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In Reply:

¹ The University of Chicago, Chicago, IL
² The University of Pennsylvania, Philadelphia, PA

Apolone et al¹ raise important issues regarding the internal and external validity of our observational study² of the effects adjuvant fluorouracil (FU) in elderly Medicare beneficiaries with stage III colon cancer, and we thank them for their close reading of our paper.

With respect to internal validity, we agree that even rigorous statistical techniques cannot overcome all the limitations of observational data, and we made every effort to highlight those limitations in our article. Clearly, a superior solution to the problem of limited information on the benefits and toxicities of chemotherapy in elderly cancer patients is to increase their participation in clinical trials. Several cooperative oncology groups have sponsored chemotherapy trials of elderly cancer patients, for which exclusionary requirements include age less than 65 years. For example, the Cancer and Leukemia Group B is currently accruing patients to a randomized, controlled, adjuvant chemotherapy trial for women 65 years of age and older with breast cancer, examining the utility of standard adjuvant regimens (ie, doxorubicin and cyclophosphamide, or cyclophosphamide, methotrexate, and FU) versus oral capecitabine. This will be the largest chemotherapy trial of patients aged 65 years and older on record, with a projected accrual of between 600 and 1,800 patients. In addition, President Clinton’s June 2000 executive memorandum directing the Department of Health and Human Services to reimburse, through Medicare, costs issuing from clinical trials, was an explicit attempt by the federal government to increase clinical trial participation of elderly American Medicare beneficiaries. Although efforts like these will likely increase the participation of the elderly on clinical trials, legitimate worries on the part of trialists about the possible interaction of comorbidity and cytotoxic chemotherapy in elderly patients will also likely prevent complete representation of elderly cancer patients on trials. Likewise, increased participation in initial trials will not fully quiet legitimate worries about whether actual implementation in the community will achieve the same rates of success.

With respect to the issue of external validity, we agree that the results cannot strictly be applied to populations other than the one we studied. However, as 96% of Americans aged 65 years and older are recipients of Medicare, we do feel confident that the results can be generalized to the population of elderly Americans with stage III colon cancer. Thus, in the face of limited clinical trial data and an enormous burden of cancer among the elderly, studies such as ours may currently be the best source of information for clinicians facing the challenge of caring for individual elderly patients with cancer, for whom individual risks, benefits, and preferences need to be considered.

REFERENCES

1. Apolone G, Cavuto S, Torri V, et al: Effectiveness of adjuvant fluorouracil in elderly colon cancer patients: the internal and external validity of nonrandomized research design. J Clin Oncol 21:1892, 2003[Free Full Text]

2. Iwashyna TJ, Lamont EB: Effectiveness of adjuvant fluorouracil in clinical practice: A population-based cohort study of elderly patients with stage III colon cancer. J Clin Oncol 20:3992–3998, 2002[Abstract/Free Full Text]

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