Efficacy and Safety of Moderate-Dose Stereotactic Body Radiation Therapy (SBRT) for Patients with Oligometastatic Lung Cancer Unfit for Standard SBRT: A Preliminary Single-Center Study

Background/Objectives: Stereotactic body radiation therapy (SBRT) is increasingly used for oligometastatic lung cancer. However, standard ablative SBRT (BED10 of 100 Gy or higher) is not feasible when lesions abut critical organs or patients have poor performance status. This study aimed to evaluate the efficacy and safety of moderate-dose SBRT (BED10 below 100 Gy but exceeding conventional palliative doses) in patients with oligometastatic lung cancer unfit for standard ablative SBRT. Methods: We retrospectively analyzed patients treated at a single institution between October 2019 and March 2025. Eligible patients had pathologically confirmed lung cancer with extracranial oligometastasis and received 25–40 Gy in 4–7 fractions. Patients with brain or bone metastases were excluded. The primary endpoint was local control. Secondary endpoints were event-free survival, disseminated disease-free survival, overall survival, and treatment-related toxicity. Results: Forty-three patients with 55 lesions were analyzed. The mean age was 66 years, and lymph node metastases were the most frequent site (69.1%). The most common regimen was 35 Gy in 5 fractions (63.6%). At a median follow-up of 14.7 months, objective response (complete or partial) was achieved in 54 of 55 lesions (98.2%). The 1-year and 2-year local recurrence-free survival rates were 89.7% and 86.9%, respectively, and the 1-year and 2-year overall survival rates were 83.2% and 56.1%, respectively. Local control differed by metastatic site, with 2-year rates of 95.5% for lymph node lesions and 56.2% for lesions of the lung and chest wall (p = 0.002), whereas smaller differences were observed by BED10 and oligometastatic subtype. Treatment-related toxicities occurred in 8 of 43 patients (18.6%), all of grade 1–2, and radiation pneumonitis was the most common (9.3%). No grade 3 or higher events occurred. Conclusions: In this preliminary single-center experience, moderate-dose SBRT achieved favorable local control with acceptable toxicity in oligometastatic lung cancer patients unfit for standard ablative SBRT, supporting a risk-adapted approach.