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Indian Journal of Cancer, Vol. 48, No. 3, July-September, 2011, pp. 373-374 Letter to Editor Detecting bone marrow metastasis in cerebellar medulloblastoma: Value of disease surveillance with FDG-PET in this setting S Basu1, T Gupta2, R Jalali2, T Shet3 1 Radiation Medicine Centre, Bhabha Atomic Research Centre, Mumbai, India Code Number: cn11100 PMID: 21921346 DOI: 10.4103/0019-509X.84922 Sir, In this communication, the role of fluorodeoxyglucose positron emission tomography FDG-PET imaging in the detection of bone marrow metastasis in medulloblastoma is underscored. Skeletal involvement is relatively rare in the natural history of medulloblastoma. [1] However, this tumor shows the highest incidence of bone marrow metastasis among the other central nervous system malignancies. [2] We herein illustrate a 27-year-old male, who was diagnosed to have left cerebellar medulloblastoma who had disease recurrence in the form of extensive bone marrow metastasis detected by FDG-PET imaging and subsequently proven by bone marrow biopsy. He had undergone surgery for excision of the tumor one and a half year before. Postoperatively, he had undergone treatment with tomotherapy-based intensity modulated radiation therapy IMRT followed by six cycles of adjuvant chemotherapy one year back and was overall disease-free in the follow-up one-year period. Magnetic resonance imaging (MRI) of brain and spine done three months before did not reveal any disease at either of the sites. There was only cerebrospinal fluid CSF signal intensity area in the left cerebellar hemisphere. It appeared hypointense on T1W images and hyperintense on T2W images and did not show any post-contrast enhancement. The recent whole-body FDG-PET demonstrated diffuse and patchy FDG uptake in the entire axial skeleton and bilateral humerii and femora-consistent bone marrow involvement [Figure - 1]. The bone marrow biopsy revealed diffuse replacement of marrow with hyperchromatic small round cells with moderate pleomorphism. On immunohistochemistry these cells were strongly positive for synaptophysin and negative for cytokeratin, epithelial membrane antigen and desmin, ruling out other tumors. Delicate bands of fibrosis were seen around tumor cells [Figure - 2]. The detection of skeletal involvement impacts the treatment intent and modality adopted for medulloblastoma. Hence, a sensitive diagnostic modality for disease surveillance of extra-cranial metastases is of significant value in the management of patients with this group of tumors. Skeletal scintigraphy has been commonly employed for the skeletal survey in cancer patients. However, as it is based upon the principle of an indirect method i.e. reactive bone formation, (a) osteolytic metastases with poor bone formation and (b) the metastases that are confined to the bone marrow, can be missed with this approach. [3] MRI has been utilized to address the latter issue of detecting bone marrow involvement where multiple areas of altered marrow signal intensity involving multiple vertebral bodies can be observed in the presence of bone marrow metastases. FDG-PET as a sensitive whole-body molecular imaging technique has demonstrated great promise in this area and the results obtained argues this to be the modality of choice in detecting disease activity at the bone marrow and also monitoring the efficacy of therapeutic intervention in this setting. FDG hypermetabolism can be observed following granulocyte macrophage colony stimulating factor (GM-CSF), however, this concern can be obviated by careful observation of uptake pattern and a repeat study after a certain time interval. The aforementioned case vignette is presented to emphasize the fact that (a) disease recurrence in the bone marrow after an apparent disease-free period can occur in medulloblastoma and (b) this might call for a careful surveillance, where FDG-PET can play a critical role in whole-body disease burden assessment. References
Copyright 2011 - Indian Journal of Cancer The following images related to this document are available:Photo images[cn11100f1.jpg] [cn11100f2.jpg] |
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