N 024   Monday March 2017 Retinoblastoma E-Poster Podium Session 3:55pm – 4:13pm CLINICAL AND GENETIC FEATURES OF RETINOBLASTOMA T.Ushakova, T.Kazubskaya, V.Kozlova, E.Alekseeva*, V. Strelnikov*, L.Lubchenko, V.Polyakov N.N. Blokhin Russian Cancer Research Center, Moscow, Russian Federation *Medical Genetics Research Center, Moscow, Russian Federation

Introduction and Aim The quality of life of patients with retinoblastoma (RB) is strongly dependent upon the early detection of tumor. The use of molecular methods in the study of RB opens up the possibility of early diagnosis, the choice of tactic of treatments and prevention of hereditary forms of the disease. The etiology of hereditary and most non-hereditary form of retinoblastoma caused by a mutation RB1 gene located on the chromosome 13 (13q14.2) If the RB1 mutation is inherited   from the affected parent or if it occurs at a very early embryogenesis -   the disease is often bilateral, multifocal If both RB1 mutations occurred in somatic ie. the retinal cells of the eye, the disease often monolateral and one-sided Germline mutation transmitted to offspring with 50% risk in each pregnancy В нас случ пер. мутац происходит обычно в герминальных клетках одного из родителей соматические мутации двух аллелей гена вызывают только ретинобастому, The aim is to show clinical-genetics peculiarities of RB in the Russian population 2

Patients and Methods The study evaluates cohort of 393 Russian children from 351 families who were examined, treated and observed at a single center between 1994 and 2013 and who were referred for genetic evaluation Molecular-genetic analysis was conducted for 75 patients and 137 their relatives. Peripheral blood was evaluated for RB1 mutations, DNA typically extracted from white blood cells In the early stages of retinoblastoma Retinal thickening, whitish-yellowish glow of the pupil Diagnostics of RB hereditary forms complex, requiring clinical, genealogical, syndromological and molecular genetic studies The overall, RB patients with hereditary predisposition revealed at 44% cases. The families forms identified in 8,6%, bilateral – in 38%. The second primary tumors were accounting for 3,1% RB children. Congenital abnormalities, such as heart anomaly, kidney hypospadias, cleft lip and palate, spina bifida were found in 4.8% of patients, exceeding the general population frequency (3%). It is interesting that patients with unilateral RB have congenital defects more frequently (4.6%) compared to bilateral RB (3.2%)

Results Germline mutations of RB1 gene were detected in 70% testing patients, among children with bilateral RB pathogenic variant of RB1 were found in 85% and with unilateral - in 14%. The most common germline mutations of RB1 gene in patients were: a missens, nonsens, site splice, insertion, intragenic deletions. The monitoring of patients with different types of RB1 mutations was revealed genotype-phenotype correlation. Children with nonsense mutation, insertions and large deletions had significantly hard clinical picture of disease (bilateral, multifocal retinal lesion, early-onset RB, appearing new focus RB in spite of organ-saving therapy) Families harboring missense and site splice mutations in RB1 shown a low-penetrance with reduced expressivity of the disease (unit foci of tumor, late clinical manifestation).

and incomplete penetrance. Some families with RB1 pathogenic variants may be with reduced expressivity and incomplete penetrance. Pedigree. Familial RB with incomplete penetrance. Pedigree. In this family harboring site splice RB1 mutation (g.61807G >A, exon 9) only child (III-1) and his uncle (II-1) had unilateral RB. Father (II-2) and grandfather (I-2) with the same underling phatogenic mutation were unaffected carriers showing incomplete penetrance of mutation (g.61807G >A, exon 9). I 1 2 3 4 5 II 1 2 3 RB -unilateral one month III RB -unilateral 1 In two our families where one of the parents were affected RB preimplantation genetic diagnosis has allowed to be born healthy children Patients who have had the RB in childhood, need for genetic counseling, retinoblastoma education and a proposed management plan. Management of children carriers of pathogenic variant of RB1 requires close collaboration among ophthalmologist, oncologist, genetic counselors because the optimal treatment of these children is dependent upon the early detection of tumors and feasibly allowing organ-preserving focal treatment 5

Summary RB patients have an increased risk for the second primary tumors and congenital malformations. The patients with germline mutation in the RB1 gene showed genotype-phenotype correlation. Some families with RB1 pathogenic variants may be with reduced expressivity and incomplete penetrance. Molecular testing mutation RB1 gene should be offered to all patients, their first-degree relatives, including the unilateral cases.