In men, tem­por­ary impot­ence (the inab­il­ity to get an erec­tion) and loss of interest in sex are com­mon side effects of radio­ther­apy. This is often caused by feel­ing tired after radio­ther­apy and being anxious about the treat­ment or ill­ness. Radio­ther­apy to the pel­vic area can cause tem­por­ary impot­ence by affect­ing the nerves in and around your penis. Most other radio­ther­apy treat­ments will not make you infer­tile or cause any prob­lems if you decide to have chil­dren in the future.