57 B1/6 mice than in delta 9-tetrahydrocannabinol-treated BALB/c mice. This difference could not be attributed to strain differences. 2 cannabidiol- and 1 cannabinol-treated C57 B1/6 females with the fastest growing synovial sarcomas were pregnant and, in addition, 2 of them developed mammary adenocarcinomas, indicating that they were rich in estrogen. On the other hand, it is known that delta 9-tetrahydrocannabinol causes a decrease in the sex hormone. It is consequently thought that the cannabinoids are only initiators of synovial sarcoma, while growth or promotion of the latter is influenced partially or entirely by the sex hormone.

Experimentally induced synovial sarcoma

Synovial sarcoma has been induced in the knee joints of rats by intra-articular injection of 9-10-dimethyl-1-2-benzanthracene. Tumours developed from three to six months after the last injection. The neoplasms obtained were classified as synovial sarcoma (50%), fibrosarcoma (25%), giant cell sarcoma (15%), malignant fibrous histiocytoma (10%). The synovial membrane in the treated knee joints presented a chronic synovitis associated with fibrosis and proliferation of the lining cells. The primitive tumour spread locally infiltrating muscle and the adjacent bones. Metastases occurred most frequently to the lungs (70%) and liver (20%); lymph nodes were involved in 10%.