POSITRON EMISSION TOMOGRAPHY WITH FLUORODEOXYGLUCOSE TO EVALUATE TUMOR RESPONSE AND CONTROL AFTER RADIATION-THERAPY

Purpose: Following radiation therapy, evaluation of viable tumor can o ften be difficult with anatomic imaging criteria (tumor size alone). I n this study, the utility of biochemical imaging with the glucose anal og 2-[F-18]fluoro-2-deoxy-D-glucose and positron emission tomography w as investigated in patients treated with radiation therapy. Methods an d Materials: Between 1990 and 1992, 19 patients were studied, includin g 15 patients with head and neck cancer, 4 oropharynx, 4 sinus, 3 lary nx, 2 hypopharynx, 2 oral cavity [one patient], 1 nasopharynx), and 4 patients with breast cancer. Post-radiation positron emission tomograp hy with 2-[F-18]fluoro-2-deoxy-D-glucose studies were done in all pati ents, with 9 head and neck patients receiving pre-radiation positron e mission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose scans as well . Results were correlated with other imaging techniques and pathology. Results: Positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-g lucose detected head and neck primary tumors and lymph node metastases in all nine pre-radiation scans, while magnetic resonance imaging fai led to detect two primary tumors. Serial positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose showed a significant decrease in tumor activity after radiation therapy, compared to pre-radiation lev els, (p < 0.05), except for two patients with increased uptake at the primary site. Biopsies of these two patients showed persistent/recurre nt disease after radiation therapy, which was not detected by magnetic resonance imaging. Six additional head and neck patients, with suspic ious examination and inconclusive magnetic resonance imaging, were ima ged with positron emission tomography after radiation therapy only. Fi ve patients had increased positron emission tomography activity, with corresponding biopsies positive in four patients, and negative in one patient with clinically worsening symptoms. The remaining sixth patien t had minimal and stable positron emission tomography uptake, and is i mproving clinically. Four patients had mammogram findings suspicious f or recurrence after conservation treatment for breast cancer. Positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose showed no f ocal activity in the breast in two patients, and increased activity in the ares suspicious for recurrence in the other two patients. Biopsie s correlated with positron emission tomography results. Conclusion: Ch anges and presence of positron emission tomography with 2-[F-18]fluoro -2-deoxy-D-glucose activity correlated with pathologic findings in hea d and neck and breast cancer patients in this series. In patients with elevated or rising positron emission tomography activity after radiat ion therapy, persistent or recurrent disease was found in 89% of patie nts, (8/9). Magnetic resonance imaging did not detect the head and nec k recurrences, and mammography was suspicious in patients with both be nign and malignant breast changes after radiation therapy. In addition , our data indicate that in head and neck patients with pre-radiation positron emission tomography scans, a significant decrease in activity should occur after radiaton therapy, if local control is to be expect ed.