Dostarlimab’s Accelerated Approval in Rectal Cancer

The Food and Drug Administration’s October 19, 2026, decision permits use of dostarlimab (Jemperli) for the biomarker-defined population specified in the prescribing information. The agency assessed efficacy in 154 patients in AZUR-1, a study of adults with eligible stage II or III locally advanced rectal cancer.

For clinicians, the immediate implication is that dostarlimab can now be discussed as an FDA-authorized option when a patient meets the label’s disease, biomarker and treatment-history criteria. The equally important qualification is regulatory: accelerated approval rests on an endpoint judged reasonably likely to predict clinical benefit. Continued authorization can depend on subsequent evidence confirming that benefit.

What supported the authorization

AZUR-1 evaluated dostarlimab in 154 patients for the FDA’s efficacy assessment. The relevant evidence concerned clinical complete response and the durability of that response after immunotherapy, rather than a randomized comparison of survival, recurrence or quality of life against established multimodality treatment.

A clinical complete response means that no residual tumor is detected through the protocol’s clinical assessments. That outcome is consequential in rectal cancer because avoiding immediate surgery, radiation or cytotoxic chemotherapy could preserve organ function and reduce treatment burden. It is not, however, identical to pathological complete response, which is established by examining surgically removed tissue, nor does it by itself prove that recurrence or mortality will be reduced over many years.

The FDA decision page and prescribing information are the controlling sources for the exact response estimate, confidence interval, assessment schedule, data cutoff and reported duration of follow-up. Those details matter when counseling patients: an enrollment count or headline response rate cannot show how long responses will last, and confidence intervals describe statistical precision rather than certainty for an individual.

How accelerated approval changes the interpretation

Accelerated approval is an FDA approval, not experimental-use status. It allows a drug to be marketed for the authorized indication and enables clinicians to prescribe it within ordinary US practice, subject to the label, professional judgment, local capability and coverage rules.

But the pathway answers a narrower question than traditional approval, which is supported by mature clinical outcomes. Under the FDA’s accelerated approval program, authorization may be based on a surrogate endpoint or an intermediate clinical endpoint considered reasonably likely to predict benefit. A sponsor must generally complete confirmatory work, and the FDA can pursue withdrawal if later evidence does not verify benefit or if required studies are not conducted with due diligence.

Treatment discussions should make that distinction explicit. The decision establishes that the FDA found the available evidence sufficient for earlier access in the defined population. It does not mean that dostarlimab has already been shown, in a randomized trial with long follow-up, to improve overall survival, disease-free survival, permanent organ preservation or quality of life compared with chemoradiation and surgery.

The absence of a concurrent comparator also limits causal interpretation. AZUR-1 can characterize responses observed after dostarlimab, but it cannot directly estimate how the same participants would have fared under another strategy. Cross-study comparisons are particularly vulnerable to differences in tumor biology, staging, assessment methods, follow-up and patient selection.

What the decision means in practice

Eligibility begins with the FDA label. Clinicians should verify the required tumor biomarker status using an appropriate assay and confirm that the stage, anatomic setting and prior-treatment history fit the authorized indication. “Stage II or III rectal cancer” alone is not sufficient; the approval applies to a selected population rather than all patients with locally advanced disease.

Baseline staging and multidisciplinary review remain important. A response-based strategy requires expertise in rectal MRI, endoscopy, digital examination and longitudinal surveillance. Assessments should be interpreted together because no single test can reliably exclude small-volume residual disease in every patient.

Treatment discussions should place potential organ preservation alongside uncertainty. A patient may value avoiding a permanent ostomy, pelvic radiation, chemotherapy or the functional effects of rectal surgery. Those potential advantages must be balanced against immune-related toxicities, the possibility of incomplete or temporary response, intensive follow-up and the need for subsequent local or systemic treatment if disease persists or returns.

Accelerated approval may also affect access without guaranteeing it. Payers can apply prior authorization, biomarker documentation and site-of-care requirements. Institutions may need pathways defining who confirms eligibility, how response is assessed and when patients are referred for surgery or other treatment. Coverage policies should reflect the FDA indication while avoiding language that turns a conditional evidence base into a claim of proven long-term superiority.

Shared decision-making should therefore distinguish three ideas: the treatment is FDA authorized; the observed response evidence was strong enough for accelerated access; and the ultimate effect on durable cancer control and survival remains to be confirmed. These statements are compatible, not contradictory.

Important evidence gaps

The central limitation is study design. Without randomization or a concurrent control group, AZUR-1 cannot determine comparative effectiveness or rule out the influence of selection and assessment practices. Its size—154 patients in the efficacy analysis—also limits evaluation of uncommon toxicities and outcomes in narrowly represented subgroups.

Follow-up is another constraint. Rectal cancer can recur after an apparent clinical complete response, so early response and short-term durability cannot substitute for mature local-regrowth, distant-metastasis, disease-free-survival and overall-survival data. Long-term organ preservation must include patients who later require salvage treatment, not only those who initially avoid surgery.

Trial eligibility, specialist imaging, and close surveillance may limit generalizability. Outcomes in routine practice could differ if biomarker testing, response assessment or follow-up is less standardized. Financial burden, access to experienced multidisciplinary teams and patient capacity for frequent surveillance also influence whether the strategy is workable outside a study.

Confirmatory evidence should clarify how durable responses are, whether delayed surgery remains effective after regrowth, and how patient-reported bowel, urinary, sexual and overall quality-of-life outcomes compare with established care. The FDA’s Project Confirm framework emphasizes that accelerated oncology approvals require timely verification and public tracking of post-approval obligations.

Questions clinicians ask

Does accelerated approval mean dostarlimab is now standard treatment for every stage II or III rectal cancer?

No. It is an FDA-authorized option only for adults who meet the full label criteria, including the specified biomarker and clinical characteristics. Stage alone does not establish eligibility, and multidisciplinary discussion remains necessary because the evidence does not cover all locally advanced rectal cancers.

Can a clinical complete response be treated as a cure?

No. A clinical complete response means that protocol-defined examinations do not detect residual tumor at that time. Microscopic disease may remain, and local or distant recurrence can occur later; sustained surveillance and mature recurrence data are therefore essential before long-term clinical benefit can be considered confirmed.

How should the lack of a randomized comparator be explained?

The study shows what happened among patients who received dostarlimab, but it does not directly show that dostarlimab produced better survival, organ preservation or quality of life than established treatment. Comparisons with historical cohorts cannot fully account for differences in patient selection, staging and follow-up.

Could the indication change after accelerated approval?

Yes. Continued approval may depend on confirmatory evidence verifying clinical benefit. The FDA can revise labeling or pursue withdrawal if required studies fail to confirm benefit, are delayed, or change the treatment’s benefit-risk assessment; clinicians should therefore follow regulatory updates and emerging long-term outcomes.

References

1. FDA grants accelerated approval to dostarlimab for locally advanced rectal cancer — US Food and Drug Administration, 2026 2. Accelerated Approval Program — US Food and Drug Administration, n.d. 3. Project Confirm — US Food and Drug Administration, n.d.