Sj-subway, a Predictor for the Recurrence of High-risk Hormone Receptor-positive Breast That is Sensitive to Extended Endocrine Therapy
Sj-subway, a Predictor for the Recurrence of High-risk Hormone Receptor-positive Breast That is Sensitive to Extended Endocrine Therapy
Hormone receptor-positive breast cancer accounts for about 70% of all breast cancers.
 Extended endocrine therapy with aromatase inhibitor is the current main treatment for hormone
 receptor-positive breast cancer. However, previous studies have shown a long-lasting risk of
 the recurrence of hormone receptor-positive breast cancer at early stage, and disease
 recurrence is considered inevitable only depending on a 5-year of adjuvant endocrine therapy.
 Therefore, extended endocrine therapy is considered as a possible measure to reduce the risk
 of recurrence.

 Numerous clinical studies have focused on extended endocrine therapy in patients with
 specific types of breast cancer. In 2017, the National Comprehensive Cancer Network (NCCN)
 updated the recommends for extended endocrine therapy with aromatase inhibitor, where
 postmenopausal early-stage breast cancer patients wo have high risk factors may be considered
 to be given an extended 5-year endocrine treatment with aromatase inhibitor after the initial
 5-year treatment. In 2019, the Chinese Society of Clinical Oncology also suggested that
 postmenopausal hormone receptor-positive patients who have been well tolerated to the initial
 5 years of adjuvant endocrine therapy can be given the extended endocrine therapy under some
 restrictions.

 However, extended endocrine therapy may also cause other risks in patients. Long-term
 tamoxifen treatment can significantly increase the incidence of adverse reactions such as
 endometrial cancer, thrombotic disease, and dyslipidemia, and long-term aromatase inhibitor
 treatment can also increase the incidence of osteoporosis, fractures, dyslipidemia, and
 hypertension. Although anti-cancer treatment can reduce cancer deaths, it may increase deaths
 due to cardiovascular diseases.

 An attempt has been proposed to find out an indicator that can effectively determine the
 necessity of extended endocrine therapy in such patients, not only improving the prognosis of
 breast cancer patients, but also reducing treatment-related side effects. The author's team
 recently discovered sj-subway, a possible factor with a long tubular structure in breast
 cancer lesions. The authors found that the higher expression of sj-subway indicates the worse
 patient's prognosis. So the positive expression of sj-subway may be a predictor of recurrence
 and metastasis in high-risk hormone receptor-positive patients. However, whether this
 predictor can be used clinically remains to be studied.

 This real-world study intends to analyze the difference in the clinical efficacy of extended
 endocrine therapy under different sj-subway expression in high-risk hormone receptor-positive
 breast cancer patients, and to explore whether sj-subway can screen out the patients who can
 benefit from extended endocrine therapy, thus providing a therapeutic help for hormone
 receptor-positive breast cancer patients.
Breast cancer has been one of the most common malignant tumors in women, accounting for 23%
 of all the malignancies. There are estimated 1,300,000 new cases of breast cancers and
 400,000 deaths due to breast cancers every year in the world. Hormone receptor-positive
 breast cancer accounts for about 70% of all breast cancers.

 Since ovarian resection was first used in the treatment of advanced breast cancer in the late
 19th century, with more than a century of development, endocrine therapy has become the most
 important adjuvant therapy for hormone receptor-positive breast cancers, especially for
 advanced breast cancers. Increasing clinical trials of adjuvant endocrine therapy such as
 ATAC, BIG1-98, and IES, which have been implemented since 2002, have ascertained the effect
 of adjuvant endocrine therapy with aromatase inhibitor, and the guidelines for the diagnosis
 and treatment of breast cancer have been also changed accordingly.

 Although early-stage hormone receptor-positive breast cancer patients have a better prognosis
 than HER-2 positive and triple-negative patients, there is still a long-lasting risk of
 postoperative recurrence, which has been confirmed in two large-scale meta-analyses reported
 by the Early Breast Cancer Trialists' Collaborative Group (EBCTCG). A meta-analysis released
 by the EBCTCG in 1998 indicated that early-stage hormone receptor-positive breast cancer
 patients, especially lymph node-positive patients, experienced the second recurrence peak at
 2-3 years and 7-9 years after completion of endocrine therapy. In 2016, the EBCTCG released
 another relevant study at the annual meeting of the American Society of Clinical Oncology
 (ASCO), in which the long-term recurrence rate within 5-20 years was up to 14% in T1N0 breast
 cancer patients who had undergone 5 years of adjuvant endocrine therapy. Therefore, the 5
 years of standard adjuvant endocrine therapy cannot eliminate the risk of recurrence. Most
 scholars have suggested that the duration of endocrine therapy should be extended to reduce
 the recurrence risk of breast cancer.

 Numerous clinical trials have focused on the use of extended endocrine therapy in patients
 with specific types of breast cancer. In the MA17R trial, patients received 3-5 years of
 tamoxifen or 5 years of aromatase inhibitor treatment, followed by another 5 years of
 aromatase inhibitor treatment. The extended aromatase inhibitor treatment was found to
 significantly improve the disease-free survival time of hormone receptor-positive early
 breast cancer patients, while also reducing the risk of contralateral breast cancer and
 distant relapse. In the NSABP B42 trial, patients who had received initial 5 years of
 aromatase inhibitor treatment or initial 5 years of tamoxifen + aromatase inhibitor treatment
 were all treated with extended aromatase inhibitor. Although the primary endpoint (P = 0.048)
 did not reach the expected value, extended treatment with aromatase inhibitors significantly
 reduced the secondary endpoints - breast cancer-free interval and distant relapse, confirming
 the conclusion of the MA17R study. In the DATA trial, although extended treatment with
 aromatase inhibitor did not benefit in general, subgroup analysis showed that some high-risk
 patients, such as patients with positive lymph nodes, tumors larger than 2 cm in diameter, or
 receiving chemotherapy, could benefit from 6 years of anastrozole treatment. The IDEAL trial
 showed that there is a trend of benefit in patients with positive lymph nodes. With the
 support of many large-scale clinical studies published in succession, the NCCN practice
 guidelines for breast cancer released in 2017 recommends an additional 5 years of aromatase
 inhibitor treatment following the initial 5-year treatment in postmenopausal patients with
 early-stage breast cancer at high risk for relapse. As per the Chinese Society of Clinical
 Oncology guidelines published in 2019, the extended endocrine therapy is also recommended for
 postmenopausal hormone receptor-positive patients who have been well tolerated to the initial
 5-year adjuvant treatment. However, there are some restrictions, such as positive lymph
 nodes, G3 or other risk factors that require adjuvant chemotherapy. For premenopausal hormone
 receptor-positive patients who have been well tolerated to the initial 5 years of endocrine
 treatment, extended endocrine therapy is also recommended in some situations, such as the
 presence of positive lymph nodes, G3, less than 35 years old at diagnosis, high-level Ki-67
 or pT2 and above.

 However, the extended endocrine therapy also has some adverse events. Multiple studies have
 shown that long-term use of tamoxifen can significantly increase the incidence of adverse
 reactions such as endometrial cancer, thrombotic disease, and dyslipidemia. Similarly,
 long-term treatment with aromatase inhibitors can also increase the incidence of adverse
 reactions such as osteoporosis, fractures, dyslipidemia, and hypertension. In the ATLAS
 trial, the incidence of endometrial cancer in patients treated with 10 years of tamoxifen was
 higher than that in patients treated with 5 years of tamoxifen. Similar results are
 discovered in the aTTom trial. In the IDEAL trial, the incidence rates of osteoarthritis and
 osteoporosis in patients treated with 5 years of letrozole was increased by 14% and 10% of
 that in patients undergoing 2.5 years of treatment. A study involving nearly 100,000 breast
 cancer patients showed that only 49.9% of breast cancer patients died of breast cancer, 16.3%
 died of cardiovascular disease, and 33.8% died of other causes. Among them, breast cancer and
 cardiovascular disease were the main causes of death in well- and poor-tolerated patients,
 respectively. This suggests that although anti-cancer treatment can reduce cancer deaths, it
 may increase the death due to cardiovascular disease. Such deaths are often offset, which
 often improves the BCFI, but does not benefit the overall survival.

 Therefore, an effective predictor for relapse risks that can accurately determine the
 necessity of extended endocrine therapy is expected to be discovered. The use of this
 predictor will both improve patient's prognosis and reduce treatment-related side effects.
 The author's team recently discovered a possible factor with a long tubular structure in
 breast cancer lesions using immunofluorescence staining, which was named as sj-subway. The
 authors conducted a retrospective analysis based on the specimen library and case follow-up
 library of the Breast Center of Shengjing Hospital Affiliated to China Medical University.
 They found that sj-subway was positively expressed in various subtypes of breast cancer
 tissues, and mostly expressed in the hormone receptor-positive subtype. The group with more
 sj-subway expression had a higher positive expression of hormone receptor/ progesterone
 receptor. Further survival analysis also revealed the worse prognosis of patients with the
 existence of higher sj-subway expression. Therefore, the authors speculate that positively
 expressed sj-subway may become a predictor of recurrence and metastasis in high-risk patients
 with hormone receptor positive. However, the clinical use of this factor to screen the
 population benefiting from extended endocrine therapy remains to be studied.

 This real-world study intends to observe the difference in the clinical efficacy of extended
 endocrine therapy under different sj-subway expression in high-risk hormone receptor-positive
 breast cancer patients, and to analyze whether the use of sj-subway can further screen out
 the population with benefit from extended endocrine therapy, thus further improving the
 survival of such patients without additional adverse events.
Inclusion Criteria:

 -  early-stage invasive breast cancer positive for estrogen receptor and / or
 progesterone receptor is pathologically confirmed;

 -  patients who have completed standard endocrine therapy for 5 years without recurrence
 and metastasis;

 -  18-70 years old;

 -  patients with one of the following six manifestations: KI67 ≥ 30%; tumor size > 2 cm;
 positive lymph nodes; histological grade III; vascular cancer thrombus; HER-2 gene
 overexpression or amplification.

 Exclusion Criteria:

 -  with a history of other malignancies;

 -  patients who have severe abnormalities in important organs, such as the heart, liver,
 and kidney or who cannot be tolerant to extended treatment due to poor constitution;

 -  patients with severe osteoporosis or dyslipidemia, or those who cannot tolerate
 endocrine therapy ;

 -  patients who have participated in other clinical trials.