Gallium-67 scintigraphy for monitoring therapy response and follow-up of paracoccidioidomycosis

Objectives: The current tools to evaluate patients' therapy response in paracoccidioidomycosis (PCM) are based on clinical, immunological and radiological data. However, these criteria may be of limited value in the follow-up of asymptomatic lesions, negative pre-treatment serological tests and in severe pulmonary involvement whose chest radiography usually doesn't differentiate active from fibrotic lesions. The purpose of this study was to determine the value of Ga imaging for monitoring therapy response and follow-up of PCM patients. Methods: We studied 45 patients with confirmed PCM. Each patient underwent 2 to 7 Ga scintigraphies (total:147 scans) during a follow-up period of 4 months to 8,5 years. The Ga findings were compared to the clinical outcome and serum specific antibody levels. Results: Most patients showed improvement in the sequential Ga scans during the treatment with progressive decrease in number and intensity of sites with active infectious process. Ga scan was performed in nine patients with clinical cure and negative or persistently low levels of serum antibody following prolonged treatment. The scintigraphy confirmed the absence of inflammatory disease in all of these cases. Three patients with clinically suspected recurrence after irregular treatment showed positive Ga scans, confirming disease reactivation. Conclusion: Ga imaging is helpful in monitoring therapy response of PCM patients. Moreover, this method may be used to evaluate disease activity by confirming apparent cure and clinical recurrence