📬 Breast Cancer Intelligence Digest — Week 2026-W36

ASCO's 2026.1.0 Living Guideline for stage I-III HR+/HER2- breast cancer ties adjuvant intensification to 10-year mortality thresholds, OlympiA reports sustained olaparib benefit at 6.1 years, and elacestrant combinations, HER2 ADCs and first-line mTNBC algorithms dominated the week's discussion.

⚡ TL;DR

📄 Publications

Medical Therapy for Hormone Receptor-Positive, HER2-Negative Stage I-III Breast Cancer: ASCO Living Guideline, Version 2026.1.0. — Forty-five randomized clinical trials (68 references) published from 2018-2026 informed the guideline
Sustained benefit of adjuvant olaparib in women with germline BRCA1- and BRCA2- -associated high-risk HER2-negative early breast cancer: Updated results from the OlympiA phase III trial. — At 6.1 years median follow-up, olaparib benefit was maintained for IDFS (HR 0.65), DDFS (HR 0.65) and OS (HR 0.72)

🐦 Twitter / 🦋 Bluesky

ASCO Living Guideline 2026.1.0 pegs adjuvant intensification in HR+/HER2- disease to 10-year mortality thresholds — and clinicians ask which model generates the number — The guideline links treatment decisions to thresholds for 10-year risk of breast cancer death: OFS + AI if >10%, CDK4/6i recommended if >25% and considered at 10-25%, with the same framework for olaparib
OlympiA at 6.1 years: adjuvant olaparib holds a 4% overall survival gain with no late MDS/AML signal — At 6.1 years median follow-up olaparib maintained IDFS HR 0.65, DDFS HR 0.65 and OS HR 0.72
ELEVATE published: elacestrant plus everolimus reaches 8.3-month median PFS after CDK4/6 inhibition, regardless of ESR1 or PIK3CA status — The elacestrant/everolimus arm of ELEVATE (n=73) used recommended doses of elacestrant 345 mg plus everolimus 7.5 mg and produced median PFS of 8.3 months irrespective of ESR1/PIK3CA mutations
First-line metastatic TNBC algorithms: ADCs move into the front line and inavolisib's evidence-matched patient gets harder to find — The 2026 shift places ADCs in the first-line conversation, with pembrolizumab plus sacituzumab govitecan for CPS >=10 and DFI >=6 months, and Dato-DXd or SG for PD-L1-negative, gBRCA-wild-type disease
TROPION-Breast02: Dato-DXd nearly triples time to deterioration in quality of life versus chemotherapy in first-line mTNBC — Dato-DXd produced a near 3-fold prolongation in quality-of-life preservation versus chemotherapy, with time to deterioration 23.5 versus 8.3 months and HR 0.64

Full details below ↓

📄 What's Being Published

Manuscripts:

SHR-A2102, a nectin-4 directed antibody-drug conjugate, in patients with pretreated advanced solid tumours: a multicentre, single-arm, phase 1 trial. — Zhong Runbo et al., Lancet Oncol

This phase 1 trial enrolled and treated 395 patients across study stages, including 32 with hormone receptor-positive, HER2-negative breast cancer and 36 with triple-negative breast cancer. Grade 3–4 treatment-related adverse events occurred in 212 (54%) of 395 patients, most commonly decreased neutrophil count (30%). One dose-limiting toxicity — a grade 4 decreased platelet count — occurred at 10 mg/kg, and the maximum tolerated dose was not reached.

Clinical bottom line: A nectin-4 directed topoisomerase I payload ADC is tolerable across a 2–10 mg/kg range and produced activity in a phase 1 population that included 68 patients with HR+/HER2- or triple-negative breast cancer, making breast cohorts a legitimate target for the ongoing programme.

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Medical Therapy for Hormone Receptor-Positive, HER2-Negative Stage I-III Breast Cancer: ASCO Living Guideline, Version 2026.1.0. — Caswell-Jin Jennifer L et al., J Clin Oncol

Forty-five randomized clinical trials (68 references) published from 2018–2026 informed the guideline, with supplemental searches identifying six individual patient data meta-analyses and 21 retrospective studies. Endocrine therapy remains the foundation of treatment for stage I–III hormone receptor-positive, HER2-negative breast cancer, with chemotherapy and targeted therapies reserved for selected patients to further reduce the risk of recurrence and breast cancer death.

Clinical bottom line: Adjuvant decisions in stage I–III HR+/HER2- disease should now be driven by estimated absolute recurrence risk and genomic assays rather than eligibility alone, with endocrine therapy as the non-negotiable backbone.

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Sustained benefit of adjuvant olaparib in women with germline BRCA1- and BRCA2- -associated high-risk HER2-negative early breast cancer: Updated results from the OlympiA phase III trial. — Garber J E et al., Ann Oncol

The OlympiA trial randomised 1,836 patients with germline BRCA1 or BRCA2 pathogenic variants and high-risk HER2-negative early breast cancer to one year of adjuvant olaparib or placebo. At 6.1 years median follow-up, olaparib benefit was maintained for IDFS (HR 0.65, 95% CI: 0.53, 0.78), DDFS (HR 0.65, 95% CI: 0.53, 0.81), and OS (HR 0.72, 95% CI: 0.56, 0.93), with 6-year OS of 87.5% versus 83.2% (difference 4.4%, 95% CI: 0.9%, 6.7%). Adverse events of special interest were not increased with olaparib versus placebo (6.3% versus 9.3%), including MDS/AML (0.4% versus 0.7%).

Clinical bottom line: With six years of follow-up and no excess MDS/AML, one year of adjuvant olaparib should be offered to every patient with a germline BRCA1/2 variant and high-risk HER2-negative early breast cancer, including those with hormone receptor-positive disease.

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Systemic Therapy Considerations in Older Adults With Early-Stage Breast Cancer: A Review. — Smith Claire E et al., JAMA Oncol

This review addresses the complex decision-making involved in treating older adults with early-stage breast cancer, where recurrence risk must be weighed against treatment harm in a population still underrepresented in therapeutic trials. Novel strategies covered include adjuvant CDK4/6 inhibitors in hormone receptor-positive disease and neoadjuvant pembrolizumab in triple-negative breast cancer. The authors caution against both overtreatment of lower-risk cancers and undertreatment of higher-risk cancers, noting that each carries distinct mortality consequences in older patients.

Clinical bottom line: In patients over 70, chemotherapy decisions should follow geriatric assessment, toxicity risk, and competing mortality rather than chronological age, because both reflex de-escalation and reflex escalation cost lives.

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Pathologic Complete Response (pCR) Rate and Predictors of Response to Taxane, Trastuzumab, and Pertuzumab in HER2‑Positive Breast Cancer: Secondary Analyses of EA1181/CompassHER2 pCR. — Tung Nadine et al., J Clin Oncol

Among 2,141 patients who initiated THP, the overall pCR rate was 43.8%: 63.7% in HER2+/ER-negative and 32.4% in HER2+/ER-positive tumors, drawn from a total enrolled population of 2,175 patients. Higher pCR rates were observed in tumors that were ER-negative or low ER expressing, progesterone receptor-negative or low expressing, HER2 IHC 3+, and in patients treated with once per week paclitaxel. Among 569 patients assessed for HER2DX pCR score, a high score was independently associated with higher pCR rates after adjustment for clinicopathologic variables.

Clinical bottom line: With the full CompassHER2-pCR secondary analysis now published in JCO, chemotherapy-light neoadjuvant THP clears nearly two-thirds of HER2+/ER-negative tumors, weekly paclitaxel should be preferred over q3w docetaxel, and HER2DX adds predictive information beyond standard clinicopathology.

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🗂 Every paper considered this week, including the ones that didn’t make it →

🗣️ What People Were Discussing This Week

How these are chosen: filtered for clinical relevance, grouped by the new development discussed, then ordered by engagement (bookmarks and reposts).

ASCO Living Guideline 2026.1.0 pegs adjuvant intensification in HR+/HER2- disease to 10-year mortality thresholds — and clinicians ask which model generates the number

The most notable structural change in ASCO's 2026.1.0 guideline is that it ties adjuvant treatment decisions to explicit 10-year breast cancer mortality thresholds: ovarian function suppression plus an aromatase inhibitor is recommended if risk exceeds 10%; CDK4/6 inhibitors are recommended above 25%, considered at 10–25%, and generally not offered below 10%; olaparib follows the same greater-than-25% / 10–25% / less-than-10% framework; and anthracyclines are favored above 25%, considered at 20–25%, and generally avoided below 20%. The panel favors abemaciclib over ribociclib when both are applicable and prioritizes one year of adjuvant olaparib over CDK4/6 inhibition in high-risk germline BRCA1/2 or PALB2 carriers; for low ER expression (<10%) stage II–III disease, neoadjuvant treatment may follow a TNBC-style regimen with taxane, carboplatin, anthracycline, and pembrolizumab, while neoadjuvant CDK4/6 inhibitors have insufficient evidence for routine use. Clinicians reviewing the guideline have noted that these are pragmatic panel-set cutoffs rather than predictive cutoffs derived from randomized trials, and that the guideline does not specify which risk model should be used — a point sharpened by the observation that so-called low-risk disease today may carry long-term risk shaped by the choice and duration of endocrine therapy. After two days of review, key questions remained open: when, under which treatments, and with which tool risk should be estimated.

Discussed by: @womenofteal, @OncBrothers, @EladSharonMD, @womenofteal, @K_Yadavir, @ulvyeoflas

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OlympiA at 6.1 years: adjuvant olaparib holds a 4% overall survival gain with no late MDS/AML signal

At 6.1 years median follow-up, OlympiA confirms that one year of adjuvant olaparib in patients with high-risk, germline BRCA1/2-mutated, HER2-negative early breast cancer maintains an approximately 9% IDFS benefit and 4% OS benefit: IDFS HR 0.65 (95% CI: 0.53, 0.78), DDFS HR 0.65 (95% CI: 0.53, 0.81), OS HR 0.72 (95% CI: 0.56, 0.93), and 6-year OS of 87.5% versus 83.2% (difference 4.4%, 95% CI: 0.9%, 6.7%). The benefit remains consistent across key subgroups, and adverse events of special interest were not increased — MDS/AML occurred in 0.4% versus 0.7% with olaparib versus placebo. ASCO's new early breast cancer guideline offers one year of adjuvant olaparib to selected high-risk germline BRCA1/2/PALB2 carriers, though questions about how olaparib interacts with pembrolizumab and CDK4/6 inhibitors remain open.

Discussed by: @stolaney1, @K_Yadavir, @womenofteal

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ELEVATE published: elacestrant plus everolimus reaches 8.3-month median PFS after CDK4/6 inhibition, regardless of ESR1 or PIK3CA status

In the phase Ib/II ELEVATE trial, elacestrant 345 mg plus everolimus 7.5 mg produced a median PFS of 8.3 months and an ORR of 19.5% in ER+/HER2-negative metastatic breast cancer after CDK4/6 inhibition, with activity irrespective of ESR1 or PIK3CA mutation status. Among 50 phase 2 patients, most adverse events were grade 1–2, with low rates of treatment withdrawal or dose reduction, and the lower dose of everolimus was noted to be effective with less toxicity. Read alongside evERA and VIKTORIA-1, these findings suggest that the primary potential of oral SERDs may lie less in monotherapy and more in serving as an endocrine backbone for PI3K/AKT/mTOR pathway inhibitors, with the phase 3 ADELA trial ongoing to confirm these results.

Discussed by: @stolaney1, @stolaney1, @stolaney1, @OncoAlert

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First-line metastatic TNBC algorithms: ADCs move into the front line and inavolisib's evidence-matched patient gets harder to find

The 2026 shift in first-line metastatic TNBC places ADCs directly into the treatment conversation: the proposed decision sequence runs PD-L1, then disease-free interval, then germline BRCA status, then early relapse, with pembrolizumab plus sacituzumab govitecan favored for CPS ≥10 with DFI ≥6 months, and datopotamab deruxtecan or sacituzumab govitecan for PD-L1-negative, germline BRCA-wild-type disease. The contemporary fit of inavolisib is narrowed by the fact that INAVO120 enrolled an essentially CDK4/6-naive population — 98.8% had no prior CDK4/6 inhibitor exposure. Both TROP2 ADCs hold NCCN 2026 category 1 status in first-line mTNBC with no head-to-head trial and no sequencing trial, and prior TOP1 ADC exposure collapses activity from the next agent at 52 days versus 455; as ADCs with similar targets and payloads accumulate, sequencing and dose-optimization data are needed to establish which drug, for whom, in what order, and at what dose.

Discussed by: @ChandrakanthMv, @ChandrakanthMv, @JaniceTNBCmets, @DrBarbiOnc

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TROPION-Breast02: Dato-DXd nearly triples time to deterioration in quality of life versus chemotherapy in first-line mTNBC

The ASCO 2026 PFS2 analysis of TROPION-Breast02 adds to the established first-line mTNBC data for datopotamab deruxtecan: PFS2 was 15.6 versus 11.8 months and time to first subsequent therapy was 10.9 versus 5.6 months versus chemotherapy. On patient-reported outcomes, Dato-DXd produced a near three-fold prolongation in quality-of-life preservation versus chemotherapy, with time to deterioration of 23.5 versus 8.3 months and HR 0.64 — a dataset that clinicians characterized as signaling a shift toward quality survival in the absence of direct comparisons between the two category 1 TROP2 ADCs.

Discussed by: @Dr_Oncologista, @DrBarbiOnc

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RC48-C006: disitamab vedotin doubles PFS versus lapatinib plus capecitabine in HER2+ breast cancer with liver metastases, but not against T-DXd

RC48-C006 reported that in HER2-positive breast cancer with liver metastases, disitamab vedotin improved PFS versus lapatinib plus capecitabine at 9.9 versus 4.9 months (HR 0.56). For context, in DESTINY-Breast03 among patients with visceral disease, PFS with T-DXd versus T-DM1 was 22.2 versus 5.7 months (HR 0.28), though a liver-specific analysis was not reported. Because prior ADC therapy was excluded from RC48-C006, the trial cannot answer whether disitamab vedotin retains activity after T-DXd as an ADC with a different payload — its most plausible clinical niche. Separately, HORIzON-Breast01 placed trastuzumab rezetecan on the HER2 ADC map with PFS of 18.0 versus 5.6 months (HR 0.28) over pyrotinib plus capecitabine in previously treated HER2-positive metastatic disease, though OS data remain immature and no comparison against T-DXd exists.

Discussed by: @stolaney1, @ChandrakanthMv

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🔥 Top Ranked Tweets

PrECOG @PrECOGonc

RT @eaonc: ICYMI: @FDA has approved palbociclib w/ trastuzumab, +/- pertuzumab, & endocrine therapy for the treatment of HR+, HER2+ locally advanced or metastatic #BreastCancer. This is based on the PATINA trial, for which @PrECOGonc was a collaborator. https://t.co/vjr4yFEMX8

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