• Biosimilar: A biosimilar is a copy of a biologic drug such as trastuzumab, shown to be as safe and effective as the original once its patent expires, usually at a lower price.
• Dual HER2 blockade: Using two HER2 antibodies (trastuzumab and pertuzumab) at once, which works better than one.
• Trastuzumab cardiotoxicity: HER2 drugs can weaken the heart's pumping, usually reversibly, so heart function is checked every three months during treatment.
• 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.
• HER2-positive brain metastases: Up to half of women with metastatic HER2-positive breast cancer develop brain metastases, because antibodies control the body but historically not the brain.
• Doing less to the armpit: Over thirty years surgeons went from clearing every lymph node in the armpit, to taking only the first one or two, to leaving even a cancerous node in place, to not operating on the armpit at all in low-risk cases.
• Breast reconstruction: Rebuilding the shape of a breast after a mastectomy, either with an implant or with the woman's own tissue, at the same operation or years later.
• Lymphoedema after breast cancer treatment: Swelling of the arm, hand or breast that happens when lymph fluid cannot drain because the lymph nodes have been removed or irradiated.
• Radiotherapy after mastectomy: Radiotherapy to the chest wall, and often the nearby lymph node areas, after the breast has been removed.
• Breast conservation or mastectomy: For most early breast cancers, removing the lump with a rim of healthy tissue and then giving radiotherapy leads to exactly the same chance of being alive in twenty years as removing the whole breast.

Biomarker results to ask for: HER2 IHC 3+ or ISH-amplified, HR status, pCR after neoadjuvant therapy, HER2 IHC 3+ or IHC 2+ with ISH amplification (ASCO/CAP 2018 criteria); HER2 heterogeneity, HR status (drives triple-positive management, PATINA eligibility), Pathologic complete response after neoadjuvant therapy (selects T-DM1/T-DXd post-neoadjuvant), Early FDG-PET response (PHERGain de-escalation), LVEF by echocardiography or MUGA every 3 months on anti-HER2 therapy, Brain MRI when symptomatic; surveillance MRI debated, HER2 status on re-biopsy at progression (conversion in 10-15%), PIK3CA mutation (lower pCR; INAVO122 tests inavolisib in HER2+), ctDNA MRD (investigational for post-neoadjuvant escalation).

Scans and tests linked to this cancer: Companion diagnostics, Cytogenetics and FISH, FDG PET, Histopathology & immunohistochemistry, Mammography & tomosynthesis, AI in radiology.

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

• Stage I (≤2-3 cm, node-negative): Surgery then weekly paclitaxel × 12 + trastuzumab × 1 year (APT); T-DM1 × 17 cycles is an alternative (ATEMPT). Endocrine therapy if HR+. (APT (adjuvant paclitaxel-trastuzumab), Paclitaxel / nab-paclitaxel, Trastuzumab, Trastuzumab emtansine)
• Stage II-III, neoadjuvant: TCHP (docetaxel, carboplatin, trastuzumab, pertuzumab) or anthracycline-taxane + HP; from 2026, T-DXd × 4 → THP (DESTINY-Breast11, pCR 67%). PET-adapted chemotherapy omission (PHERGain) in trials. (DESTINY-Breast11, Trastuzumab deruxtecan, Pertuzumab, PHERGain)
• Post-neoadjuvant, pathologic complete response: Complete 1 year of trastuzumab (± pertuzumab if node-positive at diagnosis); endocrine therapy if HR+; radiation per stage. (Trastuzumab, Pertuzumab, APHINITY, HERA, NSABP B-31 & NCCTG N9831 (adjuvant trastuzumab))
• Post-neoadjuvant, residual invasive disease: T-DXd (DESTINY-Breast05, iDFS HR 0.47 vs T-DM1; approved 2026) replacing T-DM1 (KATHERINE); consider extended adjuvant neratinib for HR+ high-risk. (DESTINY-Breast05, KATHERINE, Trastuzumab deruxtecan, Trastuzumab emtansine, Neratinib)
• Adjuvant (upfront surgery), node-positive: Chemotherapy + trastuzumab + pertuzumab for 1 year (APHINITY); trastuzumab alone for lower risk; 6 months acceptable where resources are limited (PERSEPHONE). (APHINITY, PERSEPHONE, Pertuzumab, Trastuzumab)
• Metastatic, first line: T-DXd + pertuzumab (DESTINY-Breast09, PFS 40.7 months; approved 2025) or taxane + trastuzumab + pertuzumab (CLEOPATRA) followed by maintenance: HP ± tucatinib (HER2CLIMB-05) and, if HR+, endocrine therapy + palbociclib (PATINA, approved 2026). (DESTINY-Breast09, CLEOPATRA, HER2CLIMB-05, Trastuzumab deruxtecan, Pertuzumab, Tucatinib, Palbociclib)
• Brain metastases: Systemic: tucatinib triplet or T-DXd (DESTINY-Breast12, intracranial ORR 72%); local: stereotactic radiosurgery or surgery for symptomatic or large lesions; whole-brain RT reserved. (HER2CLIMB, DESTINY-Breast12, Tucatinib, Trastuzumab deruxtecan, SBRT / SABR (stereotactic radiotherapy))
• Metastatic, second line: T-DXd if not used first line (DESTINY-Breast03, PFS HR 0.33 vs T-DM1); tucatinib + trastuzumab + capecitabine, especially with brain metastases (HER2CLIMB). (DESTINY-Breast03, HER2CLIMB, Trastuzumab deruxtecan, Tucatinib)
• Metastatic, later lines: T-DM1; neratinib or lapatinib + capecitabine; margetuximab + chemotherapy; trastuzumab + chemotherapy (continued HER2 blockade); zanidatamab and Chinese ADCs (trastuzumab rezetecan, disitamab vedotin) where available; trials. (Trastuzumab emtansine, Neratinib, Lapatinib, Margetuximab, Zanidatamab, Trastuzumab rezetecan, Disitamab vedotin)
• Cardiac monitoring and survivorship: LVEF every 3 months during anti-HER2 therapy; hold and cardioprotect for declines; anthracycline-free regimens preferred; long-term surveillance for late recurrence in HR+/HER2+. (Cardio-oncology, PERSEPHONE)

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