Chromosomal Analysis in the Aqueous Humor of Retinoblastoma eyes is predictive of globe salvage: the Surrogate Tumor Biopsy

Abstract

Purpose : The aim of this study was to identify somatic chromosomal copy number alterations (SCNA) in tumor-derived cell-free DNA (cfDNA) in the aqueous humor (AH) of retinoblastoma (Rb) eyes and to correlate with clinical outcomes particularly globe salvage.

Methods : AH was extracted via paracentesis from Rb eyes at the time of intravitreal injection of chemotherapy or enucleation; cfDNA was extracted. Shallow whole genome sequencing was performed on an Illumina platform to assess the presence of cell-free tumor DNA fractions and known, highly recurrent SCNAs in Rb which include gain of 1q, 2p, 6p and loss of 13q and 16q. Patient demographics including age at diagnosis, Group Classification, treatment regimen and globe salvage were recorded.

Results : Twenty-six patients with Rb were included. Three patients underwent primary enucleation, 3 intra-arterial chemotherapy and 20 systemic chemotherapy; 3 patients had both eyes included for 29 total eyes. Group B classification was diagnosed in 1, Group C in 2, Group D in 18 and Group E in 8 eyes. From the 29 eyes, 63 samples of AH were analyzed; 5 post-enucleation and 58 from 24 eyes during intravitreal chemotherapy injection. Ultimately 13 eyes required enucleation and 16 eyes were salvaged with treatment. Follow-up ranged from 8-43 months (median 17 months).

6p gain was the most common SCNA found in 10/13 (77%) enucleated eyes compared to 4/16 (25%) of salvaged eyes. 6p gain is significantly more common in enucleated than salvaged eyes (p=0.009). The average amplitude of 6p gain was 1.8 in the enucleated group versus 1.4 in the salvaged group. The presence of a detectable SCNA in enucleated eyes was 11/13 (85%); the rate of in salvaged eyes was 6/16 (38%) (p=0.022). The average of the CNA profiles in each of the two groups are compared in Figure 1. The probability of globe salvage was improved in eyes without detectable SCNAs (p=0.028) (Figure 2).

Conclusions : This is the first study to correlate clinical outcomes with highly-recurrent SCNAs in the AH from Rb eyes. This study suggests that not only can the AH serve as a surrogate to tumor biopsy but could contribute to prognostication of tumor response to therapy.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Figure 1: CNA profile from the AH from salvaged eyes (A) and enucleated eyes (B). The amplitude of 6p gain is greater in enucleated eyes.

 

Figure 2: Kaplan-Meier Curves Demonstrating Globe Salvage by the presence of SCNAs