The colossal circumvention of the lung lesion duringlung stereotaxy

This is a case report on stereotaxic (stereotactic body radiotherapy-sbrt) forlung cancer located in the left lower lobe (segment 6, s6). there have beenno reports on marked displacement of the peripheral lung cancer duringradiotherapy. a pulmonary nodule was discovered on computed tomography(ct) conducted for a persistent cough in an 87-year-old male. according todiagnostic imaging, this nodule was clearly delineated and had an irregularmargin. the image diagnosis was t1n0m0, stage i primary lung cancerlocated in the left lower lobe and no pathological type was identified. thepatient was treated with sbrt using a linear accelerator (linac) at a totaldose of 48 gray (gy) in 4 fractions. on performing cone beam ct (cbct) atthe third fraction, the tumor position had moved caudally by about 3centimeters (cm). for this reason, we canceled further treatment and thecase was re-planned. four days after discontinuing treatment, 4-dimensionalct (4dct) images were obtained before initiation of the remaining fractionsof sbrt. therefore, the patient completed 4 fractions of sbrt and the tumorlocation was confirmed before beam delivery. the tumor location differedbased on the patient’s position (i.e., standing versus lying in a supineposition), and we considered that it moved due to adhesion to the pleurawhen the patient was standing. if reproducibility of the tumor position cannotbe guaranteed, the patient should undergo to ct re-simulation. oncologistsshould re-evaluate the movement of the tumor on respiration and adjust themargins accordingly.