The aging of the population and the resultant increase in older cancer patients will necessitate a change in the design, implementation, and reporting of clinical cancer trials. Dr. Hurria's paper touches on a number of key points illustrating the important issues involved. As has been amply demonstrated, older patients are underrepresented in clinical trials. Reports from the Southwest Oncology Group, the National Cancer Institute of Canada Clinical Trials Group, and the Food and Drug Administration have shown that older patients are disproportionately underrepresented in clinical trials of diseases that primarily affect them. The reasons for this are multifactorial.
Reasons for UnderrepresentationIn the seminal trial evaluating barriers to participation, Kemeny et al in the Cancer and Leukemia Group B found that physician reluctance to enter patients on clinical trials was due to the perception that older patients would experience excessive toxicity. Additional issues were lack of awareness of an available trial, eligibility issues, comorbidity, and tolerance. It has been reported that when older patients are eligible for clinical trials, they do not experience excessive toxicity and they do benefit as much as younger patients.[2-4] The study also showed the need for new clinical trial designs that take into account the problems that are particular issues for the elderly, such as complicated treatment regimens, comorbidity, decline in function, polypharmacy, and the need for increased social supports.
One area of need is the evaluation of the pharmacology of anticancer therapy. The underrepresentation of older patients on trials also has been reflected in the lack of data available on the pharmacology of chemotherapy in the elderly. The importance of these studies is that as we age, a number of physiologic changes occur that can affect pharmacokinetics. The most clinically relevant is the change that occurs in renal function with aging independent of comorbidity.
Dr. Hurria points out problems that can ensue when renal function is not evaluated carefully in the older-patient group. One very important point is that serum creatinine should not be used to evaluate renal function. Various formulae are available for this determination, and a recent review summarizes the data. Comorbidity with advancing renal insufficiency magnifies this problem. A number of excellent studies have evaluated chemotherapy with end-organ dysfunction (renal and hepatic), but more work needs to be done in this setting.
Bone marrow reserve and hematopoietic toxicity has long been an issue in the elderly. The efficacy of hematopoietic growth factors and their incorporation into treatment guidelines have mitigated this problem. Their use has shifted the parameter of dose-limiting toxicity toward nonhematologic events such as neurotoxicity and cutaneous toxicity. The standard toxicity assessments need to be altered in evaluating the older patient.The future of clinical trials for older patients is strongly tied to the development of simple, easily administered, and predictive comprehensive geriatric assessments (CGAs). Dr. Hurria's paper examines the traditional comprehensive geriatric assessment as it applies to the elderly cancer patient. The author provides detailed coverage of functional status, comorbidity, nutritional status, cognition, social support, psychological state, and polypharmacy. She points out that CGA can be predictive of survival, chemotherapy toxicity, and pain management requirements, and most importantly, uncovers problems not recognized by routine history and physical examination.
Recommendations for Change
The question confronting the entire oncology community is, where do we go from here? Age-specific clinical trials are a necessity. Preliminary work has shown the advantages of this approach. Is this discrimination against younger patients, or a different level of care? I do not think so. While older patients are theoretically eligible for trials, they are not entered, and therefore the data are lacking. We need to think about clinical trials differently. As the paper states, we need to establish novel endpoints for clinical trials. In addition, the entire process needs to be altered. Suggestions to consider include the following measures: