Melanoma risk in astronauts: Clinical screening, surveillance, and the microgravity paradox

Astronauts show significantly elevated melanoma incidence and mortality relative to the general population, a finding with direct relevance to an expanding civilian spaceflight population. We conducted a systematic review to characterize this risk and translate it into practical guidance for dermatologists. Of 11 studies meeting eligibility criteria, only one was a human clinical or epidemiological study; the remainder were experimental, and consistently showed that simulated microgravity suppresses melanoma proliferation, adhesion, migration, and invasion while promoting apoptosis through collapse of FAK-RhoA-mTORC1-ERK1/2 mechanotransduction, a laboratory finding in direct tension with the clinical risk observed in astronauts. The majority of astronauts studied were career pilots, an occupational group with an independently established approximately two-fold melanoma incidence and elevated mortality specifically among pilots from cockpit UVA exposure accrued before spaceflight, which we identify as the most clinically substantial explanation for this paradox. We recommend risk-stratified pre-flight total-body skin examination with dermoscopy, deferral of dermatologic management to the ground rather than in-flight, post-flight surveillance after long-duration missions, and individualized counseling that distinguishes career astronauts from the demographically distinct civilian spaceflight population now emerging through missions such as Inspiration4 and Polaris Dawn.