Week of November 2 to November 9, 2026
Biology and frailty, not age, should guide primary endocrine therapy
Housekeeping first: the SITC 2026 Annual Meeting wrapped up November 8 in Phoenix after four days with several breast-relevant combination signals (covered below), SABCS is on the horizon in December, and the next breast-relevant regulatory date is the November 30 PDUFA for adjuvant giredestrant. This window was quiet at FDA and carried no phase 3 readout that changes management today. The lead item is a large evidence synthesis that reframes a decision breast NPs make constantly: whether an older woman with ER-positive disease needs surgery at all.
Practice-Relevant Clinical
The lead: primary endocrine therapy vs upfront surgery in older women with ER-positive breast cancer
A systematic review and meta-analysis published in JAMA Network Open (media release November 6) pooled 29 studies: 6 randomized trials and 23 observational cohorts, 22,821 patients total, median age 83.1 years (IQR 77.0 to 85.0). RCT participants were younger (median 77.0 years) and were all deemed fit for surgery, and every trial used tamoxifen as the endocrine agent, spanning five decades. Key results:
- Pooled overall survival for primary endocrine therapy vs surgery: HR 1.14 (95% CI, 0.98 to 1.33), not statistically significant, though the point estimate favored surgery. Breast cancer-specific survival: HR 1.10 (95% CI, 0.83 to 1.46), also nonsignificant. The CRC trial was the only individual trial showing a significant OS advantage for surgery; in leave-one-out sensitivity analyses the point estimate consistently favored surgery but significance varied, and BCSS never reached significance.
- Local control was the tradeoff. In the ER-enriched Nottingham II/EPS II trial (median follow-up 6.5 years), in-breast recurrence was 38% at 5 years and 43% at 10 years with primary endocrine therapy, most of it front-loaded, yet regional recurrence, distant recurrence, BCSS, and OS did not differ between arms.
- Durability tracked with biology. Median time to progression was 19.7 months (range, 13.5 to 26.0) in tamoxifen-era, biology-unselected cohorts, roughly 21 months (range, 19.2 to 24.0) in contemporary ER-confirmed cohorts, and more than 50 months in highly ER-selected, aromatase inhibitor-treated cohorts. High ER expression, low grade or low Ki-67, and smaller size predicted durable response. Frailty indices, comorbidity burden, functional status, and advanced age drove worse OS through non-breast-cancer mortality. Baseline ctDNA positivity and lack of ctDNA clearance were associated with progression in one recent cohort.
Practice implication: for the frail 82-year-old with a strongly ER-positive, low-proliferation tumor, this supports offering an aromatase inhibitor as definitive therapy with an honest conversation about local recurrence risk, rather than defaulting to surgery on age alone or reflexively to endocrine therapy on age alone. The caveats are real: the randomized base is only 813 patients, hazard ratios in four of six trials were reconstructed from Kaplan-Meier curves, and the pooled point estimate still favors surgery, so this is not evidence of equivalence. The biology-plus-frailty selection framework is explicitly conceptual and needs prospective validation. Also note the tamoxifen-era caveat: modern practice substitutes AIs, which is where the greater-than-50-month durability was observed.
Operationalizing ctDNA-guided ESR1 switching after the camizestrant approval
An OncLive perspective from Erica L. Mayer, MD, MPH, published November 2 lays out how to use the September 4 accelerated approval of camizestrant (Etcamah) plus a CDK4/6 inhibitor for emergent ESR1-mutated HR+/HER2-negative advanced breast cancer. SERENA-6 screened patients on first-line AI plus CDK4/6 inhibitor for at least 6 months with ctDNA roughly four times per year, timed to routine restaging. The 315 patients found to have an emergent ESR1 mutation without radiologic progression were randomized to switch to camizestrant 75 mg daily while continuing the CDK4/6 inhibitor (n=157) or to continue the AI (n=158): median PFS 16 months (95% CI, 12.7 to 18.2) vs 9.2 months (95% CI, 7.2 to 9.5), HR 0.44 (95% CI, 0.31 to 0.60), P < .00001. Molecular analyses showed sharp declines in ESR1 variant allele frequency and complete ctDNA clearance in a substantial proportion of switchers.
Implication: the workflow question now belongs to the clinic. That means selecting an FDA-authorized ESR1 assay, deciding whether to piggyback ctDNA on restaging labs at a SERENA-6-like cadence, and counseling patients that a mutation detected before scan progression now has an on-label action. One piece of regulatory history worth keeping straight: an April ODAC voted 6-3 against this indication and the FDA extended review in May without assigning a new date, so anyone who wrote camizestrant off in the spring should update; the accelerated approval stands.
FDA Landscape
Honest bottom line: no breast-specific FDA actions landed between November 2 and November 9. The FDA oncology approval notifications page, checked November 9, still lists the October 7 approval of tucatinib plus trastuzumab and pertuzumab for maintenance in unresectable locally advanced or metastatic HER2-positive disease as the most recent breast action. The only in-window oncology approval notification was amivantamab plus hyaluronidase-lpuj for head and neck squamous cell carcinoma on November 5, which is not breast. FDA cautions that it does not announce every approval or label update, so a small labeling or assay action could exist that I could not confirm against a primary source.
What is coming, with dates verified against a calendar updated November 8 and a detailed OncLive regulatory recap:
- Adjuvant giredestrant (Roche), priority review for ER-positive, HER2-negative stage I to III breast cancer: PDUFA date November 30, 2026, unchanged. The NDA rests on lidERA (more than 4,100 patients with medium- or high-risk disease), which reduced the risk of invasive disease recurrence or death by 30% vs standard endocrine therapy (HR 0.70; 95% CI, 0.57 to 0.87; P = .0014), with 3-year invasive disease-free survival of 92.4% vs 89.6%. Discontinuation for side effects was 5.3% vs 8.2%. If approved, this would be the first oral SERD in the adjuvant setting and will land directly in adjuvant counseling conversations, per Cure Today's review of the pending applications.
- Giredestrant plus everolimus for ESR1-mutated, ER+/HER2- locally advanced or metastatic disease after progression on a prior endocrine-based regimen: PDUFA date December 18, 2026. Basis is evERA, which met coprimary investigator-assessed PFS endpoints: in the ESR1-mutated population, median PFS 9.99 months (95% CI, 8.08 to 12.94) vs 5.45 months (95% CI, 3.75 to 5.62), HR 0.38 (95% CI, 0.27 to 0.54), P < .0001; in the ITT population, 8.77 months vs 5.49 months, HR 0.56 (95% CI, 0.44 to 0.71), P < .0001.
No slipped PDUFA dates, advisory-committee outcomes, or complete response letters surfaced in the window. If either giredestrant decision lands early, as the Trodelvy first-line TNBC review did in June when it cleared a month ahead of its goal date, the December edition will cover it.
Survivorship / Supportive Care
A thin week for this section; two items, and only one with verified numbers.
Imaging after bilateral mastectomy for DCIS
A Cancer Letter report from November 6 covers a UCLA-led study concluding that women who underwent double mastectomy for DCIS may derive little benefit from routine mammograms or other breast imaging afterward. I could verify only the study summary this week, not the underlying effect estimates, so treat this as a watch item rather than a practice change; it does add to the accumulating case against reflexive surveillance imaging in this population.
Quality of life on continued CDK4/6 inhibitor therapy
The SERENA-6 patient-reported outcome analysis, resurfaced in this week's camizestrant coverage, is worth having in mind when patients ask what switching buys them: time to deterioration in patient-reported global health status was a median 21.0 months after switching to camizestrant vs 6.4 months continuing the aromatase inhibitor plus CDK4/6 inhibitor (HR 0.54; 95% CI, 0.34 to 0.84). Staying on a CDK4/6 inhibitor longer while feeling better longer is a genuine supportive-care argument for the switch strategy.
Translational / Horizon
Guardrail: nothing in this section is practice-changing today. These are phase 1/2 signals, platform-trial readouts, and etiologic associations, and none should alter a treatment plan this week.
Invikafusp alfa plus sacituzumab govitecan (STARt-002, SITC 2026)
Interim data from the phase 1b/2 STARt-002 trial (NCT06827613), discussed by Steven Isakoff, MD, PhD, MMSc, on November 7: 48 patients enrolled (38 efficacy-evaluable) with metastatic TNBC or HR+/HER2- disease, data cutoff October 16. Invikafusp alfa (STAR0602) is a first-in-class dual T-cell agonist; correlative work confirmed selective Vβ6-positive T-cell expansion in all 8 patients examined during cycle 1. Objective response rate including unconfirmed responses was 28% in the TNBC cohort (n=18) and 25% in HR+/HER2- (n=20), with disease control rates of 67% and 80%; among patients with no prior topoisomerase I inhibitor ADC, ORRs were 36% (n=14) and 27% (n=15). Responses included a complete response ongoing beyond 12 months in TNBC and a complete response in a patient after prior T-DXd. Toxicities matched the known profiles of both agents: cytokine release syndrome in 85.4% (mostly grade 1/2; grade 3 in 16.7%), decreased neutrophil count in 68.8% (grade 3/4, 58.3%), diarrhea in 62.5%, and no treatment-related deaths. The signal worth watching is whether T-cell priming can restore or extend ADC activity in topo-I-exposed patients, but this is a small single-arm dataset and the design was not built to measure efficacy.
Rilvegostomig plus T-DXd in I-SPY2.2
Reported November 6: the anti-PD-1/TIGIT bispecific rilvegostomig combined with T-DXd (RT-DXd) in high-risk stage II/III HER2-negative early breast cancer, including HER2-low and HER2-ultralow disease. Of 377 eligible patients, 105 received RT-DXd in the first treatment block. Modeled pCR was 54% in immune-positive disease, similar across hormone receptor status; 62% of immune-positive patients who achieved pCR did so on RT-DXd alone, and 97% of that group avoided anthracycline. Immune-negative tumors responded poorly, which is the limiting signal. Safety: 13 ILD cases (one grade 3), all resolved; six serious adverse events including three pulmonary emboli. This extends the I-SPY2.2 pattern of response-gated, chemo-sparing neoadjuvant strategies, with the usual caveats about modeled estimates and adaptive randomization.
PFAS exposure and ER-negative breast cancer
An NIH analysis of the Sister Study covered by Healio on November 6 measured 17 PFAS in prediagnostic blood from 1,609 women who later developed breast cancer and 2,269 comparators. For ER-negative disease, highest vs lowest quartile risks were HR 1.67 for perfluorooctanoic acid (95% CI, 1.1 to 2.53) and HR 1.93 for perfluorooctanesulfonic acid (95% CI, 1.15 to 3.22); a meta-analysis of seven studies with prediagnostic measurements gave RR 1.3 for PFOA (95% CI, 1.05 to 1.62) and RR 1.2 for PFOS (95% CI, 0.91 to 1.58). No consistent association emerged for overall or ER-positive disease. An invited commentator appropriately flagged the relative-versus-absolute-risk caveat: modest relative effects on an uncommon subtype. Useful as an etiologic clue to ER-negative disease and honest acknowledgment of uncertainty when patients ask about chemical exposures, not a screening or prevention recommendation.
Androgen receptor tumor suppression mechanism
Adelaide University work in npj Breast Cancer (press coverage November 6) identified HRRINT3, an enhancer embedded within ZBTB16, as required for androgen receptor-mediated growth suppression in ER-positive breast cancer; CRISPR deletion of the enhancer weakened suppression, disrupted AR signaling, and increased proliferation. Background worth having as AR-agonist strategies move through testing in endocrine-resistant ER-positive disease.
Cuts Made
- ESMO 2026 late-breakers whose detailed trade coverage appeared this week but whose presentations date to October 23 to 27, before this window: izalontamab brengitecan (EGFRxHER3 bispecific ADC) in PANKU-Breast01, PFS 8.2 vs 4.0 months, HR 0.41 (ASCO Post, November 4), and trastuzumab rezetecan in HORIZON-Breast06, PFS 16.4 vs 6.8 months, HR 0.27 (Limbic, November 5). Held back as out of window; ask if you want a recap if the October 26 edition did not cover them.
- A methylation-based ctDNA MRD study in HER2-positive metastatic long-term responders (detectable in 4 of 40 long-term responders vs 10 of 11 with active disease): I could not confirm its publication date falls within this window, so it waits.
- Two small survivorship items, a peer-support intervention for Black breast cancer survivors (feasibility only, n=20) and a digital health umbrella review published October 23; the latter is out of window and the former too preliminary to act on.
- The FDA's November 5 amivantamab approval is head and neck cancer only, excluded on scope.