DENVER — Moderate-dose radiotherapy is highly effective in achieving sustained remission in patients with high-risk pigmented villonodular synovitis, Brian O'Sullivan, M.B., said at the annual meeting of the American Society for Therapeutic Radiology and Oncology.
Through 20 years of experience in managing this proliferative disease, he has concluded that the best approach is surgical gross total removal of the lesion followed by radiotherapy (RT). But when surgery is likely to compromise function, RT alone will achieve control of gross disease, according to Dr. O'Sullivan, a radiation oncologist at Princess Margaret Hospital and professor of radiation oncology at the University of Toronto.
Pigmented villonodular synovitis (PVSN) is a rare monoarticular proliferative process originating in synovial membranes. Although it can affect any mobile joint, the knee is the most common site. Lesions can also arise in bursae or tendon sheaths. PVSN can be a destructive process involving invasion of cartilage, bone, and adjacent tissues, with resultant major loss of function and, occasionally, amputation. Its treatment poses technical challenges, especially in patients with large circumferential lesions of the knee, for whom the goal is to deliver enough RT to control the disease while sparing some of the often limited quantity of normal tissue.
“I get more calls about PVSN than any other disease I treat,” the physician said.
The classic PVSN scenario involves a swollen joint with episodes of painful acute swelling related to acute hemarthrosis. “It often mimics the type of joint a hemophiliac patient has,” said Dr. O'Sullivan.
PVSN comes in two forms. Nodular PVSN consists of a pedunculated lesion surrounded by normal synovium. The diffuse form is far more problematic, with recurrence rates of 50%–90% quoted in various series. The arthroscopic appearance of diffuse PVSN typically features a shaggy “large beard” villous proliferation with a thickened, overgrown synovium, often accompanied by bony scalloping or erosion.
Dr. O'Sullivan presented a series of 41 patients with PVSN who were prospectively followed for a mean of 77 months after RT. Of these, 23 presented with recurrent disease for which they had undergone a mean of two prior surgical procedures. The other 18 had what he described as “primary disease of prodigious proportions.” The lesion originated in the knee in 15 patients, and in another joint in 21 others; in 5 patients the disease arose in a periarticular tendon sheath. All patients had the poorer prognosis (diffuse) type of PVSN. All but one had both intra- and extraarticular disease. Three-quarters of the lesions were larger than 5 cm, and 17 were larger than 10 cm.
The RT regimen has evolved over time. Dr. O'Sullivan has settled on a dose of 40 Gy administered in 20 fractions over 3 weeks as optimal. This is supplemented by a final 8-Gy boost to the area of fullest disease. Arthroscopic surgery port sites also get a bolus, because he has observed that PVSN preferentially spreads there.
At a mean of 77 months, 40 of 41 patients remain in good local control as defined either by an absence of clinical and imaging evidence of disease in patients free of overt disease at the time of RT, or by stable disease on serial follow-up imaging studies. One patient developed lesion growth starting 4 years post RT. Functional status was deemed good in 31 patients and adequate in 5. Both patients whose functional status was rated as poor had significant preexisting bone involvement. There have been no RT-induced neoplasias.
In response to audience questions, Dr. O'Sullivan said he often holds off on RT until he can evaluate the tempo of the disease. But he tends to intervene early in large progressive knee and hip lesions. “The problem is, if you let this disease persist and it continues to grow, it will destroy the joint,” he warned.
This excised synovium demonstrates the fronds and nodules that are typical of pigmented villonodular synovitis. ©Saunders 2005. Kumar: Robbins and Cotran: Pathologic Basis of Disease, 7E