In an article published in the Journal of Clinical Oncology, the American Society of Clinical Oncology (ASCO) provided recommendations for treating obese adult patients with cancer using chemotherapy.  To develop these guidelines, ASCO examined literature from 1996 to 2010 in the areas of medical and gynecologic oncology, clinical pharmacology, pharmacokinetics and pharmacogenetics, and biostatistics.

A systematic review of these studies, which primarily examined breast, ovarian, colon, and lung cancers, identified a pattern of medical practice that capped the dosage of chemotherapy drugs for obese patients.  These caps meant that up to 40 percent of obese patients were receiving limited doses that were not based on their weight.  Some practitioners expressed concerns about toxicity, which resulted in capping doses.  However, these concerns were unfounded.  The article recommends using full weight–based cytotoxic chemotherapy doses, at least when the goal of chemotherapy is to cure cancer.  Fixed doses are rarely justified.

The existing practice of capping doses may have been the reason why obese patients are less likely to survive cancer, reports USA Today.  Obese patients that have been receiving limited doses may have been receiving less than 85 percent of the weight-based dose.  Cases in which limiting doses may be appropriate include patients with diabetes, cardiac problems, or other conditions that limit their ability to handle the physiological stress of chemotherapy.

A study, published in the journal Nature, found that a 20 percent reduction in doses of chemo drugs cut remission and cure rates by as much as 50 percent in animal experiments.  Also, the reduced doses helped develop resistance to the drugs in the tumors.  This further supports concerns that capping doses inhibits a person’s chance of surviving cancer.

USA Today goes on to state that clinical treatment of cancer can adapt to scale up or scale back doses of chemotherapy drugs.  Even when a patient is having a problem related to chemo treatment, doctors can dial down the treatment levels temporarily.  However, it is important to then try a full dose the next time around so the patient gets all the treatment intended.

Obesity can also increase the development and impact of cancer.  Tumors can be fueled by estrogen, which is made in abundance by fat tissue.  This means that obese patients with cancer may see a more rapid development of tumors.  Limiting treatment doses of chemotherapy can exacerbate the problem.  The fat tissue can produce estrogen to fuel tumor development and the limited doses may make those tumors resistant to further treatment.