Space Oncology: A Comprehensive Scoping Review

Space exploration exposes astronauts to unique conditions such as microgravity and space radiation, potentially influencing gene expression and triggering carcinogenesis. Paradoxically, these extreme environments could uncover other pro-treatment aspects of cancer biology. Despite numerous reviews addressing these aspects in isolation, a comprehensive synthesis of the effects of space stressors on cancer development is incomplete. This scoping review aims to provide a holistic perspective on the influence of spaceflight and associated stressors-including gravitation (hyper- and microgravity), radiation, and vibration-on the potential for cancer development and altered cellular mechanisms. We adhered to the PRISMA-ScR checklist for our review. A multitiered search strategy was employed in English, starting with a preliminary keyword identification in Google Scholar and PubMed. Subsequently, the main search was conducted across five databases-Cochrane, Embase, PubMed, Scopus, and Web of Science-until 22 February 2024. All included studies were thoroughly assessed by two independent reviewers. Of the 15,553 identified articles, 158 were deemed eligible. The majority (92%) were experimental studies, predominantly cell-based (74.17%). Breast (15.19%), thyroid (13.92%), and hematopoietic (11.40%) cancers were the most frequently examined. Spaceflight stressors could affect different biological systems variably, with microgravity impacting spatial growth and metastasis, and cosmic radiation exerting both tumor-suppressive and mutagenic effects. Our findings highlight the need for large-scale, prolonged analog studies mimicking space conditions to enhance mission safety and shed light on the nuanced effects of space stressors on cancer. Additionally, further extensive studies need to be performed in the true weightlessness of spaceflight, both animal-based and on human tissue (cell cultures and potentially whole perfusion organ models), in addition to crew pre/intra/post-flight long-duration evaluations. Furthermore, this unique research avenue may reveal cancer cell sensitivities to these stressors, opening new pathways for innovative therapeutic strategies in cancer treatment.