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Background@#Multiple myeloma (MM) patients are at risk of skeletal-related events (SREs) like spinal cord compression, pathologic fractures, bone surgery, and radiation to bone. Realworld data regarding SREs in MM are limited. @*Methods@#We conducted a large, retrospective, nationwide cohort study using the Korean Health Insurance Review and Assessment Service (HIRA) database from 2007 to 2018. @*Results@#Over a 12-year study period, we identified 6,717 patients who developed symptomatic MM. After a median follow-up of 35.1 months (interquartile range [IQR], 20.8–58.2 months), 43.6% of these patients experienced SREs, and 39.6% had four or more SREs. One in five patients (20.0%) experienced pathologic fractures within the first year of follow-up. The median time to first SRE was 9.6 months (IQR, 1.2–25.8 months), with 3.0 months in the group with prior SREs and 19.8 months in the group without prior SREs.During follow-up, 78.5% of patients received bisphosphonates. Multiple logistic regression analysis revealed several factors associated with an increased risk of SREs, including being female (odds ratio [OR], 1.44), aged 50 or older (OR, 1.87), having cerebrovascular disease (OR, 1.34), undergoing first-line chemotherapy regimens not containing bortezomib or lenalidomide (OR, 1.49), and being in the group with prior SREs and bisphosphonate use (OR, 5.63), compared to the group without prior SREs and without bisphosphonate use. @*Conclusion@#This population-based study is the first to report the incidence and risk factors of SREs in Korean MM patients, which can be used to assess their bone health.
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In recent years, next-generation sequencing (NGS)–based genetic testing has become crucial in cancer care. While its primary objective is to identify actionable genetic alterations to guide treatment decisions, its scope has broadened to encompass aiding in pathological diagnosis and exploring resistance mechanisms. With the ongoing expansion in NGS application and reliance, a compelling necessity arises for expert consensus on its application in solid cancers. To address this demand, the forthcoming recommendations not only provide pragmatic guidance for the clinical use of NGS but also systematically classify actionable genes based on specific cancer types. Additionally, these recommendations will incorporate expert perspectives on crucial biomarkers, ensuring informed decisions regarding circulating tumor DNA panel testing.
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Purpose@#The programmed death-ligand 1 (PD-L1) SP142 assay identifies patients with triple-negative breast cancer (TNBC) who are most likely to respond to the anti–PD-L1 agent atezolizumab. We aimed to compare PD-L1 (SP142) expression between primary and recurrent/metastatic TNBCs and elucidate the clinicopathological features associated with its expression. @*Materials and Methods@#Primary and recurrent/metastatic TNBCs tested with PD-L1 (SP142) were collected, and clinicopathological information of these cases was obtained through a review of slides and medical records. @*Results@#PD-L1 (SP142) positivity was observed in 50.9% (144/283) of primary tumors and 37.8% (31/82) of recurrent/metastatic TNBCs with a significant difference. Recurrent or metastatic sites were associated with PD-L1 positivity, with high PD-L1 positivity in the lung, breast, and soft tissues, and low positivity in the bone, skin, liver, and brain. When comparing PD-L1 expression between primary and matched recurrent/metastatic TNBCs using 55 paired samples, 20 cases (36.4%) showed discordance; 10 cases revealed positive conversion, and another 10 cases revealed negative conversion during metastatic progression. In primary TNBCs, PD-L1 expression was associated with a higher histologic grade, lower T category, pushing border, and higher tumor-infiltrating lymphocyte infiltration. In survival analyses, PD-L1 positivity, especially high positivity, was found to be associated with favorable prognosis of patients. @*Conclusion@#PD-L1 (SP142) expression was lower in recurrent/metastatic TNBCs, and substantial cases showed discordance in its expression between primary and recurrent/metastatic sites, suggesting that multiple sites may need to be tested for PD-L1 (SP142) when considering atezolizumab therapy. PD-L1 (SP142)–positive TNBCs seems to be associated with favorable clinical outcomes.
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Purpose@#The female sex is reported to have a higher risk of adverse events (AEs) from cytotoxic chemotherapy. Few studies examined the sex differences in AEs and their impact on the use of medical services during adjuvant chemotherapy. This sub-study aimed to compare the incidence of any grade and grade ≥ 3 AEs, healthcare utilization, chemotherapy completion rate, and dose intensity according to sex. @*Materials and Methods@#This is a sub-study of a multicenter cohort conducted in Korea that evaluated the impact of healthcare reimbursement on AE evaluation in patients who received adjuvant chemotherapy between September 2013 and December 2016 at four hospitals in Korea. @*Results@#A total of 1,170 patients with colorectal, gastric, or non–small cell lung cancer were included in the study. Female patients were younger, had fewer comorbidities, and experienced less postoperative weight loss of > 10%. Females had significantly higher rates of any grade AEs including nausea, abdominal pain, stomatitis, vomiting, and neutropenia, and experienced more grade ≥ 3 neutropenia, nausea, and vomiting. The dose intensity of chemotherapy was significantly lower in females, and they also experienced more frequent dose reduction after the first cycle. Moreover, female patients receiving platinum-containing regimens had significantly higher rates of unscheduled outpatient visits. @*Conclusion@#Our study found that females experienced a higher incidence of multiple any-grade AEs and severe neutropenia, nausea, and vomiting, across various cancer types, leading to more frequent dose reductions. Physicians should be aware of sex differences in AEs for chemotherapy decisions.
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In recent years, next-generation sequencing (NGS)–based genetic testing has become crucial in cancer care. While its primary objective is to identify actionable genetic alterations to guide treatment decisions, its scope has broadened to encompass aiding in pathological diagnosis and exploring resistance mechanisms. With the ongoing expansion in NGS application and reliance, a compelling necessity arises for expert consensus on its application in solid cancers. To address this demand, the forthcoming recommendations not only provide pragmatic guidance for the clinical use of NGS but also systematically classify actionable genes based on specific cancer types. Additionally, these recommendations will incorporate expert perspectives on crucial biomarkers, ensuring informed decisions regarding circulating tumor DNA panel testing.
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Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease that affects multiple organs. More than half of the patients with SLE have kidney involvement, and up to 10% of patients with lupus nephritis develop end-stage renal disease (ESRD). Central nervous system (CNS) involvement in SLE occurs in 21% to 95% of patients. Severe neurological manifestations such as seizures, cerebrovascular disease, meningitis, and cerebrovascular accidents can develop in childhood-onset SLE, but cerebral infections, such as brain abscess and hemorrhage, are seldom reported in lupus nephritis, even in adults. Here, we report a rare case of childhood-onset SLE with ESRD, a cerebral abscess, and hemorrhage. A 9-year-old girl diagnosed with lupus nephritis was administered high-dose steroids and immunosuppressant therapy to treat acute kidney injury (AKI) and massive proteinuria. The AKI deteriorated, and after 3 months, she developed ESRD. She received hemodialysis three times a week along with daily peritoneal dialysis to control edema. She developed seizures, and imaging showed a brain abscess. This was complicated by spontaneous cerebral hemorrhage, and she became unstable. She died shortly after the hemorrhage was discovered. In conclusion, CNS complications should always be considered in clinical practice because they increase mortality, especially in those with risk factors for infection.
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Purpose@#This single-arm phase II trial investigate the efficacy and safety of S-1 plus oxaliplatin (SOX) in patients with metastatic breast cancer. @*Materials and Methods@#Patients with metastatic breast cancer previously treated with anthracyclines and taxanes were enrolled. Patients received S-1 (40-60 mg depending on patient’s body surface area, twice a day, day 1-14) and oxaliplatin (130 mg/m2, day 1) in 3 weeks cycle until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR) according to Response Evaluation Criteria in Solid Tumor 1.1. Secondary endpoints included time-to-progression (TTP), duration-of-response (DoR), overall survival (OS), and adverse events. @*Results@#A total of 87 patients were enrolled from 11 institutions in Korea. Hormone receptor was positive in 54 (62.1%) patients and six (6.9%) had human epidermal growth factor receptor 2–positive disease. Forty-eight patients (85.1%) had visceral metastasis and 74 (55.2%) had more than three sites of metastases. The ORR of SOX regimen was 38.5% (95% confidence interval [CI], 26.9 to 50.0) with a median TTP of 6.0 months (95% CI, 5.1 to 6.9). Median DoR and OS were 10.3 months (95% CI, 5.5 to 15.1) and 19.4 (95% CI, not estimated) months, respectively. Grade 3 or 4 neutropenia was reported in 28 patients (32.1%) and thrombocytopenia was observed in 23 patients (26.6%). @*Conclusion@#This phase II study showed that SOX regimen is a reasonable option in metastatic breast cancer previously treated with anthracyclines and taxanes.
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Purpose@#Several predictive models have been developed to predict the pathological complete response (pCR) after neoadjuvant chemotherapy (NAC); however, few are broadly applicable owing to radiologic complexity and institution-specific clinical variables, and none have been externally validated. This study aimed to develop and externally validate a machine learning model that predicts pCR after NAC in patients with breast cancer using routinely collected clinical and demographic variables. @*Methods@#The electronic medical records of patients with advanced breast cancer who underwent NAC before surgical resection between January 2017 and December 2020 were reviewed. Patient data from Seoul National University Bundang Hospital were divided into training and internal validation cohorts. Five machine learning techniques, including gradient boosting machine (GBM), support vector machine, random forest, decision tree, and neural network, were used to build predictive models, and the area under the receiver operating characteristic curve (AUC) was compared to select the best model. Finally, the model was validated using an independent cohort from Seoul National University Hospital. @*Results@#A total of 1,003 patients were included in the study: 287, 71, and 645 in the training, internal validation, and external validation cohorts, respectively. Overall, 36.3% of the patients achieved pCR. Among the five machine learning models, the GBM showed the highest AUC for pCR prediction (AUC, 0.903; 95% confidence interval [CI], 0.833–0.972).External validation confirmed an AUC of 0.833 (95% CI, 0.800–0.865). @*Conclusion@#Commonly available clinical and demographic variables were used to develop a machine learning model for predicting pCR following NAC. External validation of the model demonstrated good discrimination power, indicating that routinely collected variables were sufficient to build a good prediction model.
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Background@#In vitro fertilization-embryo transfer (IVF-ET), an expensive option for infertile couples, started to be fully covered by the National Health Insurance (NHI) from October 2017 in South Korea. We investigated the association between woman’s socioeconomic status (SES) and abortive outcomes in pregnancies after IVF-ET in the setting of universal coverage of the treatment. @*Methods@#Using the NHI database in South Korea, we conducted a retrospective cohort study of all women who achieved clinical pregnancy after ET between October 2017 and February 2019. A total of 44,038 clinical pregnancy episodes of 29,847 women who underwent ET were analyzed. We used employment status, income in percentiles, and living in the Seoul capital area as indicators of SES. Relative risks (RRs) for abortive pregnancy outcomes were calculated for each socioeconomic stratum, using log-binomial regression models included woman’s age, body mass index, fasting blood glucose, fresh ET, month of ET, and history of smoking. @*Results@#While most pregnancy outcomes were live births (n = 30,783, 69.9%), 11,215 (25.5%) cycles ended with abortion or early pregnancy loss, 1,779 (4.0%) cycles were ectopic pregnancy, 45 (0.1%) were coded as molar pregnancy, and 224 (0.5%) were fetal death in utero or stillbirth. The risk of overall abortive outcomes was higher when a woman was unemployed (adjusted RR, 1.08; 95% confidence interval [CI], 1.05–1.11) or living in a nonSeoul capital area (1.11; 95% CI, 1.08–1.14). The association between relative income level and abortive outcomes was close to null. Living outside Seoul capital area was associated with the greater risk of abortive outcomes especially in younger women. @*Conclusion@#Unemployment and living in non-capital areas were associated with a higher risk of abortive outcomes among pregnancies after ET, even in the setting of universal coverage of IVF-ET. This suggests potential impact of socioeconomic position on the IVF-ET pregnancy.
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Next-generation sequencing (NGS) is becoming essential in the fields of precision oncology. With implementation of NGS in daily clinic, the needs for continued education, facilitated interpretation of NGS results and optimal treatment delivery based on NGS results have been addressed. Molecular tumor board (MTB) is multidisciplinary approach to keep pace with the growing knowledge of complex molecular alterations in patients with advanced solid cancer. Although guidelines for NGS use and MTB have been developed in western countries, there is limitation for reflection of Korea’s public health environment and daily clinical practice. These recommendations provide a critical guidance from NGS panel testing to final treatment decision based on MTB discussion.
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Objectives@#In South Korea, a significant number of patients with obstructive sleep apnea have benefited from the insured continuous positive pressure for sleep apnea as of 2018. However, there is limited information on public awareness of sleep apnea syndrome in the country. A nationwide survey was conducted to evaluate the current status of public awareness on the diagnosis and treatment of sleep apnea. @*Methods@#We conducted an online survey using structured questionnaires on symptoms and knowledge of diagnosis and treatment modalities for sleep apnea. A total of 4,000 participants aged 21 to 69 were proportionally allocated according to the residential area, gender, and age group. @*Results@#The STOP questionnaire, a screening tool for sleep apnea, revealed that 1,044 (21.6%) scored ≥2 points, 327 (8.1%) scored ≥3 points, and 64 (1.6%) scored 4 points. However, only 19 of the 1,044 patients were being treated for sleep apnea, and 13 had been using continuous positive airway pressure. For the diagnosis of sleep apnea, 1,318 participants (33.0%) responded that polysomnography was necessary. For sleep apnea treatment, 1,954 (48.9%) participants responded that lifestyle modification was the treatment of choice, while 1,036 (25.9%) chose continuous positive pressure. @*Conclusions@#Although one-fifth were at high risk for sleep apnea, this disorder is still underestimated. Therefore, publicity and support are needed to improve public awareness of sleep apnea.
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Purpose@#The benefit of adjuvant chemotherapy for stage II colon cancer has not been clearly demonstrated even in cases with high-risk factors. This study aimed to compare the effectiveness of oral fluoropyrimidine monotherapy as adjuvant chemotherapy with that of intravenous fluoropyrimidine-based chemotherapy for high-risk stage II colon cancer. @*Methods@#This single-institution, retrospective study included patients who underwent curative resection for high-risk stage II colon cancer between 2003 and 2014. Patients were classified into 3 postoperative treatment groups: observation, oral fluoropyrimidine monotherapy group (OG), or intravenous fluoropyrimidine-based chemotherapy group (IVG). @*Results@#We identified 356 patients, including 87 (24.4%) in the observation group, 172 (48.3%) in the OG, and 97 (27.2%) in the IVG. Patients in the OG were older (63.8 ± 10.7 vs. 56.5 ± 10.8, P < 0.001) and had a lower number of T4 lesions (12.8% vs. 35.1%, P < 0.001) than those in the IVG. Regarding survival outcomes, the 5-year overall and disease-free survival rates were not different between the OG and IVG (91.2% vs. 92.6% [P = 0.090] and 85.1% vs. 81.9% [P = 0.535], respectively). In multivariate analysis, age over 70 years and no adjuvant chemotherapy were associated with poor overall survival and disease-free survival. Fewer chemotherapy-related adverse events of grade ≥3 were observed in the OG than in the IVG (12.2% vs. 34.0%, P < 0.001). @*Conclusion@#In high-risk stage II colon cancer, adjuvant oral fluoropyrimidine monotherapy can be an effective and convenient alternative to intravenous fluoropyrimidine-based chemotherapy as it has comparable oncological outcomes and reduced chemotherapy-related complications.
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Purpose@#We aimed to assess the real-world efficacy of nab-paclitaxel in metastatic breast cancer patients. @*Materials and Methods@#This is a retrospective study performed in two tertiary referral hospitals in Korea. Patients with metastatic breast cancer treated with nab-paclitaxel (Abraxane®) between March 2016 and March 2020 were enrolled. @*Results@#A total of 102 patients with metastatic breast cancer were included. Patients were heavily pre-treated with a median of four prior lines of chemotherapy (5 lines when including endocrine therapy in hormone-receptor-positive patients), and 66 patients (64.7%) were exposed to taxanes in the metastatic setting. According to St. Gallen molecular subtypes, 36 patients (35.3%) were luminal A, 28 (27.5%) were luminal B, 18 (17.7%) were human epidermal growth factor receptor 2–positive and 20 (19.6%) had triple-negative disease. Fifty patients (49.0%) were treated with a 3-weekly regimen (260 mg/m2 on day 1 every 3 weeks), and 52 (51.0%) were treated with a weekly regimen (100 mg/m2 every week). Objective response rate was 22.9%. After a median follow-up of 22.0 months, median progression-free survival (PFS) was 4.0 months (95% confidence interval [CI], 2.6 to 4.8) and median overall survival was 8.7 months (95% CI, 7.5 to 11.2). Patients treated with weekly regimen had longer PFS compared to 3-weekly regimen (5.5 vs. 2.3 months, p < 0.001). Multivariate analysis revealed the treatment regimen as an independent prognostic factor for PFS. There was no grade 3 or 4 hypersensitivity reaction. @*Conclusion@#This real-world data shows that nab-paclitaxel is a reasonable treatment option in heavily pre-treated and/or taxane-exposed metastatic breast cancer patients.
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Purpose@#We aimed to develop a prognostic model to assist palliative care referral at least 3 months before death in advanced cancer patients treated at an outpatient medical oncology clinic. @*Materials and Methods@#In this prospective cohort study, a total of 200 patients were enrolled at a tertiary cancer center in South Korea. The major eligibility criterion was an expected survival of less than a year as estimated by their oncologists. We analyzed the influences of known prognostic factors along with chemotherapy status, mid-arm circumference, and triceps skinfold thickness on survival time. @*Results@#The mean age of the patients was 64.5 years, 36% were female, and the median survival time was 7.6 months. In the multivariate analysis, we found 6 significant factors related to poor survival: a poor Eastern Cooperative Oncology Group (ECOG) performance status (≥2), not undergoing chemotherapy, anorexia, a low lymphocyte level (<12%), a high lactate dehydrogenase (LDH) level (≥300 IU/L), and a low mid-arm circumference (<23 cm). We developed a prognostic model (score, 0-8.0) to predict 3-month survival based on the multivariate analysis. Patients who scored ≥4.0 points had a short survival of less than 3 months (p<0.001). The discriminating ability of the prognostic model using the area under the receiver operating characteristic curve (AUC) was 0.88. @*Conclusion@#The prognostic model using ECOG performance status, chemotherapy status, anorexia, lymphocytes, LDH, and mid-arm circumference can predict 3-month survival in medical oncology outpatients. It can alert oncologists to refer patients to palliative care specialists before it is too late.
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An emblem is a symbolic representational image that stands for a certain organization, concept, team, or society. This study investigated the emblems of the sleep societies in South Korea and the international sleep societies in which they were registered as members. Three South Korean sleep societies were found by searching for the keyword ‘sleep’ in the Korea Citation Index. Subsequently, we identified three international societies in which the three South Korean conferences participate. The emblems can be classified according to their composition. Taegeuk patterns represent yin and yang, electroencephalography that stands for the objective indicator of sleep, and the acronym or abbreviation indicating the name of the society. All emblems in this study were combinations of pictorial images and letters. The pictorial image of the Korean Sleep Research Society is the only emblem representing an inset with Hangeul. The emblem is a medium that conveys diverse meanings beyond representation. The societies have attempted to embody the identity as well as their directions.
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Background@#High-dose chemotherapy followed by autologous stem cell transplantation (HDC-ASCT) as a consolidation treatment is a promising approach for eligible patients with newly diagnosed primary central nervous system lymphoma (PCNSL). @*Methods@#In this retrospective analysis, 22 patients with newly diagnosed PCNSL received chemotherapy with rituximab, methotrexate, procarbazine, and vincristine. Those who showed complete or partial response subsequently received consolidation HDC-ASCT with a thiotepa-based conditioning regimen but did not undergo radiotherapy. @*Results@#The PCNSL patients had a median age of 57 years (range, 49‒67 yr); of the total patients, 9.1% had a performance status of 2 or higher, and 72.1% had multiple lesions.Approximately 82% of patients received six cycles of induction chemotherapy, which was well tolerated with excellent disease control. The rate of confirmed or unconfirmed complete response increased from 45.5% at the period of interim analysis to 81.8% prior to the initiation of HDC-ASCT. With a median follow-up of 19.6 months (range, 7.5‒56.5 mo), the 2-year progression-free survival and overall survival estimates were 84% and 88%, respectively. No treatment-related deaths occurred. Grade 3 toxicity was recorded in 90.9% of the patients after undergoing the HDC-ASCT, and the most common grade 3 adverse event was febrile neutropenia without sepsis. @*Conclusion@#The discussed treatment approach is feasible in patients with newly diagnosed PCNSL, yielding encouraging results.
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Purpose@#Despite curative resection, the 5-year survival for patients with resectable pancreatic cancer is less than 20%. Recurrence occurs both locally and at distant sites and effective multimodality adjuvant treatment is needed. @*Materials and Methods@#Patients with curatively resected stage IB-IIB pancreatic adenocarcinoma were eligible. Treatment consisted of chemotherapy with gemcitabine 1,000 mg/m2 on days 1 and 8 and cisplatin 60 mg/m2 on day 1 every 3 weeks for two cycles, followed by chemoradiotherapy (50.4 Gy/28 fx) with weekly gemcitabine (300 mg/m2/wk), and then gemcitabine 1,000 mg/m2 on days 1 and 8 every 3 weeks for four cycles. The primary endpoint was 1-year disease-free survival rate. The secondary endpoints were disease-free survival, overall survival, and safety. @*Results@#Seventy-four patients were enrolled. One-year disease-free survival rate was 57.9%. Median disease-free and overall survival were 15.0 months (95% confidence interval [CI], 11.6 to 18.4) and 33.0 months (95% CI, 21.8 to 44.2), respectively. At the median follow-up of 32 months, 57 patients (77.0%) had recurrence including 11 patients whose recurrence was during the adjuvant treatment. Most of the recurrences were systemic (52 patients). Stage at the time of diagnosis (70.0% in IIA, 51.2% in IIB, p=0.006) were significantly related with 1-year disease-free survival rate. Toxicities were generally tolerable, with 53 events of grade 3 or 4 hematologic toxicity and four patients with febrile neutropenia. @*Conclusion@#Adjuvant gemcitabine and cisplatin chemotherapy followed by chemoradiotherapy with gemcitabine and maintenance gemcitabine showed efficacy and good tolerability in curatively resected pancreatic cancer.
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In the PALOMA-3 trial, the median progression-free survival (PFS) was longer among patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer (ABC) treated with palbociclib plus fulvestrant than those treated with placebo plus fulvestrant. This subgroup analysis examined the efficacy and safety of palbociclib among Korean patients enrolled in PALOMA-3 (n = 43 [palbociclib group, n = 24; placebo group, n = 19]). In both groups, > 40% of patients were pre/perimenopausal at enrollment. The median PFS was significantly prolonged with palbociclib vs. placebo (12.3 [95% confidence interval (CI), 9.1–not estimable] vs. 5.4 months [95% CI, 1.9–9.2]; hazard ratio, 0.40 [95% CI, 0.19–0.83]; one-sided p = 0.005), and the confirmed objective response was 21.1% and 11.8%, respectively (odds ratio, 2.0 [95% CI, 0.24–24.8]). Neutropenia was the most common adverse event associated with palbociclib. Overall, palbociclib plus fulvestrant was effective and generally safe among Korean patients with HR+/HER2− ABC, regardless of menopausal status.
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An emblem is a symbolic representational image that stands for a certain organization, concept, team, or society. This study investigated the emblems of the sleep societies in South Korea and the international sleep societies in which they were registered as members. Three South Korean sleep societies were found by searching for the keyword ‘sleep’ in the Korea Citation Index. Subsequently, we identified three international societies in which the three South Korean conferences participate. The emblems can be classified according to their composition. Taegeuk patterns represent yin and yang, electroencephalography that stands for the objective indicator of sleep, and the acronym or abbreviation indicating the name of the society. All emblems in this study were combinations of pictorial images and letters. The pictorial image of the Korean Sleep Research Society is the only emblem representing an inset with Hangeul. The emblem is a medium that conveys diverse meanings beyond representation. The societies have attempted to embody the identity as well as their directions.
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Purpose@#YoungPEARL (KCSG-BR15-10) trial demonstrated a significant progression-free survival (PFS) benefit for premenopausal patients with hormone receptor–positive/human epidermal growth factor receptor 2–negative (HR+/HER2–) metastatic breast cancer (MBC) for palbociclib plus exemestane with ovarian function suppression compared to capecitabine. However, the number of tamoxifen-sensitive premenopausal patients was small because most recurrences occurred early during adjuvant endocrine therapy (ET), with tamoxifen being the only drug used; hence, the data for these patients were limited. Here we present a subgroup analysis according to tamoxifen sensitivity from the YoungPEARL study. Materials and Methods Patients were randomized 1:1 to receive palbociclib+ET (oral exemestane 25 mg/day for 28 days, palbociclib 125 mg/day for 21 days, plus leuprolide 3.75 mg subcutaneously every 4 weeks) or chemotherapy (oral capecitabine 1,250 mg/m2 twice daily for 14 days every 3 weeks). Tamoxifen resistance was defined as: relapse while on adjuvant tamoxifen, relapse within 12 months of completing adjuvant tamoxifen, or progression while on first-line tamoxifen within 6 months for MBC. @*Results@#In total, 184 patients were randomized and 178 were included in the modified intention-to-treat population. PFS improvement in the palbociclib+ET group was observed in tamoxifen-sensitive patients (hazard ratio, 0.38; 95% confidence interval, 0.12 to 1.19). Furthermore, palbociclib+ET prolonged median PFS compared with capecitabine in tamoxifen-sensitive (20.5 months vs. 12.6 months) and tamoxifen-resistant (20.1 months vs. 14.5 months) patients. Palbociclib+ET demonstrated a higher rate of objective response, disease control, and clinical benefit in tamoxifen-sensitive patients. Conclusion This post hoc exploratory analysis suggests that palbociclib+ET is a promising therapeutic option for premenopausal HR+/HER2– MBC patients irrespective of tamoxifen sensitivity.