Reviews/Perioperative Immunotherapy Solid Tumours/Pathological complete response surrogate for triple-negative breast cancer immune checkpoint inhibitor therapy
Tnbc · PERIO-TNBC-02 · v2
When patients with triple-negative breast cancer have no cancer left after neoadjuvant immunotherapy plus chemotherapy, they do markedly better on event-free survival than patients with residual disease. KEYNOTE-522 [9] shows 5-year event-free survival of 92.2% in pembrolizumab-treated patients who reached a pathological complete response versus 62.6% in those who did not, and the residual-burden analyses [7],[12] show fewer events as residual disease shrinks. The link to overall survival is biologically expected and is strongly supported in TNBC broadly [15], but within the immunotherapy trials themselves it is not yet mature: KEYNOTE-522 overall-survival follow-up is still ongoing [9] and IMpassion031's overall-survival estimate [8] is favourable but statistically uncertain in a small trial. The panel judged the event-free survival half of the claim close to settled in this setting, while the overall-survival half rests partly on pre-immunotherapy and exploratory data. That split is why the claim was not placed in the top tier.
Within immunotherapy-plus-chemotherapy TNBC the event-free survival association is direct and strong: [9] reports 5-year event-free survival of 92.2% versus 62.6% split by pathological complete response status in the pembrolizumab arm, and [7] and [12] show lower residual cancer burden (RCB-0 equals pathological complete response) carrying fewer events. [8] reports long-term event-free, disease-free and overall survival all favouring atezolizumab plus chemotherapy. The underlying prognostic strength of pathological complete response in TNBC is carried by [15] (EFS HR 0.24, OS HR 0.16) and by I-SPY2 [3] (EFS HR 0.19) and [5]. Overall survival specifically within the immunotherapy trials remains immature: [9] states overall-survival follow-up is ongoing and [8] reports an overall-survival HR of 0.56 with a confidence interval crossing 1. The contested point: The division is entirely on the overall-survival limb. The event-free survival association is directly demonstrated in the immunotherapy setting [9],[7], but mature overall-survival-by-response data from within these trials does not yet exist ([9] ongoing; [8] non-significant), so that half of the claim leans on pre-immunotherapy pooled data [15] and exploratory analyses.
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The OS limb of the claim is not carried by the ICI corpus itself: KEYNOTE-522 [9] states OS follow-up is ongoing, and IMpassion031 [8] reports a non-significant OS HR 0.56 (95% CI 0.30-1.04) in only 333 patients. The robust pCR-OS evidence [15] predates ICI entirely.
The pCR-stratified survival figures in [9] are explicitly a 'prespecified, non-randomized, exploratory analysis'; pCR is a post-randomization prognostic marker, so pCR-vs-non-pCR survival differences are confounded by tumour biology rather than reflecting a randomized contrast.
Where it remains uncertain. Overall survival within the immunotherapy trials is immature ([9] follow-up ongoing; [8] overall-survival HR 0.56 with CI crossing 1), so the overall-survival limb rests partly on pre-immunotherapy pooled data [15].
Aleatory
IMpassion031 [8] has only 333 randomized patients, so its overall-survival HR 0.56 carries a wide interval (0.30-1.04) driven by few events.
Epistemic
KEYNOTE-522 [9] states overall-survival follow-up is ongoing, so the key immunotherapy trial has no reported overall-survival-by-response result yet.
Inferential
Pathological complete response is achieved after randomization, so comparing responders to non-responders [9] reflects tumour biology, not a randomized contrast.
The load-bearing papers from a corpus of 26, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
pembro+chemo TNBC; lower residual burden (RCB-0 = pCR) carries fewer EFS events.
“These findings demonstrate that pembrolizumab not only increased pCR rates, but also improved EFS among most patients who do not have a pCR.”
Panel auditInternal validity: high · scope of inference: Treatment effect of pembrolizumab across residual-disease strata in high-risk early TNBC.Key limitations: contrast is treatment arm not pCR status · wide CIs within strata
Second ICI+chemo TNBC trial showing EFS/DFS/OS favouring the ICI arm, though CIs cross 1.
“Long-term outcomes favored the atezolizumab group (event-free survival hazard ratio (HR), 0.76; 95% confidence interval (CI), 0.47-1.21; disease-free survival HR, 0.76; 95% CI, 0.44-1.30; overall survival HR, 0.56; 95% CI, 0.30-1.04).”
Panel auditInternal validity: high · scope of inference: Long-term outcomes and ctDNA dynamics of atezolizumab plus chemotherapy in stage II/III TNBC.Key limitations: no direct pCR-vs-nonpCR survival estimate · descriptive secondary endpoints · wide CIs
Direct pCR-stratified EFS in ICI+chemo TNBC: pCR patients have markedly higher 5-yr EFS.
“Follow-up for OS is ongoing”
Panel auditInternal validity: high · scope of inference: Early-stage TNBC treated with neoadjuvant pembrolizumab plus chemotherapy then adjuvant pembrolizumab.Key limitations: pCR subgroup analysis non-randomized/exploratory · OS follow-up ongoing, OS not reported · no HR/CI for pCR contrast
Individual-level pCR-EFS/DRFS association across subtypes and regimens, supporting generality.
“Hazard ratios for pCR vs non-pCR were 0.19 for EFS (95% CI, 0.12-0.31) and 0.21 for DRFS (95% CI, 0.13-0.34)”
Panel auditInternal validity: high · scope of inference: High-risk stage 2/3 breast cancer across subtypes and 9 novel regimens; not isolated to ICI-treated TNBC.Key limitations: not ICI-specific · mixed subtypes/regimens · reports DRFS not OS
4 of 26 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.
The EFS association is near-established in the ICI setting while OS is biologically well-supported but immature in ICI trials and rests partly on exploratory, non-randomized and pre-ICI data, holding the bundled claim at Likely.
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.
Mature overall survival by pCR within ICI trials. The overall-survival half of the claim currently has no mature within-regimen evidence; [9] follow-up is ongoing and [8] is non-significant. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: Report long-term overall survival stratified by pathological complete response from KEYNOTE-522 [9] and pooled immunotherapy-plus-chemotherapy TNBC cohorts at extended follow-up.
Open question: Does pathological complete response after neoadjuvant immunotherapy plus chemotherapy predict improved overall survival within the immunotherapy trials themselves? Why it is still open: KEYNOTE-522 overall-survival follow-up is ongoing [9] and IMpassion031's overall-survival HR 0.56 crosses 1 in 333 patients [8].
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 21 Oct 2026 · protocol v0.19