The importance of image guided radiotherapy in small cell lung cancer: Case report and review of literature.

ABSTRACT

AIM: Describe the anatomical changes and tumor displacement due to a rapid response of a patient's small cell lung cancer (SCLC) during definitive chemoradiotherapy (CRT). BACKGROUND: The treatment for SCLC is based on CRT. If interfractional changes during RT are incorrectly assessed they might compromise adequate coverage of the tumor or increase dose to organs at risk. Image guided RT with cone-beam computed tomography (CBCT) allows to identify daily treatment variations. MATERIAL AND METHODS: Describe a SCLC case with rapid changes in size, shape and location of the primary tumor during RT. CASE REPORT A 62-year-old woman was diagnosed with SCLC with complete obstruction of the anterior and lingular bronchi and incomplete left thorax expansion due to a 12 × 15 cm mass. During CRT (45 Gy in 1.5 Gy per fraction, twice daily) the patient presented rapid tumor response, leading to resolution of bronchi obstruction and hemithorax expansion. Tumor shifted up to 4 cm from its original position. The identification of variations led to two new simulations and planning in a 3-week treatment course. CONCLUSIONS: The complete radiological response was possible due to systematic monitoring of the tumor during CRT. We recommend frequent on-site image verification. Daily CBCT should be considered with pretreatment tumor obstruction, pleural effusion, atelectasis, large volumes or radiosensitive histology that might resolve early and rapidly and could lead to a miss of the tumor or increased toxicity. Further research should be made in replanning effect in coverage of microscopic disease since it increases uncertainty in this scenario.