SARON: Consolidation Radiotherapy Improves PFS but Not Overall Survival in Oligometastatic NSCLC

For patients with synchronous oligometastatic non-small cell lung cancer , the rationale for aggressive local treatment is compelling: if systemic therapy controls microscopic disease while radiotherapy eradicates the limited sites of visible cancer, could that strategy meaningfully delay progression, or even extend survival?

The randomized phase II SARON trial, presented at ESMO Congress 2026 , provides one of the most important prospective tests of that strategy specifically in patients with synchronous oligometastatic NSCLC without actionable genomic alterations. Adding consolidation radiotherapy to first-line systemic anticancer therapy significantly improved progression-free survival and substantially reduced progression at the sites of disease already present at diagnosis.

However, that improvement did not translate into longer overall survival. Median PFS was 13.9 months with systemic therapy plus radiotherapy compared with 8.9 months with systemic therapy alone, corresponding to an HR of 0.64 (95% CI 0.43–0.95; P=0.03). The effect on local disease control was even more striking.

Progression at sites of initial disease occurred in 13.0% of patients receiving consolidation radiotherapy versus 39.5% with systemic therapy alone. Yet median overall survival was virtually identical: 31.0 versus 28.0 months, with an HR of 0.99 (95% CI 0.63–1.55; P=0.95). SARON therefore supports the biological effectiveness of treating all visible disease in selected oligometastatic NSCLC, but it also defines the limits of that approach: better local control and longer PFS do not necessarily mean patients live longer.

Testing Local Consolidation in Synchronous Oligometastatic NSCLC The oligometastatic concept proposes that some patients with a limited metastatic burden occupy an intermediate biological state between localized and widely disseminated cancer. For these patients, aggressively treating every known site of disease could theoretically prevent existing metastases from becoming sources of further dissemination and extend the period before systemic progression.

Earlier randomized data provided support for this strategy. In the landmark randomized phase II trial led by Daniel Gomez and colleagues, patients with NSCLC and three or fewer metastatic sites who had not progressed following first-line systemic therapy experienced markedly longer PFS with local consolidative therapy.

Longer follow-up also showed an OS advantage, with median OS of 41.2 months versus 17.0 months in the maintenance or observation group. However, that study randomized only 49 patients and was conducted before the modern immunotherapy era. The broader SABR-COMET trial, which enrolled patients with several different tumor types, also strengthened the oligometastatic treatment concept by demonstrating durable survival outcomes after stereotactic ablative radiotherapy, although only a minority of participants had lung cancer.

SARON was designed to address the question in a larger, NSCLC-specific randomized population. How SARON Was Designed SARON was a multicenter randomized phase II study conducted across 22 centers in the United Kingdom. Patients had NSCLC without a targetable driver alteration and one to five synchronous metastases involving up to three organs, with all metastatic sites amenable to stereotactic ablative radiotherapy or stereotactic radiosurgery.

Patients initially received approximately six to eight weeks of systemic anticancer therapy. Those with complete response, partial response or stable disease and adequate performance status could proceed to randomization. In the final analysis, 140 patients were randomized, with 70 assigned to systemic therapy alone and 70 to systemic therapy followed by consolidation radiotherapy.

The radiotherapy strategy was comprehensive rather than metastasis-only treatment. The primary lung tumor, with or without involved lymph nodes, was treated with conventional radical radiotherapy or SABR, while metastatic sites received SABR or stereotactic radiosurgery when appropriate.

Patients were then followed for up to three years or until death, with maintenance systemic treatment permitted where clinically indicated. The population was representative of clinically selected oligometastatic disease rather than exclusively very low-volume stage IV cancer. Median age was 68 years, 59.3% were men and 58.6% had adenocarcinoma.

More than half had N2 or N3 nodal disease. Most patients had a single oligometastatic site, but patients with as many as five metastases were eligible. Importantly, the trial crossed major changes in NSCLC systemic treatment.

Enrollment ran from 2016 through 2023, and the control strategy was modified after immunotherapy entered routine first-line practice. Overall, 40% of patients received chemotherapy, 15% received immunotherapy and 45% received combined chemoimmunotherapy. That makes SARON more relevant to contemporary practice than older chemotherapy-era studies, but also introduces treatment heterogeneity when interpreting the overall result.

Consolidation Radiotherapy Significantly Improved PFS After a median follow-up of approximately 37.4 months, SARON demonstrated a statistically significant improvement in progression-free survival. Median PFS increased from 8.9 months with systemic therapy alone to 13.9 months with systemic therapy plus consolidation radiotherapy.

The HR of 0.64 represents an approximately 36% reduction in the hazard of progression or death. The absolute improvement in median PFS was five months. For an oligometastatic population, however, understanding where progression occurred may be even more informative than the median PFS difference itself.

That analysis provides perhaps the clearest evidence that the radiotherapy strategy achieved exactly what it was biologically intended to achieve. Radiotherapy Dramatically Reduced Failure at Known Disease Sites Among patients receiving systemic therapy alone, the cumulative incidence of progression at sites of disease already present at baseline reached 39.5%.

With consolidation radiotherapy, that rate fell to 13.0%. The difference was highly significant. This approximately threefold reduction in progression at initial disease sites demonstrates that comprehensive local treatment was highly effective at suppressing the disease that clinicians could see and target.

The pattern was very different for the appearance of metastases at completely new sites. New-site progression occurred in 32.3% with systemic therapy alone and 36.2% with systemic therapy plus radiotherapy, with no statistically significant difference. That distinction may help explain the trial’s overall outcome.

Radiotherapy controlled existing lesions, but it could not eliminate occult micrometastatic disease already present elsewhere in the body. In other words, SARON appears to have changed where and when progression occurred, without fundamentally eliminating the systemic metastatic potential of the disease.

Better PFS Did Not Translate Into Longer Survival The primary overall survival result is therefore critical. Median OS was 31.0 months with consolidation radiotherapy and 28.0 months with systemic therapy alone. The HR was 0.99, with a P value of 0.95.

There was essentially no evidence of an overall survival advantage. This is particularly important because previous smaller randomized studies helped establish enthusiasm for aggressive local consolidation partly by suggesting that improved local control might eventually produce longer survival.

SARON confirms the PFS component of that hypothesis but does not reproduce an OS benefit. Several explanations are possible. Subsequent treatments after progression may reduce survival differences between arms.

Patients progressing after systemic therapy alone may still receive salvage radiotherapy. Modern immunotherapy and other systemic approaches may also improve post-progression outcomes, making an incremental survival effect from early radiotherapy harder to demonstrate. It is also possible that oligometastatic NSCLC remains fundamentally systemic in many patients despite having only a small number of radiographically visible metastases.

The absence of a reduction in new metastatic sites in SARON supports that interpretation. The Modern Immunotherapy Era Complicates Interpretation One of the most important features of SARON is also one of its major limitations. The study began in 2016, before immune checkpoint inhibitors became routine first-line therapy across much of advanced NSCLC, and continued through 2023.

The systemic treatment backbone therefore evolved during enrollment. Forty percent of patients received chemotherapy alone, 15% immunotherapy and 45% chemoimmunotherapy. This means SARON cannot fully answer whether consolidation radiotherapy provides the same magnitude of benefit in a population treated uniformly with contemporary chemoimmunotherapy.

That question is increasingly important because durable systemic disease control is now achievable in a subgroup of patients receiving checkpoint blockade. At the same time, modern therapy may make identification of the right candidates for consolidation even more relevant. Patients with deep responses to initial systemic therapy and persistent limited residual disease could represent a biologically distinct population in whom ablating remaining sites has greater value.

Future studies will need to incorporate systemic response, molecular characteristics, circulating tumor DNA and other biomarkers rather than relying exclusively on the number of visible metastases. Safety Did Not Show a Major Price for Local Consolidation A concern surrounding comprehensive radiotherapy in metastatic NSCLC is whether treating the primary tumor, lymph nodes and multiple metastatic sites adds clinically meaningful toxicity.

In SARON, grade ≥3 adverse events occurred in 28.6% of patients in both treatment groups. Six patients experienced grade 3 events considered possibly related to radiotherapy. Quality-of-life outcomes assessed with EORTC instruments were similar between groups.

These findings are reassuring. The PFS improvement therefore was not achieved at the cost of a major increase in overall severe toxicity or measurable deterioration in quality of life. This becomes clinically relevant when discussing consolidation with carefully selected patients.

Even in the absence of an OS advantage, delaying progression while maintaining quality of life may still be valuable, particularly when progression at existing sites could produce symptoms or require subsequent intervention. SARON Does Not End the Oligometastatic Treatment Paradigm A negative OS result should not be interpreted as showing that local therapy has no role in oligometastatic NSCLC.

The trial provides clear evidence that radiotherapy works at the sites it treats. It improved PFS and dramatically reduced recurrence at known sites of disease. What SARON challenges is the assumption that those advantages automatically translate into longer overall survival.

This distinction should influence clinical discussions. For an individual patient with one or a few residual lesions after a strong systemic response, particularly lesions that could later produce significant morbidity, consolidative radiotherapy may remain highly reasonable. But the rationale should increasingly focus on durable disease control, delaying progression and preventing local failure rather than promising a survival advantage that SARON did not demonstrate.

The findings also argue against treating every patient with oligometastatic NSCLC identically. Oligometastatic disease defined purely by lesion count is likely biologically heterogeneous. Some patients may truly have limited metastatic potential.

Others may simply have systemic disease that has not yet become radiographically visible. Identifying which group a patient belongs to may ultimately be more important than the technical ability to irradiate every visible lesion. What SARON Adds to Previous Evidence Previous randomized trials established the possibility that local consolidation could improve outcomes in oligometastatic NSCLC, but many were small and preceded modern immunotherapy.

The Gomez study demonstrated striking improvements in both PFS and OS after local consolidative therapy, but included fewer than 50 randomized patients. SARON contributes a substantially larger disease-specific randomized dataset and includes patients treated during the immunotherapy era.

Its findings are simultaneously supportive and cautionary. They support aggressive local treatment as an effective way to control known oligometastatic disease. But they weaken the assumption that comprehensive radiotherapy necessarily extends life.

That distinction may ultimately make the oligometastatic treatment paradigm more precise rather than less relevant. OncoDaily Takeaway The randomized phase II SARON trial demonstrates that adding consolidation radiotherapy to first-line systemic therapy in synchronous oligometastatic, actionable-genomic-alteration-negative NSCLC significantly improves disease control.

Median PFS increased from 8.9 to 13.9 months, corresponding to an HR of 0.64. The clearest biological effect was seen at the sites already known at diagnosis: progression at initial disease sites fell from 39.5% with systemic therapy alone to 13.0% with systemic therapy plus radiotherapy.

However, radiotherapy did not reduce the development of new distant metastatic sites, which occurred in approximately one-third of patients in both groups. Most importantly, improved PFS and local control did not translate into an overall survival benefit. Median OS was 31.0 versus 28.0 months, with an HR of 0.99.

Severe toxicity was not increased overall, and quality of life remained similar. SARON therefore should not be framed as proving that consolidation radiotherapy prolongs survival in oligometastatic NSCLC. Its more defensible message is that local therapy can meaningfully delay progression by controlling known disease sites, with acceptable toxicity, but systemic metastatic relapse remains the limiting problem.

The next challenge is no longer simply determining whether all visible metastases can be treated. It is identifying which patients have disease biology in which treating all visible metastases can meaningfully alter the natural history of their cancer. Source McDonald F, et al.

Primary results of SARON: A randomised-controlled trial of consolidation radiotherapy for synchronous oligometastatic non-small cell lung cancer. Presented at ESMO Congress 2026, Madrid, October 25, 2026. ClinicalTrials.gov identifier: NCT02417662.

Sponsored by University College London and funded by Cancer Research UK.