Non-invasive approach to treat primary solid solitary pulmonary nodule: a narrative review by the radiation oncologist perspective

Objective: The aim of this review is to evaluate the role of stereotactic body radiotherapy (SBRT) in treating solitary lung nodule without pathological confirmation. Background: Lung cancer is one of the leading causes of cancer death worldwide. Taking into account the increasing number of new diagnoses of solid solitary pulmonary nodules, the issue is to identify when an invasive procedure is needed before planning a radical treatment. The role of SBRT is crucial, particularly in those patients at greater risk of complications after invasive procedures or surgery. Methods: This review focused on selection criteria of patients submitted to SBRT for solid solitary lung nodules in clinically diagnosed lung cancer. A literature search in Medline was performed until April 2021. Terms used were a combination of "solitary pulmonary nodule", "radiotherapy", "stereotactic body radiotherapy", "pathological confirmation", and "lung". We identified 149 records and 20 studies were selected, analyzed and discussed. All studies but two are retrospective. In 6 studies only patients without pathological confirmation were included, while 14 compared histologically proven and not subgroups. All studies were published between 2009 and 2019. SBRT was used in all except one, even if different doses were administered. SBRT resulted as an efficient treatment with high rates of local control in patients affected by early stage non -small -cell lung cancer (NSCLC), even if overall survival varies greatly depending on different factors (population features, lesion diameter, clinical stage, radiation therapy doses). Three-year local control was higher than 75% in all studies in which it was reported, while 3 -year overall survival was different in each one (range, 38.6-90%). Acute and late toxicities were generally low. Conclusions: Validated probability test together with the use of metabolic imaging may facilitate the clinical diagnosis of cancer in patients with solitary pulmonary nodule. SBRT seems to be a very efficient radical treatment for these subgroups of patients with early stage clinically diagnosed lung cancer, even if more prospective trials are needed.