Rectal cancer, which accounts for approximately 40% of colorectal cancers, remains a major clinical concern. Recent advances in diagnostic imaging, surgical techniques, radiotherapy, and systemic treatment have steadily improved rectal cancer outcomes. Considering this, the Korean Rectal Cancer Multidisciplinary (KRCM) Committee has aimed to provide clinicians and policymakers with up-to-date, evidence-based clinical practice guidelines to support optimal decision-making, reflecting current evidence, the Korean healthcare context, and patient values and preferences. The Clinical Practice Guidelines for Rectal Cancer version 2.0 were developed through multidisciplinary collaboration with related academic societies, building upon and updating the KRCM Clinical Practice Guidelines version 1.0 (titled “Multidisciplinary guidelines for the management of rectal cancer”). These consensus guidelines of the KRCM were established based on a comprehensive literature review, evidence synthesis, with recommendation development guided by the GRADE (Grading of Recommendations Assessment, Development and Evaluation) methodology, and consideration of applicability in real-world clinical practice under the national health insurance system. Each recommendation has been presented with its strength and level of evidence.

Purpose: Guidelines from the aromatase inhibitor era for early breast cancer (EBC) treatment recommend maintaining a body mass index (BMI) below 25. In the current era of cyclin-dependent kinase (CDK) 4/6 inhibitors, now standard in metastatic breast cancer (MBC), limited data exist on treatment outcomes in obese patients. This study investigates how adiposity affects the treatment outcome of CDK 4/6 inhibitors in patients with hormone receptor–positive, human epidermal growth factor receptor 2–negative MBC. Materials and Methods: We searched PubMed, MEDLINE, and Embase databases, assessing efficacy outcomes such as progression-free survival (PFS) based on obesity markers, including BMI and visceral adipose tissue (VAT) index. Results: Twelve studies were reviewed, with seven studies and 1,812 patients included in a pooled meta-analysis. Among patients with BMI ≥ 25, modest improvement in PFS was observed, with a pooled hazard ratio (HR) of 0.944 (95% confidence interval [CI], 0.909 to 0.980; p=0.003). Besides, add-on analysis using VAT to define obesity revealed a notable PFS improvement, with a pooled HR of 0.452 (95% CI, 0.256 to 0.798; p=0.006). Conclusion While BMI-defined obesity showed slight PFS improvement with CDK 4/6 inhibitors and endocrine therapy, using VAT to define obesity revealed significant PFS gains. This highlights the need for further research on biomarker to clarify the role of adiposity in MBC, which may differ from its impact in EBC.

Purpose: Radiotherapy (RT) remains a cornerstone of curative treatment for localized and locally advanced prostate cancer. However, dose escalation to improve tumor control is often constrained by the proximity of the rectum, which increases the risk of gastrointestinal (GI) and genitourinary toxicities. Biodegradable rectal spacers inserted between the prostate and rectum have emerged as an effective approach to reduce rectal radiation exposure. This guideline provides evidence-based recommendations on indications, contraindications, procedural standards, and clinical management for biodegradable rectal spacer insertion during prostate cancer RT. Materials and Methods: This guideline was developed by a multidisciplinary expert panel through a systematic review of the literature, analysis of international guidelines (National Comprehensive Cancer Network, European Association of Urology, American Society for Radiation Oncology), and expert consensus among radiation oncologists, radiologists, and urologists with clinical experience in spacer insertion. The strength of each recommendation and the level of evidence were classified according to the modified GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) system. Results: Spacer insertion is conditionally recommended (Grade C, Level I) for patients receiving definitive external-beam RT without rectal invasion. It reduces the high-dose rectal irradiation volume (V70–75) by >50%, decreases acute GI toxicity, and helps maintain bowel-related quality of life. However, the benefit for late severe toxicity (grade 2 or higher) remains debated in recent meta-analyses. Contraindications include rectal invasion, anatomical inaccessibility, infection, and material hypersensitivity. Procedures should be performed under local anesthesia in a sterile environment by trained physicians. Short-course antibiotics and simulator-based training, including completion of multiple supervised cases, are advised. Conclusion Biodegradable rectal spacer insertion is clinically validated and effective in reducing acute rectal toxicity. Although pivotal trials demonstrated a favorable procedural safety profile, real-world postmarket data include reports of rare but severe procedural complications. This guideline provides standardized recommendations tailored to Korean clinical practice while remaining consistent with international standards, emphasizing the importance of operator training and careful patient selection.

Purpose: This study aimed to characterize the clinical patterns and severity of brain injury in neonates who survived extracorporeal membrane oxygenation (ECMO) therapy for acute respiratory failure during the neonatal period, to evaluate their short-term neurodevelopmental outcomes, and to identify the factors associated with these outcomes. Methods: We retrospectively reviewed the medical records of neonates who survived ECMO between 2018 and 2024. Based on brain magnetic resonance imaging (MRI) findings, the patients were classified into two groups: no/mild and moderate/severe brain injury. Neurodevelopmental outcomes were assessed at 12–40 months of age using the Bayley Scale of Infant Development II/III and/or the Korean Developmental Screening Test. Results: Among the 19 neonates included in the study, 18 (94.7%) showed varying degrees of brain injury on MRI (mild: 12, moderate: 1, severe: 5). Neonates with moderate/severe brain injury had significantly longer durations of ECMO support and extended durations of mechanical ventilation and were more likely to receive continuous renal replacement therapy than those with no or mild injury. Developmental delay was identified in 36.8% of survivors and was significantly associated with prolonged mechanical ventilation, longer neonatal intensive care unit stays, and a higher incidence of seizures. Conclusion Brain injury is frequently observed on MRI in neonates treated with ECMO. However, its direct association with adverse neurodevelopmental outcomes is not definitive. Since MRI findings alone cannot predict developmental outcomes, clinical and environmental factors should be integrated into prognostic assessments.

Background: Active surveillance (AS) has emerged as a viable management strategy for low-risk papillary thyroid microcarcinoma (PTMC), following pioneering trials at Kuma Hospital and the Cancer Institute Hospital in Japan. Numerous prospective cohort studies have since validated AS as a management option for low-risk PTMC, leading to its inclusion in thyroid cancer guidelines across various countries. From 2016 to 2020, the Multicenter Prospective Cohort Study of Active Surveillance on Papillary Thyroid Microcarcinoma (MAeSTro) enrolled 1,177 patients, providing comprehensive data on PTMC progression, sonographic predictors of progression, quality of life, surgical outcomes, and cost-effectiveness when comparing AS to immediate surgery. The second phase of MAeSTro (MAeSTro-EXP) expands AS to low-risk papillary thyroid carcinoma (PTC) tumors larger than 1 cm, driven by the hypothesis that overall risk assessment outweighs absolute tumor size in surgical decision-making. Methods: This protocol aims to address whether limiting AS to tumors smaller than 1 cm may result in unnecessary surgeries for low-risk PTCs detected during their rapid initial growth phase. By expanding the AS criteria to include tumors up to 1.5 cm, while simultaneously refining and standardizing the criteria for risk assessment and disease progression, we aim to minimize overtreatment and maintain rigorous monitoring to improve patient outcomes. Conclusion This study will contribute to optimizing AS guidelines and enhance our understanding of the natural course and appropriate management of low-risk PTCs. Additionally, MAeSTro-EXP involves a multinational collaboration between South Korea and Australia. This cross-country study aims to identify cultural and racial differences in the management of low-risk PTC, thereby enriching the global understanding of AS practices and their applicability across diverse populations.

Purpose: The technique for transanal resection of rectal tumors has evolved from conventional methods to minimally invasive approaches. However, the research comparing long-term results between these approaches is limited. Methods: Between 2016 and 2022, a total of 133 patients who underwent transanal excision were analyzed. Patients were classified into 2 groups according to surgical approach: conventional transanal approach (CTA) and minimally invasive transanal approach (MTA). Medical records were analyzed to compare surgical and oncological outcomes between the 2 groups. Results: There were no significant differences observed in patient’s demographics and tumor characteristics, except the MTA group exhibited a statistically longer distance from the anal verge. Although statistical significance was not reached, the MTA group demonstrated a 100% margin-negative rate in contrast to the CTA group, which had worse outcomes for both margin status and fragmentation. Recurrence was observed only in the CTA group containing pT1 rectal cancer and grade 1 neuroendocrine tumor, with negative margins and no fragmentation. Conclusion The minimally invasive approach did not demonstrate statistical superiority but showed technical feasibility through the absence of margin-positive cases and the use of the clip handle method. Further studies are needed to validate these findings and assess broader applicability.

Purpose: The technique for transanal resection of rectal tumors has evolved from conventional methods to minimally invasive approaches. However, the research comparing long-term results between these approaches is limited. Methods: Between 2016 and 2022, a total of 133 patients who underwent transanal excision were analyzed. Patients were classified into 2 groups according to surgical approach: conventional transanal approach (CTA) and minimally invasive transanal approach (MTA). Medical records were analyzed to compare surgical and oncological outcomes between the 2 groups. Results: There were no significant differences observed in patient’s demographics and tumor characteristics, except the MTA group exhibited a statistically longer distance from the anal verge. Although statistical significance was not reached, the MTA group demonstrated a 100% margin-negative rate in contrast to the CTA group, which had worse outcomes for both margin status and fragmentation. Recurrence was observed only in the CTA group containing pT1 rectal cancer and grade 1 neuroendocrine tumor, with negative margins and no fragmentation. Conclusion The minimally invasive approach did not demonstrate statistical superiority but showed technical feasibility through the absence of margin-positive cases and the use of the clip handle method. Further studies are needed to validate these findings and assess broader applicability.

Purpose: The technique for transanal resection of rectal tumors has evolved from conventional methods to minimally invasive approaches. However, the research comparing long-term results between these approaches is limited. Methods: Between 2016 and 2022, a total of 133 patients who underwent transanal excision were analyzed. Patients were classified into 2 groups according to surgical approach: conventional transanal approach (CTA) and minimally invasive transanal approach (MTA). Medical records were analyzed to compare surgical and oncological outcomes between the 2 groups. Results: There were no significant differences observed in patient’s demographics and tumor characteristics, except the MTA group exhibited a statistically longer distance from the anal verge. Although statistical significance was not reached, the MTA group demonstrated a 100% margin-negative rate in contrast to the CTA group, which had worse outcomes for both margin status and fragmentation. Recurrence was observed only in the CTA group containing pT1 rectal cancer and grade 1 neuroendocrine tumor, with negative margins and no fragmentation. Conclusion The minimally invasive approach did not demonstrate statistical superiority but showed technical feasibility through the absence of margin-positive cases and the use of the clip handle method. Further studies are needed to validate these findings and assess broader applicability.

Purpose: While fluoropyrimidine-based chemotherapy regimens are recommended second-line treatment for patients with advanced biliary tract cancer (BTC), there have been no studies comparing different regimens head-to-head. Materials and Methods: We performed individual patient-level meta-analysis based on data from the intention-to-treat population of the phase 2b NIFTY trial (liposomal irinotecan [nal-IRI] plus fluorouracil and leucovorin [5-FU/LV] vs. 5-FU/LV; NCT03542508) and the phase 2 FIReFOX trial (modified oxaliplatin plus 5-FU/LV [mFOLFOX] vs. modified irinotecan plus 5-FU/LV [mFOLFIRI]; NCT03464968). Pairwise log-rank tests and multivariable analysis using Cox proportional hazards modeling with shared frailty to account for the trial's effect were used to compare overall survival (OS) between regimens. Results: A total of 277 patients were included. The nal-IRI plus 5-FU/LV group (n=88) showed significantly better OS compared to the mFOLFOX group (n=49, pairwise log-rank, p=0.02), and mFOLFIRI group (n=50, p=0.03). Multivariable analysis showed consistent trends in OS with adjusted hazard ratios of 1.39 (mFOLFOX vs. nal-IRI plus 5-FU/LV: 95% confidence interval [CI], 0.93 to 2.07; p=0.11) and 1.36 (mFOLFIRI vs. nal-IRI plus 5-FU/LV: 95% CI, 0.92 to 2.03; p=0.13), respectively. Compared to the 5-FU/LV group, the mFOLFOX group and the mFOLFIRI group did not show differences in terms of OS (pairwise log-rank p=0.83 and p=0.58, respectively). The nal-IRI plus 5-FU/LV group experienced more frequent diarrhea, while the mFOLFOX group experienced peripheral neuropathy. Conclusion Nal-IRI plus 5-FU/LV showed favorable survival outcomes compared to mFOLFOX, mFOLFIRI, or 5-FU/LV. The safety profiles of these regimens should be considered along with efficacy.

Background: Active surveillance (AS) has emerged as a viable management strategy for low-risk papillary thyroid microcarcinoma (PTMC), following pioneering trials at Kuma Hospital and the Cancer Institute Hospital in Japan. Numerous prospective cohort studies have since validated AS as a management option for low-risk PTMC, leading to its inclusion in thyroid cancer guidelines across various countries. From 2016 to 2020, the Multicenter Prospective Cohort Study of Active Surveillance on Papillary Thyroid Microcarcinoma (MAeSTro) enrolled 1,177 patients, providing comprehensive data on PTMC progression, sonographic predictors of progression, quality of life, surgical outcomes, and cost-effectiveness when comparing AS to immediate surgery. The second phase of MAeSTro (MAeSTro-EXP) expands AS to low-risk papillary thyroid carcinoma (PTC) tumors larger than 1 cm, driven by the hypothesis that overall risk assessment outweighs absolute tumor size in surgical decision-making. Methods: This protocol aims to address whether limiting AS to tumors smaller than 1 cm may result in unnecessary surgeries for low-risk PTCs detected during their rapid initial growth phase. By expanding the AS criteria to include tumors up to 1.5 cm, while simultaneously refining and standardizing the criteria for risk assessment and disease progression, we aim to minimize overtreatment and maintain rigorous monitoring to improve patient outcomes. Conclusion This study will contribute to optimizing AS guidelines and enhance our understanding of the natural course and appropriate management of low-risk PTCs. Additionally, MAeSTro-EXP involves a multinational collaboration between South Korea and Australia. This cross-country study aims to identify cultural and racial differences in the management of low-risk PTC, thereby enriching the global understanding of AS practices and their applicability across diverse populations.