RB1 CIRCULATING TUMOR DNA IN THE BLOOD OF PATIENTS WITH RETINOBLASTOMA INCREASES IN UNTREATED PATIENTS.

Abstract

Circulating tumor DNA (ctDNA) in plasma has been identified in many cancers, including retinoblastoma at diagnosis. It has previously been shown that with treatment (enucleation or ophthalmic artery chemosurgery), all ctDNA disappears; if there is persistent plasma ctDNA after treatment, metastases develop. The purpose of this study was to determine how the ctDNA RB1 variant allele frequency changes in patients with retinoblastoma who have delayed treatment. Circulating tumor DNA RB1 was detected, and variant allele frequency was measured at diagnosis and again before any intervention at some time later ranging from 2 days to 28 days. Four patients with five ctDNA RB1 mutations were detected at diagnosis, and variant allele frequency was increased on reevaluation of the same RB1 mutations in ctDNA. In this small cohort, every patient (4) and every RB1 mutation (5) plasma level VAF% increased when measured at two time periods before treatment was initiated suggesting that growing tumors demonstrate increasing plasma ctDNA.