Day 3 — Sunday, May 31¶

This was the load-bearing day of ASCO 2026: the Plenary Session, where five late-breaking abstracts (LBA1–LBA5) were chosen as the meeting's most consequential. The standing-ovation headline belonged to GI — RASolute 302, the first positive phase 3 of a pan-RAS inhibitor in pancreatic cancer — but the Plenary spanned prostate, sarcoma, and two practice-shifting lung readouts, and the GI track delivered a second win in colorectal cancer alongside it.

The Plenary headliner: pancreatic cancer finally moves¶

In second-line metastatic pancreatic ductal adenocarcinoma, the oral RAS(ON) multi-selective inhibitor daraxonrasib nearly doubled median overall survival versus investigator's-choice chemotherapy — 13.2 vs 6.7 months (HR 0.40, P<.0001) — with PFS 7.2 vs 3.6 months, ORR 31.6% vs 11.2%, and fewer grade ≥3 events (43.6% vs 57.5%). RASolute 302 (LBA5, N=500) is the first phase 3 RAS-inhibitor win in PDAC and was published simultaneously in NEJM — described from the podium as the most consequential shift in pancreatic treatment in over a decade.

GU and sarcoma: two more Plenary firsts¶

PROTEUS (LBA1) established a new standard for high-risk localized prostate cancer: perioperative apalutamide + ADT cut metastasis/death risk 20% versus ADT alone (MFS HR 0.80), with pCR/MRD of 8.9% vs 1.0% and subsequent therapy delayed by 33 months (N=2,109).

SARC041 (LBA2) was the first-ever positive phase 3 in dedifferentiated liposarcoma: abemaciclib extended median PFS to 9.7 vs 1.5 months, a ~62% reduction in progression/death versus placebo — a genuine new option in a track starved of them.

Lung: an adjuvant first and a bispecific OS win¶

Two of the five Plenary slots went to thoracic oncology. LIBRETTO-432 (LBA3) made adjuvant selpercatinib the first targeted option for resected RET fusion–positive NSCLC, reporting an 83% reduction in recurrence or death (EFS) versus placebo. HARMONi-6 (LBA4) delivered the first overall-survival win for a PD-1×VEGF bispecific: ivonescimab + chemo beat tislelizumab + chemo in 1L squamous NSCLC, mOS 27.89 vs 23.69 months. A subtype subanalysis of IMforte (Abstract 8014) also reported during the session, dissecting whether SCLC transcriptomic subtypes drive the maintenance lurbinectedin + atezolizumab benefit.

GI, beyond the Plenary: BREAKWATER in BRAF mCRC¶

The day's GI momentum carried into the late-breaking oral sessions. BREAKWATER showed first-line encorafenib + cetuximab + FOLFIRI nearly doubled PFS versus FOLFIRI ± bevacizumab in BRAF V600E mCRC — 15.2 vs 8.3 months (HR 0.44, P=.0002) — with ORR 64.4% vs 39.2% and OS not reached vs 20.3 months (HR 0.56). The regimen already carries full FDA approval in this setting.

Breast: a confirmatory 1L TNBC signal¶

In 1L PD-L1+ (CPS≥10) metastatic triple-negative breast cancer, the ASCENT-04 update confirmed sacituzumab govitecan + pembrolizumab over chemo + pembro (PFS 11.2 vs 7.8 months, HR 0.65), with benefit holding across biomarker subgroups — deepest in high Trop-2 (Q4 HR 0.57) and retained in tBRCA wild-type and HER2 IHC 0 disease.

Bottom line: Sunday delivered the meeting's defining moment — a pan-RAS inhibitor doubling survival in pancreatic cancer — wrapped in a Plenary that also reset standards in prostate, liposarcoma, and RET-positive lung, with a colorectal win for good measure.

Sources: ASCO Post — daraxonrasib in PDAC · OncDaily — ASCO 2026 Plenary preview · Healio — abemaciclib in liposarcoma · CancerNetwork — BREAKWATER EC+FOLFIRI · ASCO press release — ASCO 2026