Oncological Results and Toxicities of Stereotactic Body Radiotherapy in Ultracentral Lung Tumors

Stereotactic body radiotherapy (SBRT) is an effective and safe treatment for early stage lung cancer and lung metastasis. However, SBRT dosing schedules are still controversial due to the risk of toxicity when considering the therapeutic index in ultracentral tumors. In the current study, patients with ultracentral tumors who underwent SBRT were evaluated retrospectively in terms of both oncological outcomes and toxicity. 34 patients who underwent SBRT due to ultracentral lung tumor between 2017 and 2023 were evaluated. It is considered as ultracentral if planning target volume (PTV) touched the proximal bronchial system, esophagus or pulmonary vein or pulmonary artery, and overall survival (OS), progression-free survival (PFS), SBRT oncological response and toxicities were evaluated. Median age is 66 years. The most common ultracentral location is that the PTV is on or in contact with the main airway in 30 patients. At a median follow-up of 24 months, 14 patients are alive and 20 (12 patients are metastatic, 8 patients are early stage) patients are dead. PFS after SBRT is median 12 (0-60) months and OS is median 23 (4-78) months. Median OS in early stage lung cancer and oligometastatic disease were 47 and 22 months, respectively (p= 0.65). There was local recurrence in 10 (29.4%) patients, regional recurrence in 14 (41.2%) patients, and distant recurrence in 14 (41.2%) patients. Toxicity developed in a total of 8 patients, 5 of whom were acute and 6 of whom were chronic. Grade 5 toxicity was observed in one patient. All patients with toxicity were male (p= 0.30). Considering the tumor type, 6 patients had metastatic and 2 patients had early stage lung cancer (p= 0.23). Six patients with toxicity had a history of chemotherapy in the last one month before SBRT (p= 0.25). There is no standard definition and treatment scheme for ultracentral lung SBRT. SBRT is a very effective treatment option in patients with early stage lung cancer and lung metastases who are medically inoperable or who do not accept surgery. However, ultracentrally located tumors have a high risk of toxicity due to their location close to organs at risk. Multicenter dose escalation studies are needed to create a SBRT scheme with an ideal therapeutic index, with both effective oncological treatment and acceptable side effects.