Radiation Oncology Trials You May Have Missed at ASCO 2026

The 2026 American Society of Clinical Oncology (ASCO) Annual Meeting brought forward a wave of practice-changing data, with radiation oncology taking center stage in several pivotal discussions. From innovative, localized delivery systems to optimized chemoradiotherapy regimens, the presentations highlighted a strong push toward maximizing therapeutic efficacy while preserving patient quality of life.

Whether you were unable to attend or simply need a recap of the packed schedule, keeping up with the rapid pace of oncology breakthroughs can be a challenge. To help you stay ahead of the curve, CancerNetwork® has synthesized radiation oncology data across tumor types presented this year.

Post-operative Stereotactic Radiation Vs Resection and Cesium-131 Tile-Based Radiation

The phase 3 ROADS trial (NCT04365374) demonstrated superior efficacy for patients with newly diagnosed surgical brain metastases who were treated with resection plus tile-based radiation therapy.¹ The collagen tiles were embedded with cesium-131 seeds and placed at surgery, which helped to initiate focal radiation.

The median time to surgical bed recurrence (SBR) was not reached in the tile-based arm vs 17.4 months in the stereotactic radiotherapy (SRT) arm (HR, 0.06; 95% CI, 0.01-0.06; P = .007). The 12-month cumulative incidence of SBR was 1.3% vs 15.4%, respectively (HR, 0.07; 95% CI, 0.01-0.56; P = .012). The median surgical bed recurrence-free survival was not reached in the tile-based arm but was 10.9 months in the SRT arm (HR, 0.48; 95% CI, 0.30-0.76; P = .0021).

The median overall survival (OS) was 42.5 months vs 17.6 months in each arm (HR, 0.59; 95% CI 0.37-0.96; P = .032). Additionally, the 24-month OS rate was 61.7% (95% CI, 48.4%-72.5%) in the tile-based arm and 35.7% (95% CI, 20.2%-51.5%) in the SRT arm. Distant brain failure remained similar in each arm (HR, 0.93; 95% CI, 0.57-1.54; P = .79).

Adverse effects (AEs), serious AEs, or grade 3 or higher treatment-related AEs remained well-balanced between both treatment arms.

“In patients with newly diagnosed surgical brain metastasis, the phase 3 ROADS trial compared resection with tile-based radiation therapy to the standard of care resection followed by stereotactic radiation therapy,” Jeffrey S. Weinberg, MD, FAANS, FACS, professor of Neurosurgery, deputy chair and vice-chair of Clinical Operations in The Department of Neurosurgery, and director of the Intraoperative MRI Program at The University of Texas MD Anderson Cancer Center, said during the presentation. “Superior efficacy did not come at the expense of increased toxicity.”

STAMP: Adjuvant Pembrolizumab Plus SOC Radiation Therapy Vs Observation/SOC

Patients with surgically resected Merkel cell carcinoma (MCC) were treated with adjuvant pembrolizumab (Keytruda) plus standard of care (SOC) radiation, which was initiated within 14 days of cycle 1, day 1, compared with observation vs SOC radiation, according to results from the phase 3 STAMP trial (NCT03712605).² Those in the pembrolizumab arm had a trend toward improved RFS and significantly prolonged distant metastasis-free survival (DMFS).

A numerical but not statistically significant improvement in RFS was noted with pembrolizumab (HR, 0.77; 90% CI, 0.55-1.08; P = .102). The 12-month RFS rate was 83% (90% CI, 77%-88%) in the pembrolizumab arm vs 72% (90% CI, 65%-78%) in the SOC arm. The 24-month rates were 72% (90% CI, %65-77%) vs 66% (90% CI, 59%-72%), respectively.

DMFS was significantly improved in the pembrolizumab arm (HR, 0.58; 90% CI, 0.35-0.96; P = .035). The 18-month DMFS rate was 87% (90% CI, 81%-91%) in the pembrolizumab arm vs 80% (90% CI, 74%-85%) in the SOC arm.

No significant difference was noted with OS between each arm (HR, 1.62; 90% CI, 0.94-2.81; P = .928).

“EA6174 demonstrated that pembrolizumab given after surgery resulted in a trend toward improved RFS,” Janice M. Mehnert, MD, professor in the Department of Medicine at NYU Grossman School of Medicine, director of the Melanoma Medical Oncology Program, and associate director of Clinical Research at Perlmutter Cancer Center, said during the presentation.

Hypofractionated RT and QOL Outcomes in Locally Advanced Cervical Cancer

A compromise in health-related quality of life (HRQOL) or functional outcomes was not observed with the use of hypofractionated radiotherapy for patients with locally advanced cervical cancer, according to results from a phase 2 trial (NCT03750539).³

Based on the EORTC QLQ-C30, the global health status/QOL was 66.9 at baseline followed by 65.7 during treatment and recovering to 79.1 in the standard fractionation arm vs 65.8 at baseline in the hypofractionation arm and transitioning to 64.6 during treatment and followed by 74.4 (P = .001). For physical functioning, the rates were 86.6, 75.2, and 86.4 in the standard fractionation arm vs 88.0, 79.0, 86.8 in the hypofractionation arm (P = .001).

Fatigue was assessed between both arms of 29.0, 67.0, and 57.2 vs 27.9, 67.4, and 57.0 (P = .001). For those with diarrhea the baseline rate was 90.1, followed by 77.7, and 92.5 vs 86.6, 67.6, and 91.1 (P = .001). Finally, appetite loss was 78.2, 66.6, and 89.7 vs 78.8, 66.6, and 83.3 (P = .001).

“Future research should focus on prospective multicenter studies with larger patient populations and longer follow-up to validate these findings and better define long-term outcomes, including survival and late toxicities,” David Francisco Cantu De Leon, MD, of Instituto Nacional de Cancerología, Mexico City, Mexico, lead study author of the presentation, and coauthors, wrote.

Non-Inferior Efficacy/Lower Toxicities With Carboplatin-Based Induction-Concurrent CRT in HNC

For patients with locally advanced nasopharyngeal carcinoma (LA-NPC), receipt of carboplatin-based induction-concurrent chemoradiotherapy (IC-CCRT) showed noninferior efficacy and less frequent toxicities compared with cisplatin-based IC-CCRT, based on findings from a phase 3 trial (NCT03919552).⁴

Failure-free survival (FFS) in the intent-to-treat population with events noted in 12.4% in the carboplatin arm vs 14.5% in the cisplatin arm, and 3-year rates were 84.8% (95% CI, 79.5%-90.1%) vs 86.8% (95% CI, 82.1%-91.5%). In the per-protocol population, the 3-year FFS rate was 84.7% (95% CI, 79.0%-90.4%) vs 86.1% (95% CI, 81.0%-91.2%), respectively (HR, 1.10; 95% CI, 0.65-1.88; P = .656).

In the carboplatin arm, the 3-year OS rate was 96.2% (95% CI, 93.5%-98.9%) vs 97.4% (95% CI, 95.0%-99.8%) in the cisplatin arm (HR, 0.85; 95% CI, 0.33-2.21; P = .745). Additionally, the 3-year DMFS rates were 91.0% (95% CI, 86.7%-95.3%) vs 89.6% (95% CI, 85.5%-93.7%), respectively (HR, 1.59; 95% CI, 0.87-2.92; P = .130). Of note, the locoregional FFS 3-year rate was 91.6% (95% CI, 87.3%-95.9%) vs 95.3% (95% CI, 92.4%-98.2%), in each arm, respectively (HR, 0.83; 95% CI, 0.41-1.70; P = .613).

“These findings support carboplatin-based IC-CCRT as a promising alternative treatment landscape for LA-NPC,” Jian Guan, MD, oncologist at Nanfang Hospital and Southern Medical University in Guangzhou, China, and principal investigator of the phase 3 study, stated in the presentation.

References

1. Weinberg JS, Lin HY, McAleer MF, et al. Final results of a randomized, controlled, phase 3 trial comparing resection and post-operative stereotactic radiation versus resection and cesium-131 tile-based radiation for treatment of newly diagnosed brain metastases. J Clin Oncol. 2026;44(suppl 16):LBA2000. doi:10.1200/JCO.2026.44.17_suppl.LBA2000
2. Mehnert JM, Lee SJ, Gastman B, et al. Updated outcomes from STAMP: surgically treated adjuvant Merkel cell carcinoma with pembrolizumab, a phase III trial–ECOG-ACRIN EA6174. J Clin Oncol. 2026;44(suppl_16):LBA9505. doi:10.1200/JCO.2026.44.17_suppl. LBA0505
3. Cantu De Leon DF, Gallardo Alvarado LN, Moreno-Flores G, et al. Quality of life outcomes following hypofractionated radiotherapy in locally advanced cervical cancer. J Clin Oncol. 2026;44(suppl 16):5534. doi:10.1200/JCO.2026.44.16_suppl.5534
4. Wang XQ, Chen M, Liu X, et al. Carboplatin-based versus cisplatin-based induction-concurrent chemoradiotherapy with locoregionally advanced nasopharyngeal carcinoma: a multicenter, parallel-group, non-inferiority, randomized, phase 3 trial. J Clin Oncol. 2026;44(suppl 15):6004. doi:10.1200/JCO.2026.44.16_suppl.6004