You need ionizing radiation like UV rays or shorter wavelengths to cause cancer. Phone radios can't generate UV rays, and that's not an engineering/software thing, that's Actual Physics. Furthermore, harmful ionizing radiation caused by photons would cause distinctive sunburn injuries. Also wouldn't penetrate clothing unless it was up into x-ray radiation and you need specialized machines to do that, phones simply don't have the power needed.
Also, cancer from radiation isn't an instant thing, it requires years and years of compounding cell replication errors to eventually stumble into the right combination of mutations. We're talking years to decades from initial exposure to cancer, and it's not even 100% likely to kill you.
If the CIA wanted you dead they'd just shoot you or cut your brake lines or something similarly quick and easy.