Updated from 1:44 p.m. EST

Shares in

RITA Medical Systems

(RITA)

surged in heavy trading Thursday on optimism about the device maker's cancer treatment.

Shares finished in

Nasdaq

trading Thursday at $3.99, up 87 cents, or 27.88%, but had reached as high as $5.23. Volume was more than 11 million shares, compared with the typical 125,000 a day.

The California-based company announced that 18-month survival statistics of the Rapture lung cancer clinical trial reported at the Radiological Society of North America's annual meeting in Chicago this week showed RITA's radiofrequency ablation treatment, or RFA, had potential.

The company said in a multicenter study, in which seven centers from the United States, Europe and Australia took part, 106 patients with a total of 186 tumors were treated and that RFA was technically feasible in 99% of the patients. The data presented at medical conference are the first reported survival rates from the Rapture trial.

Radiofrequency ablation is a process by which a special needle is inserted into tumors through which radiofrequency energy is then passed, heating and (hopefully) treating the tumor by breaking up its cells and killing them.

Almost 8.9 million shares changed hands, compared with average volume of about 125,000 a day.