Nanomedicine offers unique advantages in treating human cancers. However, physiological and pathological barriers within normal and disease tissues, which are highly variable among individuals, often hinder its effectiveness. The body possesses specific innate responses to nanoparticles (NPs), which when combined with unique pathophysiological signatures in the tumor microenvironment, can severely limit the utility of nanomedicine in the oncological setting. Furthermore, with the successes of cancer immunotherapies, understanding nanoimmune interactions and developing immune-smart cancer nanomedicine that can take advantage of the body's immune functions will increasingly become clinically relevant. Therefore, a better understanding of the important native and acquired biological processes that dictate the fate of nanomedicine is integral to developing more effective individualized platforms for treating cancer patients.