Do more fractionated regimens reduce severe toxicity over SBRT in patients with ILD and early-stage NSCLC?

I personally think fewer fractions are safer, such as 30 Gy x 1 instead of 10 Gy x 5, for patients with advanced COPD or ILD. Why? It's because each time a burst of ionization events is delivered to pulmonary tissues, a wound is created that recruits an inflammatory response, which can exacerbate the fragile balance of patients with COPD or ILD. Hence, fewer "events" might be better, despite the visceral concern many have about "too big" of an ionization event when delivered in a single fraction. I realize many will scratch their heads about this hypothesis, given what we've been taught about alpha-beta ratios and various BED models. Yet, the pair of phase II randomized trials comparing single vs multi-fraction SBRT suggested fewer adverse ...

We attempted to address the question of fractionation and dose in relation to lung function. Our study, published in the International Journal of Radiation Oncology, Biology, and Physics (Vol. 11, p. 528) and the British Journal of Cancer (Vol. 55, Suppl VII, pp. 324-326), involved using single, fractionated, and hyperfractionated whole-lung radiation on Sprague Dawley rats. We sacrificed the animals at various time intervals to examine lung damage. The key finding was that a higher dose per fraction resulted in more severe and earlier onset of lung fibrosis compared to hyperfractionated radiation with lower doses per fraction. We hypothesized that large single doses damage stem cells so that repair is decreased, and there is enhanced damag...

I've come to bet on single-fraction lung SBRT for these patients and have yet to see a complication. I generally deliver 25 Gy for subsolid and 30 Gy for solid tumors. I always use some sort of motion mgt strategy for these high-risk cases and won't treat them with uncontrolled free-breathing IGTV targets.