Increased favorability of small breast cancers.

Abstract

e12576 Background: Breast cancer is classified into three prognostic groups based on the following biologic factors: estrogen-receptor (ER) status, progesterone-receptor (PR) status, and nuclear grade (NG). According to this classification, we determined the biological behavior in order to understand if a small breast cancer is biologically more favorable than a large one (T1-2 breast cancers). Methods: The inclusion criteria for this study were (1) presence of T1-2 breast cancer measurable by magnetic resonance imaging (MRI) or ultrasound(US), and (2) availability for determination of ER, PR, and NG histological status. Inflammatory breast cancer, male breast cancer, tumors of unknown size on MRI or US, and complications due to other cancers were excluded from this study. From April 2007 to December 2019, 1173 patients with surgically proven breast cancer presented at National Hospital Organization Nagasaki Medical Center, and 1080 patients were retrospectively analyzed. The favorable (F), intermediate (I), and unfavorable (UF) groups were defined as follows. F: NG1 (ER+PR+, ER+PR-, ER-PR+), UF: NG2 (ER-PR-) or NG3 (ER-PR-, ER+PR-, ER-PR+). IF: all other types of F and UF. Overall survival (OS) was calculated using the Kaplan-Meier method. All statistical analyses were performed using JMP 9.0.2, and probability values of <0.05 were considered statistically significant. Results: Number (%), age (year), size (cm), and 10-year OS (%) in the F, I, and UF groups are presented in the table. The tumor size in F group was significantly smaller than that in the other groups and had better prognoses. The F, I, and UF distribution of tumors less than 1 cm in size were 66%, 29%, and 5%, respectively. On the other hand, the F, I, and UF distribution of tumors 1-2 cm, 2-3 cm, 3-4 cm, 4-5 cm in sizes were (42%, 41%, 17%), (34%, 46%, 20%), (31%, 39%, 30%), and (27%, 45%, 28%), respectively. The 10-year OS of F group stage I, I group stage I, F group stage II, and UF group stage I were 99%, 94%, 93%, and 80%, respectively. Conclusions: Small breast cancers, especially those less than 1 cm in size, were shown to be significantly biologically favorable. Small breast cancers are candidates for de-escalation of treatment. [Table: see text]