Treatment details listed by disease site are described in Table 1. Prior radiation therapy was delivered to the treated area in 40% of patients, and 30% of patients received post-SBRT chemotherapy for at least one cycle. The target volume for radiotherapy was delineated by the fusion of the simulation CT scan with pre-treatment diagnostic CT or CT/FDG-PET imaging, to encompass the gross tumor volume (GTV) on CT or volume with SUV > 3.5 units (body weight) on FDG-PET. A planning target volume (PTV) was constructed by adding a custom 2-5mm margin radially around the GTV. Respiratory gating with a 4-D CT simulation Inhibitors,research,lifescience,medical was performed with 9 treated

sites (39%). Radiation was delivered in a single fraction (87% sites), or fractionated over 2 to 3 treatments, each Inhibitors,research,lifescience,medical at least 3 days apart. Isodose lines of typical treatment

plan for a metastatic colon adenocarcinoma lymph node treated with one fraction is depicted in Figure 1. Table 1 Patient characteristics Figure 1 Isodose lines of typical treatment plan for a metastatic colon adenocarcinoma lymph node treated with one fraction For image guidance, the interventional radiology service implanted radio-opaque fiducial markers in close proximity to the tumor target in 18 (78%) sites. At the time of treatment, these markers were utilized as on-board imaging targets for kv-kv image matching, incorporating Inhibitors,research,lifescience,medical respiratory gating as appropriate. Of the remaining 5 treated sites, image guidance was performed by cone beam CT at the time of treatment in 3 cases. Treatment setup was confirmed in the final 2 sites

by bony kv-kv image matching. A inhibitors purchase summary of treatment characteristics is listed in Table 2. Table 2 Treatment characteristics Treatment response and local control Treatment response based on CT & Inhibitors,research,lifescience,medical FDG-PET imaging at 1 month, 3 months, and last follow-up is presented in Table 3, with a median follow-up of 6.3 months after SBRT (range Inhibitors,research,lifescience,medical 1.5-12.2 months). The overall response rate (the sum of complete responses and partial responses) by treated site was noted in 36% (1 month), 47% (3 months) and 48% (final). A complete response was achieved in 13% (3 sites). At last follow-up, local control (sum of response rate and stable disease) all was 74% (Tab 3, Fig 2). Table 4 lists local control by specifically grouped treatment sites. Table 3 Overall response Figure 2 Local control Table 4 Local control by site Metabolic response Pre-and post-SBRT evaluable CT/FDG-PET scans were available for review in 39% of treated sites. Based on maximum reported SUV, the metabolic response rate (sum of partial and complete responders) was 85% on final analysis (Tab 5, Fig 3). 23% of sites achieved a complete response. Two treated sites (13%) did show evidence of progression at 3 months, but subsequent CT/FDG-PET scans showed a decrease in maximum SUV; no patients suffered progressive disease based on metabolic imaging at last follow-up.