(201)Thallium SPECT and H-1-MRS compared with MRI in chemotherapy monitoring of high-grade malignant astrocytomas

Purpose To compare chemotherapy treatment monitoring in astrocytoma by (201 )thallium single photon emission computed tomography (SPECT) and photon mag netic resonance spectroscopy (H-1-MRS) with magnetic resonance imaging (MRT ), and to evaluate the influence of morphological tumor changes on cerebral (201)thallium uptake and metabolic changes in H-1-MRS. Materials and methods Six patients with highly malignant astrocytomas were followed with quantitative (201)thallium SPECT, MRI, and H-1-MRS during che motherapy. Maximum follow-up included six examinations per patient by eithe r method during 18 months. Criteria were set for: (1) regression (greater t han or equal to 25% tumor reduction), (2) status quo (< 25% reduction and < 25% increase), and (3) progression of disease (greater than or equal to 25% tumor increase). Results were compared with the clinical state of disease. Changes of tumor volume, contrast enhancement, necrosis, hemorrhage and edema on MRT were co mpared to changes in (201)thallium uptake volumes and H-1-MRS metabolite ra tios. Results Six patients were followed with a total of twenty-four examin ations with (201)thallium SPECT, MRI and H-1-MRS, respectively, between Feb ruary 1997 and October 1998. Five patients developed clinical progression o f disease, 4 out of 5 cases showed SPECT progression, 4 out of 5 cases MRI progression, and 1 out of 2 interpretable cases H-1-MRS progression at fina l assessment before clinical deterioration. During the phase of clinically stable disease; (A) the criterion for regression or status quo was met in 1 0 out of 13 assessments with SPECT, 11 out of 13 with MRT, and 8 out of 9 i nterpretable H-1-MRS; (B) the criterion for progression was met in 3 out of 13 with SPECT, 2 out of 13 with MRI, and 1 out of 9 interpretable H-1-MRS. The accuracy of SPECT, MRI, and H-1-MRS in identifying changes of tumor bu rden concordant with patients' clinical course was 78%, 83%, and 82%, respe ctively. SPECT regression was associated with MRI decrease of tumor size, c ontrast enhancement, edema and hemorrhage. SPECT progression was associated with MRI increase of the same parameters and the increase of necrosis. H-1 -MRS regression was associated with decrease of edema. H-1-MRS progression was associated with increase of tumor size, hemorrhage, and increase or dec rease of contrast enhancement. Conclusions Both (201)thallium SPECT and H-1-MRS evaluation showed sensitiv ity for detection of astrocytoma progression. We did not find a higher accu racy of SPECT or MRS than of MRT in astrocytoma chemotherapy monitoring. Tr eatment induced MRI changes were associated with (201)thallium uptake varia tions. H-1-MRS was difficult to apply for astrocytoma treatment monitoring. Improvements regarding size of measurement area such as multivoxel MRS and fat suppression pulses appeared desirable, and also the use of functional techniques with superior resolution such as dual isotope SPECT. However, ou r results suggest that (201)thallium SPECT and H-1-MRS can provide addition al information to MRI for chemotherapy efficacy evaluation in selected case s.