Dual isotope single-photon emission computerized tomography used for prediction of histology and survival in patients after high-dose radiotherapy for malignant astrocytoma

Abstract

<jats:p>This study was conducted to determine the sensitivity of dual-isotope single-photon emission computerized tomography (SPECT) in predicting tumor recurrence and survival in patients treated with high-dose radiotherapy for malignant gliomas.</jats:p> <jats:p>Studies using SPECT with thallium-201 (Tl-201) and technetium-99m (Tc-99m) hexamethypropyleneamine oxime (HMPAO) in 50 consecutive patients with malignant astrocytomas treated by surgery and high-dose radiotherapy were performed 1 day before reoperation. Maximum uptake of Tl-201 in the lesion was expressed as a ratio to that of the contralateral scalp, and uptake of Tc-99m HMPAO was expressed as a ratio to that of the cerebellar cortex. Patients were stratified into groups based on maximum radioisotope uptake values in their tumor beds. Differences in tumor histopathology at reoperation and 1-year survival between SPECT groups were determined by using chi-square analysis.</jats:p> <jats:p>The majority of patients in Group IA (Tl-201 ratio less than 2 or Tc-99m HMPAO ratio less than 0.5) showed radiation changes in their biopsy specimens (85.7%); they had an 85.7% 1-year survival rate. Group II (Tl-201 ratio between 2 and 3.5) had predominantly infiltrating tumor (78.6%); they had a 42% 1-year survival rate. Almost all of the patients in Group III (Tl-201 ratio greater than 3.5) had solid tumor (93.3%) and they had a 6.7% 1-year survival. Survival and pathological data differed significantly among groups (p less than 0.009).</jats:p> <jats:p>Dual-isotope SPECT data correlates with histological findings on reoperation and postoperative survival in patients with malignant gliomas.</jats:p>

Cerebral Radiation Necrosis

“…High-grade tumors have a higher thallium index than low-grade tumors. In a series of 15 biopsy-proven cases, Schwartz et al found an excellent correlation between imaging and histology (14/15 cases) using dual-isotope SPECT scanning with thallium-201 and 99mTc-HMPAO (27). Further study revealed a high thallium uptake in recurrent tumor and low thallium uptake in radiation necrosis.…”

The role of the gamma knife in the treatment of malignant primary and metastatic brain tumors

“…Differentiating between radiation necrosis and tumor progression is often difficult, and radioisotope brain scanning with thallium or position emission tomographic (PET) scanning may help in determining the pathologic basis of such reactions 52,53 . In some cases, a stereotactic biopsy may be required to establish the correct pathology, but our own experience in the radiosurgical treatment of primary malignant brain tumors indicates that most of what appears on scans to be radiation necrosis is actually a combination of necrotic tissue and viable tumor cells.…”

The present and future of cerebral tumor surgery in children

“…Three years later a mass recurred, which was demonstrated to be active on SPECT scanning. (Dualisotope SPECT has been shown to be a reliable test for distinguishing recurrent tumor from radiation necrosis [58,71].) This resulted in stereotactic radiosurgery with the linear accelerator.…”