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Abstract
Background. A planning study investigated whether reduced target volumes defined on FDG-PET/CT during radiotherapy allow total dose escalation without compromising normal tissue tolerance in patients with esophageal cancer.
Material and methods. Ten patients with esophageal squamous cell carcinoma (SCC), candidate to curative-intent concomitant chemo-radiotherapy (CRT), had FDG-PET/CT performed in treatment position, before and during (Day 21) radiotherapy (RT). Four planning scenarios were investigated: 1) 50 Gy total dose with target volumes defined on pre-RT FDG-PET/CT; 2) 50 Gy with boost target volume defined on FDG-PET/CT during RT; 3) 66 Gy with target volumes from pre-RT FDG-PET/CT; and 4) 66 Gy with boost target volume from during-RT FDG-PET/CT.
Results. The median metabolic target volume decreased from 12.9 cm3 (minimum 3.7–maximum 44.8) to 5.0 cm3 (1.7–13.5) (p = 0.01) between pre- and during-RCT FDG-PET/CT. The median PTV66 was smaller on during-RT than on baseline FDG-PET/CT [108 cm3 (62.5–194) vs. 156 cm3 (68.8–251), p = 0.02]. When total dose was set to 50 Gy, planning on during-RT FDG-PET/CT was associated with a marginal reduction in normal tissues irradiation. When total dose was increased to 66 Gy, planning on during-RT PET yielded significantly lower doses to the spinal cord [Dmax = 44.1Gy (40.8–44.9) vs. 44.7Gy (41.5–45.0), p = 0.007] and reduced lung exposure [V20Gy = 23.2% (17.3–27) vs. 26.8% (19.7–30.2), p = 0.006].
Conclusion. This planning study suggests that adaptive RT based on target volume reduction assessed on FDG-PET/CT during treatment could facilitate dose escalation up to 66 Gy in patients with esophageal SCC.
Declaration of interest: The authors thank David Voisard (radiation oncology and Medical Physics, Henri Becquerel Center) for his help in developing this article. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
Supplementary material available online
Supplementary Table I to be found online at http://informahealthcare.com/doi/abs/10.3109/0284186X.2014.973062.