KEY POINTS
- ONE STOP (NCT06236516) was a prospective pilot trial testing direct-to-unit, simulation-free lung SBRT for stage I–IIA NSCLC or pulmonary oligometastases. Tumors had to be ≤5 cm, at least 2 cm from the proximal bronchial tree, and demonstrate <1 cm superior-inferior motion.
- Diagnostic CT or PET/CT provided the pre-planning anatomy, while a 60-second slow CBCT acquired on a Varian Ethos/HyperSight system defined the treatment-day ITV. A 5-mm isotropic PTV margin was then applied and the plan was re-optimized directly on CBCT.
- 8/10 patients (80%) completed the direct-to-unit workflow, exceeding the predefined feasibility threshold of ≥70%. One patient failed screening because respiratory motion exceeded 1 cm; another was converted to conventional treatment because online optimization produced unacceptable dosimetry.
- Seven treated patients received 34 Gy in one fraction and one received 30 Gy. All delivered adaptive plans satisfied protocol Priority-1 organ-at-risk constraints; the lowest PTV V100% among treated patients was 85.1% where organ-at-risk priorities limited coverage.
- Target coverage was not significantly different between direct-to-unit and backup simulation-based plans: median differences were −2.2 percentage points for PTV V100% (p=0.55), +1.9 for ITV D99% (p=0.46), and +0.6 for PTV D95% (p=0.67). Formal non-inferiority was not demonstrated because of the very small sample.
- Direct-to-unit plans had significantly higher intermediate-dose spillage, with R50 increased by a median 0.74 (p=0.008). Median total vault time was 72.35 minutes (range 62.7–94.8), with a median 6 CBCTs per patient; mid-treatment imaging prompted couch corrections after >2-mm deviations in five scans across four patients.
CLINICAL TAKEAWAY
ONE STOP demonstrates that selected small peripheral lung tumors can technically proceed from prior diagnostic imaging to adaptive single-fraction SBRT without conventional simulation. The workflow is promising for reducing visit burden, but it remains resource-intensive, selection-dependent, and supported by only eight successfully treated patients; clinical outcome data are still pending.