Patterns of Failure and Origin of Recurrence on Positron Emission Tomography/Computed Tomography for Laryngeal Cancer Patients Treated with Definitive Intensity Modulated Radiation Therapy

To report on patterns of failure using detailed information from follow-up positron emission tomography-computed tomography (PET/CT) scans for patients with laryngeal squamous cell carcinoma treated with definitive radiation therapy using IMRT with simultaneous integrated boost. We identified 18 patients with laryngeal squamous cell carcinoma treated with definitive RT using IMRT with simultaneous integrated boost and with loco-regional recurrence diagnosed via follow-up PET/CT scans. These follow-up scans were then fused to the original treatment planning computed tomography (CT) scan using deformable image registration. Recurrence volumes were then delineated on the co-registered PET/CT scans. We then calculated the mathematical focal epicenter of the high-uptake region to identify the origin of recurrence for each patient. This was done using a previously published method that finds the point within the recurrence volume for which the maximum distance to the surface of the surrounding recurrence volume is smaller than for any other point. The failure pattern was then determined by whether the point of recurrence origin fell within the GTV70, CTV70, PTV70 (all receiving 70 Gy) or intermediate-risk PTV59 (receiving 59.4 Gy) or low-risk PTV54 (receiving 54.12 Gy), in the original treatment planning CT. Twenty-one primary/nodal recurrences in the 18 patients were included in the analysis. Eighty-six percent (18/21) of the recurrences originated in the high-dose treatment volume, as seen in Table 1. The 4 recurrences that originated in the high-dose (70 Gy) volume but outside the GTV70 were on average within 1.4 mm from the edge of the GTV70. There were 3 nodal failures all within low/intermediate CTV. Eighty-six percent of the recurrences for laryngeal cancer patients treated with definitive radiation therapy using IMRT with simultaneous integrated boost in this analysis originated from within the high dose region. This can have implications for reducing clinical target volume expansions to constrain dose to critical areas. In addition, a risk-adaptive treatment approach to further escalate the dose to the gross tumor might improve local control rates.Abstract 1135; Table 1Pattern of failure for the laryngeal cancer patients included in the study.Target volumeGTV70CTV70PTV70PTV59PTV54Nr. of recurrences (% of total)14 (67%)17 (81%)18 (86%)19 (90%)20 (95%) Open table in a new tab