🧠 TL;DR Nivolumab is a PD-1 immunotherapy that activates your immune system against cancer Used in lung, head & neck, esophagus, melanoma, kidney, lymphoma, colorectal (MSI-high) Long-acting (~26 days) → small delays are usually safe Side effects are immune-related (not infection-related) Timing of side effects gives major diagnostic clues Can be used safely in kidney failure, dialysis, liver dysfunction (non-immune) Cost in India has dropped from ₹4.5 lakh → ~₹1 lakh/month