Analysis of Second Primary Tumours in Cutaneous Lymphoma Populations

The elevated incidence of second primary tumors (SPTs) has been reported in certain subtypes of cutaneous T-cell lymphomas (CTCLs) and cutaneous B-cell lymphomas (CBCLs), but remains unclear for overall primary cutaneous lymphomas (PCLs). Using Surveillance, Epidemiology and End Results (SEER) data, we analyzed 20,970 patients with PCLs and evaluated standardized incidence ratios (SIRs) and survival outcomes of SPTs stratified by lymphoma subtype (indolent vs. aggressive). A total of 2,589 SPTs were identified (SIR = 1.40, 95% CI 1.35-1.45), with significantly elevated risks across sex, ethnicity, stage, latency, year of diagnosis, and treatment. Both indolent and aggressive CTCLs were associated with increased SPT risk, with SIRs of 1.27 (1.16-1.39) and 1.38 (1.11-1.69), respectively. Lymphatic and hematopoietic malignancies predominated in indolent CTCLs, along with thyroid cancer, whereas aggressive CTCLs were mainly associated with extranodal non-Hodgkin lymphoma and myeloma. Increased SPT incidence was also observed in indolent and aggressive CBCLs (SIR = 1.49 and 1.38), with indolent CBCLs showing a broad SPT spectrum including lung cancer and cutaneous melanoma. Patients younger than 30 years, with stage I disease or aggressive PCLs, had decreased age-adjusted overall and disease-specific survival, indicating a need for more intensive surveillance.