Poster Presentation Australasian Society for Dermatology Research Annual Scientific Meeting 2024

Unpredictable interdependence in the trajectory between diagnoses of multiple primary melanoma (#119)

Sam Kahler 1 , Chantal Rutjes 1 , Brigid Betz-Stablein 1 , Clare Primiero 1 , Dilki Jayasinghe 2 , Aideen McInerney-Leo 1 , Monika Janda 1 , Peter H Soyer 1
  1. Frazer Insitute, The University of Queensland, Dermatology Research Centre, Brisbane, Queensland, Australia
  2. Centre for Health Services Research, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia

Background

Surveillance for high-risk melanoma patients aims for early detection of subsequent melanoma before invasive transformation. In this scenario, excision of melanoma in situ should coincide with a reduction in invasive melanoma incidence. However, we report the unpredictable occurrence of invasive melanomas arising, amidst multiple melanoma in situ, throughout regular surveillance.

 

Methods

We analysed the retrospective chronological incidence of histopathology-confirmed melanoma diagnosed within a high-risk cohort receiving intensive surveillance. The cohort included 310 individuals accumulating 826 melanoma diagnoses within a follow-up of 2-20 years since first diagnosis. A subset of 197 individuals were diagnosed with multiple primary melanoma before a median age of 54. Sankey diagrams identified the incidence of subsequent invasive melanoma after prior trajectories of invasive and in situ melanoma.

 

Results

Sankey diagrams identified that invasive melanoma unpredictably arose throughout surveillance despite multiple prior melanoma in situ. Subsequent invasive melanoma was detected after approximately 15% of melanoma in situ diagnoses at each sequential diagnosis up to the sixth consecutive melanoma (Range 12-16%). The probability for a subsequent invasive melanoma was explored after trajectories of first and second melanoma. Individuals diagnosed with an initial in situ, followed by an invasive melanoma, were most likely to develop a subsequent second invasive melanoma (59%). The second invasive melanoma was detected either the next consecutive diagnosis (28% of 59%), or after a second in situ diagnosis (31% of 59%). Individuals with a first and second melanoma in situ, observed the lowest likelihood (22%) of developing a subsequent invasive melanoma.

 

Conclusions

Subsequent invasive melanoma were observed to unpredictably break through surveillance at a rate of 12-16% that warrants careful consideration in high-risk settings. Individuals that recorded a phenomenon of first melanoma followed by a subsequent invasive may warrant escalated surveillance for early detection of a subsequent invasive melanoma.