Local Therapy and Survival in Breast Cancer

The effect of local therapy on the survival of patients with breast cancer has been debated for decades. Three viewpoints have been proposed on the basis of various hypotheses concerning the biology of breast cancer. Is breast cancer a local disease that spreads predictably over time to develop distant metastases?

Is it a systemic disease from the outset, with distant metastases present well before diagnosis? Or is the truth somewhere in between, with many cancers being localized at diagnosis and, if untreated or recurrent, acquiring the ability to metastasize and kill?

These differing views have vastly different implications for the treatment of patients. Recently, several lines of evidence have emerged that suggest answers to these questions.

Three Theories of Cancer Spread

Throughout the first half of the 20th century, the prevailing theory of the development of distant metastasis in breast cancer was shaped by the thinking of Dr. William Halsted and his disciples. The "Halstedian" theory proposed that breast cancer begins as a strictly local disease and that tumor cells spread over time in a contiguous manner away from the primary site through lymphatics. According to this theory, even distant metastases are the result of direct extensions of local involvement (affecting the breast, the chest wall, axillary and supraclavicular lymph nodes, or any combination of the sites). The Halstedian approach thus dictated that aggressive local therapy for control of disease in the breast, chest wall, and regional lymph nodes would have a substantial effect on survival. His ideas also provided justification for ever more radical breast-cancer surgery.

The "systemic" view arose in reaction to the Halstedian theory, since disease develops at distant sites in many women with breast cancer, even though the primary cancer is well controlled locally with aggressive surgery. On the basis of this information, Dr. Bernard Fisher and others promulgated the view that breast cancer is a systemic disease and that it can be divided into two distinct groups: tumors that have the ability to metastasize to distant sites and those that lack this ability. According to this view, which prevailed in the last half of the 20th century, if distant metastases were destined to develop, such metastases had already occurred at the time of diagnosis of the breast tumor. Because the length of a patient's overall survival is a function of distant disease, this theory predicted that treatments that improve local control would have little or no effect on overall survival. Instead, the emphasis was on the importance of effective systemic therapy in breast-cancer treatment. Over the past three decades, the development of systemic therapy has indeed been associated with substantial improvements in the overall survival of patients with clinically localized breast cancer. During this time, patients were counseled that the prevention of a local recurrence was of limited importance with regard to survival, since such a recurrence could be treated when it developed, and that the development of a local recurrence would not lead to the development of metastatic disease.