ESMO Breast 2026 Conference Intelligence

Full approval based on VERITAC-2 (n=624, 270 ESR1m): mPFS 5.0 vs 2.1 mo (HR 0.57, p=0.0001) and ORR 19% vs 4% vs fulvestrant in the ESR1m population. Approved a month ahead of PDUFA. Guardant360 CDx co-approved as companion diagnostic. 200 mg once daily oral.

Approval based on DESTINY-Breast09: T-DXd + pertuzumab achieved mPFS 40.7 vs 26.9 mo (HR 0.56, p<0.0001) and ORR 87% vs 81% vs THP. Granted Priority Review and Breakthrough Therapy Designation. OS data immature at PFS analysis (16% events).

Despite a 56% PFS improvement in SERENA-6 (16.0 vs 9.2 mo, HR 0.44), ODAC rejected pre-progression switching as a paradigm — citing immature OS (63% follow-up), cardiac signals (QTc, Torsades with ribociclib), and the unresolved question of whether switching at ESR1m vs radiographic progression actually benefits patients long-term. Lipkowitz: PFS alone doesn't establish meaningful benefit here.

Pre-meeting briefing flags immature OS, cardiac safety (heart-rate lowering, QT prolongation, Torsades event with ribociclib), and the unresolved question of whether switching at ESR1m detection vs at radiographic progression provides long-term benefit. FDA: overall positive benefit-risk not established. Direct primary-source PDF.

Phase 3 trial in 927 patients: T-DXd followed by paclitaxel + trastuzumab + pertuzumab significantly outperformed ddAC-THP in pCR (67.3% vs 56.3%, +11.2 points, p=0.003) with markedly lower grade ≥3 AEs (37.5% vs 55.8%) and reduced LV dysfunction.

Phase 3 in 644 patients: Dato-DXd improved mPFS to 10.8 vs 5.6 months (HR 0.57, p<0.0001) and mOS to 23.7 vs 18.7 months (HR 0.79, p=0.029) vs investigator-choice chemotherapy, with comparable grade ≥3 AEs and lower discontinuation (4% vs 7%).

ctDNA-guided switch from AI to camizestrant + CDK4/6i at ESR1m emergence delayed deterioration in global health (HR 0.54), pain (HR 0.57), fatigue (HR 0.75), and physical functioning (HR 0.74) vs continued AI + CDK4/6i.

Phase 3 final OS analysis confirms inavolisib triplet improves overall survival vs placebo + palbociclib + fulvestrant in 1L PIK3CA-mutated, endocrine-resistant advanced breast cancer — establishing new standard for this molecularly defined subset, with benefit consistent across hyperglycemia status.

Priority Review granted for T-DXd in patients with residual invasive HER2+ disease after neoadjuvant treatment. Based on DESTINY-Breast05: 53% reduction in IDR or death vs T-DM1 (HR 0.47, p<0.0001), 51% reduction in distant-recurrence risk, 36% reduction in brain-metastasis risk. Decision expected just after ESMO Breast 2026.

Filing based on DESTINY-Breast11: T-DXd → THP delivered 67.29% pCR vs 56.25% with ddAC-THP (Δ +11.17 pts, p=0.003). PDUFA target action date sits 10 days after the close of ESMO Breast 2026, positioning a potential decision during or immediately after the congress. China NMPA already conditionally approved Mar 27, 2026 — first global ADC approval in curative-intent eBC.

sBLA based on TROPION-Breast02 (n=644): mPFS 10.8 vs 5.6 mo (HR 0.57), mOS 23.7 vs 18.7 mo (HR 0.79, p=0.0291), cORR 62.5% vs 29.3%. Reviewed under Project Orbis. PDUFA target Q2 2026 — possible decision during or shortly after ESMO Breast 2026.

First pan-mutant selective PI3Kα inhibitor to receive BTD. ReDiscover Phase 1/2 at Phase 3 dose (400 mg BID): 11.1 mo mPFS in heavily pretreated patients, ORR 43% (52% in 2L). Activity comparable across kinase and non-kinase domain mutations. Phase 3 ReDiscover-2 launching.

First-in-class oral DNA polymerase theta (Polθ) inhibitor combined with olaparib. Phase 1/2a (NCT05898399) showed favorable tolerability monotherapy, no DDI with olaparib, and clinical signals across DNA-damage-response–altered solid tumors. Global randomized Phase 2 launching in gBRCA HER2- BC.

Filing based on Phase 3 evERA: giredestrant + everolimus reduced risk of progression or death by 44% ITT and 62% in ESR1m population vs SOC endocrine + everolimus. Could become first oral SERD combo approved post-CDK4/6i.

Giredestrant reduced risk of invasive disease recurrence or death by 30% (HR 0.70, p=0.0014) vs SOC endocrine therapy in ER+/HER2- early breast cancer at pre-specified interim analysis — first major endocrine advance in 20+ years. 3-year IDFS 92.4% vs 89.6%.

Company press recap of T-DXd, Dato-DXd and HER3-DXd data at ESMO Breast 2026 — covering DESTINY-Breast11 RCB analysis, TROPION-Breast02 OS, and HERTHENA program updates as Daiichi positions to transform standards of care across breast cancer subtypes.

Phase 3 final OS analysis confirms inavolisib triplet improves overall survival in 1L PIK3CA-mutated, endocrine-resistant advanced breast cancer — establishing new standard for this molecularly defined subset.

Biotheryx Phase 1A dose-escalation in heavily pretreated HR+/HER2- MBC: BTX-9341 — a first-in-class oral CDK4/6 bifunctional degrader that also inhibits CDK2 transcription — produced 41.7% clinical benefit rate post-CDK4/6i with neutropenia as the principal toxicity. Moving into expansion cohorts.

Global Phase 2 of BNT325/DB-1305 (TROP2 ADC) plus pumitamig (PD-L1 × VEGF-A bispecific) plus chemotherapy: cORR 61.5%, uORR 71.8%, DCR 92.3% — activity preserved in PD-L1 low/negative disease. Phase 3 ROSETTA-BREAST-01 launching as a 1L mTNBC registrational study.

Pivotal Phase 3 randomizes 1:1 to HER3-DXd monotherapy vs physician-choice chemotherapy (paclitaxel, nab-paclitaxel, capecitabine, liposomal doxorubicin) or trastuzumab deruxtecan in pretreated HR+/HER2- MBC. ESMO Breast 2026 update: enrollment progressing globally.

Preclinical data show robust activity across PDX models with low-to-high FAP expression and a Tumor Selectivity Index 3× higher than marketed ADCs. First patient dosed in FOCUS-01 Phase 1 in March 2026; initial clinical readout expected later in 2026.

Olubukola Ayodele (Leicester) frames the conference's three central themes: chemotherapy de-escalation in HER2+ disease (DESTINY-Breast11, PHERGain-2, TRAIN-4), ADC dominance across subtypes, and biomarker-driven sequencing.

Comprehensive preview of TROPION-Breast02, DESTINY-Breast11, SATEEN, HER2CLIMB-02, PREcoopERA, PERSEVERE, MIRINAE, SACI-IO HR+, and other key abstracts shaping breast oncology practice.

Marla Lipsyc-Sharf (UCLA): real-world Signatera data from 7,984 adjuvant breast cancer patients shows positive ctDNA changes management in >80% of cases, with median 13.3 months lead time before radiographic recurrence.

In 5,724 surveillance samples from high-risk HR+/HER2- eBC patients, ctDNA was detected in only 1.87%; 42.9% of those positives already had radiographic recurrence at first detection (65.9% at Month 0). Morganti argues ultrasensitive tumor-informed assays and earlier first sampling are needed for MRD utility.

SATEEN (sacituzumab govitecan + trastuzumab post T-DXd) showed ORR 3.7%, mPFS 2.3 mo, mOS 9.2 mo in heavily pretreated HER2+ MBC. Patritumab deruxtecan also showed limited activity in TOPO1-ADC–pretreated patients — Grinda argues the shared TOPO1 payload, not the target, drives cross-resistance.

Video discussion of HER2CLIMB-02 data: tucatinib added to T-DM1 in HER2+ MBC after prior trastuzumab + taxane, with PFS and intracranial activity reviewed alongside safety and emerging sequencing implications post T-DXd.

In small node-negative HER2 3+ tumors, neoadjuvant trastuzumab + pertuzumab alone delivered 59.6% pCR; pCR responders staying chemo-free had a 37.3% rate of ≥10% HRQoL decline vs 51.9% for non-responders requiring T-DM1 ± chemo — reinforcing PHERGain’s PET-adapted de-escalation philosophy.

28-day window study in untreated ER+/HER2- premenopausal eBC: giredestrant + triptorelin reduced Ki67 by 79.6% (geometric mean) vs 73.7% for anastrozole + triptorelin and 68.2% for giredestrant alone — confirming ovarian suppression remains essential and that giredestrant alone did not meet non-inferiority.

Updated safety/PRO analysis: dexamethasone mouthwash cut grade ≥2 stomatitis to 14.4% vs 21.1% without prophylaxis and delayed onset to 20 vs 13 days. Time to deterioration in role functioning numerically favored giredestrant arm (7.3 vs 4.6 mo, HR 0.73).

Lambertini frames the conference’s through-line: prospective trials (DESTINY-Breast11, PHERGain/PHERGain-2, TRAIN-3/4) increasingly support biomarker- and imaging-guided de-escalation — yet a 38-country survey shows uneven uptake across Europe blocked by test access, costs, and reimbursement.