What dose do you use for single fraction SBRT when treating a small, peripheral early stage NSCLC?

There have been two randomized phase II studies of single fraction versus multi-fraction lung SBRT for medically inoperable early stage lung cancer patients. In RTOG 0915, 82% of patients were T1. In the Roswell Park Cancer Institute study, 86% of patients were stage IA. With that in mind, the current tumor under discussion is reported as 2.7 cm and thus would have been appropriate to be considered for either regimen. Although there is an obvious numeric difference in the single fraction dosing of 0915 vs. RPCI, i.e., 34 Gy vs. 30 Gy, the protocols differed in their planning, so that 30 Gy was planned homogeneously. A paper from Cleveland Clinic (Videtic et al., PMID 25015198) compared patients treated with both these regimens (on and off p...

Will echo Dr. @Dr. First Last's comments.

We treat exclusively with 34 Gy in 1 fx to all non-central lung tumors. Previously treated 27 Gy in 1 fx. While the initial trial was with 30 Gy, that was without heterogeneity correction so the delivered dose was likely 27 Gy to the periphery with het correction. We recently escalated up to 34 Gy after we found our LF rate to be ~12% at 5 years. Dosimetry-wise, our GTV mean is ~120% with Dmax ~125% within the GTV. Typically delivered using a phase-based approach to an iGTV with 5 mm margins.

With either 27 Gy or 34 Gy, we have found this regimen to be exceptionally well tolerated irrespective of proximity to the chest wall or brachial plexus (Iovoli et al., PMID 36581198). CCF has published on CW to...

The Stanford iSABR international phase II trial used an individualized volume, location, and histology adapted SABR dosing regimen.

Out of 285 treated tumors, 159 were small (GTV<10cc), peripheral tumors that were prescribed 25 Gy single fraction per protocol. 5-year treated tumor recurrence rate was 6% in this group. This is now our standard for this scenario.

Caveats:

1. Colorectal metastasis tumors were excluded from this regimen.
2. Post hoc analysis found a 5-year treated tumor recurrence of 23% in squamous histology, so we only use this for non-squamous. We also genotype tumors whenever possible and would not use this regimen in the presence of radioresistance mutations in KEAP1 or NFE2L2.
3. Technical details: heterogeneous plans with median ma...

Interesting question and to be honest, I have only done a few cases of single fraction SBRT and tend to favor the 3-5 fraction approach but in the cases I have done it, I go to 34 Gy based on RTOG 0915. If I am not able to meet an OAR, then I would consider fractionating to 3-5 and not underdosing my PTV.