Background
Open-label, randomised phase 3 trial (Netherlands + France). N=174 newly diagnosed stage IIIA-C, HER2-negative breast cancer with homologous recombination deficiency (germline BRCA1/2 mutation or HRD tumour), aged 18-66. Tested intensified alkylating chemotherapy with autologous stem-cell rescue (IACT) against a contemporary HRD-targeting regimen of conventional chemotherapy plus olaparib.
Results
Interventions and follow up: Arm A: IACT — dose-dense AC ×4, then tandem high-dose cyclophosphamide/thiotepa/carboplatin with autologous stem-cell transplantation (n=87)
Arm B: Dose-dense AC ×4 → carboplatin-paclitaxel → 1 year olaparib 300 mg PO twice daily (n=87)
Primary endpoint: Overall survival (ITT)
mFollow up: 41 months
Results: 4-year OS: 77.0% (IACT) vs 76.4% (olaparib arm), HR for death 1.11 (95% CI 0.57–2.17), P=.37 (not significant)
Arm B: Dose-dense AC ×4 → carboplatin-paclitaxel → 1 year olaparib 300 mg PO twice daily (n=87)
Primary endpoint: Overall survival (ITT)
mFollow up: 41 months
Results: 4-year OS: 77.0% (IACT) vs 76.4% (olaparib arm), HR for death 1.11 (95% CI 0.57–2.17), P=.37 (not significant)
Adverse events
Grade 3-4 hematologic: thrombocytopenia 99% vs 19%; neutropenia 95% vs 61%; anemia 62% vs 41%
Serious adverse events: 47% vs 26%
Febrile neutropenia: 44% vs 12%
Treatment-related deaths: none
Serious adverse events: 47% vs 26%
Febrile neutropenia: 44% vs 12%
Treatment-related deaths: none
Conclusions
Intensified chemotherapy with autologous stem-cell rescue provided no overall-survival advantage over conventional chemotherapy plus olaparib in stage III HER2-negative HRD breast cancer, and caused far more toxicity. HRD-targeting with an olaparib-containing regimen is the preferred, less-toxic approach.
Key Limitations
Small trial (N=174) in a rare subgroup; the OS confidence interval is wide (HR 1.11, 0.57–2.17). Both arms achieved high 4-year OS (~77%), and the study was not designed to test olaparib against a no-olaparib control. Follow-up is ongoing and OS may mature further.
Clinical Context
OlympiA established 1 year of adjuvant olaparib for high-risk germline-BRCA HER2-negative breast cancer (FDA-approved). SUBITO reinforces that an olaparib-containing conventional regimen matches high-dose chemotherapy with stem-cell rescue while being far safer, confirming ASCT has no role here. No new approval; supports current NCCN/ESMO positioning of olaparib.