Role of 18F-FDG-PET/CT Scanning in Management of Patients with Locally Advanced Head and Neck Cancer

Abstract

Purpose: to compare between 18F-FDG-PET/CT versus CT scan in staging, target volumes delineation, and monitoring response to therapy in patients with locally advanced Head and Neck Squamous cell carcinoma treated by concurrent radiotherapy with systemic therapy.

Patients and Methods: 31patients with histologically confirmed primary HNSCC were enrolled. All patients had planning CT and combined PET/CT in treatment position. All the GTVs (for the primary and nodal disease) were defined from both 18F-FDG-PET/CT (GTV- PET) and CT (GTV- CT). A 40% intensity level relative to the tumor maximum (SUV max) was used to delineate the margins of the GTV- PET.The CTVs, as well as the PTVs, were created from the GTV s. All volumes had been measured and expressed in cubic centimeters. PET-CT and CT scan had been performed 12 weeks after completion of treatment.

Results: PET resulted in change of stage for 3 cases, 2 was up staged to metastatic disease (1 of them was excluded and patient was treated with palliative intent) and 1 was down staged. GTVs delineated using CT scan (C-GTV) were larger than those delineated using combined PET/CT scan (PET-GTV) with median volume of 31.71cc compared to 15.13cc of (C-GTV) and (PET-GTV) respectively with high statistical significance (P < 0.001). The PTV-Boosts volumes ranged 48.52 - 157.92 cc and 47.31 - 155.8 in PTV-CT-Boost and PTV-PET-Boost respectively, with larger PTV- CT- Boost median (96.23 cc)versus(93.58 cc) for PET/CT(P<0.001).No statistically significant difference in the volumes when applied to nodal GTVs, CTVs and PTVs. PET/C and detecting residual disease yet this was not statistically significant (P= 0.824).

Conclusion: the use of PET/CT resulted in change of disease's stage, the primary tumor and nodal GTVs were changed with the implementation of combined PET/CT; that translate into a smaller and statistically significant difference in GTV of the primary tumor and PTV- boost, however, such difference in the volumes was not statistically significant when applied to nodal GTVs, CTVs and PTVs. PET/CT is superior than traditional imaging modality in evaluating response to therapy and detecting residual disease.