Unless this past environment was one that actually kills cancers cells (I don't know how the Big Lebowksi might do that) or perhaps reduces tumor growth I can't imagine any way how this can work.
What I can imagine is going on a time out, reducing stress and thus biological stress responses does have an influence on a tumor. I hope they are compensating for this effect. They should have a control group in a reduced stress environment (or something that mimics all evironmental variables of the back-in-time room but for the back-in-time aspect) perhaps with a bluray disc of Lucy.
Hey or perhaps dumbphones induce less stress. Perhaps you get better sleep in the 2003 environment, light/circadian rithm is known to influence cancer: http://en.wikipedia.org/wiki/Risk_factors_for_breast_cancer#...
Et cetera et cetera, et cetera