In oncology, how do 'hot' and 'cold' tumors differ in terms of immune infiltration and response to immunotherapy?

• A. Hot tumors have low infiltration and poor response.
• B. Hot tumors have inflamed immune infiltration and respond better to immunotherapy.
• C. Both have the same level of infiltration and response.
• D. Cold tumors respond better to immunotherapy.

Answer: (B)

Hot tumors are defined by an inflamed tumor microenvironment with robust immune cell infiltration, especially cytotoxic CD8+ T cells, along with active interferon signaling and often higher PD-L1 expression. This immune presence makes the tumor more recognizable to the immune system, so therapies that unleash T cells, like PD-1/PD-L1 or CTLA-4 inhibitors, tend to work better. Cold tumors, on the other hand, have little T-cell infiltration and a suppressive environment, so they usually respond poorly to immunotherapy unless strategies are used to recruit or activate immune cells or enhance antigen presentation. The statement about hot tumors having low infiltration or cold tumors responding better contradicts these patterns, and claiming equal infiltration and response is also inaccurate. In practice, some cold tumors can be converted to hot with combination approaches, potentially improving responses.