It is already known that obesity increases the risk of developing kidney cancer. However, obese people seem to do better after treatment compared with people of normal weight. Researchers at Memorial Sloan Kettering Cancer Center in New York have discovered that the fat surrounding kidney tumours may play a key role in the effectiveness of kidney cancer treatments.
The team found that tumours in obese people may grow slower because a key cancer-promoting gene is less active. Therefore, tumours in obese people are more likely to be detected earlier, improving survival. However, even late stage kidney tumours that have spread seem to respond better to treatment. In 2016, the researchers published a study to show that obese people with kidney cancer have better outcomes after being treated with drugs that interfere with a tumour’s ability to grow blood vessels. Other research has shown these individuals also respond better to immunotherapy.
Recently, the researchers have discovered why this is: fat surrounding kidney tumours is highly inflamed, which draws immune cells to the site of the tumour to attack it.
However, this discovery remains intriguing, because the kidney tumours themselves do not seem to be stimulating an immune-system attack. Tumours that respond well to immunotherapy are full with immune T cells, i.e., they are “hot”, indicating that the body has recognised the cancer as a threat and mounted a response. But when the researchers examined kidney tumour samples from obese patients, they were surprised to find that the tumours lacked immune T cell infiltration — they were “cold.”
“This shows that it’s not as simple as just looking at the tumour,” said Dr Hakimi, a member of the research team. “You have to factor in other components, specifically the surroundings of the tumour.”
Read more on the Memorial Sloan Kettering Cancer Center website