Use of PET/CT in Radiotherapy Planning for Head and Neck Cancer Provides Excellent Clinical Outcomes

Using a combination of positron emission tomography (PET) and computed tomography (CT) for radiation therapy treatment planning in head and neck carcinoma patients provides for excellent, local, and regional disease control when compared to CT alone, according to a recent study.

CT has been the standard choice for staging and radiation therapy treatment planning for head and neck squamous cell carcinomas, which account for approximately 5% of malignancies worldwide; but PET has been shown to have advantages over CT and other imaging modalities in detecting primary tumors involving lymph nodes and distant metastatic disease not clearly otherwise identified. PET alone does have several disadvantages, however, such as poor correlation to precise anatomic structures, but these negative impacts are significantly reduced when PET and CT are combined by fusing the separate scans taken on a hybrid scanner.

While it has been proven in several studies that PET/CT imaging is feasible for head and neck radiation therapy planning, very few studies have been done to determine the clinical outcomes. Therefore, researchers in the departments of radiation oncology, radiology, neoplastic and related disorders, and otolaryngology at the Medical College of Wisconsin (Milwaukee, USA) conducted this study to evaluate the clinical outcomes, including overall survival, disease-free survival, and the incidence of recurrence of patients receiving PET/CT-guided radiation therapy and the correlation of the clinical outcomes to the maximum standard uptake value obtained on the PET scan.

Between December 2002 and August 2006, 42 patients with a median age of 55, who were diagnosed with head and neck squamous cell carcinoma, were given PET/CT imaging as part of their radiation therapy planning. All patients were observed for at least six months following their treatment, with a mean follow-up time of 32 months.

Overall survival of the 42 study patients was 82.8% at two years and 74.1% at three years, superior to the survival rate that was found in a Radiation Therapy Oncology Group study in which patients received standard fractionation or accelerated fractionation with concomitant boost. That study was the largest randomized trial of radiation therapy in locally advanced head and neck cancer.

Disease-free survival for the 42 study patients was 71% and 66.9% at two and three years respectively. The cumulative incidence of recurrence was 18.7%. 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 effective 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, M.D., professor of radiation oncology at the 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.”

The study was published in the March 1, 2008, issue of the International Journal for Radiation Oncology*Biology*Physics.


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