Unilateral vs. Bilateral Retinoblastoma

Pediatric retinoblastoma can occur in one or both of the child’s eyes. When the condition occurs in one eye, it is classified as unilateral retinoblastoma. The term “unilateral” roughly translates to “one side.” When present in both eyes, the condition is classified as bilateral retinoblastoma. The term “bilateral” equates to “two sides.” According to pediatric retinoblastoma research, bilateral retinoblastoma is known to present at an earlier age than unilateral retinoblastoma. It is estimated that roughly two-thirds of pediatric retinoblastoma cases are unilateral, and the remaining one-third of cases are bilateral.

Genetics of Unilateral vs. Bilateral Retinoblastoma

Pediatric retinoblastoma is also classified based on whether or not the child inherited the condition from the genetics of one or both parents. These classifications are referred to as hereditary retinoblastoma and non-hereditary retinoblastoma. The majority of bilateral retinoblastoma cases are also hereditary. Likewise, the majority of unilateral retinoblastoma cases are non-hereditary. Non-hereditary retinoblastoma is also referred to as sporadic retinoblastoma.

Genetic Mutation

Hereditary retinoblastoma, and therefore many cases of bilateral retinoblastoma, occurs as a result of a genetic mutation that the child inherits genetically. The mutation occurs in the gene RB1, which controls cell growth in the retina. When RB1 is mutated, cells may grow uncontrollably. This results in one of more pediatric retinoblastoma tumors. Genetic testing may be a factor for patients with bilateral retinoblastoma. Additionally, the results of this genetic testing may provide insight into the risk factors of pediatric retinoblastoma in other family members.

Retinoblastoma Treatment Differences

Treatment of unilateral vs. bilateral retinoblastoma tends to differ. In bilateral retinoblastoma, children have a higher tendency of developing more tumors as time passes. These tumors may occur in the eye, as well as in other areas of the body. Therefore, treatment of each tumor may be less aggressive.

In many cases, treatment of bilateral retinoblastoma may involve “focal treatments.” These treatments focus more directly on shrinking tumors and using treatments such as laser therapy, cryotherapy, or brachytherapy. For cases where retinoblastoma has spread, chemotherapy and radiation therapy may be used.

Laser therapy



Retinoblastoma Enucleation

Enucleation is the complete removal of the eye. Enucleation is more common in unilateral retinoblastoma than in bilateral retinoblastoma. For many, enucleation is the last considered form of treatment when other forms of therapy are ineffective. Enucleation may also be the only attempted form of treatment in the event that the pediatric retinoblastoma is advanced, or focal treatments have otherwise been deemed an ineffective option.


Draper, GJ, BM Sanders, and et al. “Patterns of Risk of Hereditary Retinoblastoma and Applications to Genetic Counselling.” PubMed.gov. U.S. National Library of Medicine, n.d. Web. 27 Nov 2013. <http://www.ncbi.nlm.nih.gov/pubmed/1637670>.

Polomeno, R C. “Bilateral Retinoblastoma.” Canadian Medical Association Journal 120.2 (1979): 126. MEDLINE with Full Text. Web. 5 Dec. 2013.

“Retinoblastoma Treatment.” National Cancer Institute. U.S. Department of Health and Human Services, 24 Oct 2013. Web. 5 Dec 2013. <http://www.cancer.gov/cancertopics/pdq/treatment/retinoblastoma/healthprofessional>.