Thoracic / Lung
One trial, one lesson: consolidative thoracic RT and IO maintenance don't safely combine in ES-SCLC on this data.
TREASURE NCT04462276
ForUnselected ES-SCLC, ≥SD after induction chemo-IO (carbo/etoposide/atezo)
TL;DRmOS 6.7 vs 13.4mo (HR 1.55, P=.34) adding consolidative TRT to atezo maintenance; SAEs 61% vs 18%, halted early for harm.
Why it mattersRadiation oncology
The transferable signal is patient selection: low baseline DLCO marked the fatal arm-A deaths, and post-TRT lymphocyte depletion is the proposed driver of the excess infections. That reframes a negative trial as a selection problem and argues against routine consolidative TRT on an IO backbone in unselected ES-SCLC.
vs leading data
- vs CREST (Slotman, Lancet 2015): modest OS benefit from consolidative TRT pre-IO; TREASURE finds net harm on an IO backbone
7 details 5 trials watching
Methods
- 🔍 Phase 2 open-label RCT, 1:1, 20 German/Austrian sites; 68 randomized (34/arm), halted early for safety
- 🔍 RT arm: 30 Gy / 10 fractions consolidative TRT after ≥SD on induction carbo/etoposide/atezo
CONSORT flow
Randomized 68
↓
Atezolizumab + TRT (30Gy/10fx)
allocated 34
Atezolizumab alone
allocated 34
Results
- 📊 Efficacy + safety by arm (30Gy/10fx consolidative TRT added vs atezolizumab maintenance alone)
Endpoint Atezo + TRT (arm A) Atezo alone (arm B) HR / P mOS 6.7 mo (5.1-9.0) 13.4 mo (10.7-17.5) HR 1.55 (0.90-2.69), P=.34 mPFS 2.4 mo (1.3-3.9) 2.6 mo (1.2-3.9) HR 0.92 (0.54-1.55), P=.85 SAEs 61.3% (19 pts) 18.2% (6 pts) P<.001 Fatal AEs 19.4% (6 pts) 3.0% (1 pt) P=.04 - 📐 Powered for 20% absolute 12-mo OS gain (72% vs 52%, HR 0.57); closed at 68 of 104 planned, underpowered for efficacy
Critique
- ⚠️ Excess SAEs were infection + respiratory disorders; persistent post-TRT lymphocyte depletion the proposed driver
- ⚠️ Fatal AEs in arm A tied to lower baseline DLCO; other baseline characteristics balanced across arms
- ⚠️ Unselected pts, no lung-function or lymphopenia gating; result may not transfer with tighter selection
Open questions
- Which ES-SCLC pts can receive consolidative TRT without excess toxicity recruiting Phase I/II Trial in ES-SCLC to Enhance Response to Atezolizumab Plus Chemotherapy With Total Body Irradiation Phase 1/2n=18 · primary completion 2027-06 · phase 1/2 safety of RT added to atezo in ES-SCLCn=46 · primary completion 2027-12 · consolidative thoracic RT in ED-SCLC on durvalumab
- Whether conformal or lower-dose TRT mitigates radiation-induced lymphopenia n=55 · primary completion 2023-05 · RT planning optimized to spare lymphocytes in SBRTn=212 · primary completion 2027-06 · lymphocyte-sparing vs conventional thoracic RTactive Thymus Dosimetric and Morphologic Predictors of Radiation-Induced Lymphopenia in Stage III NSCLCn=450 · primary completion 2027-12 · thymus dose predictors of radiation lymphopenia
📚 Sources · 📄 1 paper
Consolidative Thoracic Radiotherapy With Atezolizumab Maintenance in Extensive-Stage Small Cell Lung Cancer
Abstract
Importance Chemoimmunotherapy followed by immunotherapy maintenance is the standard first-line treatment for extensive-stage small cell lung cancer (ES-SCLC), yet data regarding efficacy and safety of consolidative thoracic radiotherapy (TRT) are lacking. Objective To determine whether combining consolidative TRT with immunotherapy maintenance in ES-SCLC is safe and improves patients’ overall survival (OS) and progression-free survival (PFS). Design, Settings, and Participants This was a multicenter open-label phase 2 randomized clinical trial recruiting patients from September 2020 to August 2022 in Germany and Austria, with the last follow-up visit in September 2024. Eligible patients had ES-SCLC with at least stable disease after induction chemoimmunotherapy (carboplatin−etoposide−atezolizumab). Although the database was locked in April 2025, a post hoc survival update was performed in April 2026. Data were analyzed from April 2025 to April 2026. Interventions Randomized (1:1) to either atezolizumab maintenance combined with consolidative TRT (30 Gy in 10 fractions) (arm A) or atezolizumab maintenance alone (arm B). Main Outcome and Measure OS (time from randomization to death due to any cause). Results Of 96 patients assessed for eligibility, 68 patients were randomized; recruitment was prematurely terminated due to safety concerns. Median OS in the combination arm was numerically shorter compared to atezolizumab only (6.7 months [95% CI, 5.1-9.0] vs 13.4 months [95% CI, 10.7-17.5]; HR, 1.55 [95% CI, 0.90-2.69]; P = .34), while median PFS was similar (2.4 months [95% CI, 1.3-3.9] vs 2.6 months [95% CI, 1.2-3.9]; HR, 0.92 [95% CI, 0.54-1.55]; P = .85). TRT plus atezolizumab was accompanied by higher frequency of severe adverse events (SAEs) (19 patients [61.3%] vs 6 patients [18.2%]; P &amp;lt; .001) and fatal outcomes (6 patients [19.4%] vs 1 patient [3.0%]; P = .04). Safety analysis revealed predominance of infection and respiratory disorder−related SAEs, possibly facilitated by a depletion of lymphocytes observed specifically in patients after TRT, and by a lower single breath diffuse capacity of the lungs for carbon monoxide in patients with fatal AEs in arm A. No further risk factors were identified, given that baseline characteristics were well balanced between both arms and between patients with and without SAEs, including fatal SAEs. Conclusions and Relevance In this randomized clinical trial, TRT combined with immunotherapy increased toxic effects in unselected patients with ES-SCLC without survival benefit, presumably due to radiation-induced lymphocyte depletion facilitating infections. Cautious patient selection and further investigation to identify those who may benefit without undue risk are required. Trial Registration ClinicalTrials.gov Identifier: NCT04462276