Final answer:
The passage expresses concern for Nicholas's ability to tolerate chemotherapy as the primary concern regarding his cancer treatment.
Step-by-step explanation:
The primary concern mentioned in the passage about Nicholas's treatment is b. Nicholas's ability to tolerate chemotherapy. Chemotherapy is a type of cancer treatment that uses drugs designed to kill cancer cells, but this treatment can often have severe side effects that not all patients can tolerate. It's important to balance the potential benefits of chemotherapy against the risks posed by its side effects, which can be particularly challenging for some patients.