An 83 percent reduction in the risk of recurrence or death is among the largest figures reported in lung cancer treatment. It is also one of the most commonly misread numbers in medical news, and understanding it requires three pieces of context that rarely fit in a headline.
The finding comes from LIBRETTO-432, a randomized, double-blind Phase 3 trial of Retevmo (generic name selpercatinib), given after surgery or definitive radiotherapy in patients with early-stage RET fusion-positive non-small cell lung cancer. The trial met its primary endpoint of investigator-assessed event-free survival. The results were published in the New England Journal of Medicine and presented in the plenary session of the 2026 ASCO Annual Meeting, so this is peer-reviewed data rather than a company claim awaiting scrutiny.
The Number Describes Relative Risk, and It Applies to a Subgroup
The first piece of context is what kind of number 83 percent is, and which patients it describes.
It is a relative risk reduction expressed as a hazard ratio, meaning the rate at which cancer recurred, progressed, or patients died was 83 percent lower in the treated group than in the placebo group over the follow-up period. It is not a statement that 83 percent of patients were cured, nor that 83 percent survived, nor that any individual patient has an 83 percent chance of benefit.
It also describes the trial's primary analysis population, the 109 participants with stage II or IIIA disease, not the full enrolled group. In that population, the hazard ratio was 0.172, with a 95 percent confidence interval running from 0.058 to 0.509. The wide interval is a signal of precision, not doubt about direction.
The absolute figures are the ones a patient should weigh. At two years, 92 percent of patients on selpercatinib remained free of an event, against 61 percent on placebo. That is roughly a 31 percentage point absolute difference. Median event-free survival was not reached in the treatment group and was 31.8 months with placebo.
Follow-up was a median of 24 months in the selpercatinib group and 27 months in the placebo group, with treatment given for up to three years. Event-free survival counts recurrence, progression, or death, which is a legitimate endpoint in the adjuvant setting but is not the same as overall survival. Longer follow-up is required before anyone can say whether preventing recurrences translates into people living longer.
RET Fusions Affect a Small Minority of Lung Cancers
The second piece of context is who the finding applies to.
RET fusions are potent cancer drivers, but they are present in only about 1 to 2 percent of lung cancers. The trial enrolled 151 patients with stage IB to IIIA disease across 22 countries, randomized one-to-one to selpercatinib or placebo following surgery with or without radiotherapy. Dosing was 160 mg twice daily for patients weighing at least 50 kg and 120 mg twice daily for those below that weight.
One hundred fifty-one patients is a small trial by lung cancer standards, which reflects how uncommon the biomarker is rather than any shortcut in design. A rare driver mutation means a small eligible population, which means small trials and wider confidence intervals around the estimate.
The practical consequence is that this result does not apply to the great majority of people with early-stage lung cancer. It applies to those whose tumors carry a RET fusion, and the only way to know that is testing.
Testing Is the Part Patients Can Act On
The third piece of context is the one with an immediate consequence.
Dr. Jonathan Goldman of UCLA, one of the study investigators, noted that up to two-thirds of patients with early-stage non-small cell lung cancer experience recurrence despite surgery or radiation followed by adjuvant chemotherapy or immunotherapy, and that no adjuvant targeted therapy had been approved for the RET fusion subset. Addressing the rarity of the biomarker directly, he said: "Rarity should not be mistaken for marginal importance."
That framing points at the actionable step. Comprehensive genomic testing at diagnosis has been standard practice in advanced lung cancer for years, but it has historically been performed less consistently in early-stage disease, where the assumption was that surgery plus chemotherapy was the whole plan. ASCO's own commentary on the trial made the same point, describing the results as reinforcing the need for comprehensive biomarker testing across all stages.
Patients with newly diagnosed non-small cell lung cancer, at any stage, can ask their oncologist whether comprehensive biomarker testing has been ordered, which alterations it covers, and whether results will be available before adjuvant treatment decisions are made. Turnaround can take weeks, which is why timing the request early matters.
The Limits Worth Holding Onto
Several things this result does not establish deserve to be stated rather than buried.
It does not demonstrate an overall survival benefit, which requires longer follow-up. It does not tell an individual patient their personal probability of benefit. It does not address patients outside stage IB to IIIA or those without a RET fusion. And the trial's size, while appropriate for the biomarker's rarity, limits the precision of the estimate.
Side effects are part of the calculation. In Lilly's report of the trial, the most common Grade 3 or higher adverse events were elevated liver enzymes, with raised AST in 19 percent of the selpercatinib group against 3 percent on placebo, and raised ALT in 17 percent against 1 percent. The company described these as manageable with dose modification, but they represent real monitoring requirements over three years of therapy.
Cost and access are unresolved specifically for the adjuvant setting. Selpercatinib is approved for advanced RET-driven cancers, and use after surgery in early-stage disease is a different indication with its own regulatory and coverage path. Patients should ask about coverage, prior authorization, and manufacturer patient-assistance programs rather than assuming an approved drug is automatically covered for a new use.
Nobody should change treatment based on a trial summary. Adjuvant therapy decisions involve recurrence risk, comorbidities, tolerance of three years of twice-daily medication, and side effects, and belong with a treating oncologist. This article is general information and is not a treatment recommendation.
MedicalDaily will report any regulatory submission or label expansion for the adjuvant indication, and longer-term survival data as it becomes available.
Frequently Asked Questions
What does an 83 percent risk reduction mean? In the trial's primary analysis population, the rate of recurrence, progression, or death was 83 percent lower with selpercatinib than with placebo. It does not mean 83 percent of patients were cured or survived.
What were the absolute numbers? At two years, 92 percent of treated patients were event-free against 61 percent on placebo, roughly a 31 percentage point difference.
Is this the same as a survival benefit? No. The endpoint was event-free survival at a median follow-up of about two years. Overall survival data requires longer follow-up.
Who does this apply to? The trial enrolled patients with stage IB to IIIA RET fusion-positive disease. The headline figure comes from the stage II to IIIA group.
How common are RET fusions? About 1 to 2 percent of lung cancers, which is why the trial enrolled 151 patients.
Has the data been reviewed? Yes. It was published in the New England Journal of Medicine and presented at the ASCO plenary session.
Is the drug available for this use? Selpercatinib is approved for advanced RET-driven cancers. Use after surgery in early-stage disease follows a separate regulatory and coverage path.
