Cancer Vaccines and Immunotherapy
Factors Affecting Immune System Status
Age. While cancer is more common in the elderly (Holmes FF et al 1991), immune strength gradually declines with age and can pose a problem for the successful use of immunotherapy in the elderly (Ginaldi L et al 1999; Pawelec G et al 2002). Although age-related decline in immune status is a natural feature of the immune system, it is also aggravated by lifestyle factors such as diet (Lesourd B et al 1999). Therefore, nutritional supplements to boost immune function may have even more significance in elderly cancer patients than in young adults.
Tumor-Induced and Surgery-Associated Immunosuppression. Two types of immunosuppression affect the successful outcome of immunotherapy: immunosuppression from the tumor and that associated with surgery to remove the tumor. Tumor-induced immunosuppression, due to the production of immunosuppressive factors by cancer cells, is overcome by surgical removal of the tumor mass (Morton DL 1978) and thus creates an environment in which immune cells can better respond to immunotherapy. However, the process of surgery and the associated use of particular anesthetic and analgesic drugs also dampens immune cell function, again reducing the effectiveness of any immunotherapy used (Vallejo R et al 2003). It is recommended that anesthetic and analgesic drugs be carefully selected to minimize immunosuppression, and that patients prepare for surgery by optimizing nutritional and immune status (Vallejo A et al 2002).
Nutritional Status. The production of immune-suppressing (immunosuppressive) agents by cancer cells presents a significant obstacle to cancer immunotherapy (Junker U et al 1996; Sarris AH et al 1999). Excessive production of pro-inflammatory cytokines and reactive oxygen species may damage the immune system, resulting in adverse immunotherapy outcome and cancer progression.
Therefore, nutritional supplements that improve the function of key immune cells will affect the efficacy of immunotherapy and could also be used to prepare patients for immunotherapy (Malmberg KJ et al 2002).
The impact of nutrition on the function of immune cells that play a key role in the efficacy of cancer immunotherapy is well established (Calder PC et al 2002b; Chandra RK 1999). Studies of cancer patients demonstrate that nutritional supplements can play a role in restoring immune status depleted by cancer and surgery to normal levels that would be more responsive to immunotherapy treatment (Malmberg KJ et al 2002).