Analysis of radiological lung changes after stereotactic body radiation therapy

Stereotactic body radiation therapy is indicated in cases of early inoperable lung cancer and surgical rejection, and it is also an option for oligometastatic, recurrent, and/or relapsing tumours. The aim of this study was to analyse the incidence of different patterns of radiological changes on CT scans, correlate their occurrence with risk factors, and analyse the usefulness of imaging information to predict treatment outcome in terms of local progression-free survival.

A retrospective review was carried out on the data from 104 patients who received lung stereotactic body radiation therapy between 2014 and 2022. A first check-up visit was carried out a month after treatment. Visits were then performed every 3 to 4months during the first year, with imaging tests (CT or PET), and every 4 to 6months after the first year. Acute radiological changes were defined as those occurring in the first 6months and chronic radiological changes as those occurring starting from 6months onwards following treatment.

Acute radiological changes were detected in 44.44 % of the patients, with up to 86 % of them appearing chronically. The modified conventional fibrosis pattern was the most prevalent. Having received lung thoracic radiotherapy and irradiation of tumours located in peripheral regions significantly increases the likelihood of chronic radiological changes appearing. Fifteen patients underwent further tests such as a PET scan for suspected local progression after the appearance of chronic changes, of which 11 were positive. No association was identified between the occurrence of either acute or chronic radiological changes with worsened survival or a higher percentage of local progression.

Proper knowledge of the different patterns of radiological changes secondary to lung stereotactic body radiation therapy and their dynamics over time is necessary to discern between a benign pathology and progression.