The Eastern Cooperative Oncology Group (ECOG) has contributed a number of important research findings to the literature that are worthy of study by surgical oncologists. Large randomized trials have been performed by ECOG in conjunction with other cooperative groups, and pilot studies have been conducted within the confines of ECOG member institutions. Although many of the ECOG studies have focused on systemic treatment, a number of studies have generated information that is directly related to and of great significance for the local regional management of breast cancer. The current chapter reviews selected ECOG studies and discusses their implications for current surgical oncology practice.
Ductal carcinoma in situ (DCIS; intraductal carcinoma) is a non-obligate precursor of invasive carcinoma of the breast. Newly diagnosed DCIS is typically detected on routine screening mammography, most commonly from suspicious microcalcifications. Patients with such findings are frequently interested in breast conservation treatment, either with or without definitive radiation. Multiple prospective randomized trials have demonstrated that the addition of radiation treatment after lumpectomy (excision) significantly reduces the risk of local recurrence.1-7 This reduction in risk is approximately 50% for local recurrence, as well as for the subset of invasive local recurrence. This risk reduction can be further improved by the addition of adjuvant tamoxifen for hormone receptor–positive DCIS tumors, although a statistically significant benefit of tamoxifen was found in only 1 of 2 randomized clinical studies.2,3,6,8,9
Notwithstanding the substantial improvement in local recurrence associated with adjuvant radiation treatment, efforts continue to attempt to identify a subset of patients with favorable DCIS who are at a sufficiently low risk of local recurrence that the omission of radiation is reasonable. A substantial fraction of patients are treated in the United States using excision alone, without radiation treatment. Although retrospective studies have suggested the possibility of omitting radiation treatment in favorable patients, no prospective trial has definitively identified such a subset of patients.
In the early 1990s, ECOG developed E5194, a registration trial for presumably favorable DCIS lesions for treatment using excision alone without radiation. At the time of study development, a number of different criteria for selecting patients with DCIS for treatment using excision alone had been proposed in various retrospective institutional studies. Thus, although recognizing there was (and is) no uniformly accepted set of criteria for selecting favorable-risk patients for omission of radiation treatment after lumpectomy, the guidelines for entry into the ECOG protocol are reasonably similar to many, if not most, retrospective studies.
Selection criteria for enrollment into E5194 study were either (1) low- or intermediate-grade DCIS, ≤2.5 cm in size, or (2) high-grade DCIS, ≤1.0 cm in size. All patients were required to have pathologically confirmed negative margins of excision, with either a minimum negative margin width of at least 3 mm or no tumor on reexcision. Complete processing of the lumpectomy specimen was required. A central pathology review was performed, ...