Powers of $2$ and $3$ and primality radius

Question

Say a non negative integer $r$ is a primality radius of $n$ if both $n-r$ and $n+r$ are prime.

Are there infinitely many such couples $(n,r)$ of the form $(p^a,q^b)$ with positive $a$ and $b$ and $\{p,q\}=\{2,3\}$?