Lung cancer is the most common cancer worldwide among men,
being the second more common one in developed countries[1,
2].
In the United States,
it is the second leading cause of new cancers and the first cause of deaths from cancer in both genders[3].
Surgical resection is considered the standard treatment of primary and metastatic resectable lung tumors[4,
5].
However,
the minority of the patients are diagnosed in a resectable stage and many patients with resectable disease are high-risk surgical candidates[6]. In this scenario,
Stereotactic Body Radiation Therapy (SBRT) has emerged as a potential treatment for lung malignancies.
As conventional radiotherapy,
SBRT also involves inflammatory changes in the normal lung surrounding the lesion.
Therefore,
an early and reproducible detection of expected inflammatory changes or local recurrence on chest computed tomography (CT) is of key importance for oncologists in order to guide treatment and improve patients’ outcome.
SBRT is a non-invasive method used to deliver high doses of ionizing radiation to a small tumor volume,
few fractions (≤8 fractions) and an equivalent biological dose (BED) ≥ 100 Gy[2].
SBRT should be performed with the aid of noninvasive tumor localization methods (imaging methods) or minimally invasive methods (use of fiducial markers) during planning as well as during applications,
and as methods of controlling internal movement of the tumor or internal organs,
when necessary,
using precise dose delivery techniques[7].
While in older radiotherapy techniques the inflammatory CT changes are easily diagnosed,
typically characterized as lung opacity with straight borders following the edges of the treatment fields[8],
the high and sharp gradient doses delivered to the lung and the 3D conformity of the treated region by SBRT allow the development of benign CT changes that can mimic disease’s recurrence,
especially when a mass-like pattern is found[9].
The benign SBRT changes have been studied and classified in patterns according to time period[10],
whereas CT recurrence features includes specific findings[11]. Incidence of expected changes on CT is high: 54–79% of patients develop acute benign changes,
and 80–100% of patients develop late ones[12]. Although these imaging features are used by radiation oncologists and radiologists throughout follow-up[13],
there is a lack of studies validating performance and reproducibility of these CT findings among radiologists.
Misclassification of expected radiation features as recurrence may result in unnecessary exams and interventions.
On the other hand,
misclassification of recurrence as benign features may delay the appropriate treatment and worsen patient's prognosis.
In this context,
the purpose of this study was to evaluate the diagnostic performance and interobserver agreement of chest CT in the diagnosis of actinic changes ad recurrence after SBRT in patients with early stage lung cancer or single pulmonary metastasis,
adding validation to the current classification[14].