Fever and stomach problem

My father , 65, is with Small Cell Lung Cancer, extensive stage, with metastases to bones, liver and lymph node at the time of diagnosis. He is now in recess after 4 times of chemo and 2 chest radiation.

Since he was back home on August 14, he has had 2 times of fever (38-39 Degrees Celcius, the normal being 35-37 Degrees Celcius). One of the fevers was accompanied with stomach problem. He also reported black color faeces during the stomach problem + fever. Anyone familiar with this condition and what it means?

Thank you.

Linda