QUANTIFICATION OF ORBITAL AND MID-FACIAL GROWTH-RETARDATION AFTER MEGAVOLTAGE EXTERNAL-BEAM IRRADIATION IN CHILDREN WITH RETINOBLASTOMA

Purpose: The late side effects of external beam irradiation in patient s with retinoblastoma such as orbital bony growth retardation, are a s erious problem in adolescence. Therefore, a quantitative study was per formed to investigate the late effects of irradiation on orbital growt h in patients with retinoblastoma. Methods: The orbits of 68 patients with retinoblastoma, 52 bilateral and 16 unilateral were divided into two treatment groups: radiotherapy alone, 77 orbits; and radiotherapy + enucleation, 43 orbits. Follow-up time was 12 to 240 months (mean, 9 5 months) in group 1 and 27 to 216 months (mean, 97 months) in group 2 . These groups were subdivided further into age groups at which radiot herapy was given. The morphometric measurements of these groups were c ompared. Results: The authors showed that irradiation causes a signifi cant growth retardation when compared with the growth of nonirradiated orbits (P < 0.001). They also demonstrated that radiotherapy in child ren younger than 6 months of age is more damaging to the orbital growt h than at an older age (P < 0.01). Finally, the authors showed that se condary enucleation does not have an additive growth-retarding effect. Conclusion: Orbital growth retardation in patients with retinoblastom a after radiotherapy is influenced mainly by the age at which irradiat ion is given and is defined at 6 months. Theoretically, it would be de sirable to postpone irradiation in children until they are older than 6 months of age if possible. The irradiation effect on these orbits is not enhanced by enucleation.