Incidence of Non-Melanoma Skin Cancers in Patients with Chronic Lymphocytic Leukaemia: A Retrospective Study in a Bay of Plenty, New Zealand Population

Background/Aims: Chronic lymphocytic leukaemia (CLL) incurs an increased risk of developing second primary malignancies (SPMs). The pathogenesis underpinning this increased SPM risk is attributable to synergism between genetic aberrations, chronic immune suppression / dysfunction and CLL treatments. Specifically, CLL associated skin cancer is a well-documented phenomenon, with common malignancies such as squamous (SCC) and basal cell (BCC) carcinomas occurring at higher frequencies in CLL patients and are often of a more aggressive phenotype. The incidence of non-melanoma skin cancers (NMSCs) among New Zealand CLL patients is unknown, as NMSCs are not required to be reported to the New Zealand Cancer Registry. Accordingly, this study aimed to analyse the incidence of NMSC in CLL patients from the Bay of Plenty region of New Zealand.

Methods: We conducted a retrospective analysis of 213 CLL patients, who were referred to Bay of Plenty District Health Board (BOPDHB) between 2015 and 2020, for the occurrence of SPMs. Clinical notes were reviewed for the demographics of sex, age at time of CLL diagnosis, CLL treatments received and occurrence and type of NMSCs. A control group of 76 patients referred to BOPDHB haematology, for anaemia or thrombocytopenia, of which the cause subsequently remained unknown and was not associated with lymphoproliferative disease, was reviewed for primary malignancy (PM), occurrence and type. NMSC incidence was also compared to a local data, on overall NMSC incidence in the general Bay of Plenty population, in 2015.

Results: The predominant SPM types occurring in this CLL patient group were NMSCs. A total of 249 and 170 histological diagnoses of SCC and BCC were made in our group of CLL patients, respectively. Of the 213 CLL patients, 48.8% had a diagnosis of at least one NMSC, with median time between CLL and NMSC diagnosis of 5 years (range, -6 to 19 years). CLL patients that were diagnosed with NMSC developed a mean number of 3.93 ± 2.94 separate lesions, compared to 2.6 ± 1.7 lesions in our control population. Note: comparison of NMSC incidence data between CLL group and Bay of Plenty population

Conclusion: Patients with CLL are at increased risk of developing multiple NMSC lesions. Therefore, we believe CLL patients should be assessed by dermatologists or general practitioners for whole-body skin examination, 6 monthly following their CLL diagnosis. This strategy promotes early diagnosis, and patient education on importance of sun protection strategies to reduce NMSC risk. This is essential to the ongoing care of CLL patients in a NZ context, given the increased incidence of NMSC associated with CLL, in combination with the high levels of UV exposure and skin damage among the NZ general population. This study also highlights how NMSC disease burden is likely to be significantly underestimated due to a lack of data collection on these malignancies by the New Zealand Cancer Registry.