There are two types of Pigmented Villonodular Synovitis. Diffuse PVNS affects the entire synovium and typically occurs in large joints such as the knee or hip. Localized, or nodular, PVNS is less common than the diffuse form and typically occurs in smaller joints such as the hands and feet. Localised PVNS often arises in the form of a large benign tumour on the tendon sheaths of the joint. As the tumor grows in the joint, it damages the surrounding bone and tissues. Treatment is primarily surgical or with radiation.Several case reprots show remarkab,e responses to Gleevec.The largest siereis of 6 patietns is by Ravi etal. 5/6 patients (83%) showed improvement in pain, swelling or joint function. FDG-PET scans were performed on 2 patients, one patient was imaged as early as 2 weeks showing a decrease in FDG uptake while the other patient was imaged at 6 weeks showing a 75% decrease in SUVmax. MRI showed decrease in size of the lesion and contrast enhancement in 3/6 (50%) patients. Stable disease was observed in 2/6 (33%) patients. Treatment was discontinued in 2 patients, one with stable disease (due to financial reasons) and the other with a partial response (due to drug toxicity). Both patients showed progression after discontinuation of imatinib. 2 patients underwent surgery following therapy with imatinib and remain disease free at 16 months and 5.5 months of follow-up. Cassoer at al did a review of 29 patients. Twenty-nine patients from 12 institutions in Europe, Australia, and the United States were included. There were 13 men, the median age was 41 years, and the most common site of disease was the knee (n = 17; 59%). Two patients had metastatic disease to the lung and/or bone. Five of 27 evaluable patients had Response Evaluation in Solid Tumor (RECIST) responses (overall response rate, 19%; 1 complete response and 4 partial responses), and 20 of 27 patients (74%) had stable disease. Symptomatic improvement was noted in 16 of 22 patients (73%) who were assessable for symptoms. Despite a high rate of symptomatic improvement and a favorable safety profile, 6 patients discontinued because of toxicity, and 4 patients decided to discontinue IM for no clear medical reason.
While there are no prospective studies, and there cannot be in such a rare condition, there are many collected cases showing a respectable efficacy for the drug.
J.-Y. Blay et al, Complete response to imatinib in relapsing pigmented villonodular synovitis/tenosynovial giant cell tumor (PVNS/TGCT)Annals of Oncology Volume19, Issue4Pp. 821-822.
V. Ravi,Imatinib in the treatment of tenosynovial giant-cell tumor and pigmented villonodular synovitis. J Clin Oncol 28:15s, 2010 (suppl; abstr 10011)
Philippe A. Cassier et al, Efficacy of imatinib mesylate for the treatment of locally advanced and/or metastatic tenosynovial giant cell tumor/pigmented villonodular synovitis