Does choroidal melanoma regression correlate with chromosome 3 loss after ruthenium brachytherapy?

Aim: To determine the reduction of choroidal melanoma thickness 6 months after ruthenium 106-brachytherapy according to chromosome 3 status, which correlates strongly with metastatic death.

Methods: Transscleral fine needle aspiration biopsy was performed prior to the insertion of a radioactive plaque if the tumour was deemed sufficiently thick and anterior for such a procedure. Transretinal biopsy with a 25-gauge vitreous cutter was performed for thin and posterior tumour within a month of plaque removal. The chromosome 3 status was determined by fluorescence in situ hybridisation from 2002 until 2006, and by either multiplex ligation-dependent probe amplification and/or microsatellite analysis after this period until the end of the study. The choroidal melanoma dimensions were obtained from outpatient visits.

Results: 149 eyes from 149 patients were included. The mean age was 60.8 years. 84 eyes (56.4%) had disomy 3 and 65 eyes (43.6%) monosomy 3. The median pretreatment tumour thickness was 3.0 mm in disomy 3 and 4.1 mm in monosomy 3 tumours (p=0.018). The follow-up duration medians were 6.3 months for disomy 3 and 6.4 months for monosomy 3 tumours (p=0.68). The rates of thickness reduction were 6.7% and 7.0% per month, respectively (p=0.59). Thickness reduction exceeding 50% occurred in 32 (38.1%) disomy 3 and 24 (36.9%) monosomy 3 tumours.

Conclusions: The rate of choroidal melanoma regression after ruthenium-106 brachytherapy does not appear to correlate with chromosome 3 loss, suggesting that tumour thickness reduction 6 months after treatment is unlikely to predict survival.