Acombination of positron emission tomography (PET) and computed tomography (CT) for radiation treatment planning in patients with head and neck carcinoma provides for excellent local and regional disease control when compared with CT alone, according to a study in the March 1 issue of International Journal of Radiation Oncology • Biology • Physics.
Researchers in the departments of Radiation Oncology, Radiology, Neoplastic and Related Disorders, and Otolaryngology at the Medical College of Wisconsin, Milwaukee, evaluated the clinical outcomes, including overall survival, disease-free survival and the incidence of recurrence in patients receiving PET/CT-guided radiation therapy, as well as the correlation of clinical outcomes to the maximum standard uptake value obtained on the PET scan.
CT has been the traditional choice for staging and radiation treatment planning for head and neck squamous cell carcinomas, which account for approximately 5 percent of malignancies worldwide. However, PET has been shown to have advantages over CT and other imaging modalities in detecting primary tumors, involved lymph nodes and distant metastatic disease not otherwise clearly identified. However, PET alone has several disadvantages, such as poor correlation to precise anatomical structures, but these are reduced significantly when PET and CT are combined by fusing the separate scans taken on a hybrid scanner.
Between December 2002 and August 2006, 42 patients with a median age of 55 years who were diagnosed as having head and neck squamous cell carcinoma underwent PET/CT imaging as part of their radiation treatment planning. All patients were observed for at least six months after treatment, with a mean follow-up of 32 months.
Patients’ overall survival was 82.8 percent at two years and 74.1 percent at three years, rates that are superior to the survival rate found in another study in which patients received standard fractionation or accelerated fractionation with concomitant boost.
Disease-free survival rates were 71 and 66.9 percent at two and three years, respectively. The cumulative incidence of recurrence was 18.7 percent. The study also found that standard uptake value is not a good predictor of local recurrence and that dose escalation based on standard uptake value is unlikely to be a fruitful treatment strategy.
"PET/CT provides a higher level of confidence that we are not missing tumors as we attempt to lessen treatment side effects by delivering radiation therapy that tightly conforms in three dimensions to a given tumor volume," said Christopher Schultz, MD, professor of radiation oncology, Medical College of Wisconsin.
"Most importantly, the PET/CT-guided conformal radiotherapy was clearly no worse, and based on our early results may in fact lead to superior clinical outcomes as compared to CT-only planned radiotherapy," he said.
