Mechanism of Action of Melatonin as a Potential Adjuvant Therapy in Inflammatory Bowel Disease and Colorectal Cancer

Inflammatory bowel disease (IBD), a continuum of chronic inflammatory diseases, is tightly associated with immune system dysregulation and dysbiosis, leading to inflammation in the gastrointestinal tract (GIT) and multiple extraintestinal manifestations. The pathogenesis of IBD is not completely elucidated. However, it is associated with an increased risk of colorectal cancer (CRC), which is one of the most common gastrointestinal malignancies. In both IBD and CRC, a complex interplay occurs between the immune system and gut microbiota (GM), leading to the alteration in GM composition. Melatonin, a neuroendocrine hormone, was found to be involved with this interplay, especially since it is present in high amounts in the gut, leading to some protective effects. Actually, melatonin enhances the integrity of the intestinal mucosal barrier, regulates the immune response, alleviates inflammation, and attenuates oxidative stress. Thereby, the authors summarize the multifactorial interaction of melatonin with IBD and with CRC, focusing on new findings related to the mechanisms of action of this hormone, in addition to its documented positive outcomes on the treatment of these two pathologies and possible future perspectives to use melatonin as an adjuvant therapy.

Abstract P4-07-25: Performance of Sentinel Lymph Node Biopsy after Neoadjuvant Chemotherapy in Clinically Node Positive Breast Cancer Patients: Systematic Review and Meta-analysis

Background There is an increase in the use of neoadjuvant chemotherapy (NACT) to downstage breast cancer. Sentinel lymph node biopsy (SLNB) has replaced Axillary lymph node dissection (ALND) as a standard of care for the treatment of breast cancer patients with negative axilla at presentation. However, the reliability of SLNB after NACT in patients with initially node-positive breast cancer is still controversial and debatable. This meta-analysis was conducted to investigate the accuracy and feasibility of SLNB after NACT in patients presented with positive axillary lymph nodes. Methods A comprehensive literature search was conducted using Medline, PubMed, Embase, Central, and SCOPUS for studies from their date of inception till April 2021 on the performance of SLNB following NACT in clinically node-positive breast cancer patients. We included prospective studies including breast cancer patients with positive lymph nodes at diagnosis, receiving neoadjuvant chemotherapy before undergoing an SLNB, irrespective of their molecular subtypes or breast cancer stage. We excluded retrospective studies, case reports, review articles, and letter to editors. The main outcomes of interest were the false negative rate (FNR) and the identification rate (IR). We also aimed to investigate the accuracy, negative predictive value (NPV), positive predictive value (PPV), specificity, and sensitivity of the SLNB procedure. Results An aggregate of 33 studies were included in this meta-analysis enrolling 4624 patients. The pooled identification rate (IR) was 88% (95% CI: 86-90; heterogeneity I2: 80.93 %) and the false negative rate (FNR) was 13% (95% CI: 11-15; heterogeneity I2: 72.31%). The pooled accuracy, NPV, PPV, specificity and sensitivity were 91.8% (95% CI: 69.39 -114.3), 82.8% (95%CI: 60.19-105.52), 98.2% (95%CI: 65.86 -130.63), 93.7% (95 CI%: 32.4 -155.03), 82.1% (95%CI: 58.38- 107.24) respectively. Conclusion In this comprehensive meta-analysis, we were able to review the largest number of studies (N=33) and patients (N=4624). We carried out this study with the intention to overcome the limitations of previously conducted meta-analyses such as including retrospective studies and a mixed population of clinically node-positive and node-negative breast cancer patients. Based on current findings, the usage of SLNB instead of ALND for the treatment of node-positive breast cancer patients is acceptable. However, further analysis is needed for the improvement of SLNB performance. Keywords: Sentinel lymph node biopsy; Breast cancer; Node positive; Neoadjuvant chemotherapy.

Citation Format: Mariam Zahwe, Abir Ghzaiel, Malak Ghezzawi, Sarah El Iskandarani, Marwa Diab, Lara Soueid, Miryam El Jibbawi, Ahmad Najia, Khalil El Asmar, Eman Sbaity. Performance of Sentinel Lymph Node Biopsy after Neoadjuvant Chemotherapy in Clinically Node Positive Breast Cancer Patients: Systematic Review and Meta-analysis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-25.

Estimating personal solar ultraviolet radiation exposure through time spent outdoors, ambient levels and modelling approaches

BACKGROUND

 Evidence on validation of surrogates applied to evaluate the personal exposure levels of solar ultraviolet radiation (UVR) in epidemiological studies is scarce.

OBJECTIVES

 To determine and compare the validity of three approaches, including (i) ambient UVR levels, (ii) time spent outdoors, and (iii) a modelling approach integrating the aforementioned parameters, to estimate personal UVR exposure over a period of six months among indoor and outdoor workers and in different seasons (summer/winter).

METHODS

 This validation study was part of the EU ICEPURE project and was performed between July 2010 and January 2011 in a convenience sample of indoor and outdoor workers in Catalunya - Spain. We developed linear regression models to quantify the variation in the objectively measured personal UVR exposure that could be explained, separately, by the ambient UVR, time spent outdoors, and modelled UVR levels.

RESULTS

Our 39 participants - mostly male and with a median age of 35 years- presented a median daily objectively measured UVR of 0.37 standard erythemal doses (SEDs). The UVR dose was statistically significantly higher in summer and for outdoor workers. The modelled personal UVR exposure and self-reported time spent outdoors could reasonably predict the variation in the objectively measured personal UVR levels (R² = (0.75, 0.79)), whereas ambient UVR was a poor predictor (R² =0.21). No notable differences were found between seasons or occupation.

CONCLUSIONS

 Time outdoors and our modelling approach were reliable predictors and of value to be applied in epidemiological studies of the health effects of current exposure to UVR.