LAWRENCEVILL, NJ ( TheStreet) -- Celsion ( CLSN) shares fell Monday after the company announced that a pivotal phase III clinical trial of its experimental liver cancer therapy will continue to a final analysis in late 2012.

Some investors had hoped that the interim look at Celsion's Thermodox study would have yielded a patient benefit large enough to stop early for success. However, the statistical hurdle to stop clinical trials early is typically set very high, making it a relatively uncommon occurrence.

For Celsion, continuing the Thermodox study to its final analysis is a small victory even if it disappoints some investors who hoped for an early holiday present. Monday's news could have been much worse. The same independent overseers could have concluded that Thermodox was not helping liver cancer patients at all and put a halt to the study for futility.

Celsion shares were down 13% to $2.43 in Monday trading. Celsion is still up 19% year to date.

The biggest investor issue facing Celsion is probably going to be complacency. Celsion estimates a final analysis of the Thermodox study could take place in "late 2012." For biotech investors typically craving short-term trading catalysts to keep their interest, Celsion may be too much of a long-term story to bother with right now.

Celsion ended the September quarter with $21 million. At its current burn rate of around $7 million per quarter means the company will likely need to raise additional money before the final results of the Thermodox study are known. How Celsion raises additional cash -- through a sale of stock or a Thermodox partnership -- isn't known.

Celsion said Monday that it plans to seek FDA permission to amend the Thermodox study design to allow for an additional interim look at the data. This opens up the possibility that the Thermodox study might end earlier than expected, although Celsion offered no timetable Monday.

Thermodox consists of tiny, heat-sensitive spheres of fat that contain a payload of the chemotherapy drug doxorubicin. When injected into the body, Thermodox accumulates at the site of the tumor. When the tumor site is heated to about 107 degrees using radio waves (radiofrequency thermal ablation, or RFA), the Thermodox spheres melt, bathing the tumor and adjacent tissue in high levels of doxorubicin.

Celsion is conducting a phase III study in which 613 patients with hepatocellular carcinoma, also known as primary liver cancer, are being treated with Thermodox plus RFA or RFA alone. The primary endpoint of the study is to determine if the addition of Thermodox to RFA can significantly delay the re-growth of liver tumors compared to treatment with RFA alone. The study is being run under a Special Protocol Agreement (SPA) reached with FDA.

--Written by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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