Resistance of solid tumors to treatment is significantly attributed to pharmacokinetic reasons at both cellular and multi-cellular levels. Anticancer agent must be bio-available at the site of action in a cytotoxic concentration to exert its proposed activity. Solid tumor tissue is characterized by high density of vascular bed however; the vast majority of these blood vessels are not functioning. The vast majority of solid tumors can be described as poorly perfused with blood; and anticancer agents need to penetrate/distribute avascularly within solid tumor micro-milieu. Classic pharmacokinetic parameters correlate drug status within central compartment (blood) to all perfused body tissues according to their degree of perfusion. Yet, these classic pharmacokinetic parameters cannot fully elucidate the intratumoral drug penetration/distribution status of anticancer drugs due to the great discrepancies in perfusion between normal and solid tumor tissues. Herein, we will discuss the recently proposed pharmacokinetic parameters that might accurately portray the distribution of anticancer agents within solid tumor micro-milieu. In addition, we will present the new challenges attributed to these new pharmacokinetic parameters towards designing nanobiomaterial drug delivery system.