Study of volume change and radioherapy timing in patients with stage Ⅳ non-small cell lung cancer by targeted therapy / 中华放射肿瘤学杂志

ABSTRACT

Objective:To investigate the primary tumor volume change and timing of radiotherapy for patients with stage Ⅳ non-small cell lung cancer with EGFR mutation during molecular targeted therapy.Methods:Simulated CT scanning measurement and analysis were performed to observe the volume changes of primary tumors before and after treatment with a time interval of 10 days in this prospective study. Positioning and volume measurement were terminated when the volume change was 5% or less between two time points before and after treatment or 90 days after treatment. Primary tumor radiation therapy was then performed, acute radiation-induced injury was recorded, and the implementation and simulation of related parameters of radiotherapy plans were compared.Results:Twenty-nine of 30 cases were included in the analysis (1 case dropped off). After EGFR-TKIs treatment, the volume of all primary tumors was decreased, but the shrinking rate was inconsistent with the speed. Until the last simulated CT scanning, the maximum and minimum shrinking rates were 90% and 28%, respectively. There was no case of termination within 30 days of treatment, and the average tumor volume was significantly decreased within 40 days and the average tumor volume significantly differed every 10 days ( P<0.001). After 40 days, the volume shrinking rate of primary tumors ≤5% gradually appeared, and one patient presented with a volume shrinking rate of >5% on 90 days. During this time, the average volume shrinking rate slowed down and became stable, ranging from 49.15% to 54.77%. Moreover, the average volume continued to gradually shrink after slight increase at 70 days. There was no significant difference in the average volume every 10 days ( P>0.05). After the termination of simulated CT scanning, the dose of primary tumor was (69±7) Gy for patients receiving radiotherapy. Two patients had grade 2 acute radiation-induced pneumonitis and 3 patients had grade 3 acute radiation-induced pneumonitis. In addition, 1 patient had grade 2 radiation-induced esophagitis. According to the technology and dose parameters of radiotherapy plan, simulated radiotherapy plans before and 40 days after EGFR-TKIs treatment were designed. The timing of implementation plan was significantly better than that before EGFR-TKIs treatment (all P<0.05), whereas it was similar to that at 40 days after EGFR-TKI treatment ( P>0.05). Conclusions:The primary tumor shrinking rate is gradually slowed down over time after EGFR-TKIs treatment in patients with stage Ⅳ non-small cell lung cancer. The average tumor volume is significantly decreased within 40 days and then the shrinking rate becomes slow. The tumor shrinking rate of each case is inconsistent. Radiotherapy at 40 days after treatment is probably the optimal timing to obtain high dose and control radiation-induced injury.