Surveillance for Distant Metastasis in Breast Cancer Patients Who Underwent Contemporary Management: A Report from the Korean Breast Cancer Society Survivor Research Group.

BACKGROUND: Current guidelines recommend against the use of routine imaging tests to detect distant metastasis in asymptomatic breast cancer patients. However, recent advancements in effective therapeutics and diagnostic accuracy have raised the need to reassess the clinical efficacy of intensive metastasis surveillance. We report the results of a multicenter retrospective study to investigate the association between intensive imaging studies and survival outcomes. PATIENTS AND METHODS: We retrospectively reviewed the data of 4130 patients who underwent surgery from 11 hospitals in Korea between January 2010 and December 2011. Patients were divided into two groups on the basis of the intensity of metastasis imaging studies during their disease-free period. The types and intervals of the imaging studies were based on each physician's decisions. RESULTS: High-intensive screening showed a shorter distant metastasis-free survival [p < 0.001, hazard ratio (HR) 1.62; 95% confidence interval (CI) 1.29-2.04], especially for patients in whom bone or lung was the first site of metastasis. With a median follow-up period of 110.0 months, the 5-year breast cancer-specific survival (BCSS) rate was 96.5%. The high-intensity screening group showed significantly poorer BCSS compared with the low-intensity screening group (p < 0.001, HR 3.13; 95% CI 2.32-4.21). However, both multivariable analysis and propensity score matching analysis showed no significant association between the screening intensity and BCSS. CONCLUSIONS: Frequent imaging studies to detect distant metastasis were associated with earlier detection of distant metastasis, especially for lung and bone metastasis. However, intensive surveillance showed no apparent association with BCSS despite the use of currently available treatments.

Association of lipid profile with obesity among breast cancer survivors: a cross-sectional study.

BACKGROUND: The role of lipid metabolism in obesity and cancer manifestations cannot be underestimated, but whether alterations in lipid metabolism can manipulate the vasculature to promote obesity among breast cancer (BC) survivors is yet to be clearly understood. This study quantified plasma lipid and particle sizes using high-throughput proton (1H) nuclear magnetic resonance (NMR) and tested their associations with obesity among breast cancer (BC) survivors. METHODS: A total of 348 (225 premenopausal and 123 postmenopausal) BC survivors enrolled from five hospitals in Korea were included. We assessed thirty-four plasma lipid biomarkers using 1H NMR, and obesity status was defined as a body mass index (BMI) of 25 kg/m2 or greater. Generalized linear and logistic regression models were applied to estimate the least-square means of BMI (kg/m2) and odds ratio (OR)s of obesity, respectively, and the corresponding 95% confidence interval (CI)s across plasma lipid levels. RESULTS: Mean (SD) values of BMI was 23.3 (3.2) kg/m2 and 90 (25.9%) had BMI of ≥ 25 kg/m2. BMI levels increased with increasing total triglycerides (TG), TG in lipoproteins and very-low-density lipoprotein (VLDL) subfractions. However, BMI levels decreased with increasing tertiles of high-density lipoprotein (HDL)-cholesterol (C) and HDL particle size (HDL-p). Similar associations were observed in the logistic regression models. The increasing and decreasing BMI trends with TG and HDL profiles respectively were predominantly limited to premenopausal BC survivors. CONCLUSIONS: Increasing levels of plasma total TG and TG in lipoproteins were associated with increasing levels of BMI among premenopausal BC survivors. High HDL-C levels and large HDL-p were inversely associated with obesity among premenopausal BC survivors. Due to the cross-sectional design of this study, longitudinal studies are necessary to examine the association between obesity and lipid profile among BC survivors.

Minimal Invasive and Individualizing Management of the Axillary Nodes.

The status of the axillary lymph nodes is one of the most important prognostic factors for patients with breast cancer. For over 100 years, axillary lymph node dissection was the standard approach to obtain and manage axillar lymph node, but now, sentinel lymph node biopsy has become a standard approach with less morbidity and equal accuracy in clinical node-negative patients. In addition, numerous studies are on the way to omit axillary lymph node dissection in specific patient subgroups. The recent trials like the ACOSOG Z0011 showed the evidence that omitting an ALND in patients with low burden nodal disease is safe in patients receiving whole-breast radiation. To reduce the use of ALND is the goal to consider when selecting an axillary management strategy.

Evaluation of sodium hyaluronate-based composite hydrogels for prevention of nasal adhesions.

During the healing process after intra-nasal surgery, the growth and repair of damaged tissues can result in the development of postoperative adhesions. Various techniques have been devised to minimize the occurrence of postoperative adhesions which include insertion of stents in the middle meatus, application of removable nasal packing, and utilizing biodegradable materials with antiadhesive properties. This study assesses the efficacy of two sodium hyaluronate (SH)-based freeze-dried hydrogel composites in preventing postoperative nasal adhesions, comparing them with commonly used biodegradable materials in nasal surgery. The freeze-dried hydrogels, sodium hyaluronate and collagen 1(SH-COL1) and sodium hyaluronate, carboxymethyl cellulose, and collagen 1 (SH-CMC-COL1), were evaluated for their ability to reduce bleeding time, promote wound healing, and minimize fibrous tissue formation. Results showed that SH-CMC-COL1 significantly reduced bleeding time compared to both biodegradable polyurethane foam and SH-COL1. Both SH-COL1 and SH-CMC-COL1 exhibited enhanced wound healing effects, as indicated by significantly greater wound size reduction after two weeks compared to the control. Histological analyses revealed significant differences in re-epithelialization and blood vessel count among all tested materials, suggesting variable initial wound tissue response. Although all treatment groups had more epithelial growth, with X-SCC having higher blood vessel count at 7 d post treatment, all treatment groups did not differ in all histomorphometric parameters by day 14. However, the long-term application of SH-COL1 demonstrated a notable advantage in reducing nasal adhesion formation compared to all other tested materials. This indicates the potential of SH-based hydrogels, particularly SH-COL1, in mitigating postoperative complications associated with nasal surgery. These findings underscore the versatility and efficacy of SH-based freeze-dried hydrogel composites for the management of short-term and long-term nasal bleeding with an anti-adhesion effect. Further research is warranted to optimize their clinical use, particularly in understanding the inflammatory factors influencing tissue adhesions and assessing material performance under conditions mimicking clinical settings. Such insights will be crucial for refining therapeutic approaches and optimizing biomaterial design, ultimately improving patient outcomes in nasal surgery.

Adherence to the American Cancer Society guidelines on nutrition and physical activity for cancer survivors and biomarkers of inflammation among breast cancer survivors.

OBJECTIVES: This study investigated whether adherence to the overall lifestyle recommendations in the American Cancer Society (ACS) guidelines on nutrition and physical activity for cancer survivors was associated with inflammation in breast cancer survivors. METHODS: The study included 409 women who had undergone breast cancer surgery at least 1 year before enrollment. A generalized linear model was used to estimate the least square means and 95% confidence intervals of plasma levels of inflammatory markers according to lifestyle factors defined in terms of adherence to the ACS guidelines. RESULTS: Higher overall adherence scores were associated with lower levels of high-sensitivity C-reactive protein (hs-CRP) (p for trend=0.015) and higher levels of adiponectin (p for trend=0.009). Similar significant associations of hs-CRP (p for trend= 0.004) and adiponectin (p for trend=0.010) levels were observed with the score for the body mass index (BMI) component of the adherence score. A higher diet component score was associated with a higher adiponectin level (p for trend=0.020), but there was no significant association for the physical activity component score. CONCLUSIONS: The present study's findings suggest that maintaining a healthy lifestyle according to the ACS guidelines was associated with beneficial effects on inflammatory marker levels, especially hs-CRP and adiponectin, among breast cancer survivors. Among the 3 components of lifestyle guidelines, the BMI component exhibited the most similar tendency to the overall adherence score in relation to inflammatory indicators. Further prospective and intervention studies are needed to investigate longitudinal associations between lifestyle factors and inflammatory markers among breast cancer survivors.

Associations of body mass index and weight change with circulating levels of high-sensitivity C-reactive protein, proinflammatory cytokines, and adiponectin among breast cancer survivors.

AIM: This study examined the associations of body mass index (BMI) and weight change with inflammatory markers among breast cancer survivors in Korea. METHODS: A total of 495 women were included who had been diagnosed with primary breast cancer and survived for at least 6 months since the surgery. Information on the body weight and height of the participants was collected both at the study enrollment and diagnosis. The plasma levels of inflammatory markers were measured, including high-sensitivity C-reactive protein, interleukin (IL)-6, IL-8, tumor necrosis factor-α, and adiponectin. A summary z-score was calculated by summing up the z-scores of each biomarker. The least-square means and 95% confidence intervals (CIs) were calculated using a generalized linear model and odds ratios (ORs) and 95% CIs for the elevated levels of inflammatory markers with a multivariate logistic regression model. RESULTS: Participants with a BMI ≥27.5 kg/m2 at the study enrollment and at diagnosis were significantly associated with elevated summary z-scores compared to those with a BMI < 23 kg/m2 ; the ORs (95% CIs) were 5.42 (2.15-13.71) for current BMI and 3.66 (1.68-7.98) for BMI at diagnosis, respectively. Additionally, a weight loss > 5% since diagnosis was associated with a lower prevalence of high summary z-scores; the OR (95% CI) was .20 (.08-.52) compared to a stable weight. CONCLUSIONS: A high BMI at diagnosis and current BMI with a greater degree were associated with unfavorable levels of inflammatory markers among breast cancer survivors. Additionally, weight loss since diagnosis was inversely associated with these markers.

Human Retrotransposons and Effective Computational Detection Methods for Next-Generation Sequencing Data.

Transposable elements (TEs) are classified into two classes according to their mobilization mechanism. Compared to DNA transposons that move by the "cut and paste" mechanism, retrotransposons mobilize via the "copy and paste" method. They have been an essential research topic because some of the active elements, such as Long interspersed element 1 (LINE-1), Alu, and SVA elements, have contributed to the genetic diversity of primates beyond humans. In addition, they can cause genetic disorders by altering gene expression and generating structural variations (SVs). The development and rapid technological advances in next-generation sequencing (NGS) have led to new perspectives on detecting retrotransposon-mediated SVs, especially insertions. Moreover, various computational methods have been developed based on NGS data to precisely detect the insertions and deletions in the human genome. Therefore, this review discusses details about the recently studied and utilized NGS technologies and the effective computational approaches for discovering retrotransposons through it. The final part covers a diverse range of computational methods for detecting retrotransposon insertions with human NGS data. This review will give researchers insights into understanding the TEs and how to investigate them and find connections with research interests.

Trimethyl chitosan postoperative irrigation solution modulates inflammatory cytokines related to adhesion formation.

Lavage or irrigation has been instilled in surgical practice for wound clearance and surgical site infection prevention during and after surgery. Herein, we developed a new irrigation solution using trimethyl chitosan (TMC), a quaternized chitosan derivative. The TMC-saline irrigation solution developed in the study possesses highly effective bactericidal properties with hemostatic and anti-adhesion properties. The anti-adhesion property of TMC was investigated in relation to inflammatory cytokine response and wound healing. TMC-saline irrigation solution showed reduced pro-inflammatory cytokine protein and gene expressions relevant in the cascade of wound healing and cytokine-related orchestration of postoperative adhesion formation. Further development of this multifunctional TMC-saline irrigation solution can be beneficial for surgical applications and postoperative wound management.

Prognosis of pregnancy after breast cancer diagnosis according to the type of treatment: A population-based study in Korea by the SMARTSHIP group.

BACKGROUNDS: In this study, we evaluated the incidence and outcomes of pregnancy after breast cancer was diagnosed in women of childbearing age. Additionally, we evaluated the prognosis of patients who became pregnant after breast cancer, according to the treatment. METHODS: This was a retrospective cohort study of women aged 20-45 years who were surgically treated for breast cancer between 2004 and 2014 using the Korean National Health Insurance database. The patients were classified into six groups according to the treatment. Propensity score matching was applied to the cohort to analyze the risk of breast cancer-associated mortality after pregnancy and childbirth. RESULTS: Of the 45,765 patients who had been newly diagnosed with breast cancer, 1826 (4%) became pregnant after breast cancer diagnosis. Among the pregnant group, the HR of the risk of death was 0.15 (95% CI, 0.06 to 0.36) for patients who became pregnant ≥49 months after the diagnosis. In patients who received endocrine therapy and chemotherapy, the pregnant group had better prognosis than the non-pregnant group. There was no significant difference between the pregnant group and the non-pregnant group in patients who received chemotherapy and trastuzumab with or without endocrine therapy. CONCLUSION: The risk of death was low in women who became pregnant ≥49 months after the diagnosis of breast cancer. The prognosis of pregnant women was non-inferior to that of non-pregnant women, even in women who received trastuzumab. These findings provide reassurance to patients with HER2-positive cancer who are considering future pregnancy.

Quaternary ammonium N,N,N-trimethyl chitosan derivative and povidone­iodine complex as a potent antiseptic with enhanced wound healing property.

The importance of developing more potent antimicrobials and robust infection prevention practices has been highlighted recently with the increase in reports of emerging bacterial resistance mechanisms and the development of antibiotic-resistant microbes. In this study, a quaternary ammonium chitosan derivative, N,N,N-trimethyl chitosan chloride (TMC) with inherent bactericidal property was synthesized and complexed with povidone­iodine (PVP-I) to create a potentially more potent antiseptic solution that could also significantly enhance the wound healing process. TMC, a positively charged, water-soluble derivative of chitosan, formed stable solutions with PVP-I at 5% w/v TMC concentration (TMC5/PVP-I). TMC5/PVP-I was significantly effective against multidrug-resistant bacteria S. aureus compared with PVP-I alone. TMC/PVP-I solutions also showed fungicidal property against C. albicans, with no cytotoxic effects when tested against human fibroblast cells cultured in vitro. Wound healing assessment in vivo revealed early collagen formation and re-epithelialization for TMC5/PVP-I treated wounds in rats relative to control and PVP-I only. Formulation of TMC/PVP-I solutions presented in the study can be easily adapted in the existing production of commercial PVP-I creating a new product with more potent bactericidal and enhanced wound healing properties for optimal wound care.

Effect of Poloxamer-Based Thermo-Sensitive Sol-Gel Agent on Upper Limb Dysfunction after Axillary Lymph Node Dissection: A Double-Blind Randomized Clinical Trial.

PURPOSE: Restricted shoulder motion is a major morbidity associated with a lower quality of life and disability after axillary lymph node dissection (ALND) in patients with breast cancer. This study sought to evaluate the antiadhesive effect of a poloxamer-based thermosensitive sol-gel (PTAS) agent after ALND. METHODS: We designed a double-blind, multicenter randomized controlled study to evaluate the clinical efficacy and safety of PTAS in reducing upper-limb dysfunction after ALND. The primary outcome was the change in the range of motion (ROM) of the shoulder before surgery and 4 weeks after ALND (early postoperative period). Secondary outcomes were shoulder ROM at six months, axillary web syndrome, and lymphedema (late postoperative period). RESULTS: A total of 170 patients with planned ALND were randomly assigned to one of 2 groups (poloxamer and control) and 15 patients were excluded. In the poloxamer group (n = 76), PTAS was applied to the surface of the operative field after ALND. ALND was performed without the use of poloxamer in the control group (n = 79). Relative to the control group, the poloxamer group had significantly lower early postoperative restrictions in total shoulder ROM at four weeks (-30.04 ± 27.76 vs. -42.59 ± 36.79; p = 0.0236). In particular, the poloxamer group showed greater reductions in horizontal abduction at four weeks (-3.92 ± 9.80 vs. -10.25 ± 15.42; p = 0.0050). The ROM of the shoulder at 24 weeks, axillary web syndrome, and lymphedema were not significantly different between the two groups. No adverse effects were observed in either group. CONCLUSION: We suggest that poloxamer might improve the early postoperative shoulder ROM in patients with breast cancer who have undergone ALND. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02967146.

Clinicopathological Features of Patients with the BRCA1 c.5339T>C (p.Leu1780Pro) Variant.

PURPOSE: Recent studies revealed the BRCA1 c.5339T>C, p.Leu1780Pro variant (L1780P) is highly suggested as a likely pathogenic. The aim of this study was to evaluate clinicopathologic features of L1780P with breast cancer (BC) using multicenter data from Korea to reinforce the evidence as a pathogenic mutation and to compare L1780P and other BRCA1/2mutations using Korean Hereditary Breast Cancer (KOHBRA) study data. MATERIALS AND METHODS: The data of 54 BC patients with L1780P variant from 10 institutions were collected and the clinicopathologic characteristics of the patients were reviewed. The hereditary breast and/or ovarian cancer-related characteristics of the L1780P variant were compared to those of BC patients in the KOHBRA study. RESULTS: The median age of all patients was 38 years, and 75.9% of cases showed triple-negative breast cancer. Comparison of cases with L1780P to carriers from the KOHBRA study revealed that the L1780P patients group was more likely to have family history (FHx) of ovarian cancer (OC) (24.1% vs. 19.6% vs. 11.2%, p < 0.001 and p=0.001) and a personal history of OC (16.7% vs. 2.9% vs. 1.3%, p=0.003 and p=0.001) without significant difference in FHx of BC and bilateral BC. The cumulative risk of contralateral BC at 10 years after diagnosis was 31.9%, while the cumulative risk of OC at 50 years of age was 20.0%. Patients with L1780P showed similar features with BRCA1 carriers and showed higher penetrance of OC than patients with other BRCA1 mutations. CONCLUSION: L1780P should be considered as a pathogenic mutation. Risk-reducing salpingo-oophorectomy is highly recommended for women with L1780P.

Urinary Bladder Injury During Colonoscopy Without Colon Perforation.

We report a case of urinary bladder perforation during colonoscopy. A 67-year-old female, who had undergone a transabdominal hysterectomy for uterine myomas 15 years ago, visited the emergency department with complaint of abdominal pain after a screening colonoscopy. Laparoscopic examination revealed severe adhesion between the sigmoid colon and the urinary bladder. The urinary bladder wall was weakened, and several perforation sites were found. The surgery was converted to a laparotomy. After a thorough examination, we performed primary repair for the perforation sites, followed by an omentopexy.

Low-grade myofibroblastic sarcoma arising in fibroadenoma of the breast-A case report.

BACKGROUND: Myofibroblastic sarcoma or myofibrosarcoma is a malignant tumor of myofibroblasts and known to develop rarely in the breast, but its underlying lesion and tumor cell origin have never been reported yet. CASE PRESENTATION: A 61-year-old female presented with a gradually growing breast mass with well-demarcated ovoid nodular shape. The tumor was histologically characterized by fascicular-growing spindle cell proliferation with large areas of hyalinized fibrosis and focally ductal epithelial remnants embedded in myxoid stroma, mimicking a fibroadenomatous lesion. It had frequent mitoses of 5-16/10 high-power fields, hemorrhagic necrosis, and focally pericapsular invasion. The spindle cells were diffusely immunoreactive for fibronectin, smooth muscle actin, and calponin, which suggest a myofibroblastic origin. Multiple irregularly thickened vessels with medial or pericytic cell proliferation were found to be merged with the intrinsic tumor cells. The tumor could be diagnosed low-grade myofibroblastic sarcoma arising in an old fibroadenoma. CONCLUSION: We report a case of a low-grade mammary myofibrosarcoma that showed a background lesion of fibroadenoma first in the worldwide literature and suggest the pericytes or medial muscle cells of the intratumoral vessels as the cell origin of the myofibroblastic sarcoma.

Differential diagnosis of breast masses in South Korean premenopausal women using diffuse optical spectroscopic imaging.

Young patients with dense breasts have a relatively low-positive biopsy rate for breast cancer (∼1 in 7). South Korean women have higher breast density than Westerners. We investigated the benefit of using a functional and metabolic imaging technique, diffuse optical spectroscopic imaging (DOSI), to help the standard of care imaging tools to distinguish benign from malignant lesions in premenopausal Korean women. DOSI uses near-infrared light to measure breast tissue composition by quantifying tissue concentrations of water (ctH2O), bulk lipid (ctLipid), deoxygenated (ctHHb), and oxygenated (ctHbO2) hemoglobin. DOSI spectral signatures specific to abnormal tissue and absent in healthy tissue were also used to form a malignancy index. This study included 19 premenopausal subjects (average age 41±9), corresponding to 11 benign and 10 malignant lesions. Elevated lesion to normal ratio of ctH2O, ctHHb, ctHbO2, total hemoglobin (THb=ctHHb+ctHbO2), and tissue optical index (ctHHb×ctH2O/ctLipid) were observed in the malignant lesions compared to the benign lesions (p<0.02). THb and malignancy index were the two best single predictors of malignancy, with >90% sensitivity and specificity. Malignant lesions showed significantly higher metabolism and perfusion than benign lesions. DOSI spectral features showed high discriminatory power for distinguishing malignant and benign lesions in dense breasts of the Korean population.

In Vivo Tumor Growth Rate Measured by US in Preoperative Period and Long Term Disease Outcome in Breast Cancer Patients.

OBJECTIVE: The aim of our study was to evaluate the effect of tumor growth rate, calculated from tumor size measurements by US, on breast cancer patients' outcome. PATIENTS AND METHODS: Breast cancer patients who received at least two serial breast ultrasonographies (US) in our institution during preoperative period and were surgically treated between 2002 and 2010 were reviewed. Tumor growth rate was determined by specific growth rate (SGR) using the two time point tumor sizes by US. RESULTS: A total of 957 patients were analyzed. The median duration between initial and second US was 28 days (range, 8-140). The median initial tumor size was 1.7 cm (range, 0.4-7.0) and median second size was 1.9 cm (range, 0.3-7.2). 523 (54.6%) cases had increase in size. The median SGR(x10-2) was 0.59 (range, -11.90~31.49) and mean tumor doubling time was 14.51 days. Tumor growth rate was higher when initial tumor size was smaller. Lymphovascular invasion, axillary lymph node metastasis, and higher histologic grade were significantly associated with higher SGR. SGR was significantly associated with disease-free survival (DFS) in a univariate analysis (p = 0.04), but not in a multivariate Cox analysis (p>0.05). High SGR was significantly associated with worse DFS in a subgroup of initial tumor size >2 cm (p = 0.018), but not in those with tumor size <2 cm (p>0.05). CONCLUSION: Our results showed that tumor growth rate measured by US in a relatively short time interval was associated with other worse prognostic factors and DFS, but it was not an independent prognostic factor in breast cancer patients.

Validation of risk assessment models for predicting the incidence of breast cancer in korean women.

PURPOSE: The Gail model is one of the most widely used tools to assess the risk of breast cancer. However, it is known to overestimate breast cancer risk for Asian women. Here, we validate the Gail model and the Korean model using Korean data, and subsequently update and revalidate the Korean model using recent data. METHODS: We validated the modified Gail model (model 2), Asian American Gail model, and a previous Korean model using screening patient data collected between January 1999 and July 2004. The occurrence of breast cancer was confirmed by matching the resident registration number with data from the Korean Breast Cancer Registration Program. The expected-to-observed (E/O) ratio was used to validate the reliability of the program, and receiver operating characteristics curve analysis was used to evaluate the program's discriminatory power. There has been a rapid increase in the incidence of breast cancer in Korea, and we updated and revalidated the Korean model using incidence and mortality rate data from recent years. RESULTS: Among 40,229 patients who were included in the validation, 161 patients were confirmed to have developed breast cancer within 5 years of screening. The E/O ratios and 95% confidence intervals (CI) were 2.46 (2.10-2.87) for the modified Gail model and 1.29 (1.11-1.51) for the Asian American Gail model. The E/O ratio and 95% CI for the Korean model was 0.50 (0.43-0.59). For the updated Korean model, the E/O ratio and 95% CI were 0.85 (0.73-1.00). In the discriminatory power, the area under curve and 95% CI of the modified Gail model, Asian American Gail model, Korean model and updated Korean model were 0.547 (0.500-0.594), 0.543 (0.495-0.590), 0.509 (0.463-0.556), and 0.558 (0.511-0.605), respectively. CONCLUSION: The updated Korean model shows a better performance than the other three models. It is hoped that this study can provide the basis for a clinical risk assessment program and a future prospective study of breast cancer prevention.

Bilateral adrenal pheochromocytoma with a germline L790F mutation in the RET oncogene.

About ten percent of pheochromocytomas are associated with familial syndrome. Hereditary pheochromocytoma has characteristics of early onset, multifocality and bilaterality. We experienced a case of 44-year-old man with bilateral pheochromocytoma without evidence of medullary thyroid cancer. Genetic test detected a L790F germline mutation of RET oncogene. The author found a necessity for genetic tests in cases of young-age, bilateral pheochromocytoma.

Estimating the risks and benefits of tamoxifen for prophylactic breast cancer chemoprevention in Korea.

PURPOSE: According to the National Surgical Adjuvant Breast and Bowel Project P1 (NSABP-P1) study, tamoxifen can prevent 49% of invasive breast cancers in patients who have a 5-year risk of 1.67% or more. Because tamoxifen is associated with both adverse effects (endometrial cancer, stroke, pulmonary embolism) and protective effect (fracture prevention), it is necessary to weigh the risks and benefits of using tamoxifen for prevention in Korean women. This study weighed those risks and benefits. METHODS: Data were reviewed on the incidences of breast cancer, hip fracture, endometrial cancer and stroke in the absence of tamoxifen treatment in Korean women. We also reviewed NSABP-P1 data on the effects of tamoxifen on these outcomes. A risk-benefit index was calculated according to age and specific risk of breast cancer. Sensitivity analyses were performed with assumptions regarding the effects of tamoxifen. RESULTS: Compared to U.S. women, the numbers of hip fractures and endometrial cancers were lower, but the number of strokes was much higher. The net benefit of tamoxifen was reduced with increasing age because of a high risk of stroke in older women. Older Korean women had more risk than benefit from tamoxifen chemoprevention. Only women younger than age 40 had a positive risk-benefit index with an average 5-year risk of breast cancer in Korea. Sensitivity analysis showed that this result was robust. CONCLUSION: Women under the age 40 had more benefit than risk from tamoxifen chemoprevention. Tamoxifen chemoprevention should be limited to Korean women younger than age 40.