Suprarenal Masses in Very Young Infants: Is It Safe to Watch and Wait? Report of a SIOPEN Observational Study Results

Simple Summary Optimal management of small suprarenal masses (sSRMs) is not clearly defined in the literature. Among the differential diagnosis of these sSRMs without a clearly defined clinical management, neuroblastoma is the malignant neuroblastic tumor, with very good prognosis in most cases at this age and a very intriguing biology. The concept of the sSRM study is to attempt to safely minimize invasive procedures (including surgery) without jeopardizing the final outcome. We report the first International Society of Paediatric Oncology European Neuroblastoma (SIOPEN) cooperative prospective study of expectant observation as primary approach for neonates and infants less than or equal to 90 days of age with small localized suprarenal masses. In most cases, patients avoided surgery and, consequently, morbidity and mortality related to surgery. The study contributes to improving knowledge about the natural history and biology of neuroblastoma during early infancy. Background: To assess whether expectant observation of infants <= 90 days old with small suprarenal masses (sSRMs) could avoid unnecessary surgery without impacting outcome. Methods: Infants <= 90 days with a <= 5 cm mass, without midline extension or lymph node or distant spread were registered (ClinicalTrials.org:NCT01728155). Once staging was completed, they were followed with ultrasound, MRI and urinary catecholamines. Surgical resection was only planned if there was a >= 40% mass volume increase or for a mass persisting after 48 weeks of the planned observation. Results: Over a 5-year period, 128 infants were registered. No infant had detectable MYCN amplification in the peripheral blood. Surgery was performed in 39 (30.5%) patients, in 18 during and in 21 after the planned 48-week observation, and 74% were confirmed to be neuroblastomas. Non-life-threatening surgical complications occurred in two cases. The 3-year overall survival and event-free survival were 100% and 87.1%, respectively. The 16 events observed were volume increase (N = 11) and progression to neuroblastoma stage MS (N = 5). Patients with solid masses or MIBG-positive masses had lower EFS. Conclusions: Expectant observation for infants with sSRMs with clinical follow-up and timely imaging (including MRI scan) is safe and effective, allowing surgery to be avoided in the majority of them.