Meningioma treated with interferon-alpha, evaluated with [C-11]-L-methionine positron emission tomography

Purpose: In meningioma patients with postoperative residual masses, recurre nt or primarily inoperable tumors, positron emission tomography (PET) with [C-11]-L-methionine was used to evaluate treatment efficacy of IFN-alpha. Experimental Design: Twelve patients were treated with IFN-alpha at a dose of 1.5-5 million IU s.c. daily. PET, computed tomography, and/or magnetic r esonance imaging were performed in all patients before and, at regular inte rvals, during IFN-alpha treatment. The ratio of tumor hot-spot uptake to ce rebellar uptake or to cortex uptake was calculated. This ratio estimates th e relative methionine accumulation in the tumor and presumably the prolifer ative activity in the tumor. Results: During IFN-alpha treatment, PET demonstrated a mean relative perce ntage of reduction in the uptake ratio (MRe1R) of 22.3% in the meningiomas. In nine patients who were considered responders, defined as patients with a positive MRe1R, the MRe1R was 30.4%. For the three nonresponders, defined as patients with a negative MRe1R, the MRe1R was -1.8%. Three patients wer e followed for a long time: two patients for 8 years and one patient for 4 years and 6 months; the two patients followed for 8 years are still on IFN. The volumes of these tumors were constant or showed a slight decrease. No correlation was found between histopathological diagnosis (PAD) WHO grading I-III of meningiomas and response to IFN-alpha treatment. Conclusions: PET was judged a useful method to predict which patients are s uitable for long-term treatment with IFN-alpha and also for dose finding. I n five patients treated from 9 months to 8 years, IFN-alpha seemed to be an effective oncostatic drug. The clinical usefulness of IFN-alpha, taking ad verse reactions into account, must be evaluated in a larger series of patie nts.