Influence of progesterone receptor on metastasis and prognosis in breast cancer patients with negative HER-2.

Background: In metastatic breast cancer patients, the site of metastasis and prognosis are related to the molecular subtype of breast cancer. There are few relevant reports to explore the clinicopathological and prognostic characteristics of different single positive hormone receptor subtypes [estrogen receptor (ER)+/progesterone receptor (PR)- and ER-/PR+] of metastatic breast cancer.

Methods: Using the Surveillance, Epidemiology and End Results (SEER) database between 2010 and 2015.We analyzed the metastatic patterns and prognosis of human epidermal growth factor receptor 2 (HER-2)-negative breast cancer patients. Cox analysis was used to analyze the influence of ER+/PR- and ER-/PR+ on the prognosis of patients in different subgroups and the risk factors affecting the prognosis of patients with single hormone receptor positivity.

Results: We included 206,187 breast cancer patients, including 7,726 stage IV patients. The loss of ER was a protective factor against bone metastasis (P<0.001) and a risk factor for visceral metastasis (P<0.001). The ER-/PR+ subtype had a similar proportion of metastatic breast cancer, and similar clinicopathological characteristics, prognosis with triple negative breast cancer (TNBC). Single PR positivity was an independent risk factor for cancer specific survival (CSS) in multi-visceral metastasis subgroup comparing to TNBC. Meanwhile, no significant difference in overall survival (OS) or breast cancer specific survival (BCSS) between ER-/PR+ and ER-/PR- patients in all breast cancer patients or in stage IV breast cancer patients. Age [hazard ratio (HR) =2.16], grade (HR =2.36), T stage (T4: HR =3.24), lymph node metastasis (>10: HR =4.33), distant metastasis (HR =4.99), and no chemotherapy or an unknown (HR =1.65) were high-risk factors but surgery (HR <0.5) were protective factors for CSS in ER-/PR+ patients.

Conclusions: ER-/PR+ subtype had a high proportion of stage IV patients. Meanwhile, such subtype breast cancer had similar clinicopathological characteristics, metastatic models (prefers to visceral metastasis), similar even worse prognosis compared with TNBC.