Association of Genetic Alterations with Prognosis in Extramammary Paget's Disease: Insights into the Involvement of somatic CDKN2A variants in Poor Prognosis.

Background: Previous studies reported the mutational landscape in extramammary Paget's disease (EMPD); however, the prognostic implications of genetic alterations remain unexplored. While CDKN2A loss is known to be associated with tumor progression or poor prognosis in some types of cancer, its significance in EMPD has not been investigated.

Objectives: To examine the association between common genetic alterations and prognosis in EMPD.

Methods: This is a retrospective cohort study analyzing EMPD cases registered until January 2024 in the Center for Cancer Genomics and Advanced Therapeutics database, which is a nationwide database recording clinical data and comprehensive genomic profiling (CGP) test results in Japan.

Results: A total of 167 cases were recorded in the database, with CDKN2A loss being the most frequent genetic variant. Survival analysis was conducted on 127 cases. Survival from chemotherapy initiation was analyzed with adjusting for length bias inherent in the database using the Kaplan-Meier estimator, an established adjustment method. Cases with BRCA2-mutant tumors (n=18) had a worse prognosis than those with BRCA2-wild-type tumors (n=109; HR=2.97, 95% CI 1.46-6.01, p=0.003). Additionally, CDKN2A-mutant group (n=72) had a significantly worse prognosis than those with CDKN2A-wild-type group (n=55; HR=1.81, 95% CI 1.06-3.07, p=0.029). Most CDKN2A variants were pathogenic, primarily characterized by loss, while most BRCA2 variants were variants of uncertain significance. In the analysis of survival from CGP enrollment based on Eastern Cooperative Oncology Group performance status (ECOG-PS), cases with ECOG-PS 1 at the time of CGP enrollment had significantly poorer prognosis than those with ECOG-PS 0 (p=0.034; median survival time, 531 vs. 259 days).

Conclusions: Somatic CDKN2A variant, mainly exhibiting loss, may be associated with poor prognosis in EMPD. Cases with BRCA2-mutant cancer might also have a worse prognosis in EMPD. In addition, CGP testing before PS deteriorates is preferable, considering the observed median survival of individuals undergoing CGP tests in an ECOG-PS-1 condition was less than 9 months.