Abstract P1-03-05: Long term survival and tumor biology of screen-detected small non-palpable breast cancer in Chinese women: The smaller, the better?
Authors: Xu Y , Pan B , Yao R , Zhou Y-D , Mao F , Zhu Q-L , Wu H-W , Lin Y , Shen S-j , Sun Q 
Published: May 2019

Background: Tumor biology would reflect the prognosis and potentially the lead time and over-diagnosis rate of screen-detected small breast cancer [PMID: 28591529, 21452022 and 24888816]. Chinese women had earlier peak age of breast cancer incidence and used ultrasound as the primary screening imaging test on a hospital-basis [2016 SABCS P5-02-05, PMID: 27689334]. In our previous work, we showed that US detected non-palpable breast cancer (NPBC) had higher percentage of invasive and lymph node positive cancer, yet still could be regarded as low-risk cancer [PMID:27689334, 28412736]. This study was performed to investigate the prognostic impact of immunohistochemical subtypes and tumor size: the smaller the NPBC, the better the tumor biology and prognosis?

Methods: From January 2001 to December 2017, 6,423 consecutive asymptomatic women underwent mammography (MG) or ultrasound (US) guided biopsy in Peking Union Medical College Hospital. Among them, 159 T1a, 239 T1b, 377 T1c and 72 T2 NPBC were diagnosed and treated. The clinicopathological features, treatment choice, 10-year disease-free survival (DFS) and overall survival (OS) of the small NPBC (defined as≤1.0cm, T1a+b) were reviewed and compared with T1c and T2 NPBC. Prognostic factors of these subgroups of invasive NPBC were identified.

Results: Compared to big NPBC, the T1a+b small NPBC showed more lymph node negative (p&lt;0.001) and low Ki67 (&lt;14%, p&lt;0.001) cancers with earlier TNM stage (p&lt;0.001), more luminal A subtype (p=0.003) and significantly improved 10-year DFS and OS (p=0.004). T1c+T2 NPBC had more triple-negative subtype and received more chemotherapy (p&lt;0.001) and targeted therapy (p=0.008). Breast conserving rate and the use of radiation and endocrine therapy showed no significant difference.

Table 1.Comparison of clinicopathological factors and long term survival of small vs big screen-detected NPBCScreen-detected NPBC(2001-2017    Clinical&prognostic factors T1a+T1b(n=398)T1c+T2(n=449)P valueScreening methodUS-NPBC(n,%)336(84.4)406(90.4)0.008 MG-NPBC(n,%)62(15.6)43(9.6) Lymph node statusNegative(n,%)343(86.2)315(70.2)&lt;0.001 Positive(n,%)55(13.8)134(29.8) TNM stageI(n,%)344(86.4)277(61.7)&lt;0.001 II(n,%)37(9.3)134(29.8)  III(n,%)17(4.3)38(8.5) Ki67&lt;14%(n,%)208(52.2)168(37.4)&lt;0.001 ≥14%(n,%)183(46.0)274(61.0) SubtypeLuminal A(n,%)164(41.3)135(30.1)0.003 Luminal B(n,%)155(38.9)218(48.6)  Her2(n,%)28(7.0)27(6.0)  TNBC(n,%)31(7.8)52(11.6)  Unknown(n,%)20(5.0)17(3.7) 10-year survivalDFS(%)94.688.80.004 OS(%)100.096.4 

Conclusion: Small asymptomatic NPBCs were detected when small because they were good in terms of low Ki67 index, favorable subtype, tumor biology and long term prognosis. On the contrary, T1c and T2 NPBCs were screened when already big or even with positive nodes without clinical symptoms indicating that they might have larger chance of becoming interval cancers.

Citation Format: Xu Y, Pan B, Yao R, Zhou Y-D, Mao F, Zhu Q-L, Wu H-W, Lin Y, Shen S-j, Sun Q. Long term survival and tumor biology of screen-detected small non-palpable breast cancer in Chinese women: The smaller, the better? [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-03-05.