The study of the feasibility of dose escalation guided by 18 F-FDG PET/CT for high metabolic region in radiotherapy of locally advanced non-small cell lung cancer / 中华放射医学与防护杂志

ABSTRACT

Objective To investigate dose escalation by metabolic sub-volume based on standard uptake values ( SUV) gradient of pre-treatment positron emission tomography/computed tomography ( PET/CT) for locally advanced non-small cell lung cancer ( NSCLC) radiotherapy. Methods The pre-treatment 18 F-FDG PET/CT images of 29 patients with locally advanced NSCLC were analyzed retrospectively. Gross tumor volume ( GTV) was delineated on the PET/CT fusion images. Tumor metabolic sub-volume was segmented according to the threshold of 50% and 75% maximum standard uptake values ( SUVmax ) . The region that under 50% SUVmax was defined as GTV1. From 50% to 75% SUVmax was defined as GTV2,and over 75% SUVmax was defined as GTV3. PTV (planning target volume), PTV1, PTV2 and PTV3 were extended from GTV, GTV1, GTV2 and GTV3, and different plans were designed subsequently. Plan 1 was designed for PTV with prescription dose 60 Gy, and Plan 2 was designed for PTV1, PTV2 and PTV3 with prescription dose 60-66 Gy, 66-72 Gy and≥72 Gy, respectively. The dosimetric parameters between tumor target and organs at risk (OARs) were compared. Results Compared to Plan 1, the absorbed dose in Plan 2 that covers 2% volume of the PTV ( D2 ) was increased from 66. 5 Gy to 78. 5 Gy and the dose was escalated by about 23. 2%. The average dose of PTV1, PTV2 and PTV3 increased by 2. 8% (62. 7-64. 4 Gy), 10. 3% (63. 5 -70. 0 Gy), 18. 7% (63. 8 -75. 8 Gy), and the average dose of PTV increased by 8. 9% (63. 2-68. 8 Gy). The sub-regional dose had been effectively improved. There was no significant difference in target coverage between Plan 1 and Plan 2 ( P >0. 05 ) . Homogeneity index (HI) was decreased with the escalation of maximum dose for Plan 2(t=23. 3, P<0. 05). There was no statistically significant difference in radiation dose of OARs between two plans ( P>0. 05 ) . Conclusions Dose escalation based on metabolic sub-volume from 18 F-FDG PET/CT was feasible, and radiation dose escalation of sub-volume with high metabolic activity can be achieved without increasing the OARs dose.