Health & the Body - 27 free documentaries about cancer & chronic illness.
Start with What does asbestos do to a person? (55 min, Veritasium), then The Reason Why Cancer is so Hard to Beat (10 min, Kurzgesagt). All 27 documentaries here are free to watch from their makers' official uploads. To read deeper, the top-rated book on cancer & chronic illness is The Emperor of All Maladies by Siddhartha Mukherjee.