• Tumour-infiltrating lymphocytes (TILs): Immune cells that have got inside the tumour.
• Residual cancer burden (RCB): A pathology score for how much cancer remains in the breast and lymph nodes after pre-surgery treatment, from 0 (none) to III (a large amount), combining tumour bed size, cellularity and nodal involvement.
• Homologous recombination deficiency (HRD): A tumour that cannot properly repair double-strand DNA breaks, usually because of BRCA or related gene loss.
• HER2-low and HER2-ultralow: Tumours with a little HER2 (IHC 1+ or 2+ without amplification), or a trace (ultralow), which older HER2 drugs ignored but Enhertu can attack.
• PAM50 / intrinsic subtypes: A 50-gene test that sorts breast cancers into luminal A, luminal B, HER2-enriched, and basal-like.
• ADC sequencing: The open question of whether a second ADC works after the first one fails, especially when both carry the same type of payload.
• Cancer health disparities and equity: Systematic differences in who gets cancer, how early it is found and who survives, driven by race, income, geography, insurance and structural racism rather than biology alone.
• Hormone receptor status (ER / PR): Whether a breast cancer's cells carry receptors for oestrogen (ER) and progesterone (PR).
• Dose-dense and metronomic chemotherapy: Two opposite ways of rescheduling the same drugs: dose-dense gives standard doses more often (every two weeks instead of three, supported by growth factors) to deny the tumour recovery time; metronomic gives small doses continuously to attack tumour blood vessels with little toxicity.
• Lumpectomy (breast-conserving surgery): Removing only the tumour with a rim of normal breast, keeping the breast; almost always followed by radiotherapy.

Biomarker results to ask for: PD-L1 (22C3 CPS ≥10 for metastatic pembrolizumab), Germline BRCA1/2 and PALB2 (PARP inhibitors, surgery choices), HRD score, TILs (prognostic; de-escalation trials), HER2-low status (T-DXd eligibility), TROP2 (not required for TROP2 ADCs; PET tracers in development), Ki-67, grade, ctDNA/MRD (Signatera, investigational), AR (LAR subtype trials), TMB / MSI (rare, tumour-agnostic IO).

Scans and tests linked to this cancer: Companion diagnostics, Germline (hereditary) testing, Histopathology & immunohistochemistry, HRD & BRCA testing, Liquid biopsy (ctDNA), Mammography & tomosynthesis.

Bring copies of scan reports, pathology and blood results, and a list of every medicine and supplement.

• Stage I (T1a-b N0): Surgery ± radiation; chemotherapy for ≥T1c; TIL-high tumours have >90% 5-year RFS even without chemotherapy (OPTimal, ETNA, TIL-CHOICE cohorts). De-escalation trials ongoing. (Sentinel lymph node biopsy, Histopathology & immunohistochemistry)
• Stage II-III: Neoadjuvant pembrolizumab + carboplatin/paclitaxel → AC/EC, surgery, adjuvant pembrolizumab (KEYNOTE-522). Germline BRCA + residual disease: olaparib 1 year (OlympiA). Residual disease without BRCA: capecitabine (CREATE-X). Radiation per stage. (KEYNOTE-522, Pembrolizumab, Carboplatin, Olaparib, OlympiA)
• Metastatic, first line, PD-L1 CPS ≥10: Pembrolizumab + chemotherapy (KEYNOTE-355) or sacituzumab govitecan + pembrolizumab (ASCENT-04, approved 2026). (KEYNOTE-355, ASCENT-04 / KEYNOTE-D19, Sacituzumab govitecan, Pembrolizumab)
• Metastatic, first line, PD-L1 negative or PD-1 ineligible: Datopotamab deruxtecan (TROPION-Breast02, OS benefit) or sacituzumab govitecan (ASCENT-03), both approved 2026; PARP inhibitor if germline BRCA; chemotherapy. (TROPION-Breast02, ASCENT-03, Datopotamab deruxtecan, Olaparib)
• Metastatic, later lines: Whichever TROP2 ADC was not used first (cross-resistance uncertain); T-DXd if HER2-low (DESTINY-Breast04); iza-bren where available; chemotherapy (eribulin, capecitabine); clinical trials. (Trastuzumab deruxtecan, Izalontamab brengitecan, DESTINY-Breast04)

From the standard of care recorded for this cancer; which apply depends on your stage and biomarkers. Ask which the team recommends and why.