Retinoblastoma is a rare eye cancer primarily affecting young children, usually before age five. It originates in the retina, the light-sensitive tissue at the back of the eye. While some cases are spontaneous, a significant portion are hereditary, passed down through families. Understanding this distinction is important for managing the condition.
Understanding Hereditary Retinoblastoma
Hereditary retinoblastoma stems from a genetic predisposition. It is linked to mutations in the RB1 gene on chromosome 13. The RB1 gene functions as a tumor suppressor, regulating cell growth and preventing uncontrolled division.
Individuals inherit one mutated RB1 gene copy from a parent. With one “hit” or mutation in every cell, they are more prone to developing cancer. A second “hit” in the remaining healthy RB1 copy in a retinal cell can lead to tumor formation. This is known as Knudson’s “two-hit hypothesis.” This inheritance pattern is autosomal dominant, meaning one altered gene copy from one parent is sufficient for predisposition.
Recognizing the Signs and Diagnosis
Identifying hereditary retinoblastoma often begins with subtle, observable signs. The most common sign is leukocoria, a white reflection in the pupil, often called a “cat’s eye reflex,” especially in flash photographs. Another indicator is strabismus, or “crossed” eyes, which occurs if the tumor affects the child’s vision and eye coordination. Parents or pediatricians might also notice a red, irritated eye or vision changes.
Once signs are observed, an ophthalmologist performs a comprehensive dilated eye exam, also known as fundoscopy. This allows a detailed view of the retina and any tumors. Imaging techniques like ocular ultrasound, MRI, and CT scans assess the tumor’s size, location, and extent within the eye and surrounding structures. Genetic testing of blood samples confirms the RB1 gene mutation, establishing the condition’s hereditary nature and informing family risk.
Treatment Approaches
Treatment for hereditary retinoblastoma is individualized, depending on tumor size, location, and whether one or both eyes are affected. Goals are to save the child’s life, preserve vision, and prevent cancer spread. For smaller tumors, eye-sparing therapies are used. These include laser photocoagulation, which uses a laser to destroy tumor cells by heating them, or cryotherapy, which freezes and destroys abnormal cells.
Chemotherapy is another treatment, delivered in various ways depending on tumor characteristics. Systemic chemotherapy involves intravenous drugs to reach cancer cells throughout the body, useful for larger tumors or those with a higher risk of spread. Intra-arterial chemotherapy delivers drugs directly to the eye through a catheter, minimizing systemic side effects. Intravitreal chemotherapy involves injecting drugs directly into the vitreous humor, while periocular chemotherapy involves injections around the eye. If the tumor is very large, has spread extensively, or failed other treatments, enucleation—surgical removal of the affected eye—may be necessary to ensure survival and prevent further spread.
Long-Term Management and Family Implications
Long-term management involves ongoing surveillance due to an elevated risk of secondary cancers later in life. These secondary malignancies, including sarcomas, melanomas, and brain tumors, are a direct consequence of the inherited RB1 gene mutation affecting all body cells. Regular follow-up examinations, including imaging studies, are therefore scheduled to detect any new tumors early.
Genetic counseling plays a role for affected individuals and their families. Counselors provide information about the inheritance pattern, risks for future children, and genetic testing availability for family members. Siblings of an affected child may undergo testing for the RB1 mutation, allowing early screening if positive. This approach helps families understand the condition’s implications, manage risks, and access psychological and social support.