"Dr Dan shares a few thoughts on ...Cabozantinib."
I will take issue with one of Dr. Petrylak's statements. He identified the Cabo bone scan response rate as 40-50% If one looks at the pooled date, the bone BSR for the 100mg dose is in the 65 to 70% range and the BSR for the 40mg dose is in the low to mid 50's. We have seen very little 60 mg data, but I would expect it to fall around 60%.
"I will take issue... He identified the Cabo bone scan response rate as 40-50%"
It seemed low to me as well. Here's a Dr Petrylak Onclive posting from 5/29/12, in which he's discussing the RDT P2 CRPC data. He's definitely talking of a higher rate here, though I doubt the RDT played much with 60mg data unless as a direct result of dose reduction.
"Another promising novel therapy for prostate cancer is cabozantinib (XL184, Exelixis), a tyrosine kinase inhibitor that blocks both MET and VEGFR2. MET and its ligand HGF drive tumor cell invasion and metastasis, and MET and VEGFR2 together promote angiogenesis, Petrylak said. Furthermore, bone metastases are associated with high levels of MET expression. “Although cabozantinib is a bone-targeted agent, soft-tissue responses have also been seen,” Petrylak said.
In a phase II randomized discontinuation trial presented at the American Society of Clinical Oncology 2011 annual meeting, cabozantinib demonstrated clinical activity regardless of prior docetaxel treatment in men with metastatic CRPC, particularly in patients with bone disease.4 Of 65 evaluable patients, 86% (56) had complete or partial resolution on bone scan as early as week six. In 28 patients receiving narcotics for bone pain, 64% had improved pain and 46% decreased or halted narcotics. Objective tumor shrinkage occurred in 84% of patients. Randomization was halted and patients unblinded due to high rates of bone scan resolution and pain relief. However, Petrylak said, looking at the results in terms of docetaxel pretreatment status is a misnomer. “We want to think in terms of a biological continuum and look for markers.”
I also think it likely that Dr Petrylak was forced relinquish his math skills to become a Yalie.