Retinoic acid for redifferentiation of thyroid cancer--does it hold its promise?

OBJECTIVES: To evaluate the effectiveness of isotretinoin for improving (131)I uptake in recurrent/metastasized thyroid cancer with no/insufficient (131)I uptake. DESIGN: Retrospective analysis of 25 patients treated between June 1999 and May 2001. METHODS: 15 female and 10 male patients were given isotretinoin at 1 mg/kg for 3 months, followed by (131)I treatment. All patients received a (131)I scan 72 h after administration, thyroglobulin measurement, chest X-ray and ultrasound of the neck, and some patients underwent a (18)F-fluorodeoxyglucose (FDG) positron emission tomography (n=14) and computed tomography scan of the chest (n=11). RESULTS: In two out of 14 patients with raised thyroglobulin but no (131)I uptake, a slightly improved (131)I uptake was seen. In a further 11 patients an improvement of (131)I uptake of known lesions was desired or further non-(131)I-accumulating lesions were known. A dosimetrically relevant improvement of uptake was seen in three of these patients. (18)F-FDG uptake and thyroglobulin did not correlate with the success/failure of the isotretinoin treatment. Side effects including a strong "sunburn", cheilitis, mucositis, conjunctivitis and raised transaminases occurred in two-thirds of patients. They were of an overall tolerable level and were reversible after isotretinoin had been stopped. CONCLUSION: From our clinical experience over a period of 2 years we conclude that the therapeutic effect of isotretinoin in thyroid cancer is certainly less than previously reported. An indiscriminate use of isotretinoin in all patients with otherwise untreatable thyroid cancer cannot be recommended.

Diagnostic value of 18F-FDG positron emission tomography for detection and treatment control of malignant germ cell tumors.

INTRODUCTION: The role of positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) is currently under evaluation in urologic oncology. The aim of the present study was to investigate the use of [18F]FDG positron emission tomography ([18F]FDG-PET) in the detection and treatment control of malignant germ cell tumors compared to computed tomography (CT). MATERIALS AND METHODS: Thirty-two PET studies and CT scans were carried out in 23 patients with histologically proven germ cell tumors (10 seminomas, 12 non-seminomatous germ cell tumors (NSGCT), 1 unclassified serologic recurrent disease) Lugano stage I-III. The scans were done either after initial diagnosis (n = 21) and/or within 3-45 days after chemotherapy was completed (n = 11). PET and CT were validated either by histology (n = 7) or clinical follow-up of 6-11 months after the last PET study has been performed (n = 16). Sensitivity, specificity, accuracy, positive and negative predictive values were determined for PET and CT. Differences between PET and CT for parameters of diagnostic value were evaluated by chi(2) test. RESULTS: Although not statistically significant, the sensitivity, accuracy and negative predictive value were higher for PET than for CT with respect to the detection of metastatic infradiaphragmatic and supradiaphragmatic lesions after initial diagnosis. The specificity and positive predictive value of PET and CT were comparable. After chemotherapy, PET was found to be significantly superior in specificity and accuracy compared to CT with respect to infradiaphragmatic lesions (p < 0.05). False-positive PET findings in supradiaphragmatic lesions after chemotherapy occurred in the case of inflammatory processes and resulted in a loss of specificity and accuracy compared to CT (p < 0.05). CONCLUSIONS: These preliminary results demonstrate [18F]FDG-PET to be a useful diagnostic tool for the initial staging and treatment control in patients with germ cell tumors. Possible advantages compared to CT, however, are as yet not clearly defined. The possibility of false-positive PET findings due to reactive supradiaphragmatic inflammatory processes early after chemotherapy have to be considered.