By John Otrompke
CHICAGO -- November 9, 2009 -- Patients diagnosed with the rare condition of uveal melanoma who are treated with proton beam radiation therapy at 56 gy, without eye wall resection, experience very high rates of local control at 5 years after surgery, according to a study presented here at the American Society of Therapeutic Radiology and Oncology (ASTRO) 51st Annual Meeting.
During the 1990s, the standard dosage was 48 gy for such patients, but after switching to a higher dose, rates of local control went up significantly at the University of California, San Francisco (UCSF), San Francisco, California.
"Our 5-year rates went up from 85% to 96%," said Kavita K. Mishra, MD, Department of Radiation Oncology at UCSF, on November 4.
For the study, researchers looked at 533 patients treated with 56 gy in 4 fractions between 1996 and 2006, as well as 42 patients who received 48 gy in 1994 and 1995. Median follow-up in the 56-gy group was 40.8 months, compared with 72 months in the earlier, lower-dose group.
In the 56-gy group, 3.8% of patients failed, compared with 19% in the lower-dose group. In the higher-dose group, distant metastasis-free survival was 86.2% at 5 years, and overall survival was 84.8%. Of those in the group that received the higher dose, 7.5% had their eye removed.
The surgeon also used a surgical technique that was sparing of the anterior structure of the eye, to reduce damage to the lens, as well as the macula, said Dr. Mishra said. The technique includes giving a margin of 2 to 2.5 mm. "We also work on the patient's gaze angle and distance out during the procedure," she said.
"Neovascular glaucoma is an important complication which requires medication drops or anti-VEGF [vascular endothelial growth factor] therapy," said Dr. Mishra. "In the worst-case scenario, it can require taking the eye out, but over the past handful of years we've been able to achieve better rates."
"While historically, the rate of neovascular glaucoma was around 35% in these patients, we've been able to get it down to 15%," she explained.
The study also identified negative prognostic factors for uveal melanoma. "Tumour diameter was the largest negative prognostic factor, along with involvement of the ciliary body," said Dr. Mishra. "In addition, the shorter the distance to the optic disc, where the optic nerves come from, the worse the local control."
[Presentation title: Outcomes With Current Technique of Proton Beam Radiation Therapy for Uveal Melanoma: The UCSF/Tumori Foundation Experience. Abstract 248]
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