Background Breast cancer is the most frequent cancer in women worldwide. Most breast cancer cases are estrogen receptor positive and epidermal growth factor receptor 2 negative (ER+/HER2-). A small proportion of these cases are metastatic with Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors being the mainstay of treatment. Evidence supports the existence of differences between the three approved cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in both preclinical and clinical settings. Abemaciclib appears to be capable of inhibiting other targets. Senescence and apoptosis took place at an earlier time and with lower concentrations of abemaciclib compared to treatment with palbociclib or ribociclib in preclinical models. Methods A search will be performed on the PubMed, Embase, and Web of Science databases following Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. A manual search of the San Antonio Breast Cancer Conference, American Society of Clinical Oncology annual conference, European Society of Medical Oncology annual conference, and European Society of Medical Oncology Breast annual conference will be performed. Discussion To our knowledge, no previous systematic review has evaluated the available evidence regarding the efficacy and safety of abemaciclib in MBC previously treated with palbociclib or ribociclib. This systematic review and meta-analysis will synthesize the existing data on the effectiveness and safety of abemaciclib after prior exposure to ribociclib or palbociclib in MBC. It will also identify the gap in the literature for potential future research. The results of this study will be of interest to multiple audiences including patients, their families, caregivers, and healthcare professionals. Results will be published in a peer-reviewed journal. Systematic review registration: PROSPERO CRD42022330355

Background: Breast cancer is the most common cancer among women worldwide. Most breast cancers are estrogen receptor-positive and epidermal growth factor receptor 2 negative (ER+/HER2-). A small proportion of these cases are metastatic, and cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors are the mainstay of treatment in this scenario. Evidence supports the existence of differences between the three approved cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in preclinical and clinical settings. However, literature regarding the use of a CDK4/6i in metastatic breast cancer patients (MBC) previously treated with another CDK4/6i is scarce. Methods: A search will be performed on the PubMed, Embase, and Web of Science databases following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. In addition, a manual search of the San Antonio Breast Cancer Conference, American Society of Clinical Oncology annual conference, European Society of Medical Oncology annual conference, and European Society of Medical Oncology Breast annual conference will be conducted. Discussion: To our knowledge, no previous systematic review has evaluated the available evidence regarding the efficacy and safety of CDK4/6i treatment in MBC previously treated with another CDK4/6i. This systematic review and meta-analysis will synthesise existing data on the effectiveness and safety of using a CDK4/6i after prior exposure to another in MBC. It will also identify gaps in the literature for potential future research. The results of this study will focus on multiple audiences including patients, their families, caregivers, and healthcare professionals. These results will be published in a peer-reviewed journal. Systematic review registration: PROSPERO CRD42022330355

Background: Human bocavirus (HBoV) is a viral pathogen from the genus Bocaparvovirus (family Parvoviridae, subfamily Parvovirinae) discovered in 2005. Most of available literature is about HBoV in children and adults with hematological malignancies and in otherwise healthy children with respiratory infections. Information regarding infection in the adult population with solid tumors is scarce. Case Report: We report the case of a 51-year-old male with metastatic castration resistant prostate cancer undergoing chemotherapy treatment who presented with fever, dyspnea, dry cough, and pleuritic pain. Imaging techniques showed signs of congestive heart failure. Symptoms, laboratory tests and echocardiography revealed a more probable infectious etiology. Antibiotic therapy was started. A polymerase chain reaction (PCR) test of nasopharyngeal exudate for respiratory viruses was positive for HBoV. The rest of the microbiological tests were negative. Bronchoalveolar lavage (BAL) was performed. Bacterial culture of BAL was negative while respiratory virus PCR confirmed positivity for HBoV. Antibiotic therapy was discontinued. The patient gradually recovered. Conclusions: Emerging infectious diseases are a notorious threat for immunocompromised populations such as solid tumor patients. This case is unique because to our knowledge this is the first case report article of HBoV in a solid tumor patient and because imaging techniques exhibited signs of congestive heart failure that did not correlate with the rest of the tests. It shows that unusual pathogens should be considered when managing serious clinical complications with uncommon presentations in cancer patients. Notable diagnostic efforts should be made to reach a diagnosis in these cases.