“…However, a recent study reporting metastasis to the bone from a 4T1-derived primary tumor [142] may provide a model system for the evaluation of bone-targeted anticancer nanomedicines or combination approaches with radiotherapy or photodynamic therapy (PDT) [143] . In general, the limitations regarding the generation of metastasis using subcutaneous and orthotopic models [64] , [131] require the application of complementary experimental models to evaluate nanomedicines that target metastasis [130] , [144] , [145] .…”