The utility of PET/CT imaging of head and neck cancer performed early after surgical resection and prior to adjuvant radiation therapy

Abstract

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Objectives: With the advent of PET/CT imaging in the care of head and neck cancer patients, the proper timing of PET/CT in the care of these patients is of concern. Post operative and inflammatory uptake can hinder interpretations when performed too early and be a limiting factor on PET/CT’s utility. We evaluated the utility of PET/CT at a relatively early time point after curative-intent surgical resection and prior to planned post-operative radiation therapy.

Methods: 91 consecutive patients (67 with new disease, 24 with recurrent disease) who were referred for post-operative radiation therapy after complete surgical resection were evaluated. Tumor histologies included 62 squamous cell cancers and 29 other patients with 12 different histologies. Median time between surgery and PET/CT was 4 weeks (range 1.9-10.7). Findings suspicious for new or recurrent/ persistent disease on PET/CT were referred for biopsy to confirm the findings. Correlation was made to changes in patient care using these data. Endpoints were the number of positive PET scans, number of positive biopsies and number of treatment changes. Treatment changes considered significant were changing from adjuvant therapy to curative salvage or palliative treatment.

Results: Based on suspicious PET/CT findings, 24 patients (26.4%) underwent biopsies of suspicious sites. Three other patients with suspicious findings did not undergo biopsy as the abnormalities were not easily accessible (frontal lobe brain, paranasal sinus, skull base). 11/24 (45.8%) biopsies were positive for cancer. Treatment was changed for 14 (15.4%) patients (11 positive biopsy patients and 3 non-biopsied patients) as a result. Treatment changes included abandonment of radiation therapy and switching to palliative chemotherapy (4), changing of radiation therapy plans (7), additional surgery (2) and adding chemotherapy to radiation therapy (1). Multiple surgeries/treatment for recurrent cancer or primary skin lesions were the best predictors of having biopsy-proven, therapy-changing PET/CT findings (p< 0.03).

Conclusions: Even with an expectedly high rate of false positive PET/CT scans in this early postoperative period, PET/CT changed patient management in a relatively large number of these patients. PET/CT can be recommended in the post-operative, pre-radiation therapy setting with the understanding that therapy-altering PET/CT findings should be confirmed by biopsy.