Impact of whole-body 18F-FDG PET on staging and managing patients for radiation therapy

Whole-body PET with F-18-FDG has proven to be a very effective imaging modality for staging of malignant tumors. This study was performed to evaluate the impact of 18F-FDG PET on staging and managing patients for radiation therapy. Methods: The treatment records of 202 consecutive patients (98 male, 104 female; mean age, 56.9 y; age range, 8-91 y) with different malignant tumors were reviewed. Radiation therapy was intended for all patients. The diagnoses were head and neck tumors (n = 55), gynecologic tumors (n = 28), breast cancer (n = 28), lung cancer (n = 26), malignant lymphomas (n = 24), tumors of the gastrointestinal tract (n = 18), and others (n = 23). Whole-body PET was performed before radiation therapy. The alteration of PET on each patient's staging and management decisions for radiation therapy were determined. Results: For 55 of 202 patients (27%), PET results changed the patients, management in radiation therapy. In 18 cases (9%), PET resulted in a cancellation of radiation therapy because of the detection of previously unknown distant metastases (8 patients), additional lymph node metastases (9 patients), residual tumor (6 patients), or the exclusion of active disease (2 patients). In 6 patients, >1 incremental reason was found for cancellation. In 21 PET examinations (10%), PET results changed the intention of radiation treatment (curative or palliative). The radiation dose was changed in 25 cases (12%). A change of radiation volume was necessary in 12 patients (6%). Conclusion: The results of this study show that 18F-FDG PET has a major impact on the management of patients for radiation therapy, influencing both the stage and the management in 27% of patients.