Feasibility of Shrinking Field Radiation Therapy through 18F-FDG PET/CT after 40 Gy for Stage III Non-Small Cell Lung Cancers

Abstract

Objective: To explore the feasibility of shrinking field technique after 40 Gy radiation through 18F-FDG PET/ CT during treatment for patients with stage Ⅲ non-small cell lung cancer (NSCLC). Methods: In 66 consecutive patients with local-advanced NSCLC, 18F-FDG PET/CT scanning was performed prior to treatment and repeated after 40 Gy. Conventionally fractionated IMRT or CRT plans to a median total dose of 66Gy (range, 60-78Gy) were generated. The target volumes were delineated in composite images of CT and PET. Plan 1 was designed for 40 Gy to the initial planning target volume (PTV) with a subsequent 20-28 Gy-boost to the shrunken PTV. Plan 2 was delivering the same dose to the initial PTV without shrinking field. Accumulated doses of normal tissues were calculated using deformable image registration during the treatment course. Results: The median GTV and PTV reduction were 35% and 30% after 40 Gy treatment. Target volume reduction was correlated with chemotherapy and sex. In plan 2, delivering the same dose to the initial PTV could have only been achieved in 10 (15.2%) patients. Significant differences (p<0.05) were observed regarding doses to the lung, spinal cord, esophagus and heart. Conclusions: Radiotherapy adaptive to tumor shrinkage determined by repeated 18F-FDG PET/CT after 40 Gy during treatment course might be feasible to spare more normal tissues, and has the potential to allow dose escalation and increased local control.

Adaptive radiotherapy in lung cancer: dosimetric benefits and clinical outcome

“…Phase I delivered 44-46 Gy to the initial planning target volume (PTV). Two Phase II plans for [16][17][18][19][20] Gy were developed on initial and mid-treatment scans, the treatment being delivered with the mid-treatment plan. The second CT structure set was fused with the initial scan data set using dose wash. Volumetric and dosimetric changes in target volumes and critical structures were assessed.…”

Individual isotoxic radiation dose escalation based on V20 and advanced technologies benefits unresectable stage III non-small cell lung cancer patients treated with concurrent chemoradiotherapy: long term follow-up

“…Firstly, several studies [ 35 – 38 ] on the impact of PET on treatment planning for NSCLC suggested an overall improvement in target volume delineation. Radiotherapy adaptive to tumor shrinkage determined by repeated PET-CT after 40 Gy during treatment course might be feasible to spare more normal tissues [ 22 ]. Secondly, results have demonstrated that, incorporation of SPECT functional information into conformal radiotherapy planning can allow reduction 3%-17% in the volume of the bilateral functional lung (FL) receiving ≥ 20 Gy, and particularly, where discrete nonfunctional regions of significant size are detected [ 17 , 19 ].…”

“…The identification of functional lung using lung perfusion information obtained from single-photon emission computed tomography (SPECT), coupled with IMRT had the potential to reduce the pulmonary toxicity [ 16 – 21 ]. Shrinking field during treatment course might be feasible to spare more normal tissues [ 22 ]. Accelerated and hyperfractionated radiotherapy schedules resulting in reduced overall treatment time and less tumor repopulation have been shown to improve outcomes in LANSCLC compared to conventional fractionation [ 23 – 24 ].…”

Potential Impact of Atelectasis and Primary Tumor Glycolysis on F-18 FDG PET/CT on Survival in Lung Cancer Patients

“…Atelectasis and tumors both appear as solid dense shadows on computed tomography, so differentiation can be difficult. Differentiation between tumor and atelectasis is crucial in order to determine the area of atelectasis and the creation of appropriate size portals during radiation therapy planning (Ding et al, 2012;Yin et al, 2013). Besides, differentiation of the tumor from atelectasis is important for CT-guided biopsy.…”