If by "proof", you mean scientific proof, then no, because no such thing exists. If you mean something more along the lines of a logical proof, then yes, within the framework of a Christian/Jewish/Islamic beleif system, prayer is useless:
Therefor, prayer has never helped anyone or anything.
I'm certain that prayer, like meditation, can certainly have it benefits to the individual, however, it is ridiculous to believe that beseeching an imaginary friend, or hoping really, really hard for something will actually cause something to happen. Additionally, the belief in prayer requires a belief in a god, for who's existence there is absolutely no evidence. In such an extraordinary claim as the existence of a god, a lack of evidence
is evidence
against that existence. Therefor, if no gods exist to pray to, then prayer has never helped anyone or anything.
I'd also argue that an appeal to the Christian god - as that's the god I'm assuming the doctor believes in - would be the most preposterous thing of all, given this god's history as far as humanitarian efforts are concerned. Killing of hundreds of millions of humans and non-humans in a massive flood, simply because they angered him. Favoring one race over another. Commanding that favored race to kill millions, smash infants against the ground, take thousands of virgin girls for themselves and wrest land from native inhabitants. Not to mention the hundreds of millions of people who will be tortured for all eternity simply because they exercised free will in he wrong direction. And its final plan was to have an innocent man brutally murdered to atone for everyone's wrong doings; an immoral concept if ever there had been one. Even if I believed in god, I'd be more inclined to beseech Kin Jong Un or one of the leaders of ISIS to do some good for the people of the earth than to ask a god who's evil out shadows all that of all of history's tyrants combined.
As a final note, the STEP Project in 2006 found that prayer had no effect on outcomes of surgery. The same findings were published in a similar study by mayo clinic, regarding coronary artery procedures and prayer.
As far as we know, it seems prayer had never helped anyone or anything.
EDIT: I typed this on a phone, so please excuse any spelling errors.