Feasibility of Proton Beam Therapy for Chordoma and Chondrosarcoma of the Skull Base

We explored the general feasibility of proton beam therapy for chordoma and chondrosarcoma of the skull base. Clinical records and treatment-planning data of patients with the pathological diagnosis of chordoma or chondrosarcoma were examined. Proton beam therapy was administered for gross tumor mass as well as microscopic residual disease after surgery. The prescribed dose was determined to maximize the coverage of the target and to not exceed predefined constraints for the organs at risk. Eight cases of chordoma and eight cases of chondrosarcoma were enrolled. The median tumor volume was 40 cm3 (range, 7 to 546 cm3). The prescribed dose ranged from 50 to 70 Gy (relative biological effectiveness [RBE]), with a median of 63 Gy RBE. The median follow-up duration was 42 months (range 9 to 80 months). The overall survival rate was 100%, and the local control rate at 3 years of chordoma and chondrosarcoma were 100% and 86%. None of the patients developed radiation-induced optic neuropathy, brain stem injury, or other severe toxicity. Proton beam therapy is generally feasible for both chordoma and chondrosarcoma of the skull base, with excellent local control and survival rates

Contrasting Actions of Selective Inhibitors of Angiopoietin-1 and Angiopoietin-2 on the Normalization of Tumor Blood Vessels

Angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2) have complex actions in angiogenesis and vascular remodeling due to their effects on Tie2 receptor signaling. Ang2 blocks Ang1-mediated activation of Tie2 in endothelial cells under certain conditions but is a Tie2 receptor agonist in others. We examined the effects of selective inhibitors of Ang1 (mL4-3) or Ang2 (L1-7[N]), alone or in combination, on the vasculature of human Colo205 tumors in mice. The Ang2 inhibitor decreased the overall abundance of tumor blood vessels by reducing tumor growth and keeping vascular density constant. After inhibition of Ang2, tumor vessels had many features of normal blood vessels (normalization), as evidenced by junctional accumulation of vascular endothelial-cadherin, junctional adhesion molecule-A, and platelet/endothelial cell adhesion molecule-1 in endothelial cells, increased pericyte coverage, reduced endothelial sprouting, and remodeling into smaller, more uniform vessels. The Ang1 inhibitor by itself had little noticeable effect on the tumor vasculature. However, when administered with the Ang2 inhibitor, the Ang1 inhibitor prevented tumor vessel normalization, but not the reduction in tumor vascularity produced by the Ang2 inhibitor. These findings are consistent with a model whereby inhibition of Ang2 leads to normalization of tumor blood vessels by permitting the unopposed action of Ang1, but decreases tumor vascularity primarily by blocking Ang2 actions