Radiobiological Determination of 18F-FDG PET/CT Guiding Dose Escalation in Esophageal Cancer

Abstract

The aim of this study is to assess the feasibility of a dose escalation guided by 18F-deoxyglucose Positron emission tomography/computer tomography (18F-FDG PET/CT) for esophageal cancer (EC). Ten patients treated with definitive RT and pre-therapeutic 18F-FDG PET/CT was included in this study. Three intensity-modulated radiation therapy (IMRT) plans were compared per patient: Plan50.4, delivering 50.4 Gy to PTV50.4 defined on computed tomography (CT); Plan63, boosting PTV63 defined as gross tumor volume (GTV) plus a uniform margin of 0.5 cm to 63 Gy; Plan70, boosting sub-volume with FDG >50% SUVmax (GTVPET) plus a 0.5 cm margin as PTV70 to 70 Gy. A dosimetric comparison was performed, based on calculations of normal tissue complication probability (NTCP) for lung and heart. Clinically acceptable dose escalation was feasible for 8 of 10 patients in Plan63 for dose constraints to heart. One patient was not feasible for Plan70 for dose constraints to heart. Two patients were not feasible for Plan63 for dose constraints to spinal cord. Three patients were restricted by dose constraints to lung for both Plan63 and Plan70, two of which were even not suitable for Plan50.4 for the same reason. NTCP modeling for lung showed the risk of symptomatic or radiographic pneumonitis within 6 months increased from 42.23% of Plan50.4 to 45.89% of Plan63 (p = 0.005) or 45.53% of Plan70 (p = 0.007). The difference between Plan63 and Plan70 was no significantly (p = 0.169). Similarly, the risk of symptomatic or radiographic fibrosis after 6 months increased from 25.79% of Plan50.4 to 29.79% of Plan63 (p = 0.005) or 29.38% of Plan70 (p = 0.007). The difference between Plan63 and Plan70 was no significantly (p = 0.109). NTCP modeling for heart showed an increased risk of 6.38% of Plan50.4 to 8.88% of Plan70 (p = 0.009) or 9.79% of Plan63 (p = 0.007). The risk of heart mortality was significantly higher for Plan63 than Plan70 (p = 0.047). Selective boosting of sub-volumes based on 18F-FDG PET/CT would improve local control, which is beneficial to OS. Meanwhile, the risk of cardiac and lung toxicities may be reduced, compared with boosting of the whole GTV.