The SENS approach to cancer is pretty much to turn off its ability to grow in unlimited fashion. If you could compensate for the side-effects, it would be possible to delete telomerase and ALT genes from humans, which would produce cancer free humans - if cancers can't lengthen their telomeres, they die.
Unfortunately, it would also produce humans would be dependent on some form of periodic telomerase therapy targeted to stem cells, or stem cell replacement, or similar. This might be a net gain in a suitably high-tech environment.
A better approach would be something other than permanent removal of telomerase and ALT genes, but perhaps suppressing them globally for a while, or suppressing them in cancerous tissue only. RNAi or other methodologies are pretty reliable for this sort of thing at the present time in the general sense.