Some researchers worry it could create a rebound effect that can make the disease grow faster under some circumstances.

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Roche says there is no evidence for any rebound effect in people.

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But most of the evidence for this rebound effect comes from a pair of studies in mice recently published in Cancer Cell that used Avastin-like drugs.

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Such a "rebound effect" could explain why Avastin therapy is not resulting in bigger survival gains even as the drug makes pictures on imaging scans look better.

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Even after adjusting for the 48, 000 temporary Census workers hired and a rebound effect from the February snowstorms, this number suggests an increase in underlying payroll employment.

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The experience of doctors treating a rare and deadly brain tumor called glioblastoma, which afflicts 10, 000 people a year and is almost always fatal, seems to some to provide evidence for a rebound effect.

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Analysts would surely argue that firms have aggressively cut costs and have made themselves more profitable, so should revenues really start to rebound there would be a multiplier effect on earnings per share.

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