Age-related variations in the use of axillary dissection

Truong and coworkers (1) are to be commended for their efforts to deal with the vast amount of clinical and therapeutic information on early-stage breast cancer in British Columbia available in the Breast Cancer Outcomes Unit Database. This paper is important for several reasons, the first being sample size and composition. In any scientific inquiry, one seeks to define an adequate sample size from which to make observations or test hypotheses. The validity of the study conclusions depends first on the adequacy of the sample. The sample must be large enough to reflect the characteristics of the entire population and to avoid undue influence from random events. In an effort to control important variables and to adhere to scientific principles in study design, clinical trials frequently include only well-defined subsets of patients who are willing to submit to the randomization process. If many variables are controlled, the entry criteria may eliminate willing participants who would constitute an important part of a representative sample. The randomization process, if it is between two very different treatment arms that are likely to be associated with significantly different outcomes in either disease control or toxicity, may be unacceptable to many adequately informed potential participants, with additional impact on the adequacy of the sample. Thus, clinical trials often may not comprise an adequate sample of the entire population, leading to the possibilities that conclusions may be erroneous or irrelevant. Population-based studies such as this one can provide a broader context in which issues, trends, and patterns can be discerned that raise questions that can then be tested in focused controlled clinical trials. This population-based study provides an excellent contrast to recent clinical trials in breast cancer in which questions have been raised regarding nonrepresentative disease stage or histologic features, surgical technique, or RT field selection and technique. This study represents a true slice of the complex life of breast cancer management in British Columbia, with the only controlled variables being tumor size (T1–T2) and the absence of overt metastases at diagnosis. It identified subsets of patients and practice variations that are rarely represented in clinical trials. It has taken, so to speak, the pulse of the entire breast cancer community of patients and physicians in British Columbia and identified an issue that, difficult as it may be, needs to be addressed: the impact of axillary dissection (AD) on outcome. One important trend identified in this study is that AD has been omitted from the management of a large proportion of patients: 4% of patients aged 50–64, 8% aged 65–74, and 22% of those 74 years. AD has been an integral part of the standard management of invasive breast cancer for the past century. As the authors noted, several controlled cooperative group trials, as well as several noncontrolled, singleinstitution studies, have addressed the question, but clearly the breast cancer community has not reached a consensus as to the consequences of omitting AD. The second strength of the paper is the attention to many variables that could confound the results of an analysis of the impact of AD on outcome. Potential interactions are explored among numerous clinical variables (age, tumor grade and size, lymphovascular space invasion, estrogen receptor status, clinical node palpability) and treatment variables (surgical margin status, use of various types of systemic therapies, and RT). The result of the analysis is a complicated set of interactions that the authors carefully interpreted. The key findings include the following: