Early-Onset Cancer: An Epidemiologic Perspective examines cancers diagnosed before age 50 through a population-based lens and argues that interpretation must be site specific, cohort aware, and grounded in care pathways, rather than treated as a single phenomenon. The introduction synthesizes global magnitude, cohort effects and clinico-biological distinctiveness, explains why population registries are indispensable for measuring trends, stage, survival and equity, and frames the detection versus disease question alongside plausible mechanisms in genetics, the exposome, epigenetics and the microbiome.
Against this background, five registry-anchored studies are presented. A Geneva analysis of testicular cancer shows incidence concentrated under 40, improving stage-specific survival over decades, and a clear excess of second primaries in survivors. Two studies build a dedicated framework for young breast cancer: a registry cohort with validated first locoregional and first distant recurrence endpoints, linkage to genetic counselling, and reconstructed reproductive history, followed by a recurrence analysis that provides absolute risks and timing by age within the young band, stage, receptor status and surgical margins. A Swiss multicentre study situates care nationally, confirming high survival with guideline-concordant therapy and highlighting geographic variability in components of care, with outcomes chiefly driven by stage and biology. Finally, a sex and gender burden profile in 20- to 49-year-olds quantifies the higher incidence in women, clarifies the contribution of breast, thyroid and melanoma to invasive diagnoses, and treats the large CIN3 burden as a screening-performance signal.
The conclusions return to the central premise of this thesis: early-onset cancer is best interpreted by site, cohort and care pathway, and population-based methods are essential to produce comparable, decision-relevant indicators. Overall, the thesis translates a broad perspective on early-onset cancer into comparable, decision-ready indicators. Ongoing projects extend this logic to Vaud and Geneva incidence with outcomes, a national early-onset colorectal analysis with preliminary evidence of an adverse stage mix, and an all-age survivorship and Right-toBe-Forgotten study with specific attention to younger survivors. The next phase keeps the same discipline of population-based data, standardized outcomes and purposeful linkages, while adding timeliness and aetiologic depth so trends are not only described but acted upon.
