Reviews/Targeted Therapy Breast Cancer/Alpelisib in PIK3CA-mutant hormone receptor-positive metastatic breast cancer
Pi3k Akt · BC-PI3K-01 · v2
A large, high-quality randomized trial [1] tested adding alpelisib to fulvestrant in people with this exact type of advanced breast cancer whose disease had grown after hormone therapy, and the combination delayed cancer growth for about 11.0 months versus 5.7 months without it. A phase 2 trial [18], a comparison against real-world care [7], and a large real-world registry [9] all point the same direction. Patients did not clearly live longer overall, and the gain was measured by delay in progression rather than survival [2]. In everyday practice the delay was more modest, especially in heavily pre-treated patients [9]. The panel concluded the delay in progression is well supported for this population while noting that the strongest evidence comes mainly from a single trial and that the benefit comes with significant side effects.
The pivotal phase 3 double-blind RCT [1] met its primary progression-free survival endpoint in the PIK3CA-mutant cohort (11.0 vs 5.7 months, HR 0.65, P<0.001), the exact population and setting of the claim. Its final analysis [2] reaffirmed that PFS benefit even though overall survival did not reach significance (HR 0.86, P=0.15). The phase 2 BYLieve trial [18] met its endpoint (50.4% progression-free at 6 months) and its matched real-world comparison [7] favoured alpelisib (7.3 vs 3.7 months), while a large prospective registry [9] reported a median PFS of 5.3 months. Within-trial biomarker [10] and dose-intensity [15] analyses were directionally consistent. Direction of benefit is uniform across every included source. The contested point: The panel divides on how much weight the signal carries beyond its existence: four included sources ([1],[2],[10],[15]) are all SOLAR-1, so the randomized evidence is effectively one trial, and overall survival never reached significance [2]. Real-world magnitude is also markedly smaller (5.3 months in [9] vs 11.0 months in [1]), so the size of the benefit is setting-dependent even where its direction is not.
All 18 papers behind this claim with their DOIs and what each does to it, the panel’s arbitration, the evidence gap map and the open research questions. Free, and sent to your inbox.
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One reviewer's only job is to attack the finding. The challenges below were weighed before the grade was set.
The randomized PFS signal rests essentially on a single pivotal trial: four of the included sources ([1],[2],[10],[15]) are all SOLAR-1, so evidential independence is weaker than the citation count suggests.
Overall survival did not reach statistical significance (HR 0.86, P=0.15, did not cross the prespecified boundary); the demonstrated benefit is on PFS, a surrogate, without a confirmed survival advantage.
Where it remains uncertain. The randomized evidence is concentrated in one trial, overall survival did not reach significance (HR 0.86, P=0.15 [2]), and real-world PFS was more modest (5.3 months [9]).
Aleatory
The PFS hazard ratio in [1] spans 0.50 to 0.85, and the point estimate of benefit varies with sampling even within the one pivotal trial.
Epistemic
The randomized evidence is concentrated in SOLAR-1 ([1],[2],[10],[15]); no independent RCT in the corpus confirms the magnitude.
Inferential
Benefit is demonstrated on PFS; overall survival did not reach significance (HR 0.86, P=0.15 [2]), so a survival advantage cannot be inferred.
The load-bearing papers from a corpus of 18, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Pivotal RCT establishing a statistically significant PFS improvement in the exact claim population.
“In the cohort of patients with PIK3CA -mutated cancer, progression-free survival at a median follow-up of 20 months was 11.0 months (95% confidence interval [CI], 7.5 to 14.5) in the alpelisib-fulvestrant group, as compared with 5.7 months (95% CI, 3.7 to 7.4) in the placebo-fulvestrant group (hazard ratio for progression or death, 0.65; 95% CI, 0.50 to 0.85; P<0.001)”
Panel auditInternal validity: high · scope of inference: Men and postmenopausal women with PIK3CA-mutated, HR-positive, HER2-negative advanced breast cancer previously treated with endocrine therapy.Key limitations: investigator-assessed PFS · high discontinuation for adverse events (25%)
Longer-follow-up analysis of the same RCT reaffirming the PFS benefit.
“these results further support the statistically significant prolongation of PFS observed with alpelisib plus fulvestrant in this population, which has a poor prognosis due to a PIK3CA mutation”
Panel auditInternal validity: high · scope of inference: SOLAR-1 PIK3CA-mutant cohort; the primary reported endpoint here is OS, which did not cross its significance boundary (HR 0.86, P=0.15).Key limitations: OS not significant · PFS only restated, not re-reported
Comparative real-world evidence favouring the regimen on PFS.
“Postadjustment, median PFS for patients treated with alpelisib in BYLieve was 7.3 versus 3.7 months in the real-world cohort, and 6-month PFS was 54.6% versus 40.1%, respectively”
Panel auditInternal validity: low · scope of inference: Patients with PIK3CA-mutant HR-positive HER2-negative ABC after a CDK4/6 inhibitor plus AI (post-CDK4/6i setting).Key limitations: non-randomized comparison · matching/weighting confounding · post-CDK4/6i subpopulation
Within-trial biomarker analysis showing the PFS benefit is maintained across gene-alteration subgroups.
“The unique mut profile of PIK3CA-alt tumors did not affect ALP + FUL benefit in pts with HR+, HER2– ABC”
Panel auditInternal validity: medium · scope of inference: SOLAR-1 PIK3CA-altered cohort subgrouped by co-mutations and tumour mutational burden.Key limitations: retrospective subgroups · no multiplicity adjustment · subset with evaluable tissue
4 of 18 papers shown. The full review lists all of them, with the panel’s arbitration →
Claims are graded at each quarterly release, and re-graded between releases only when a pivotal trial lands. Every change is a new version of the claim.
A directly on-target pivotal RCT with a significant primary PFS result, consistently corroborated, carries the PFS-scoped claim at the top tier despite limited independence and surrogate-only benefit.
Release 2026-q4 re-graded every claim from its corpus under protocol v0.19. An earlier release's grade is shown for the record; it came from an earlier protocol and is not a movement.
Assumptions that carry weight but are not themselves established.
The panel records the gap that would most move the claim, and the study that would close it.
Independent confirmatory RCT. The randomized PFS signal is concentrated in SOLAR-1, so a second independent trial is needed to establish the effect beyond one study. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: A separate randomized double-blind trial of alpelisib plus fulvestrant versus fulvestrant in the same population, reporting investigator-assessed PFS.
Open question: Does adding alpelisib to fulvestrant extend overall survival, not only progression-free survival, in this population? Why it is still open: The final SOLAR-1 analysis [2] reported a 7.9-month numeric OS gain but HR 0.86, P=0.15, which did not cross the prespecified boundary.
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 23 Oct 2026 · protocol v0.19