Pharmacodynamic Biomarkers of Standard Anti-microtubule Drugs as Assessed by Early Tumor Biopsy

During the screening visit, the following will be taken: medical history; physical exam; ECOG performance status; a pregnancy test if indicated per physician (confirmation of the clinical testing result or assessment of the treating physician whether or not the subject is capable of pregnancy); AST, ALT, CBC (per oncologist); 15 mL blood sample for drug level assessment; 15 mL blood sample for circulating tumor DNA (ctDNA); follow up assessments of cancer; RECIST 1.1 response measurements; and an archived FFPE sample (8 slides) will be obtained. While enrolled on study, subjects will have the following procedures: * 15 mL blood sample for drug level assessment on C1D2 * 15 mL blood sample for circulating tumor DNA (ctDNA) on C1D2 and at progression or end of study for a total of 30 mL * Adverse events related to study procedures (research biopsy \& blood draws) will be assessed on C1D2 and at progression or end of study * Toxicity evaluations will occur throughout the study per the treating MD * Follow-up assessments of cancer will occur throughout the study per the treating MD * RECIST 1.1 response measurements will be taken at standard of care imaging * Fresh biopsy or tumor sampling (4 cores) for analysis of intratumoral drug levels and biomarkers including: markers of proliferation (mitotic index), aneuploidy, and sequencing analysis (ctDNA) on C1D2. The tests being performed on the samples as part of this study are not investigational. Subjects will be followed with imaging scans and tumor markers as deemed appropriate by the treating physician. Follow-up scans will be recommended every \~3 cycles as per standard of care. Subjects will be followed for the duration of treatment initiated while taking part in this study. Follow-up will discontinue either 2 months following completion of planned breast cancer treatment or upon the systemic imaging following therapy completion (whichever is later).