Reccurence of Kaposi's sarcoma after increased exposure to sirolimus

The conversion to sirolimus treatment is recently indicated as an effective therapy of Kaposi's sarcoma (KS) in transplant patients. We present two treatment modalities in patients with KS and recurrence of the disease after increasing sirolimus dose. Among 1034 renal transplants performed at our center, three (0.3%) suffered from KS. Initial immunosuppression consisted of cyclosporine, azathioprine and prednisone in one patient; and tacrolimus, mycophenolate mofetil and prednisone in two patients. KS symptoms appeared within one year post-transplantation. Two patients developed cutaneous tumor; one disseminated disease, including the skin, mediastinal lymph nodes and both lungs. After histological confirmation of KS immunosuppression was minimized: Two were converted to sirolimus (1-2 mg/day, level 5-8 ng/ml) treatment; the third patient discontinued tacrolimus and was administered 1 g/day mycophenolate mofetil. Gradual regression of KS was observed in all the patients. In one patient, 8 months after regression of lung KS, the dose of sirolimus was increased to 2 mg/day (level raised to 13.8 ng/ml). Recurrent disease developed afterwards involving diffuse interstitial infiltrates with nodular changes in both lungs. For the second time the dose of sirolimus was reduced to 1 mg/day (level 4-5 ng/ml) and lung lesions regressed 5 months later. Renal function was stable (creatinine 1.3-1.9 mg/dl) in all patients, 24 months from KS onset.

treatment by low sirolimus or mycophenolate mofetil doses caused regression of KS. Recurrence of KS after increasing sirolimus dose suggests that regression of KS is a result of diminished immunosuppression, not the direct antineoplastic effect of sirolimus. Careful maintenance of low sirolimus levels is suggested.