Wilke I., Schaudig U.

Augenklinik und Poliklinik, Universitäts-Klinikum-Eppendorf, Martinistrasse 52, 20246 Hamburg

Background: There is an ongoing debate about the ideal dosage for Ru¹⁰⁶/Rh¹⁰⁶ brachytherapy regarding radiation dose to the tumour apex or base, dose rate and radiation period.
Aim of the study: To analyze the influence of radiation parameters on tumour regression of malignant melanomas of the choroid.
Material and methods: The clinical data of 222 patients treated during the periods from 1985 to 1990 and 1993 to 1999 was analyzed retrospectively. Tumour regression was defined as the reduction in height and volume during a period of 30 months after radiation. Rank variance analysis was used to test for correlation of total scleral dose, radiation dose and radiation period.
Results: The total scleral dose influences tumour reduction in height and volume with a probability of 36% in medium size tumours in the first two years after radiation. There was no linear correlation of scleral dose and regression of small and large tumours. The most prominent regression within the first two years were present after a total dose of 800 -1000 Gy. Dose rate and radiation period had no influence on tumour regression.
Conclusion: Dose rate and radiation time have no influence on tumour regression after brachytherapy for malignant melanoma of the choroid. There is no linear correlation of total scleral dose and tumour regression regarding all melanomas, but there is a strong probability that there is a correlation for medium size tumours. The results support previous studies suggesting a total dose of over 700 Gy at the tumour base, even though a minimal dose cannot be determined with sufficient statistical significance.

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