Abstract
Radiation therapy (RT) is integral in the treatment of head and neck cancer (HNSCC), with intensity-modulated radiotherapy (IMRT) and other techniques allowing for more accurate and precise dose delivery to tumor while sparing normal tissues. 18Fluorodeoxyglucose-PET, when used in concert with CT scanning (PET/CT), can assist in RT planning for HNSCC. First, PET/CT can identify additional foci of disease burden, changing radiation planning if not overall therapeutic intent. Second, PET data can influence gross tumor volume (GTV) delineation, typically producing smaller and more accurate target volumes. Consequently, dose escalation can be performed to a more limited tumor volume, either from the outset of therapy or at various times during an adaptive RT course. Follow-up PET/CT may be useful for early detection of recurrences and assessment of response after therapy; however, the optimal timing of the posttherapy study is still under investigation. A significant issue in the standardized use of PET/CT for RT planning remains the appropriate algorithm for segmenting the PET signal to delineate the GTV. Nonetheless, PET/CT-guided RT planning appears to pose multiple benefits for radiation oncologists and will likely continue to be an important advancement in the treatment of HNSCC with chemoradiotherapy.
Highlights
Squamous cell head and neck cancer (HNSCC) is the sixth most common cancer worldwide, comprising 3 to 5 % of all cancers in the USA with over 50,000 new cases per year
positron emission tomography (PET)/CT- based imaging for HNSCC provides several significant advantages for radiation oncologists. It modifies staging information in nearly 40 % of cases, modifying therapeutic goals. It may assist in disease surveillance and the assessment of treatment response
It allows for delineation of gross tumor volume (GTV) that appear to correlate more closely with “true” pathologic tumor volumes
Summary
Squamous cell head and neck cancer (HNSCC) is the sixth most common cancer worldwide, comprising 3 to 5 % of all cancers in the USA with over 50,000 new cases per year. A recent study of 152 HNSCC patients with residual nodes >1 cm in axial dimension on CT following chemoradiotherapy found that PET/CT had only a 53 % sensitivity and 73 % NPV for having nodal disease. A recent study of 24 HNSCC patients found that visually contoured primary tumor GTVPET were smaller than GTVCT 80 % of the time, while out of 55 lymph node GTVs, there was no volumetric difference between modalities [4]. Schinagl et al compared these various segmentation strategies in a cohort of 78 patients with HNSCC [28] They found that contours based on these different strategies were highly variable, with using a fixed SUV value of 2.5 and above being a poor method. Another study reported OS and disease-free survival rates of 82.8 and 71.0 %, respectively, at 2 years, and 74.1 and 66.9 % at 3 years, among 42 patients treated with
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