Follow-up of cystic pineal glands in retinoblastoma patients does not increase detection of pineal trilateral retinoblastoma

PURPOSE: To evaluate the effectiveness of baseline screening and follow-up with magnetic resonance imaging (MRI) for detecting trilateral retinoblastoma (TRb) and assessing the risk of TRb development. DESIGN: Prospective multicenter cohort study. METHODS: A total of 607 retinoblastoma patients from 2012 through 2022 were included and followed up until September 1, 2023. At each center, a neuroradiologist categorized pineal glands on baseline and follow-up scans into 4 groups: (A) normal, (B) cystic gland, (C) suspicious gland, or (D) TRb. Different follow-up schedules were assigned to each category. Categories B and C were followed up with MRI after approximately 3 months and repeated 3 months later if suspicion remained. On each MRI, they measured the height and width, evaluated the aspect (solid, partly cystic, and completely cystic) of the pineal gland, and evaluated radiologic features suspicious of pineal TRb. The effectiveness of the current TRb screening method was assessed by evaluating its sensitivity and specificity to detect TRb. Determining the TRb incidence was a secondary outcome measure. RESULTS: Heritable retinoblastoma patients had a risk of 3.78% to develop TRb. One of 4 pineal TRbs was detected during a follow-up scan and 4 of 5 nonpineal TRbs were detected on the baseline MRI. Screening for pineal TRb had a sensitivity of 25% and specificity of 100%; for nonpineal TRb, the sensitivity was 80%. It required 494 follow-up scans to detect 1 pineal TRb. However, when restricting the follow-up to solely suspicious glands, only 22 scans were required to detect 1 pineal TRb. CONCLUSION: During extended follow-up after baseline MRI, only 1 pineal trilateral retinoblastoma was detected in our study. Follow-up after 3 months should be restricted to patients with a suspicious pineal gland defined as irregular thickening of the cyst wall (>2 mm), fine nodular aspect of the cyst wall, or when a solid or cystic gland exceeds the upper 99% prediction interval for size; patients with an unsuspicious cystic gland should not be followed up. Baseline MRI screening was able to detect most nonpineal trilateral retinoblastomas.