Further studies of the effect of vitamin D on retinoblastoma. Inhibition with 1,25-dihydroxycholecalciferol.

We present evidence that calcitriol (1,25-dihydroxycholecalciferol) decreases tumor takes and tumor growth of subcutaneous retinoblastomas in athymic mice. Histopathologic studies showed that the calcitriol also induced necrosis of the retinoblastomas. The calcitriol, however, did not induce tumor calcification. Unfortunately, the dose of calcitriol used in this experiment caused significant toxic effects. If the toxicity of vitamin D can be alleviated without compromising its antineoplastic effect, vitamin D may be a useful chemotherapeutic agent against retinoblastoma.