This is peculiar logic if you break it into its most fundamental. Dealing with cancer's entire purpose is extending the average human life expectancy. Right now cancer is the cause in about 12.5% [1] of all deaths. And the average years of life lost from cancer victims is 15.7 [2]. So if we completely eliminated all cancer we'd expect to extend the life expectancy for everybody by 0.125 * 15.7 = 1.97 years on average. In the US 22% [3] of deaths are from cancer, so it would be .22 * 15.7 = 3.5 years.

So we change our life expectancy in the US from 79.3 years to 82.8 and now suddenly we can become a space faring civilization? Doesn't really make a whole lot of sense does it?

[1] - https://en.wikipedia.org/wiki/List_of_causes_of_death_by_rat...

[2] - https://www.progressreport.cancer.gov/end/life_lost#field_mo...

[3] - https://www.cdc.gov/nchs/fastats/leading-causes-of-death.htm