The first 60 days: HER2-positive breast cancer
HER2-positive breast cancer was once the most aggressive subtype and is now one of the most treatable, thanks to trastuzumab and, more recently, Enhertu. Below, week by week, is what OnCo's record of HER2-positive breast cancer says about the first two months: the order is typical, the timing is yours to ask about. Sections appear only where the record has something to say. Orientation, not medical advice.
Weeks 1 to 2
What happens now
Staging tests establish exactly what and where the cancer is. Everything else follows from the answers.
From the recorded treatment journey
- Core biopsy with HER2 by IHC and in-situ hybridisation; imaging; echocardiogram before anti-HER2 therapy.
Biomarkers your report may list
HER2 IHC 3+ or ISH-amplifiedHR statuspCR after neoadjuvant therapyHER2 IHC 3+ or IHC 2+ with ISH amplification (ASCO/CAP 2018 criteria); HER2 heterogeneityHR 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 therapyBrain MRI when symptomatic; surveillance MRI debatedHER2 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)
Ask which of these were tested and what the results were; see the report reader for what each value means.
Tests and imaging linked to this cancer
How it is staged
These specialties appear in the standard of care for this cancer. In most centres they meet weekly as a tumour board to agree each plan; you can ask when yours was discussed and what was decided.
- RadiologistNamed in the standard of care for: Stage II-III, neoadjuvant.
- SurgeonNamed in the standard of care for: Early stage, Stage I (≤2-3 cm, node-negative), Brain metastases.
- Medical oncologistNamed in the standard of care for: Early stage, Metastatic, Stage I (≤2-3 cm, node-negative), Stage II-III, neoadjuvant and 8 more.
- Clinical oncologist (radiotherapy)Named in the standard of care for: Post-neoadjuvant, pathologic complete response, Brain metastases.
- Palliative and supportive care teamNamed in the standard of care for: Cardiac monitoring and survivorship.
A second opinion from a centre that treats many similar cases is normal, not rude; the standard of care tells you what to compare it against.
Each row is a setting from the standard of care, in the order it usually arises. Not all will apply to you; your stage and biomarkers decide which do. The guideline grade, where recorded, says how strong the evidence is.
- 1.Early stageNCCN category Category 1, preferred: neoadjuvant pertuzumab + trastuzumab + chemotherapy; adjuvant trastuzumab; T-DM1 for residual disease Category 1, ESMO-MCBS A (KATHERINE); A (HERA); C (NeoSphere, APHINITY), NCCN Guidelines: Breast Cancer
Neoadjuvant THP or T-DXd → surgery → trastuzumab/pertuzumab (pCR) or T-DXd/T-DM1 (residual).
Surgery then weekly paclitaxel × 12 + trastuzumab × 1 year (APT); T-DM1 × 17 cycles is an alternative (ATEMPT). Endocrine therapy if HR+.
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.
Complete 1 year of trastuzumab (± pertuzumab if node-positive at diagnosis); endocrine therapy if HR+; radiation per stage.
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.
Chemotherapy + trastuzumab + pertuzumab for 1 year (APHINITY); trastuzumab alone for lower risk; 6 months acceptable where resources are limited (PERSEPHONE).
- 7.MetastaticESMO-MCBS 4 (DESTINY-Breast03); 4 (CLEOPATRA); 4 (HER2CLIMB), NCCN Guidelines: Breast Cancer
T-DXd + pertuzumab first line (DESTINY-Breast09); tucatinib + trastuzumab + capecitabine for brain metastases; palbociclib maintenance if HR+.
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).
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.
T-DXd if not used first line (DESTINY-Breast03, PFS HR 0.33 vs T-DM1); tucatinib + trastuzumab + capecitabine, especially with brain metastases (HER2CLIMB).
T-DM1; neratinib or lapatinib + capecitabine; margetuximab + chemotherapy; trastuzumab + chemotherapy (continued HER2 blockade); zanidatamab and Chinese ADCs (trastuzumab rezetecan, disitamab vedotin) where available; trials.
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+.
Decision points in the recorded journey, Stage II-III (operable)
- Was there a pathological complete response?
Generated from this cancer's standard of care, biomarkers and open problems. Take the group that matches where you are. To tick, add your own and print, open the one-page appointment sheet.
Newly diagnosed
- What is my exact diagnosis, stage, and grade, and which tests established them?Everything else follows from an accurate stage and subtype.
- Which biomarkers have been tested on my tumour (for example HER2 IHC 3+ or ISH-amplified, HR status, pCR after neoadjuvant therapy, HER2 IHC 3+ or IHC 2+ with ISH amplification; HER2 heterogeneity, HR status), and what were the results?These results decide eligibility for targeted therapy, immunotherapy, and trials.
- Which subtype is my cancer, and does that change the recommended treatment?Recognised subtypes for this cancer include HER2-enriched, HR+/HER2+, HR-/HER2+.
- Is germline (inherited) genetic testing recommended for me or my family?Inherited variants can change treatment and matter for relatives.
Early stage
- For my situation (early stage), which of the standard options do you recommend and why?Guideline options include: Neoadjuvant THP or T-DXd → surgery → trastuzumab/pertuzumab (pCR) or T-DXd/T-DM1 (residual).
- Am I a candidate for Trastuzumab, Trastuzumab deruxtecan, Trastuzumab emtansine, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of DESTINY-Breast11 apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Metastatic
- For my situation (metastatic), which of the standard options do you recommend and why?Guideline options include: T-DXd + pertuzumab first line (DESTINY-Breast09); tucatinib + trastuzumab + capecitabine for brain metastases; palbociclib maintenance if HR+.
- Am I a candidate for Tucatinib, Palbociclib, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of DESTINY-Breast09 apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Stage I (≤2-3 cm, node-negative)
- For my situation (stage i (≤2-3 cm, node-negative)), which of the standard options do you recommend and why?Guideline options include: Surgery then weekly paclitaxel × 12 + trastuzumab × 1 year (APT); T-DM1 × 17 cycles is an alternative (ATEMPT). Endocrine therapy if HR+.
- Am I a candidate for Paclitaxel / nab-paclitaxel, Trastuzumab, Trastuzumab emtansine, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of APT (adjuvant paclitaxel-trastuzumab) apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Stage II-III, neoadjuvant
- For my situation (stage ii-iii, neoadjuvant), which of the standard options do you recommend and why?Guideline options include: 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.
- Am I a candidate for Trastuzumab deruxtecan, Pertuzumab, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of DESTINY-Breast11 and PHERGain apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Post-neoadjuvant, pathologic complete response
- For my situation (post-neoadjuvant, pathologic complete response), which of the standard options do you recommend and why?Guideline options include: Complete 1 year of trastuzumab (± pertuzumab if node-positive at diagnosis); endocrine therapy if HR+; radiation per stage.
- Am I a candidate for Trastuzumab, Pertuzumab, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of APHINITY and HERA, NSABP B-31 & NCCTG N9831 (adjuvant trastuzumab) apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Post-neoadjuvant, residual invasive disease
- For my situation (post-neoadjuvant, residual invasive disease), which of the standard options do you recommend and why?Guideline options include: 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.
- Am I a candidate for Trastuzumab deruxtecan, Trastuzumab emtansine, Neratinib, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of DESTINY-Breast05 and KATHERINE apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Adjuvant (upfront surgery), node-positive
- For my situation (adjuvant (upfront surgery), node-positive), which of the standard options do you recommend and why?Guideline options include: Chemotherapy + trastuzumab + pertuzumab for 1 year (APHINITY); trastuzumab alone for lower risk; 6 months acceptable where resources are limited (PERSEPHONE).
- Am I a candidate for Pertuzumab, Trastuzumab, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of APHINITY and PERSEPHONE apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Metastatic, first line
- For my situation (metastatic, first line), which of the standard options do you recommend and why?Guideline options include: 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).
- Am I a candidate for Trastuzumab deruxtecan, Pertuzumab, Tucatinib or related drugs, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of DESTINY-Breast09 and CLEOPATRA apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Metastatic, second line
- For my situation (metastatic, second line), which of the standard options do you recommend and why?Guideline options include: T-DXd if not used first line (DESTINY-Breast03, PFS HR 0.33 vs T-DM1); tucatinib + trastuzumab + capecitabine, especially with brain metastases (HER2CLIMB).
- Am I a candidate for Trastuzumab deruxtecan, Tucatinib, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of DESTINY-Breast03 and HER2CLIMB apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Metastatic, later lines
- For my situation (metastatic, later lines), which of the standard options do you recommend and why?Guideline options include: T-DM1; neratinib or lapatinib + capecitabine; margetuximab + chemotherapy; trastuzumab + chemotherapy (continued HER2 blockade); zanidatamab and Chinese ADCs (trastuzumab rezetecan, disitamab vedotin) where available; trials.
- Am I a candidate for Trastuzumab emtansine, Neratinib, Lapatinib or related drugs, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
Brain metastases
- For my situation (brain metastases), which of the standard options do you recommend and why?Guideline options include: 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.
- Am I a candidate for Tucatinib, Trastuzumab deruxtecan, and what side effects should I expect?Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of HER2CLIMB and DESTINY-Breast12 apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Cardiac monitoring and survivorship
- For my situation (cardiac monitoring and survivorship), which of the standard options do you recommend and why?Guideline options include: 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+.
- How do the results of PERSEPHONE apply to someone like me?Trial populations differ from individual patients; ask how closely you match.
Any stage
- Are there clinical trials I could join, for example of HER2 PET, Zanidatamab, Disitamab vedotin, TQB2102?Trials are how the next standard of care is set; asking early keeps options open.
- Would a second opinion at a high-volume centre change anything, and can you help arrange it?Rare or high-stakes decisions benefit from a centre that treats many similar patients.
- What supportive care (symptom control, nutrition, exercise, mental health, financial help) is available from the start?Supportive care improves quality of life and helps patients complete treatment.
- I read that “Brain metastases in ~50% of metastatic patients”. How does that affect my plan?Open problems are where trials and second opinions matter most.
- I read that “Which patients can skip chemotherapy entirely”. How does that affect my plan?Open problems are where trials and second opinions matter most.
Trials open now for this cancer in OnCo, largest phase first. Joining a trial is a decision like any other: ask what the comparison arm is, whether a placebo is used, and what happens if you leave. The cancer page searches ClinicalTrials.gov live for more.
- A Clinical Study of Neoadjuvant Treatment With TQB2102 for Injection for Human Epidermal Growth Factor Receptor 2 (HER2) Positive Breast CancerPhase 3 · recruiting · NCT07043725A Randomized, Open-label, Multicenter, Parallel-controlled Phase III Clinical Trial to Evaluate the Efficacy and Safety of TQB2102 for Injection Versus TCbHP in Neoadjuvant Treatment of Breast Cancer With Positive HER2 Expression
- A Clinical Study of TQB2102 Versus Docetaxel Plus Trastuzumab and Pertuzumab in the Treatment of HER2 Positive Recurrent or Metastatic Breast CancerPhase 3 · recruiting · NCT07003074A Randomized, Open, Multicenter, Parallel-controlled Phase III Clinical Trial to Evaluate the Efficacy and Safety of TQB2102 for Injection Versus Docetaxel Plus Trastuzumab and Pertuzumab in the Treatment of Human Epidermal Growth Factor Receptor 2 (HER2) Positive Recurrent or Metastatic Breast Cancer
- A Phase III Study of KN026 in Combination With HB1801 ± Carboplatin as Neoadjuvant Treatment for Early or Locally Advanced HER2-Positive Breast CancerPhase 3 · active · NCT06747338A Randomized, Controlled, Open-label, Multicenter, Phase III Clinical Trial to Compare the Efficacy and Safety of KN026 Combined With HB1801 ± Carboplatin Versus Trastuzumab Combined With Pertuzumab and Docetaxel ± Carboplatin in Neoadjuvant Treatment of Early or Locally Advanced HER2-positive Breast Cancer
- A Phase III Study of KN026 in Combination With HB1801 as Adjuvant Therapy for Resectable HER2-Positive Breast CancerPhase 3 · recruiting · NCT07441460A Randomized, Controlled, Open-label, Multicenter, Phase III Clinical Study to Evaluate the Efficacy and Safety of KN026 Combined With HB1801 and Chemotherapy Versus Trastuzumab Combined With Pertuzumab and Chemotherapy as Adjuvant Therapy in Resectable HER2-positive Breast Cancer
- A Phase III Study of SHR-A1811 Injection With or Without Pertuzumab in HER2-Positive Recurrent or Metastatic Breast CancerPhase 3 · active · NCT06057610A Phase III Multicenter, Randomized, Open-label, Active-Controlled Study of SHR-A1811 With or Without Pertuzumab Versus Trastuzumab, Pertuzumab and Docetaxel in HER2-Positive Recurrent or Metastatic Breast Cancer
Much of what helps in the first weeks is free if you know to ask: testing, helplines, rides and lodging, second opinions, trial travel.
- HER2-positive breast cancer: the full pageHER2-positive breast cancer was once the most aggressive subtype and is now one of the most treatable, thanks to trastuzumab and, more recently, Enhertu.
- One-page appointment sheetYour questions, the words you may hear, what to bring, and space for the answers. Print it.
- Treatment journey: Stage II-III (operable)Chemotherapy with two HER2 antibodies for about four months before surgery; what the surgeon finds decides the next year of anti-HER2 treatment (antibodies alone, or the ADC T-DM1 if cancer remained).
- Guidelines comparedNCCN, ESMO and NICE side by side for this cancer.
- Treatment sequencingWhich treatment tends to follow which, line by line.
- NavigatorStandard of care for your stage, what you have tried, and trials near you.
Words this page and the cancer page use
- 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.
- 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.
- 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.
- Interstitial lung disease (ILD) / pneumonitis: Interstitial lung disease (ILD) is lung inflammation, a serious side effect of some ADCs (especially Enhertu) and immunotherapy.
- 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 (IHC 3+ or ISH-amplified): A cancer with too much HER2 growth-signal protein, either scored 3+ on the stain or shown to have extra copies of the gene.
- Deauville score and PET-adapted therapy: A 1-to-5 scale for how brightly a lymphoma lights up on a PET scan, compared with the liver and the middle of the chest.
- Lumpectomy (breast-conserving surgery): Removing only the tumour with a rim of normal breast, keeping the breast; almost always followed by radiotherapy.
- Deep inspiration breath-hold (DIBH): Taking and holding a deep breath during each radiation beam.
Every term links to the glossary.