While I suspect that improvements in energy management coupled with magnetic field technologies are the cost-effective way forward when it comes to engineering defenses against radiation for space travel, it is certainly possible to consider classes of biomedical solution that could in principle greatly improve resistance to radiation in mammals. Insofar as that would require an improved capacity for cells to manage and repair oxidative damage and DNA damage, it seems likely that success would lead to treatments and enhancement biotechnologies that also slow the progression of aging.
The degree of slowing, and how it breaks down into cancer resistance versus other aspect of aging, depends on the degree to which DNA damage and oxidative damage are important in normal aging, versus the contributions of other causes and processes. The evidence of recent decades doesn’t provide sufficient support for a definitive view on this topic. That will continue to be the case, I suspect, until such time as effective ways to repair or remove individual contributions to aging in isolation from one another are developed and extensively tested. So far theory and inspection have proven poor approaches to the production of