Response of SkCaP-CR PDX in castrated hosts to serial bipolar androgen therapy (sBAT). sBAT cycles initiated when cancers were ~0.3 cc [early sBAT, (red)] vs. ~0.9 cc [delayed sBAT, (blue)]. Testosterone cypionate was given via subcutaneous silastic implants (green up arrow), which elevated serum testosterone levels from <100 ng/dL to 17,300 +/− 900 ng/dL within 48 hours (i.e., SPT). When the silastic implants were removed (red down arrow), serum testosterone decreased to <100 ng/dL within 24 hours (i.e., castrate).