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There has been some chatter regarding off label use and insurance reimbursing for it on the Yahoo! boards.

My opinion hasn't changed, I just don't see significant off label sales here. Interesting anecdotal evidence, again with that renal patient. Interesting that a gastric cancer patient's doctor was able to pursue off label usage for Cabo in gastric cancer without confirmation of good efficacy in the RDT. (From what I remember gastric was included in RDT, but the signal was weak compared to other indications)

An intriguing part of this Cabo story to me is with this renal cancer trial. The poster below shows results of that early renal study. Some observations about the 4 patients with bone metastasis at baseline.

1. Only 1 patient was followed by bone scan, and that patient observed a bone response.

2. 2/2 patients with bone pain had a bone pain response. One patient had a pain score of 5/10 with complete resolution of pain for 73+ weeks. The other patient had pain response until 25 weeks.

What makes the observations very interesting is the fact that renal cancer patients that have bone metastasis are predominately osteolytic in nature. If you follow the literature typically 70% of the bone lesions are osteolytic in RCC. Now if 70% of lesions are typically osteolytic, I would imagine that patient with extreme complete pain response lasting 73+ weeks would have majority of bone lesions being of osteolytic variety. Osteolytic lesions typically are not demonstrated by bone scan. Judging by how followup was weak by bone scan criteria in the other patients, I suspect that there wasn't another imaging modality used to measure baseline and followup osteoclastic lesion response.(after all only 1/4 patients were followed by bone scan, and that patient happened to respond by bone scan criteria) I suspect those osteolytic lesions could demonstrate sclerotic healing. I have a hard time imagining an RCC patient's dramatic durable pain response was due solely to osteoblastic therapeutic effects.

Exelixis states that cabo impacts both osteoclasts and osteoblasts, but to date we haven't really seen extent on osteolytic lesions. I am really intrigued to see what therapeutic extent on osteoclastic lesions we are seeing? Are we seeing some new bone growth in these lytic regions?
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