Single-fraction stereotactic radiotherapy for lung malignancies: preliminary results of a mono-institutional...

The use of stereotactic body radiotherapy for primary and secondary lung lesions is well established. Although being supported by international guidelines, the application of single-fraction treatments is less reported in the literature.

We report a mono-institutional, retrospective analysis of inoperable patients with small lung lesions-including both primary tumors and oligometastases-treated with single-fraction SBRT (SF-SBRT) via a helical tomotherapy linac. Although analyzed retrospectively, all data were prospectively collected. Acute and late toxicities were graded using CTCAE v5.0, while local control (LC), distant progression-free survival (DPFS), and overall survival (OS) were estimated via Kaplan-Meier and Cox regression models.

From August 2023 a total of 50 lung lesions in 49 patients. median age of 77 years (IQR, 72-80) received SF-SBRT. Thirty patients (61.2%) were male. Seven patients (14.3%) had a pacemaker or implantable cardioverter-defibrillator. Of the 50 treated lesions, 30 (60.0%) were primary NSCLC and 20 (40.0%) were pulmonary metastases, being colorectal cancer the most frequent non-pulmonary primary tumor. Most lesions were located in the right lung (62.0%) and in the upper lobe (64.0%). The median maximum tumour diameter was 1.9 cm (IQR, 1.6-2.4), and median prescription dose, for the entire cohort, was 27 Gy (IQR, 26-28), corresponding to a median BED₁₀ of 100 Gy (IQR, 93.6-106.4). At a median follow-up of 13.7 months, one local recurrence was observed among the 50 treated lesions (2.0%), distant progression occurred in six of 49 patients (12.2%), while three patients (6.1%) died during follow-up. The estimated 12-month local control, distant progression-free survival and overall survival rates were respectively 100.0%, 89.4% (95% CI, 78.7-100.0%) and 89.5% (95% CI, 78.9-100.0%). No grade 3 or higher adverse events were recorded for both acute and late toxicity patterns.

In elderly patients with a significant burden of comorbidities presenting with isolated lung malignancies, single-fraction SBRT achieved remarkable metabolic responses alongside excellent short-term tolerance and survival. Despite the limitations of a small sample size and few events, these findings support the feasibility and biological effectiveness of single-fraction RT in selected frail subjects, warranting further prospective validation.