Cardiac rhabdomyomas: clinical progression, efficacy and safety of everolimus treatment.

Background: Primary cardiac tumors are extremely rare. Cardiac rhabdomyoma is the most common primary cardiac tumor. 50-80% of solitary rhabdomyomas and all multiple rhabdomyomas are associated with tuberous sclerosis complex. Due to spontaneous regression, surgery is necessary only in severe hemodynamic compromise and persistent arrhythmias. Everolimus, a mechanistic target of rapamycin (mTOR) inhibitor, can be used in the treatment of rhabdomyomas seen in tuberous sclerosis complex. We aimed to evaluate the clinical progression of rhabdomyomas followed-up in our center between the years 2014-2019 and evaluate the efficacy and safety of everolimus treatment on tumor regression.

Methods: Clinical features, prenatal diagnosis, clinical findings, tuberous sclerosis complex presence, treatment and follow-up results were evaluated retrospectively.

Results: Among 56 children with primary cardiac tumors, 47 were diagnosed as rhabdomyomas, 28/47 patients (59.6%) had prenatal diagnosis, 85.1% were diagnosed before one year of age and 42/47 patients (89.3%) were asymptomatic. Multiple rhabdomyomas were present in 51% and median diameter of tumors was 16mm (4.5 - 52 mm). In 29/47 patients (61.7%) no medical or surgical treatment were necessary while 34% of these had spontaneous regression. Surgery was necessary in 6/47 patients (12.7%). Everolimus was used in 14/47 patients (29.8%). Indications were seizures (2 patients) and cardiac dysfunction (12 patients). Regression in size of rhabdomyomas was achieved in 10/12 patients (83%). Although, in the long-term, the amount of tumor mass shrinkage was not significantly different between patients who received everolimus and untreated patients (p=0.139), the rate of mass reduction was 12.4 times higher in patients who received everolimus. Leukopenia was not detected in any of the patients, but, hyperlipidemia was noted in 3/14 patients (21.4%).

Conclusions: According to our results, everolimus accelerates tumor mass reduction, but not amount of mass regression in the long term. Everolimus may be considered for treatment of rhabdomyomas which cause hemodynamic compromise or life-threatening arrhythmias before surgical intervention.