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ESMO Congress 2026

October 23–27, 2026 · Madrid · 3132 items

← Floor

POSTMONARCH

★★★

22 people · 23 posts · 1 abstract

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Heat now 8·Peak in the comparable set 12 (Oct 24 19:00)·Change over 24h in the comparable set –·Participants now 15

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Deep dive

In HR+/HER2- advanced breast cancer, the evidence base for abemaciclib plus fulvestrant rests on two phase III trials: MONARCH 2 in the CDK4/6i-naive setting and postMONARCH in pretreated patients, each showing the combination superior to fulvestrant alone [4]. postMONARCH was a double-blind phase III study that randomly assigned 368 patients 1:1 (abemaciclib + fulvestrant n=182; placebo + fulvestrant n=186), with investigator-assessed PFS as the primary endpoint [1]; the abemaciclib + fulvestrant arm yielded a PFS of 6.0 months, and only 8% of enrolled patients had prior abemaciclib [3]. Continuing CDK4/6 pathway inhibition beyond progression — same agent or switching to another CDK4/6i with a changed endocrine partner — had been regarded as a strategy with potential but limited evidence, with rather unsatisfactory benefit in biomarker-unselected populations [2].

At ESMO26, Kevin Kalinsky and colleagues presented the final OS analysis of postMONARCH in a rapid oral presentation (Oct. 24): among 368 patients with HR+/HER2- advanced breast cancer progressing on prior CDK4/6i + endocrine therapy, randomized to abemaciclib or placebo plus fulvestrant, median OS was 32.1 vs 24.6 months, HR 0.80 (0.60–1.06), p=0.1145, statistical significance not reached; updated PFS HR 0.78 (0.62–0.99), nominal p=0.0390; safety was consistent with the established abemaciclib profile, with no new signals.

Relative to the published primary analysis with PFS as the primary endpoint [1], this readout extends the evidence to final OS: median OS was numerically longer by 7.5 months, below the significance threshold but directionally consistent with the PFS signal. The on-site takeaway was that despite modest absolute PFS benefit, the overall evidence supports considering abemaciclib-based treatment after progression on prior CDK4/6i + ET. Several commentators framed the crux as patient selection — who remains CDK-dependent after progression — echoing the review's view that benefit is limited in biomarker-unselected populations and that ctDNA-guided continuation of CDK4/6i awaits phase III validation [2]. Notably, only 8% of postMONARCH patients had prior abemaciclib [3]; evidence for same-agent rechallenge mainly comes from the phase II again study (overall median PFS 4.2 months; 7.1 months in those switching to fulvestrant) [3].

Limitations: OS did not reach statistical significance (p=0.1145) and the PFS p-value was nominal, insufficient on its own to establish an OS benefit; the on-site posts disclosed no biomarker subgroup or subsequent-treatment data, so which patients truly benefit from continued CDK4/6 inhibition remains to be defined — as commentators noted, this is the precision question postMONARCH leaves open.

References
  1. 1.Abemaciclib Plus Fulvestrant in Advanced Breast Cancer After Progression on CDK4/6 Inhibition: Results From the Phase III postMONARCH Trial · J Clin Oncol 2025
  2. 2.Unveiling the Potential of Cyclin-Dependent Kinases 4 and 6 Inhibitors Beyond Progression in Hormone Receptor Positive/Human Epidermal Growth Factor Negative Advanced Breast Cancer - A Clinical Review · Curr Treat Options Oncol 2024
  3. 3.Abemaciclib rechallenge after progression on abemaciclib plus endocrine therapy in patients with hormone receptor-positive HER2-negative metastatic breast cancer: results from the phase II again study (WJOG14220B) · Breast Cancer Res Treat 2026
  4. 4.Imlunestrant plus abemaciclib versus fulvestrant plus abemaciclib in ER-positive, HER2-negative advanced breast cancer: an indirect treatment comparison of three phase III trials · ESMO Open 2026
  5. 5.Models of Early Resistance to CDK4/6 Inhibitors Unveil Potential Therapeutic Treatment Sequencing · Int J Mol Sci 2025
Evidence
1RO

Overall survival from the phase 3 postMONARCH trial of abemaciclib + fulvestrant vs placebo + fulvestrant for HR+, HER2- advanced breast cancer following progression on a prior CDK4/6 inhibitor + endocrine therapy

https://esmocongress.esmo.org
Floor
  3. Gil Morgan, MD

    postMONARCH 🦋 to be presented at #ESMO26

    引用@

    OncoAlert 4Sight Abstracts to be Presented at #ESMO26 1RO: Final Overall Survival Analysis of postMONARCH: Abemaciclib Plus Fulvestrant After Progression on Prior CDK4/6 Inhibitor in HR+, HER2– Advanced Breast Cancer @KalinskyKevin @BianchiniGP @ErikaHamilton9 @DrSGraff @drsarahsam @MuozMateu 🔬 Phase 3, double-blind trial (n=368): abemaciclib or placebo plus fulvestrant in HR+, HER2– ABC after progression on prior CDK4/6i + ET. Final OS analysis. ➡️ Median OS 32.1 vs 24.6 mo; HR 0.80 (0.60–1.06); p=0.1145, statistical significance not reached ➡️ Updated PFS HR 0.78 (0.62–0.99); nominal p=0.0390 ➡️ Safety consistent with the established abemaciclib profile; no new signals ✅ Numerically longer median OS, not statistically significant. While absolute PFS benefit was modest, overall evidence supports considering abemaciclib-based treatment after disease progression on prior CDK4/6i + ET. #BreastCancer 🎙️ Kevin Kalinsky 👥 Giampaolo Bianchini · Erika Hamilton · Stephanie Graff · Kyong Hwa Park · Rinath Jeselsohn · Umut Demirci · Miguel Martin · Rachel Layman · Sara Hurvitz · Sarah Sammons · Peter Kaufman · Montserrat Muñoz · Jiun-I Lai · Holly Knoderer · Cynthia Sandoval · Aarti Chawla · Bastien Nguyen · Yanhong Zhou · Elizabeth Ravenberg · Lacey Litchfield · Lillian Smyth · Seth Wander (4Sight Made from Abstracts publicly available at the ESMO website) Pinging OncoAlert Breast Cancer Faculty @matteolambe @aftimosp @E_de_Azambuja @DrSGraff @ErikaHamilton9 @hoperugo @stolaney1 @BianchiniGP @aftimosp @kevinpunie @ElisaAgostinett @to_be_elizabeth @GaiaGriguolo @JankovicK @raalbany @JavierCortesMD @JaniceTNBCmets @Prof_Nadia_H @LoiSher @jamecancerdoc @Lucarecco @Dr_Oncologista

    Same topic POSTMONARCH · 22 people#BREASTCANCER659 views11 likes2 reposts0 replies
  4. Kristina Jankovic, MD

    🚨 @OncoAlert 4Sight Abstracts to be presented at #ESMO26 🇪🇸 | Final OS results from #postMONARCH ✨👀 👇

    引用@

    OncoAlert 4Sight Abstracts to be Presented at #ESMO26 1RO: Final Overall Survival Analysis of postMONARCH: Abemaciclib Plus Fulvestrant After Progression on Prior CDK4/6 Inhibitor in HR+, HER2– Advanced Breast Cancer @KalinskyKevin @BianchiniGP @ErikaHamilton9 @DrSGraff @drsarahsam @MuozMateu 🔬 Phase 3, double-blind trial (n=368): abemaciclib or placebo plus fulvestrant in HR+, HER2– ABC after progression on prior CDK4/6i + ET. Final OS analysis. ➡️ Median OS 32.1 vs 24.6 mo; HR 0.80 (0.60–1.06); p=0.1145, statistical significance not reached ➡️ Updated PFS HR 0.78 (0.62–0.99); nominal p=0.0390 ➡️ Safety consistent with the established abemaciclib profile; no new signals ✅ Numerically longer median OS, not statistically significant. While absolute PFS benefit was modest, overall evidence supports considering abemaciclib-based treatment after disease progression on prior CDK4/6i + ET. #BreastCancer 🎙️ Kevin Kalinsky 👥 Giampaolo Bianchini · Erika Hamilton · Stephanie Graff · Kyong Hwa Park · Rinath Jeselsohn · Umut Demirci · Miguel Martin · Rachel Layman · Sara Hurvitz · Sarah Sammons · Peter Kaufman · Montserrat Muñoz · Jiun-I Lai · Holly Knoderer · Cynthia Sandoval · Aarti Chawla · Bastien Nguyen · Yanhong Zhou · Elizabeth Ravenberg · Lacey Litchfield · Lillian Smyth · Seth Wander (4Sight Made from Abstracts publicly available at the ESMO website) Pinging OncoAlert Breast Cancer Faculty @matteolambe @aftimosp @E_de_Azambuja @DrSGraff @ErikaHamilton9 @hoperugo @stolaney1 @BianchiniGP @aftimosp @kevinpunie @ElisaAgostinett @to_be_elizabeth @GaiaGriguolo @JankovicK @raalbany @JavierCortesMD @JaniceTNBCmets @Prof_Nadia_H @LoiSher @jamecancerdoc @Lucarecco @Dr_Oncologista

    Same topic POSTMONARCH · 22 peopleabemaciclib#POSTMONARCH552 views6 likes5 reposts0 replies
  11. Dra. María Natalia Gandur Quiroga

    🧬 Progression on a CDK4/6 inhibitor does not always mean the pathway is exhausted.

    引用@

    OncoAlert 4Sight Abstracts to be Presented at #ESMO26 1RO: Final Overall Survival Analysis of postMONARCH: Abemaciclib Plus Fulvestrant After Progression on Prior CDK4/6 Inhibitor in HR+, HER2– Advanced Breast Cancer @KalinskyKevin @BianchiniGP @ErikaHamilton9 @DrSGraff @drsarahsam @MuozMateu 🔬 Phase 3, double-blind trial (n=368): abemaciclib or placebo plus fulvestrant in HR+, HER2– ABC after progression on prior CDK4/6i + ET. Final OS analysis. ➡️ Median OS 32.1 vs 24.6 mo; HR 0.80 (0.60–1.06); p=0.1145, statistical significance not reached ➡️ Updated PFS HR 0.78 (0.62–0.99); nominal p=0.0390 ➡️ Safety consistent with the established abemaciclib profile; no new signals ✅ Numerically longer median OS, not statistically significant. While absolute PFS benefit was modest, overall evidence supports considering abemaciclib-based treatment after disease progression on prior CDK4/6i + ET. #BreastCancer 🎙️ Kevin Kalinsky 👥 Giampaolo Bianchini · Erika Hamilton · Stephanie Graff · Kyong Hwa Park · Rinath Jeselsohn · Umut Demirci · Miguel Martin · Rachel Layman · Sara Hurvitz · Sarah Sammons · Peter Kaufman · Montserrat Muñoz · Jiun-I Lai · Holly Knoderer · Cynthia Sandoval · Aarti Chawla · Bastien Nguyen · Yanhong Zhou · Elizabeth Ravenberg · Lacey Litchfield · Lillian Smyth · Seth Wander (4Sight Made from Abstracts publicly available at the ESMO website) Pinging OncoAlert Breast Cancer Faculty @matteolambe @aftimosp @E_de_Azambuja @DrSGraff @ErikaHamilton9 @hoperugo @stolaney1 @BianchiniGP @aftimosp @kevinpunie @ElisaAgostinett @to_be_elizabeth @GaiaGriguolo @JankovicK @raalbany @JavierCortesMD @JaniceTNBCmets @Prof_Nadia_H @LoiSher @jamecancerdoc @Lucarecco @Dr_Oncologista

    Same topic POSTMONARCH · 22 peopleabemaciclibHER2#BREASTCANCER#CDK46#ENDOCRINETHERAPY#PRECISIONONCOLOGY247 views3 likes3 reposts0 replies
  12. Mirrors of Medicine

    Looking forward to the final OS from postMONARCH at #ESMO26 👀 A 7.5-month numerical OS gain (32.1 vs 24.6 mo) that didn’t reach significance, but with a consistent PFS signal. Eage

    引用@

    OncoAlert 4Sight Abstracts to be Presented at #ESMO26 1RO: Final Overall Survival Analysis of postMONARCH: Abemaciclib Plus Fulvestrant After Progression on Prior CDK4/6 Inhibitor in HR+, HER2– Advanced Breast Cancer @KalinskyKevin @BianchiniGP @ErikaHamilton9 @DrSGraff @drsarahsam @MuozMateu 🔬 Phase 3, double-blind trial (n=368): abemaciclib or placebo plus fulvestrant in HR+, HER2– ABC after progression on prior CDK4/6i + ET. Final OS analysis. ➡️ Median OS 32.1 vs 24.6 mo; HR 0.80 (0.60–1.06); p=0.1145, statistical significance not reached ➡️ Updated PFS HR 0.78 (0.62–0.99); nominal p=0.0390 ➡️ Safety consistent with the established abemaciclib profile; no new signals ✅ Numerically longer median OS, not statistically significant. While absolute PFS benefit was modest, overall evidence supports considering abemaciclib-based treatment after disease progression on prior CDK4/6i + ET. #BreastCancer 🎙️ Kevin Kalinsky 👥 Giampaolo Bianchini · Erika Hamilton · Stephanie Graff · Kyong Hwa Park · Rinath Jeselsohn · Umut Demirci · Miguel Martin · Rachel Layman · Sara Hurvitz · Sarah Sammons · Peter Kaufman · Montserrat Muñoz · Jiun-I Lai · Holly Knoderer · Cynthia Sandoval · Aarti Chawla · Bastien Nguyen · Yanhong Zhou · Elizabeth Ravenberg · Lacey Litchfield · Lillian Smyth · Seth Wander (4Sight Made from Abstracts publicly available at the ESMO website) Pinging OncoAlert Breast Cancer Faculty @matteolambe @aftimosp @E_de_Azambuja @DrSGraff @ErikaHamilton9 @hoperugo @stolaney1 @BianchiniGP @aftimosp @kevinpunie @ElisaAgostinett @to_be_elizabeth @GaiaGriguolo @JankovicK @raalbany @JavierCortesMD @JaniceTNBCmets @Prof_Nadia_H @LoiSher @jamecancerdoc @Lucarecco @Dr_Oncologista

    Same topic POSTMONARCH · 22 people#BREASTCANCER375 views3 likes3 reposts0 replies
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