In a separate study they found that IMRT's higher doses let 90% of early-stage patients remain cancer free for five years, up from 77% of patients treated with older methods.

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"It was like, 'No one has ever entered this country before, let's go in and take some pictures, '" says study author Michael Grandner, an instructor in psychiatry and member of the Center for Sleep and Circadian Neurobiology at Penn.

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