Defining the needs for adjuvant therapy of rectal and colonic cancer

Current trials concerned with the adjuvant therapy for large bowel cancer demonstrate for the first time that improvements in survival through the use of adjuvant therapy may be possible in rectal cancer. Similar results in well-designed studies are not evident for colonic cancer. These trials deserve confirmation. In addition, they demonstrate the biologic difference in the behavior of colonic and rectal cancer despite similar requirements in defining curative surgical resection. A comparison of trials unique to individual institutions suggests that the lenient criteria for patient selection and the use of historical control groups make the data from these studies impossible to interpret for extrapolation to wide clinical use. The variations in the survival rates of historical groups, both among different studies and within the same study, suggest that the design of adjuvant therapy programs without concurrent surgically treated control groups will predictably produce a study of limited value, but one that is guaranteed to generate continued controversy. Uniformity of language, staging, and method of reporting is invaluable if individual trials of adjuvant therapy are to become comparable. The development and widespread use of an agreed-upon staging method is an important step in the preparation for further adjuvant trials. The definition of additional prognostic factors (beyond mural penetration and nodal involvement) in rectal cancer and stratification for these additional factors in the design of studies concerning adjuvant therapy in rectal cancer seems to be a target of importance for future studies of adjuvant therapy. Focusing attention on which patients with rectal cancer actually derived a benefit from treatment may assist in the development of a pattern in which surgical goals and radiation goals can achieve better definition in clinical use.