Phase 1 Trial of Concurrent Sunitinib and Radiation Therapy as Preoperative Treatment for Locally Advanced or Recurrent Soft Tissue Sarcoma.

Although the introduction of multimodal treatment of soft tissue sarcoma resulted in great progress in STS treatment, local failure still occurs in 10-20% of STS patients. Therefore further improvement of local and systemic treatment is needed in order to achieve tumor control and limb salvage. The proposed study treatment will combine external beam radiation and orally administered sunitinib.

Sunitinib is a multiple receptor tyrosine kinase (RTK) inhibitor with anti-angiogenic and anti-tumoral properties. For their key role in tumor development, RTKs are regarded as excellent targets for cancer chemotherapy. External beam radiation is widely used as neoadjuvant treatment for locally advanced soft tissue sarcoma.

The concurrent application of anti-angiogenic sunitinib appears reasonable, since STS are highly vascularized tumors and overexpression of VEGFR and other RTKs has been shown for various histologic soft tissue sarcoma subtypes. At first sight, the combination of antiangiogenic treatment and radiation seems to be contradictory, since anti-angiogenic treatment attacks tumor vasculature and radiation effects are decreased by hypoxia. Yet, in animal studies the concurrent application of radiation with tyrosine kinase inhibitors such as sunitinib or other antiangiogenic agents resulted in additive, if not synergistic antitumoral effects. These results can be explained by the superiority of the anti-tumoral activity of antiangiogenic agents over their hypoxia related, radiation weakening effects; or by the hypothesis of vascular normalization. It is well known that tumor vasculature is immature and ineffective in means of blood supply and oxygenation. In preclinical models, antiangiogenic agents balanced pro- and anti-angiogenic effectors which may result in maturation of tumor vasculature with improvement of blood flow and oxygen supply.

The combination of sunitinib as an anti-angiogenic and anti-proliferative agent thus might not only add the therapeutic effects of the RTK-inhibitor and external beam radiation but might additionally lead to a radiosensitizing effect due to tumor vessel normalization. The Purpose of this study is to assess the toxicity of the combined treatment and to gather preliminary data on treatment efficacy.