Skin cancer carries a lifetime risk nearly equal to that of all other cancers combined. Following is a graph [modified from K. H. Kraemer (1997). Proc. Natl. Acad. Sci. (USA) 94:11–14] depicting the age of onset of skin cancers in patients with or without XP, where the cumulative percentage of skin cancer is plotted against age. The non-XP curve is based on 29,757 cancers surveyed by the National Cancer Institute, and the curve representing those with XP is based on 63 skin cancers from the Xeroderma Pigmentosum Registry.

Provide an overview of the information contained in the graph. 

Key Concepts

Xeroderma Pigmentosum (XP)

Xeroderma Pigmentosum is a rare genetic disorder characterized by extreme sensitivity to ultraviolet (UV) light, leading to a significantly increased risk of skin cancers. Individuals with XP have mutations in genes responsible for DNA repair, particularly those involved in nucleotide excision repair, which is crucial for correcting UV-induced DNA damage. This condition highlights the importance of genetic factors in cancer susceptibility.

Cumulative Incidence

Cumulative incidence refers to the proportion of a population that develops a specific condition over a defined period. In the context of the graph, it illustrates the percentage of individuals diagnosed with skin cancer as they age, allowing for a comparison between those with XP and the general population. Understanding cumulative incidence is essential for assessing the impact of genetic predispositions on disease risk.

Age of Onset

The age of onset is the age at which symptoms of a disease first appear. In the case of skin cancer, the graph likely shows that individuals with XP develop skin cancers at a much younger age compared to those without the condition. Analyzing the age of onset helps in understanding the progression of diseases and the effectiveness of preventive measures in genetically predisposed populations.