The various treatment modalities for retinoblastoma includes:
Enucleation of the eye – Most patients with unilateral disease present with advanced intraocular disease, so usually undergo enucleation, which results in a cure rate of 95%. In bilateral Rb, enucleation is usually reserved for eyes that have failed all known effective therapies or without useful vision. External beam radiotherapy (EBR) – The most common indication for EBR is for the eye in a young child with bilateral retinoblastoma who has active or recurrent disease after completion of chemotherapy and local therapies. However, patients with hereditary disease who received EBR therapy are reported to have a 35% risk of second cancers. Brachytherapy involves the placement of a radioactive implant (plaque), usually on the sclera adjacent to the base of a tumor. It used as the primary treatment, or more frequently, in patients with small tumors or in those who had failed initial therapy including previous EBR therapy. Thermotherapy involves the application of heat directly to the tumor, usually in the form of infrared radiation. It is also used for small tumors. Laser photocoagulation  is recommended only for small posterior tumors. An argon or diode laser or a xenon arc is used to coagulate all the blood supply to the tumor. Cryotherapy induces damage to the vascular endothelium with secondary thrombosis and infarction of the tumor tissue by rapidly freezing it. It may be used as primary therapy for small peripheral tumors or for small recurrent tumors previously treated with other methods.
The first mutational event can be inherited (germline or constitutional), which will then be present in all cells in the body. The second “hit” results in the loss of the remaining normal allele (gene) and occurs within a particular retinal cell. In the sporadic, nonheritable form of retinoblastoma, both mutational events occur within a single retinal cell after fertilization (somatic events); sporadic retinoblastoma tends to be unilateral. Several methods have been developed to detect the RB1 gene mutations. Attempts to correlate gene mutations to the stage at presentation have not shown convincing evidence of a correlation. MYCN
Not all retinoblastoma cases are with RB1 inactivation. There are cases reported with only one RB1 mutation or even two functional RB1 alleles, which indicates other oncogenic lesions of retinoblastoma. Somatic amplification of the MYCN oncogene is responsible for some cases of nonhereditary, early-onset, aggressive, unilateral retinoblastoma. MYCN can act as a transcription factor and promotes proliferation by regulating the expression of cell cycle genes. Although MYCN amplification accounted for only 1.4% of retinoblastoma cases, researchers identified it in 18% of infants diagnosed at less than 6 months of age. Median age at diagnosis for MYCN retinoblastoma was 4.5 months, compared with 24 months for those who had nonfamilial unilateral disease with two RB1 gene mutations.