Table 4.

Various challenges associated with breast cancer drug therapy and the ways nanomedicine can be used to tackle these challenges.

Challenges to Breast Cancer Drug Therapy	How Nanomedicine Can Help
1.Low specificity for breast cancer	Nanomedicine uses passive and active targeting to enhance tumor medication levels while decreasing drug levels in noncancerous cells.
2. Undesirable pharmacokinetics such as quick clearance and short half-life	Use of strategies such as PEGlyation to extend the circulation time.
3. Anticancer drugs or excipients, such as surfactants and organic co-solvents, have dose-limiting toxicity.	Tumor progression selectivity; regulated medication release from nanocarrier; solvent- and surfactant-free nanoformulation.
4. Drug resistance at cellular level, for example, increased drug efflux transport	Both passive and active targeting may improve endocytosis; some nanoformulations may block drug efflux processes; and co-delivery of medicines that target drug resistance mechanisms may improve endocytosis.
5. Lower pH, hypoxia, cancer microenvironment interaction, and other factors contribute to drug resistance in the tumour microenvironment.	Targeting tumor microenvironment; use of stimulus-responsive nanoformulations such as pH-responsive devices.
6. Difficulty in eradicating cancer stem cells	Targeting cancer stem cells.

Abbreviation: PEG, polyethylene glycol.