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📖 Full Analysis
Read the complete desktop article with full efficacy tables, safety detail, subgroup data, comparator trials, and clinical implications on kill-cancer.com.
🎯 Clinical Bottom Line
Adding capivasertib to fulvestrant doubled progression-free survival compared with fulvestrant alone in HR-positive, HER2-negative advanced breast cancer after aromatase inhibitor progression. Both co-primary endpoints were met — in the overall population and the AKT pathway–altered subgroup. Approximately 69% of patients had received prior CDK4/6 inhibitor therapy.
Key Result 1: PFS, overall population — HR 0.60 (95% CI 0.51–0.71; P<0.001) Key Result 2: PFS, AKT pathway–altered — HR 0.50 (95% CI 0.38–0.65; P<0.001)
Safety Signal: Diarrhea (any grade 72.4%), rash (grade ≥3: 12.1%), hyperglycemia (any grade 16.3%) require proactive management.
✅ Patient Eligibility
Must Have:
- HR-positive, HER2-negative locally advanced or metastatic breast cancer
- Progression on prior aromatase inhibitor ± CDK4/6 inhibitor
- ≤2 prior endocrine therapy lines and ≤1 prior chemo line for advanced disease
- ECOG PS 0–1
Cannot Have:
- Prior fulvestrant, SERD, AKT/PI3K/mTOR inhibitors
- Insulin-treated diabetes with HbA1c ≥8.0%
💊 Dosing Quick Guide
Experimental Regimen
Capivasertib: 400 mg PO twice daily, 4 days on / 3 days off Fulvestrant: 500 mg IM q14d × 3, then q28d Cycle: 28 days Duration: Until progression or unacceptable toxicity
Control Regimen
Placebo + Fulvestrant (same schedule)
Pre-/perimenopausal women also receive LHRH agonist.
Key Dose Modifications [2]
- Dose reductions required in 19.7% of capivasertib patients
- Dose interruptions in 34.9% — primarily for rash, diarrhea, hyperglycemia
- Monitor fasting glucose at baseline and regularly; CBC and hepatic function per label
Mechanism: Capivasertib is a selective AKT kinase inhibitor (AKT1/2/3) that blocks PI3K/AKT/mTOR signaling — a key driver of endocrine resistance in HR-positive breast cancer [2].
⚠️ Safety Snapshot
| Grade 3+ Toxicities | Capivasertib–Fulvestrant (n=355) | Placebo–Fulvestrant (n=350) |
|---|---|---|
| Rash (grouped term) — Gr 3 | 43 (12.1%) | 1 (0.3%) |
| Diarrhea — Gr 3 | 33 (9.3%) | 1 (0.3%) |
| Hyperglycemia — Gr 3 | 7 (2.0%) | 1 (0.3%) |
| Hyperglycemia — Gr 4 | 1 (0.3%) | 0 |
| Stomatitis — Gr 3 | 7 (2.0%) | 0 |
| Anemia — Gr 3 | 7 (2.0%) | 4 (1.1%) |
⚠️ Rash: Any grade 38.0%, Grade 3 12.1% — most frequent severe toxicity ⚠️ Diarrhea: Any grade 72.4%, Grade 3 9.3% — early antidiarrheal intervention essential
Key safety metrics:
- Treatment-related deaths: 0 vs 0
- Discontinuations due to AE: 13.0% vs 2.3%
- Dose reductions: 19.7% vs 1.7%
- Dose interruptions: 34.9% vs 10.3%
- Serious AEs: 16.1% vs 8.0%
📊 Key Numbers
Median follow-up: 13.0 months (capivasertib–fulvestrant) / 12.7 months (placebo–fulvestrant)
| Outcome (Population) | Capivasertib–Fulvestrant | Placebo–Fulvestrant | HR (95% CI) | p-value |
|---|---|---|---|---|
| PFS — overall (N=708) | 7.2 mo | 3.6 mo | 0.60 (0.51–0.71) | P<0.001 |
| PFS — AKT-altered (N=289) | 7.3 mo | 3.1 mo | 0.50 (0.38–0.65) | P<0.001 |
| OS 18-mo — overall | 73.9% | 65.0% | 0.74 (0.56–0.98) | not formally tested |
| OS 18-mo — AKT-altered | 73.2% | 62.9% | 0.69 (0.45–1.05) | not formally tested |
| BICR PFS — overall | — | — | 0.61 (0.50–0.73) | — |
| QoL time to deterioration | 24.9 mo | 12.0 mo | 0.70 (0.53–0.92) | — |
🔬 Key Comparator Context
| Trial | Regimen | Population | Primary Endpoint | Key Result | Ref |
|---|---|---|---|---|---|
| CAPItello-291 | Capivasertib + fulvestrant vs placebo + fulvestrant | HR+/HER2− ABC, post-AI ± CDK4/6i | PFS (overall) | 7.2 vs 3.6 mo; HR 0.60 | [1] |
| SOLAR-1 | Alpelisib + fulvestrant vs placebo + fulvestrant | HR+/HER2− ABC, PIK3CA-mut | PFS (PIK3CA-mut) | 11.0 vs 5.7 mo; HR 0.65 | [4] |
| EMERALD | Elacestrant vs SOC ET | HR+/HER2− mBC, post-CDK4/6i | PFS (overall) | 2.79 vs 1.91 mo; HR 0.70 | [5] |
Cross-trial comparisons are limited by differences in populations, designs, and endpoints.
🔍 Subgroups to Watch
Prior CDK4/6 inhibitor — Yes: HR 0.62 (95% CI 0.51–0.75) — benefit preserved post-CDK4/6i Prior CDK4/6 inhibitor — No: HR 0.65 (95% CI 0.47–0.91) — consistent benefit Pre-/perimenopausal: HR 0.86 (95% CI 0.60–1.20) — attenuated benefit, CI crosses 1.0 Postmenopausal: HR 0.59 (95% CI 0.48–0.71) — robust benefit AKT pathway–nonaltered (excl unknown): HR 0.79 (95% CI 0.61–1.02) — uncertain in confirmed non-altered
Subgroup analyses were not powered for formal comparisons. Results are hypothesis-generating.
📋 Regulatory Status
| Region | Status |
|---|---|
| FDA | Approved Nov 2023 for HR+/HER2− ABC with PIK3CA/AKT1/PTEN alterations, post-endocrine [2] |
| EMA | Approved 2024 for AKT pathway–altered HR+/HER2− ABC |
⚠️ Verify current regulatory status before prescribing.
NCCN: Recommended option post–CDK4/6i; PIK3CA/AKT1/PTEN testing recommended [3]
Companion diagnostic: FoundationOne CDx (PIK3CA, AKT1, PTEN)
⚡ Grey Zones
- Benefit in confirmed AKT pathway–nonaltered patients is uncertain (HR 0.79, CI crosses 1.0)
- OS data immature — formal survival analysis not yet triggered
- Pre-/perimenopausal women showed attenuated benefit versus postmenopausal — needs investigation
- Optimal sequencing vs alpelisib–fulvestrant (PIK3CA-mutated) and elacestrant (ESR1-mutated) undefined
- Patients with prior fulvestrant or PI3K/mTOR inhibitor exposure were excluded — growing clinical gap
📖 Full Analysis
Read the complete desktop article with full efficacy tables, safety detail, subgroup data, comparator trials, and clinical implications on kill-cancer.com.
About the Author
Andrew Stevenson is the founder and systems architect of kill-cancer.com. He holds 17 Google technical certifications in data systems, automation, and applied AI — the engineering foundation behind the extraction and verification pipeline that produces every article on this platform. Every number traces to its source publication. Zero calculation. Zero editorializing. Zero hallucination. Five siblings lost to cancer built the urgency. The engineering builds the trust.
📧 andrew@kill-cancer.com 🌐 kill-cancer.com 💬 kill-cancer.com/forum
For healthcare professionals only. Not medical advice. Trial results are presented as reported in the source publication. Updated data, label changes, or guideline revisions published after the source article may alter clinical applicability. Consult FDA labeling, NCCN guidelines, and institutional protocols.
References
- Turner NC, Oliveira M, Howell SJ, et al. Capivasertib in hormone receptor–positive advanced breast cancer. N Engl J Med. 2023;388:2058-2070. doi:10.1056/NEJMoa2214131
- Truqap (capivasertib) prescribing information. U.S. Food and Drug Administration. 2023.
- NCCN Clinical Practice Guidelines in Oncology: Breast Cancer. Version 1.2026. Accessed March 2026.
- André F, Ciruelos E, Rubovszky G, et al. Alpelisib for PIK3CA-mutated, hormone receptor–positive advanced breast cancer. N Engl J Med. 2019;380:1929-1940.
- Bidard FC, Kaklamani VG, Neven P, et al. Elacestrant (oral selective estrogen receptor degrader) versus standard endocrine therapy for estrogen receptor–positive, HER2-negative advanced breast cancer: results of the randomized phase III EMERALD trial. J Clin Oncol. 2022;40:3246-3256.