Is it common for a different cancer to grow after chemotherapy?

A friend went through 6 months of chemotherapy for Lymphoma (I can't remember what type), and finished chemo in October. He is now in the hospital for congestive heart failure, 2 types of systemic infections, a blood clot in his leg and today they biopsied a m they found in his hip that is wrapped around a bunch of blood vessels. He also has a super high calcium level and is diabetic. They have already stated that if it is cancer they can't operate on it due to the involvement of the blood vessels. How likely is it that it is that same or a different form of cancer this close to ending his chemotherapy. The lymphoma was completely gone on his last PET scan. I appreciate any insight.