Clot after stool. Wait for petcet scan?

So my dad  69 years old has bp problem, no other issues. has adenocarcinoma of ge junction stage 4. He completed his 6 cycle of  capox chemo.  Now his chemo medicine over 4 days back. He has Side-effects like weakness, no taste. During chemo he had stomach pain and a headache . But now hes fully active.  He eats. Says his motion also no problem. So today after he came from toilet. I could see a blood clot which was red in colour and may be 1/2 cm on the toilet seat. He told he dint see anything when he flushed. I'm not sure if he has observed his stool. And he doesn't like us talking about the cancer. May be he gets scared. But im worried. Pet cet scan is scheduled in 4 days. Is it something to worry about?? Or we can wait for petcet scan??