The findings from other studies using 18F-FLT PET to assess early responses to anti-cancer treatment have been very variable, where response to a histone deacetylase inhibitor was observed after 4 days [10], response to cisplatin is seen after 1 day [9], response to cyclophosphamide and mTOR inhibition is evident after 2 days [16] and the ErbB kinase inhibitor initiated a decrease in 18F-FLT uptake 2 days after treatment initiation whereas no response was observed at 6 and 24 hours [11]. Here, MTOR is linked to cancer.