Abstract
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). 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 66 Gy (range, 60-78 Gy) 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. 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. 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.
Highlights
Non-small cell lung cancer (NSCLC) is one of the most common malignant diseases
There is a strong case for the routine use of FDG-positron emission tomography (PET) in radiation therapy planning for non-small cell lung cancer (NSCLC), and the two most important and consistent reasons for applying PET in target volumes in NSCLC were listed (MacManus et al, 2009)
In cases with atelectasis, PET helped to demarcate the border between tumor and collapsed lung, allowing a smaller volume of lung to be treated (Nestle et al, 1999)
Summary
Non-small cell lung cancer (NSCLC) is one of the most common malignant diseases. At diagnosis, a large number of patients were in Stages IIIa or IIIb. Dose escalation is limited because of several vital normal tissues toxicity (Bradley et al, 2005; Belderbos et al, 2006), such as lung, esophagus, spinal cord, heart and so on. Continuous tumor regression during the course of conventionally fractionated radiotherapy or combined chemoradiotherapy for locally advanced NSCLC is well known (Britton et al, 2007; Guckenberger et al, 2011). This shrinkage of the gross tumor volume (GTV) indicates that irradiation field shapes and field sizes could or should be adapted during the treatment course, NSCLC patients are re-imaged and re-planned during the treatment is a possible strategy to improve treatment delivery. We sought to quantify the degree of tumor volume change during radiotherapy course, with the goal of assessing the feasibility of individualized shrinking field technique in sparing normal tissues during treatment
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