Sirtex Medical slumps up to 55 percent after study failure for SIR-Spheres

Shares in Sirtex Medical fell as much as 55 percent Tuesday after the company said that a study of its SIR-Spheres radiation therapy in patients with non-resectable metastatic colorectal cancer (mCRC) failed to meet its main goal.

The SIRFLOX study enrolled over 500 patients with non-resectable mCRC whose disease had spread to either the liver alone or the liver along with a limited number of sites outside the organ, including lymph nodes and the lungs. Participants were randomised to receive either a current first-line systemic chemotherapy regimen with the addition of a single administration of SIR-Spheres Y-90 resin microspheres or the same chemotherapy with the option to receive Roche's Avastin (bevacizumab).

Sirtex noted that a preliminary analysis showed that adding SIR-Spheres to the chemotherapy regimen did not result in a significant improvement in overall progression-free survival (PFS). However, the company indicated that SIR-Spheres did result in a significant improvement in PFS in the liver, the study's secondary endpoint. Sirtex said that the data still requires confirmation and validation through peer review, while final results will be submitted to the ASCO annual meeting.

Commenting on the news, Morgans Financial analyst Derek Jellinek said the data do not support widening the use of SIR-Spheres, which are currently used as a treatment for patients with colorectal cancer that has spread to the liver. "The treatment right now is relegated more to a salvage setting," remarked Jellinek, adding "we do not expect unfavourable results to negatively impact uptake of the device."

Meanwhile, Andy Gracey of Australian Ethical Investments remarked that although the data were "disappointing, not all is lost." Gracey noted "I wouldn't, at the moment, be assigning Sirtex to just salvage therapy," adding "we really need stronger data around the recruitment in terms of how many patients were recruited that had cancers outside the liver... It's definitely working in the liver which is exactly what it has been designed for."

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