Risk factors associated with secondary enucleation after fractionated stereotactic radiotherapy in uveal melanoma

Purpose: To evaluate risk factors for secondary enucleation after fractionated stereotactic radiotherapy (fSRT) in uveal melanoma. Methods: In this retrospective study, clinical data of 118 consecutive patients who had initially been treated with fSRT between 1999 and 2009 were collected and analysed. The patients who had undergone secondary enucleation were identified and examined for clinical, histopathological and cytogenetical (fluorescence in situ hybridization determined) data. Also, the reasons for secondary enucleation, such as treatment failure (progressive tumour growth or tumour recurrence) or complications following fSRT (painful blind eye), were recorded and examined. Results: The secondary enucleation rate was 16% after a median follow-up of 4.7 years, with 5% due to treatment failure and 11% due to complications. In the univariate analysis, large tumour diameter (p = 0.019) and large tumour height (p = 0.001) were associated with secondary enucleation, tumour involvement of the optic disc showed borderline significance (p = 0.068). Cox regression multivariate analysis displayed large tumour height as independent prognostic factor (HR 1.42, 95% CI 1.12-1.81, p = 0.004). Following secondary enucleation, mitotic figures were present in five of 18 tumours, and gain of chromosome 8q was also present in five tumours. Within the subgroup of patients who required secondary enucleation due to failed tumour control by fSRT (N = 6), mitotic figures were present in four of six tumours while gain of 8q was present in three of six tumours. Conclusion: Secondary enucleation after previous fSRT was associated with large tumour height. High mitotic counts and gain of chromosome 8q were frequently found in secondary enucleations and possibly indicate a more aggressive or radiation-resistant tumour.