Effect of subconjunctivally administered antineoplastics on experimentally induced intraocular malignant tumour

Twice-weekly subconjunctival injections of 5-fluorouracil (5-FU), 6-mercaptopurine (6-MP), cytarabine (ARA-C) and methotrexate (12.5 mg, 20 mg, 75 mg and 12.5 mg per dose respectively) were used to treat Greene melanoma implanted in the anterior chamber of the eyes of three groups of New Zealand rabbits: group 1 (14 animals), the control group, received saline, group 2 (16 animals) received treatment beginning immediately after tumour implantation and group 3 (15 animals) received treatment starting 1 week after implantation. Both 5-FU and 6-MP were effective in delaying iris tumour growth, as judged by daily clinical examination, histopathological study and reduction in tumour weight compared with control eyes after 17 days (group 2: p less than 0.001, p less than 0.05; group 3: p less than 0.025, p less than 0.05). The delay was correlated with earlier onset of treatment (group 2 v. 3: 5-FU, p less than 0.025; 6-MP, p less than 0.05). ARA-C and methotrexate were ineffective at the dosages used. Our results suggest that subconjunctivally administered 5-FU and 6-MP significantly delay tumour growth in this experimental model of iris melanoma and that efficacy is correlated with earlier initiation of treatment.