The risk of ipsilateral breast tumor recurrence (IBTR) after breast-conserving therapy (BCT) is associated with treatment and tumor-related variables, such as surgical margin status and the use of systemic therapy, and these variables have changed over time. Correspondingly, the authors of the current study hypothesized that the contemporary multidisciplinary management of breast carcinoma would lead to an improvement in IBTR rates after BCT.
Between 1970 and 1996, 1355 patients with pathologic Stage I-II invasive breast carcinoma underwent BCT (breast-conserving surgery and adjuvant radiation therapy) at The University of Texas M. D. Anderson Cancer Center. Contemporary methods of analyzing surgical margins were in routine use by 1994. To analyze the effect of this variable and others, patient and tumor characteristics and IBTR rates in patients treated during 1994–1996 were compared with those in patients treated from 1970 to 1993.
Characteristics were similar in patients treated during 1994–1996 (n = 381) and those treated before 1994 (n = 974) except for patients aged >50 years (63.3% vs. 51.7%, P < 0.001), and patients who had a family history of breast carcinoma (37.9% vs. 30.8%, P = 0.017). Patients treated after 1994 were less likely to have positive or unknown margins (2.9 % vs. 24.1 %, P = 0.0001), more likely to receive chemotherapy (40.5% vs. 26%, P < 0.001), and more likely to receive hormonal therapy (33.3% vs. 19.4%, P < 0.001), but less likely to receive radiation boosts to the primary tumor bed (59.8% vs. 89%, P < 0.001). The 5-year cumulative IBTR rate was significantly lower among patients treated in 1994–1996 than among patients treated before 1994 (1.3% vs. 5.7%, P = 0.001) largely because of the drop in IBTR rates among patients aged ≤ 50 years (1.4 % vs. 9.1 %, P = 0.0001). On multivariate analysis, age > 50 (hazards ratio [HR] = 0.401; P = 0.0001), presence of negative surgical margins (HR = 0.574; P = 0.017), and use of adjuvant hormonal therapy (HR = 0.402; P = 0.05) were independent predictors of improved 5-year IBTR-free survival. On subgroup analysis, use of chemotherapy was associated with increased IBTR-free survival among women aged ≤ 50 years (HR = 0.383; P = 0.001). Although 5-year cumulative IBTR rates were lower among women aged > 50 years than among younger women before 1994 (2.6 % vs. 9.1%, P < 0.0001), no such difference was found in the group treated in 1994–1996 (1.2 % for age > 50 yrs vs. 1.4 % for ≤ 50 yrs, P = 0.999).
The IBTR rate after BCT appears to be declining, especially among patients < 50 years of age. However, long-term follow-up is necessary to confirm this finding. This finding may reflect changes in surgical approaches and pathologic evaluation as well as an increased use of systemic therapy. The current low incidence of IBTR with multidisciplinary management of breast carcinoma may result in more patients choosing BCT over mastectomy. Cancer 2005. © 2005 American Cancer Society.