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If a person has a weakened immune system, are they more likely to get cancer? - immune system diseases more condition_symptoms

My friend had just removed a malignant tumor and is planning a trip to India in two months. I fear that his immune system is weakened, can be combined with exposure to foreign diseases that cause the immune system even weaker. I fear that such a trip can make at home sick, even more, and that cancer may return. What do you think?