Aim:
Cutaneous T-cell lymphomas (CTCL) are typically incurable, associated with significant symptom burden over prolonged time. Unique hurdles to diagnosis arise from disease rarity, overlapping morphological appearances and low biopsy-rates. This epidemiological study investigated the incidence of CTCL in Australia, and compared the geospatial distribution to (i) all rare cancers, (ii) dermatologist-density, and (iii) explored a possible causal relationship between CTCL and solar ultraviolet (UV) exposure.
Method:
All CTCL diagnoses from 1/1/2000-31/12/2019 and in persons >15 years, were obtained from the nation-wide dataset of mandatorily reported cancers. Residential areas were categorised according to federally-approved definitions. Bayesian spatial incidence models were applied.
Results:
The age-standardised incidence of CTCL was 7.7 [95%CI 7.4-7.9] per million people, equating to 285 new diagnoses per year in Australia.
Diagnostic disparity was seen between states/territories, with lower diagnosis rates in rural/remote and socio-economically disadvantaged areas. Standardised incidence ratios (SIR) exceeded the national average within the more densely populated capital cities.
Compared to SIR of all rare cancers, marked geospatial differences were seen. Consistencies between CTCL distribution and dermatologist-density were observed. No parallels were evident between the geospatial distribution of CTCL and the solar UV Index of Australia.
Conclusion:
Geographical heterogeneity exists in the distribution of CTCL across Australia, with SIR tending to reflect population density. Geospatial patterns of CTCL differed significantly from that of all rare cancers. Although these data do not support a causative link with UV exposure, the parallels between the geographical distributions of CTCL and dermatologist-density may suggest diagnostic-scrutiny as a confounding association.
