PURPOSE: To investigate the radiosensitivity of uveal melanoma cell lines
by a clonogenic survival assay, to improve the efficiency of the radiation
regimen. METHODS: Four primary and four metastatic human uveal melanoma
cell lines were cultured in the presence of conditioned medium. After
single-dose irradiation (0-12 Gy), colonies were allowed to form for 6 to
14 days. Two cutaneous melanomas cell lines were also tested for
comparison. The survival curves were analyzed by the linear quadratic (LQ)
model, and the surviving fraction at a dose of 2 Gy (SF(2)), the SF at 10
Gy (SF(10)), the ratio of initial irreparably damaged DNA
(alpha-coefficient) to the capacity to repair sublethally damaged DNA
(beta-coefficient), and the plating efficiency were calculated. RESULTS:
The melanomas displayed a wide range of initial irreparable DNA damage
(alpha-component), as well as a capacity for repair of sublethal DNA
damage (beta-component), which ultimately resulted in a wide range of
alpha/beta ratios. These findings were similar in both primary and
metastatic melanomas and were comparable with data obtained from two
cutaneous melanomas. CONCLUSIONS: Cell lines obtained from primary and
metastatic human uveal melanomas displayed a wide range of
radiosensitivity, similar to that published for cutaneous melanomas.
Translating these data to the clinical setting indicates that a
fractionated dose of 8 to 10 Gy administered in three to four fractions,
as currently delivered in many centers, should be sufficient to eradicate
tumors of approximately 1 cm(3)
