Developing Story: The Camizestrant Vote, Doctors Weigh In with Dr. Sarah Sammons & Dr. Neil Vasan
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Live from Stage 4 | Episode #031 | 06/02/2026 | Developing Story
GUESTS
Dr. Sarah Sammons, MD, is a nationally recognized breast medical oncologist, clinical investigator, and the newly appointed Co-Leader of Breast Oncology at the University of Maryland Greenebaum Comprehensive Cancer Center (UMGCCC). Previously serving as a Senior Physician at the Dana-Farber Cancer Institute and a faculty member at Harvard Medical School, she has built a distinguished career specializing in all stages of breast cancer. Dr. Sammons is widely praised for her patient-centered approach to care and her pioneering clinical trials focusing on targeted therapies, immunotherapy, and improving outcomes for patients with metastatic disease. Notably, she is a leading expert in the treatment and prevention of breast cancer brain metastases, and is spearheading a state-of-the-art, multidisciplinary CNS Metastases Clinic at UMGCCC. Recognized as one of the most influential digital opinion leaders in oncology, she seamlessly pairs cutting-edge translational research with a deeply collaborative model of patient advocacy.
Dr. Neil Vasan, MD, PhD, is a distinguished breast oncologist, physician-scientist, and the Director of Translational Research in Breast Cancer at NYU Langone Health. Armed with an Ivy League background—including degrees from Harvard and Yale—he has dedicated his career to bridging the gap between laboratory discovery and patient care. Dr. Vasan’s groundbreaking research famously identified double PIK3CA mutations as an oncogenic biomarker, a discovery that has successfully transitioned from bench to bedside to guide target treatments. In addition to running the Vasan Lab and treating patients, he serves as an Acting Chair and Standing Member of the U.S. Food and Drug Administration (FDA) Oncologic Drugs Advisory Committee (ODAC), positioning him at the absolute forefront of evaluation for next-generation cancer therapies.
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Quick Summary
Round two of our SERENA-6 ODAC coverage brings in the clinical and regulatory experts. Dr. Neil Vasan — the ODAC chair who cast one of the three yes votes — and Dr. Sarah Sammons break down what the trial actually proved, why the vote went 6–3 against, and what it means for the future of ctDNA-guided treatment. Patient advocates Janice Cowden and Abigail Johnston keep the conversation grounded in lived experience. Plus: breaking news that AstraZeneca has submitted additional data and the FDA has extended its review to August 14, 2026.
Key Topics Covered
The trial answered the wrong question. SERENA-6 proved that switching based on molecular progression is better than not switching at all — but it never tested whether switching early (at molecular detection) is better than switching later (at scan progression). That distinction was central to the ODAC's concerns.
Four critiques drove the 6–3 vote. The FDA identified: (1) unclear clinical meaning of molecular PFS as an endpoint, (2) PFS2 considered uninterpretable for regulatory use, (3) no crossover design to cleanly answer the timing question, and (4) overall survival data too immature and underpowered.
Patients felt better — but that wasn't enough. Patients on camizestrant had a median 23-month time to quality of life decline vs. 6 months on the aromatase inhibitor. Regulators couldn't act on PRO data alone without survival endpoints to back it up.
The story isn't over. AstraZeneca submitted a Major Amendment to the FDA with additional ctDNA clearance, PFS, and safety data. New decision date: August 14, 2026. A negative ODAC vote still results in approval ~30–40% of the time.
ctDNA technology is here — the trials aren't ready yet. Both clinicians agree the science is moving faster than trial design can keep up. SERENA-6 is a cautionary tale about rigor, not a rejection of the concept.
Patients are already acting on ctDNA data without clinical evidence. Janice flagged real-world concern: oncologists are switching patients based on rising Signatera results without imaging confirmation — ahead of the evidence.
The next frontier: replacing scans with ctDNA. Dr. Sammons described a planned trial that would use ctDNA levels to determine when — or whether — to scan, potentially eliminating scanxiety for stable patients.
ODAC
Based on what Dr. Vasan explains in the episode:
What ODAC Is The Oncologic Drugs Advisory Committee is one of 33 FDA advisory committees. It convenes only when the FDA faces a question of equipoise — cases that aren't a clear yes or no. Most FDA approvals never involve ODAC at all.
Who Sits on It Oncologists across cancer types, plus one permanent patient advocate. Members find out who else is on the committee just days before the meeting — the same time the public does. This is deliberate to prevent coordination.
How a Meeting Works
Briefing documents — released to the public and committee weeks in advance, often containing data not yet published
Presentations — the FDA presents its interpretation, then the sponsor (the drug company) presents theirs — a back-and-forth Dr. Vasan compared to a Lincoln-Douglas debate
Clarifying questions — specific data questions from committee members to both sides
Discussion — open group conversation; the directionality often becomes clear here
Public testimony — patients, caregivers, and advocates speak; Dr. Vasan noted this has become increasingly influential and can shift the room
Voting question — the committee agrees on precise wording, then each member votes individually and publicly
Justifications — after the vote, each member explains their reasoning on the record
What the Vote Actually Means It's advisory — the FDA makes the final decision. The FDA agrees with ODAC more than 90% of the time, but a close or split vote can still lead to approval. Dr. Vasan described it as: "like the Supreme Court of drug approvals, except we don't make the decisions."
The Vote, Uncovered
The question on the table: Is using a blood test — ctDNA detecting an ESR1 mutation — a clinically meaningful reason to switch a patient's therapy before their scan shows any tumor growth?
The result: 6 against, 3 in favor.
Why six voted no:
The majority had four core concerns:
The endpoint didn't mean what we thought. Progression-free survival was measured from the moment of molecular detection — not from actual scan progression. That's never been done in a Phase III trial before, and the FDA wasn't convinced it carries the same clinical weight as traditional PFS.
PFS2 was unreadable. The data tracking what happened after the next line of therapy showed a real difference — 40% of patients in the control arm went straight to chemotherapy or an ADC after progression, versus only 20% in the camizestrant arm. But because patients weren't randomized to their next-line therapy, the FDA considered it too biased to count.
The timing question was never answered. The trial proved switching on molecular detection is better than not switching at all — but it never tested whether switching early is better than switching at scan progression. That's the question the FDA actually needed answered.
Overall survival was inconclusive. Only 60% of the survival data was available. The FDA projected that even with full data, the trial wouldn't be powered to show a statistically significant survival benefit.
Why three voted yes — including Dr. Vasan:
The totality of endpoints — PFS, PFS2, and OS — all pointed in the same direction, even if none were definitive individually
"We can debate whether it's clinically meaningful — but to me it's not clinically meaningless"
The quality of life data was striking and real, even if regulators couldn't act on it alone
Designing a cleaner trial in 2021 — when no oral SERD was even approved — would have been practically and ethically impossible
The unusual detail: The patient advocate on the committee voted no — rare for ODAC, where patient advocates have historically been the most likely to vote yes, sometimes as the sole yes vote.
Endpoints — What They Are and Why They Mattered
What is an endpoint? An endpoint is what a clinical trial statistically sets out to prove. Dr. Vasan explained there are hard endpoints — like overall survival (did the patient live longer?) — and surrogate endpoints that correlate with survival but aren't survival itself, like progression-free survival.
The endpoints in SERENA-6:
1. Primary endpoint — PFS (Progression-Free Survival) The trial measured PFS from the moment of molecular progression — when the ESR1 mutation was detected in the blood — not from scan-confirmed tumor growth. This was novel and controversial. The FDA argued molecular PFS may not carry the same clinical meaning as traditional PFS. Neil Vasan suggested it might need its own designation: "PFS-molecular." The endpoint was met — camizestrant arm showed 16 months vs. 9.2 months — but the FDA questioned what that number actually means when the patient's scans showed no disease at the starting point.
2. PFS2 PFS2 tracks the combined time through two lines of therapy — the trial therapy plus whatever comes next. It attempts to answer: does switching early give you more total mileage? The data showed a real signal — patients in the control arm were far more likely to go to chemotherapy next (40% vs. 20%). But the FDA rejected it as uninterpretable for regulatory purposes because subsequent therapy wasn't controlled or randomized. The US doesn't recognize PFS2 as a valid regulatory endpoint — notably, Europe's EMA does.
3. Overall Survival (OS) The gold standard. The data was immature — only 60% of the expected events had occurred — and the FDA projected it wouldn't reach statistical significance even with full data. A small improvement was seen, but it wasn't significant. Dr. Vasan voted yes partly because OS trended in the right direction alongside the other endpoints.
4. Time to Chemotherapy Not a formal endpoint, but discussed as a meaningful concept. In ER-positive breast cancer, staying on oral therapies as long as possible matters deeply to patients. Dr. Vasan and Victoria both noted that the experience of being on oral vs. IV therapy is qualitatively different — scheduling, flexibility, daily life. This endpoint is hard to measure rigorously and wasn't formally tested.
5. Patient-Reported Outcomes (PROs) Patients on camizestrant reported a median 23 months before quality of life declined, versus just over 6 months on the aromatase inhibitor. Less pain, less shortness of breath, better emotional functioning. Dr. Sammons suggested this likely reflected treatment of subclinical progression — disease activity happening before scans could detect it. Powerful data, but PROs alone can't drive a regulatory decision without survival endpoints to support them.
The historical parallel: Dr. Vasan noted this isn't the first time a novel endpoint came to ODAC and sparked controversy. The Bevacizumab (Avastin) vote decades ago — which had a PFS benefit but no OS benefit — was deeply divisive and is now considered a landmark moment in regulatory history. SERENA-6 may be remembered the same way.
Clinical Studies Mentioned
SERENA-6, the central trial of this discussion. A Phase III randomized study by AstraZeneca testing camizestrant, an oral SERD in patients with HR-positive, HER2-negative metastatic breast cancer on first-line aromatase inhibitor therapy. Patients were randomized at the point of ESR1 mutation detection before radiographic progression to either continue standard care or switch early to camizestrant. The trial met its primary endpoint of PFS, showing a roughly six point eight months benefit. ODAC voted six-three not to recommend approval, citing concerns about trial design, the lack of overall survival data, and the absence of a structured crossover.
PADA-1, a French Phase II trial that also explored early switching based on ESR1 mutation emergence. Patients on palbociclib plus an aromatase inhibitor were monitored with liquid biopsy. Those who developed a rising ESR1 mutation were randomized to either switch to fulvestrant plus palbociclib or continue their current therapy until radiographic progression with crossover allowed. PADA-1 is smaller than SERENA-6, but is considered better designed in some respects precisely because of that crossover provision. It helped establish proof of concept for the early switch strategy, though its data on overall survival remains immature.
persevERA (negative comparator)
Drug: Giredestrant (another oral SERD) vs. letrozole, both paired with palbociclib
Question asked: Should giredestrant replace letrozole as the first-line endocrine partner?
Result: Negative — failed to meet its primary endpoint (March 2026)
Significance: Showed that oral SERDs don't automatically beat AIs in first-line for all patients; suggests they may be most powerful specifically in ESR1-mutant patients
