Overview

For 100 years, we had three ways to treat cancer: Cut it (Surgery), Burn it (Radiation), or Poison it (Chemo). They are brutal and kill healthy cells too. Immunotherapy is the “Fourth Pillar.” Instead of attacking the cancer directly, we teach the patient’s own immune system to do it. It is the most exciting breakthrough in oncology.

Core Idea

The core idea is Unmasking. Cancer cells are clever. They wear a “mask” that tells the immune system “Don’t eat me, I’m a friend.” Immunotherapy rips that mask off so the Killer T-Cells can see the enemy and attack.

Formal Definition

Treatment that uses certain parts of a person’s immune system to fight diseases such as cancer. This can be done by stimulating the immune system to work harder or by giving the immune system man-made immune system proteins.

Intuition

  • Chemo: Carpet bombing a city to kill the terrorists. (Lots of collateral damage).
  • Immunotherapy: Giving the police dogs the scent of the terrorists so they can hunt them down one by one.

Examples

  • Checkpoint Inhibitors (Keytruda): Cancer cells press a “brake” on T-cells (PD-1) to stop them from attacking. These drugs block the brake, unleashing the immune system. It cured Jimmy Carter’s metastatic melanoma.
  • CAR T-Cell Therapy: We take T-cells out of the patient’s blood, genetically engineer them in a lab to have a “claw” that grabs cancer, and put them back in. It’s a “living drug.”
  • Cancer Vaccines: Not to prevent cancer, but to treat it. Injecting tumor antigens to wake up the immune system.

Common Misconceptions

  • It works for everyone: Currently, it only works for about 20-30% of patients. We don’t fully know why.
  • No side effects: It can cause the immune system to go crazy and attack healthy organs (Autoimmunity). It can be deadly if not managed.
  • Monoclonal Antibodies: Lab-made proteins that mimic immune system antibodies.
  • Tumor Microenvironment: The fortress the tumor builds around itself to keep immune cells out.

Applications

  • Allergies: Immunotherapy (allergy shots) is also used to retrain the immune system to stop attacking peanuts or pollen.

Criticism / Limitations

  • Cost: CAR T-cell therapy costs $400,000+ per patient. It is incredibly expensive to manufacture.

Further Reading

  • Graeber, Charles. The Breakthrough: Immunotherapy and the Race to Cure Cancer. 2018.
  • Mukherjee, Siddhartha. The Emperor of All Maladies. 2010.