Retinoblastoma is a cancer of the eye which is important for research on the genetic component of cancer in general. There are currently 51 clinical trials listed on http://clinicaltrials.gov. Damage to the retinoblastoma tumor suppressor gene, called RB, is believed to play a role in many cancers, with much research focused on breast cancer.
Retinoblastoma generally develops in children younger than two, although cases have been reported in adults up to age 45. The average (arithmetic mean) age at diagnosis is 15 months for cancer in both eyes (bilateral), and 24 months for cancer in only one eye (unilateral). This has led to some confusion in the medical literature, where some authors report that 15 months and 24 months are the usual ages for this cancer to appear. In fact, the authors of Reference 1 show that there is a broad distribution of ages at diagnosis for both bilateral and unilateral retinoblastoma.
Fortunately, this childhood eye cancer is rare, affecting about 1 in 15,000 live births. This means that early statistical research was based on small samples. In 1971, Alfred G. Knudson Jr. developed the “two hit” hypothesis for retinoblastoma: this says two mutations are necessary for the tumor to start growing. The first hit could be inherited, and would affect both eyes. Thus bilateral disease develops relatively soon after birth, when only one more mutation occurs. The unilateral form supposedly requires two random mutations, and develops later since it takes more time, on the average, for two rare events to happen to the same individual.
In breast cancer, a deficiency of the retinoblastoma tumor suppressor protein contributes to aggressive tumor proliferation. Reference 2 reports that RB status is an important factor in determining which treatment options are likely to be effective. RB deficient cancers are less sensitive to hormonal therapies, but more sensitive to cytotoxic therapies including radiation and cisplatin.
Retinoblastoma International is a non-profit organization dedicated to preserving life and sight in children with this cancer. All families are encouraged to get eye examinations for children, and those affected with retinoblastoma should be aware of options for treatment and for genetic research.
Mastrangelo D et al, “The retinoblastoma paradigm revisited”, Med Sci Monit. 2008; 14(12): RA231-40.
Bosco EE et al, “RB in breast cancer: At the crossroads of tumorigenesis and treatment”, Cell Cycle 2007 Mar; 6(6): 667-71.
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.