According to this recent article, new findings indicate a survival benefit in heavier patients:
In one type of cancer, heavier men may live longer | Stronger Than Cancer
The researchers are quick to say that they would not encourage people to keep on weight, which could increase risk of other cancers, but that the findings might help understand this particular cancer in the study, called a diffuse large B-cell lymphoma.
Later in the article, it does point out that a heavier person is getting less chemotherapy in relation to their body weight - it's quite possible that there is a link there as well.
In cancers that treat well with chemotherapy, you may have a better survival rate if you don't cause too much damage to healthy cells in your body. Meaning - in some cases, less may be more with chemotherapy.
The belief to this point has always been to give the patient as much as they can tolerate. A young relatively healthy patient will be given higher doses, than an more fragile elderly patient. This seems to be the wrong way to dose a drug. This is fear-based drug dosing. It should be based on how the cancer responds to the drug, and what level would be least toxic to to the individual. With that one change, I think survival rates would increase.
I don't mean to dismiss where the findings are leading the researchers. It is there job to look into the particular cancer and find out what interactions may improve survival.
I would just love to see findings like this branch out into further research that looks at toxicity in dosing chemotherapy, and how to maximize the survival benefit by targeting the dosing to be most effective with the least toxicity.