F. David Kitchin

The occurrence of new retinoblastomas after treatment.

New separate tumors have developed in 11% of eyes containing retinoblastoma treated primarily with external beam radiation. The tumors were primarily found in the inferior retinal periphery and averaged 1.5 disc diameters in size. All of the tumors were controlled, with photocoagulation and cryopexy being the most frequently used treatments.

Osteogenic Sarcoma of the Humerus after Cobalt Plaque Treatment for Retinoblastoma

A 13-year-old boy developed an osteogenic sarcoma of the right humerus ten years after treatment for bilateral retinoblastoma. The bilateral retinoblastoma has been managed with enucleation of one eye and successful treatment of the solitary tumor in the other eye with a single application of a local 10-mm round cobalt plaque. Patients with bilateral retinoblastoma have a significant (15 to 20%) chance of developing a second, nonocular, neoplasm. These neoplasms have occurred from one to 42 years after the treatment for retinoblastoma. The most common of these tumors is an osteogenic sarcoma; it may occur after external beam irradiation, local cobalt plaque, or no irradiation. The tumors may be in the skull or at distant sites whether or not these patients receive radiation.

Lactate Dehydrogenase in Tears

Lactate dehydrogenase levels in tears were measured in normal subjects and in patients with retinoblastoma. When specimens were collected without trauma in normal subjects, there were usually no detectable levels of lactate dehydrogenase. When the eyelids were rubbed (probably liberating epithelial cells) lactate dehydrogenase levels were detectable and were five to ten times those of normal aqueous humor. When lactate dehydrogenase isoenzymes in such specimens were analyzed, the level of lactate dehydrogenase 5 was always higher than that of lactate dehydrogenase 1 (similar to normal aqueous humor). While occasional patients with retinoblastoma do have elevated levels of lactate dehydrogenase in tears, it is uncertain if this is due to epithelial destruction or retinoblastoma itself. Lactate dehydrogenase in tears does not appear to be a useful test for the diagnosis of retinoblastoma given present techniques for collection and analysis.