CDKN2A and breast cancer: Increases in the proportion of p16-expressing VIM+ CTCs did not seem to be indicative of response to therapy, as some of the longest durations of stable disease in breast cancer patients occurred in patients for which no increase in the proportion of p16-expressing VIM+ CTCs was observed, and all 4 response-assessable urothelial patients with VIM+ CTC data were on study for just 2 cycles of treatment, regardless of VIM+ CTC p16 expression status (Figs. 1 and 3).