MRI changes in the "normal" pineal gland following chemotherapy for suprasellar germ cell tumors

Primary CNS germ cell tumors (GCT) arise in the suprasellar and pineal regions. Suprasellar GCT may remain radiographically occult during the early symptomatic period. Although theoretically possible, it is more difficult to identify presymptomatic disease in the pineal region. Given the sensitivity of GCT to cytotoxic therapy, a decrease in size of the "normal" pineal gland following chemotherapy (CHT) could divulge preexisting disease. Such information may impact radiation treatment (RT). The authors reviewed MRIs of 15 patients with suprasellar GCT treated with pre-RT CHT. They defined a > or =50% reduction in volume of the pineal gland as a substantial decrease suspicious for preexisting occult disease. As controls, MRIs of 11 medulloblastoma patients who received cytotoxic therapy were reviewed. Pineal gland volumes could be determined for 12 of 15 patients with GCT and 7 of 11 patients with medulloblastoma. The study radiologists concurred that 2/12 GCT patients and 0/7 medulloblastoma patients had > or =50% volumetric reduction. When radiation is delivered as the sole treatment modality, the pineal region is included in at least the initial volume, but in certain clinical trials RT volume is reduced to only the suprasellar region if a complete response is achieved following pre-RT CHT. Noting changes in the "normal" pineal gland following CHT may indicate disease. CHT alone may not be sufficient to control this disease, even in cases in which a complete response is achieved. If the intent is to deliver RT to all areas of initial disease and this phenomenon can be demonstrated on a larger scale, inclusion of the pineal should be considered for patients demonstrating a substantial decrease in the size of the pineal gland after CHT.