Assessing the effectiveness of rapamycin on angiomyolipoma in tuberous sclerosis: a two years trial

Background: Tuberous sclerosis (TS) is a rare autosomal dominant systemic disease with an estimated prevalence of 1/6000. Renal angiomyolipoma (AML) is a benign tumour with high morbidity frequently present in TS. The aim of the study was to test the effect of rapamycin in reducing the volume of AML in TS. Methods: Twenty four-month prospective open-label, single arm, unicentre Phases II andIII study. The primary endpoint was to evaluate the effect of treatment on the reduction of at least 50% AML volume from baseline at 24 months. The secondary endpoints were: average tumour reduction, surgical complications, skin lesions and drug safety. The study population comprised 17 patients, aged >10 years who were diagnosed with TS and had >= 1 renal AML >2 cm of diameter and had a serum creatinine < 2mg/dl and urine protein/creatinine ratio < 22.6 mg/mmol. The trial was conducted at Fundacio Puigvert. Rapamycin was given to achieve stable plasma levels between 4 and 8 ng/ml. AML volume was estimated using orthogonal measurements by MRI at baseline, 6, 12 and 24 months. Results: Ten out of 17 patients were success responders for the main outcome -58.8%, 95% CI: 32.9% to 81.6%-. After 6 months of therapy, the mean volume decrease was 55.18% (5.01 standard error (SE); p<0.001) and 66.38% (4.41 SE; p<0.001) at year 1. There was no significant decrease between year 1 and 2. According to RECIST criteria, all patients achieved a partial response at year 1 and all but two had already achieved this partial response after 6 months. The main analysis was performed according to the intention-to-treat principle analysis. Tumour volume was analyzed over time by means of mixed models for repeated measurement analysis. We used the baseline tumour volume as a covariate for the absolute change and percentage change from baseline data. The analysis was performed using SAS version 9.2 software, and the level of significance was established at 0.05 (two-sided). Conclusions: This study show that mTOR inhibitors are a relatively safe, efficacious and less aggressive alternative than currently available options in the management of AML in TS.