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.
Overview
HER2-positive breast cancer (15-20% of cases; HER2 IHC 3+ or ISH-amplified) was the most aggressive subtype until trastuzumab (1998) made it one of the most treatable. The modern curative pathway is response-adapted: neoadjuvant chemotherapy with dual HER2 blockade (or, since 2026, T-DXd followed by THP), surgery, then either antibody completion for patients with a pathologic complete response or an ADC for residual disease (T-DM1 from KATHERINE, now T-DXd from DESTINY-Breast05). Small node-negative tumours are cured with paclitaxel-trastuzumab alone; PHERGain showed that an early PET response can spare a third of patients chemotherapy altogether. Extended adjuvant neratinib and adjuvant pertuzumab add small gains in higher-risk, node-positive disease.
Metastatic disease has been transformed twice: by CLEOPATRA's pertuzumab (OS 57 months) and then by trastuzumab deruxtecan, which beat T-DM1 by a wide margin in second line (DESTINY-Breast03) and beat THP in first line (DESTINY-Breast09, PFS 40.7 months; approved 2025). Brain metastases, which develop in up to half of patients, are now treatable systemically with tucatinib (HER2CLIMB) and T-DXd (DESTINY-Breast12). HER2CLIMB-05 (tucatinib maintenance) and PATINA (palbociclib maintenance in HR+/HER2+, approved 2026) intensify chemotherapy-free maintenance, and a wave of Chinese HER2 ADCs (trastuzumab rezetecan, BL-M07D1, ARX788, disitamab vedotin) is producing Enhertu-scale results.
Open problems are the sequencing of HER2 ADCs after T-DXd (payload cross-resistance), interstitial lung disease, cardiotoxicity across years of therapy, the cost and duration of antibody therapy, brain metastases prevention, and de-escalation: identifying the substantial fraction of patients who are over-treated. The pipeline is defined by T-DXd's move into every curative setting, tucatinib-based maintenance, next-generation and biparatopic HER2 ADCs (zanidatamab zovodotin), HER2 CAR-T and vaccines, and imaging- and ctDNA-adapted de-escalation trials.
State of the art
- T-DXd across the disease continuum.
- Chemotherapy de-escalation guided by early response.
- Response-adapted curative therapy: pCR patients de-escalate, residual disease escalates to an ADC (now T-DXd, iDFS HR 0.47 vs T-DM1).
- T-DXd across the continuum: neoadjuvant (2026), post-neoadjuvant (2026), first-line metastatic with pertuzumab (2025, PFS 40.7 months), second line, and brain metastases.
- Systemic control of brain metastases (tucatinib, T-DXd) allowing deferral of radiation.
- Chemotherapy-free maintenance intensification: tucatinib (HER2CLIMB-05) and palbociclib for HR+/HER2+ (PATINA).
- Chemotherapy omission for a third of patients using early PET response (PHERGain).
Show survival figures (1)
Averages across everyone diagnosed, often years ago. Your stage, subtype, age, fitness and the treatment you receive matter more than the average, and the numbers are improving quickly.
- Ten-year survival above 80% for early disease: the subtype with the poorest outlook in the 1990s is now one of the most treatable.
Anatomy and lymph node drainage
- Ducts (most indications start here)
- Lobules (lobular carcinoma; phyllodes tumours arise from the surrounding stroma)
- Upper outer quadrant (commonest site)
- Nipple-areola
- Nodes: axillary level I
- Nodes: axillary level II-III
- Nodes: internal mammary
- Nodes: supraclavicular
Most indications start in the ducts and drain first to the axillary nodes, which is why the armpit is checked and a sentinel node is sampled.
- Ducts (most indications start here)HER2-enriched (PAM50; highest pCR rates to HER2 blockade) · HR+/HER2+ ('triple-positive', ~50% of HER2+; lower pCR, endocrine therapy and CDK4/6 maintenance relevant) · HR-/HER2+ (higher pCR, more relapse in first 3 years) · HER2-mutant (activating mutations without amplification; T-DXd tumour-agnostic, HER2 TKIs; more common in lobular and HER2-low) · HER2 heterogeneous tumours (mixed amplified and non-amplified clones; lower pCR)
- Lobules (lobular carcinoma; phyllodes tumours arise from the surrounding stroma)HER2-mutant (activating mutations without amplification; T-DXd tumour-agnostic, HER2 TKIs; more common in lobular and HER2-low)
- Upper outer quadrant (commonest site)
- Nipple-areola
- axillary level I
- axillary level II-III
- internal mammary
- supraclavicular
Preclinical models
4 cell lines, 1 mouse models and 6 repositories are listed for this cancer.
15-20% of breast cancers (roughly 400,000 cases per year worldwide).
Show survival figures (1)
Averages across everyone diagnosed, often years ago. Your stage, subtype, age, fitness and the treatment you receive matter more than the average, and the numbers are improving quickly.
- Ten-year survival for early-stage disease treated with trastuzumab-based therapy exceeds 80%.
- FDG PETStandard of care
- Fluorothymidine F-18 (FLT)Phase 2
- HER2 PETPhase 2
Nothing recorded yet.
Also on Nuclide: Roadmaps.
Advanced diseaseShow Hide where advanced disease can reach, and what treats itThe sites decide which scans are done at staging and follow-up, and every site listed has a treatment approach.
Most people reading this do not have advanced disease. The map describes what can happen over the whole course of the illness, across autopsy and registry series; today's staging scans find spread earlier, and each site has treatments, from focused radiotherapy for a few spots to drugs that reach the brain.
What helpsT-DXd with pertuzumab first line; tucatinib and T-DXd reach brain metastases, so radiation can often be deferred; palbociclib maintenance for HR-positive disease.
Also on Nuclide: Indications.
- Bonemost common
- Livercommon
- Lungscommon
- Braincommon
Brain metastases occur in a large share of patients over the disease course; CNS activity of newer anti-HER2 drugs matters.
- Distant lymph nodescommon
Neoadjuvant THP or T-DXd → surgery → trastuzumab/pertuzumab (pCR) or T-DXd/T-DM1 (residual).
T-DXd + pertuzumab first line (DESTINY-Breast09); tucatinib + trastuzumab + capecitabine for brain metastases; palbociclib maintenance if HR+.
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).
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).
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.
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.
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+.
Subtypes & biomarkers
top- HER2-enriched (PAM50; highest pCR rates to HER2 blockade)
- HR+/HER2+ ('triple-positive', ~50% of HER2+; lower pCR, endocrine therapy and CDK4/6 maintenance relevant)
- HR-/HER2+ (higher pCR, more relapse in first 3 years)
- HER2-mutant (activating mutations without amplification; T-DXd tumour-agnostic, HER2 TKIs; more common in lobular and HER2-low)
- HER2 heterogeneous tumours (mixed amplified and non-amplified clones; lower pCR)
- Small node-negative (stage I) disease cured by de-escalated therapy
- 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)
How often this target appears
- 1987Slamon shows HER2 amplification marks aggressive disease, and a drug target
- 1987Slamon shows HER2 amplification marks aggressive disease, and a drug target
Science paper identifying HER2/neu amplification in 25-30% of breast cancers.
- 1998Trastuzumab approved
- 1998Trastuzumab approved for metastatic disease
First antibody for a solid tumour; OS benefit with chemotherapy.
- 2005Adjuvant trastuzumab halves recurrence (HERA, B-31/N9831)
- 2007Lapatinib: first HER2 pill
- 2012Pertuzumab and dual blockade (CLEOPATRA)
- 2013First solid-tumour ADC: T-DM1
- 2013T-DM1: first solid-tumour ADC; pertuzumab first pCR-based approval
- 2015APT: de-escalation for small tumours
- 2017First trastuzumab biosimilar; neratinib; APHINITY
- 2018KATHERINE: T-DM1 for residual disease
- 2019T-DXd approved; HER2CLIMB proves CNS benefit
- 2020Tucatinib, margetuximab, Phesgo approved
- 2021T-DXd beats T-DM1 (DESTINY-Breast03)
- 2021DESTINY-Breast03: T-DXd beats T-DM1
- 2024PHERGain chemotherapy omission; DESTINY-Breast12 brain metastases; zanidatamab approved (BTC)
- 2025DESTINY-Breast09 first-line approval; DESTINY-Breast05 and HER2CLIMB-05 positive; trastuzumab rezetecan approved (China, NSCLC)
- 2026T-DXd approved in early-stage disease
- 2026T-DXd approved neoadjuvant and post-neoadjuvant; palbociclib maintenance for HR+/HER2+ (PATINA)
Dated changes read from the records linked to this indication: approvals, regulatory steps, reported trials, guideline versions and milestones. Newest first; no date is inferred.
All 24 changes by month →- 2026-09-07This recordHER2-positive breast cancerFacts on this page last checked
When this page itself was last checked or edited.
- 2026MilestoneHER2-positive breast cancerT-DXd approved in early-stage disease
A milestone in how this cancer is treated.
- 2026MilestoneHER2-positive breast cancerT-DXd approved neoadjuvant and post-neoadjuvant; palbociclib maintenance for HR+/HER2+ (PATINA)
A milestone in how this cancer is treated.
- 2025MilestoneHER2-positive breast cancerDESTINY-Breast09 first-line approval; DESTINY-Breast05 and HER2CLIMB-05 positive; trastuzumab rezetecan approved (China, NSCLC)
A milestone in how this cancer is treated.
- 2024Trial resultPHERGainPHERGain reported
3-year iDFS 95.
- 2024MilestonePHERGainPHERGain chemotherapy omission; DESTINY-Breast12 brain metastases; zanidatamab approved (BTC)
A milestone in how this cancer is treated.
What is in development for HER2-positive breast cancer, drawn from the whole corpus: 3 items. Drugs are grouped by the most advanced trial phase they have reached anywhere; approved treatments sit under standard of care. Technologies are the methods being tested for this cancer, trials are the studies recorded here, and ideas are proposals not yet in a trial.
Drugs in phase 2 · 1
Technologies being tested · 1
Trials reported · 1
- PHERGain · phase 2 · 2024 · positive
Open problems and what is being done
Brain metastases in ~50% of metastatic patients.
What is being done about thisAdvanced and metastatic diseaseAlso on Nuclide: Indications.
Which patients can skip chemotherapy entirely.
Sequencing after T-DXd: no randomised data on which HER2 ADC or TKI works after TOP1-payload failure.
Interstitial lung disease with T-DXd in curative settings, where patients would otherwise be cured.
Over-treatment: which patients need pertuzumab, a full year of antibodies, or any chemotherapy at all (PHERGain-2, response-adapted trials).
Brain metastasis prevention and whether systemic-first strategies preserve cognition.
What is being done about thisAdvanced and metastatic diseaseAlso on Nuclide: Indications.
HR+/HER2+ ('triple-positive') disease: optimal integration of endocrine therapy, CDK4/6 inhibitors, and HER2 blockade.
Cardiotoxicity surveillance burden versus event rates in low-risk patients.
What is being done about thisSide effects and quality of lifeAvailable now- Site-specific conjugation & linker chemistryEstablished
In trialsNothing recorded yet.
Ideas and roadmapsNothing recorded yet.
Also on Nuclide: Dosimetry.
Global access: biosimilars have widened trastuzumab access but pertuzumab, T-DM1, and T-DXd remain unavailable in much of the world.
HER2 heterogeneity and HER2 conversion at relapse require re-biopsy strategies or HER2 PET.
Trials
topTrials recruiting now
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Landmark trials
Direct links plus the targets, companies, and technologies of this cancer's products.
technologies
4targets
1drugs
2companies
4institutions
2trials
1bottlenecks
1Latest papers
topQuery for this indication: (TITLE:"HER2-positive breast cancer" OR ABSTRACT:"HER2-positive breast cancer") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about HER2-positive breast cancer, not a curated reading list.
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