Medinews.com
January 28, 2005
High-dose chemotherapy and irradiation used to tread two types of brain tumors--supratentorial primitive neuroectodermal tumor (PNET) and medulloblastoma--can cause alterations in the brains white matter that appear like tumors when seen on magnetic resonance imaging (MRI) scans, according to a new study.
The study, conducted by researchers from St. Jude Childrens Research Hospital (Memphis, TN,USA; www.stjude.org), report that this damage, called white matter lesions (WMLs), can be mistaken for recurrent tumors, prompting physicians to treat the patient aggressively--and unnecessarily--with more chemotherapy and radiation.
Irradiation and high-dose chemotherapy are treatments we want to use as sparingly as possible. This new information represents an important caution sign for physicians who otherwise might assume that WMLs are actually tumors that need further treatment, said Amar Gajjar, M.D., director of neuro-oncology at St. Jude and senior author of the study, published in the November 15, 2004, issue of the Journal of Clinical Oncology.
WMLs often occur in patients with medulloblastoma or PNET who have been treated with radiation and high-dose chemotherapy following surgery. This research is also the first to observe the effect of these changes in white matter on intellectual outcome in children with brain tumors. Particularly, the study discovered the presence of WMLs is linked with a decline in neurocognitive, or intellectual, function.
In the vast majority of children, the changes seen on MRI scans after treatment are WMLs and not cancer. Physicians can follow up these initial findings with repeat MRI scans to determine whether the WMLs disappear. If they do disappear, then it wasnt cancer and didnt require treatment. But even though these changes tend to be only temporary, some children with these changes tends to develop permanent neurologic problems, such as difficulty swallowing, said Maryam Fouladi, M.D., from the department of hematology-oncology at St. Jude and lead author of the report.
The study was comprised of 127 patients who were followed for up to 13 months after the initial treatment for brain cancer. During the time, 22 of these patients developed WMLs following the treatment. The WMLs disappeared in 16 patients (73%) within 23.5 months after being detected. In two patients the WMLs remained after 19 and 31 months, respectively. Two other patients developed tumors again while still showing evidence of WMLs. In the remaining patients, the WMLs led to tissue breakdown, and patients with WMLs experienced a significant decrease in estimated IQ and math scores.
The investigators concluded that in patients with medulloblastomas or PNET who had been treated with irradiation and high-dose radiation, WMLs are typically short-lived and do not cause symptoms. WMLs, however, can mimic the early stages of tumor recurrence, and therefore make it hard for physicians to effectively diagnose tumor recurrence.
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