201Thallium SPECT and 1H-MRS Compared with MRI in Chemotherapy Monitoring of High-grade Malignant Astrocytomas

Purpose To compare chemotherapy treatment monitoring in astrocytoma by ²⁰¹thallium single photon emission computed tomography (SPECT) and photon magnetic resonance spectroscopy (¹H-MRS) with magnetic resonance imaging (MRI), and to evaluate the influence of morphological tumor changes on cerebral ²⁰¹thallium uptake and metabolic changes in ¹H-MRS.Materials and methods Six patients with highly malignant astrocytomas were followed with quantitative ²⁰¹thallium SPECT, MRI, and ¹H-MRS during chemotherapy. Maximum follow-up included six examinations per patient by either method during 18 months. Criteria were set for: (1) regression ( 25% tumor reduction), (2) status quo (< 25% reduction and < 25% increase), and (3) progression of disease ( 25% tumor increase). Results were compared with the clinical state of disease. Changes of tumor volume, contrast enhancement, necrosis, hemorrhage and edema on MRI were compared to changes in ²⁰¹thallium uptake volumes and ¹H-MRS metabolite ratios.Results Six patients were followed with a total of twenty-four examinations with ²⁰¹thallium SPECT, MRI and ¹H-MRS, respectively, between February 1997 and October 1998. Five patients developed clinical progression of disease, 4 out of 5 cases showed SPECT progression, 4 out of 5 cases MRI progression, and 1 out of 2 interpretable cases ¹H-MRS progression at final assessment before clinical deterioration. During the phase of clinically stable disease; (A) the criterion for regression or status quo was met in 10 out of 13 assessments with SPECT, 11 out of 13 with MRI, and 8 out of 9 interpretable ¹H-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 ¹H-MRS. The accuracy of SPECT, MRI, and ¹H-MRS in identifying changes of tumor burden concordant with patients' clinical course was 78%, 83%, and 82%, respectively. SPECT regression was associated with MRI decrease of tumor size, contrast enhancement, edema and hemorrhage. SPECT progression was associated with MRI increase of the same parameters and the increase of necrosis. ¹H-MRS regression was associated with decrease of edema. ¹H-MRS progression was associated with increase of tumor size, hemorrhage, and increase or decrease of contrast enhancement.Conclusions Both ²⁰¹thallium SPECT and ¹H-MRS evaluation showed sensitivity for detection of astrocytoma progression. We did not find a higher accuracy of SPECT or MRS than of MRI in astrocytoma chemotherapy monitoring. Treatment induced MRI changes were associated with ²⁰¹thallium uptake variations. ¹H-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, our results suggest that ²⁰¹thallium SPECT and ¹H-MRS can provide additional information to MRI for chemotherapy efficacy evaluation in selected cases.