P54 Blood tumour burden does not correlate with skin tumour burden in early-stage mycosis fungoides: analysis of the PROspective Cutaneous Lymphoma International Prognostic Index international registry

Abstract

Abstract Blood involvement B1, defined as absolute counts 250–1000 IU of an aberrant CD4+CD7– or CD4+CD26– phenotype, may be found in early-stage mycosis fungoides (MF). There is a suggestion that B1 blood involvement is a poor prognostic marker, but there is limited evidence investigating the prognostic significance of B0 or B1 blood involvement in early-stage MF. Loss of CD26 and/or CD7 expression on CD4 cells may occur in MF; however, it is unclear whether loss of either one of these immunophenotypic markers bears more significance on prognosis. For B2 blood involvement (> 1000 IU), the International Society for Cutaneous Lymphomas (ISCL) criteria define Sézary syndrome as CD26 loss of > 30% or CD7 loss of > 40%. Understanding the impact of B1 and comparative loss of CD26 and/or CD7 in early-stage MF may allow patients at higher risk of stage progression to be identified and selected for better therapeutic options. The aims of this study were to analyse B0 vs. B1 blood involvement at diagnosis in patients with early-stage MF (IA–IIA) and evaluate the relative CD4+CD7– and CD4+CD26– absolute cell counts. Prospective data from the PROCLIPI registry were analysed. Ninety-four patients with early-stage MF were identified from our database, 67 (71%) of whom were B0 [stage IA, n = 23 (34%); stage IB, n = 24 (36%); stage IIA, n = 20 (30%)] and 27 (29%) were B1 [stage IA, n = 12 (44%); stage IB, n = 10 (37%); stage IIA, n = 5 (18%)]. Median age at diagnosis in B0 patients was 59 years (range 20–91) vs. 61 years (range 21–81) in B1 patients. Median CD4+CD7– cell count was 16.4% (range 0–41%) in patients with B0 involvement and 28.1% (range12–45%) in B1 patients. Median CD4+CD26– cell count was 16% (range 0–39.1%) in B0 and 28% (range 0–44%) in B1 patients. The Median Modified Severity-Weighted Assessment Tool score in B1 patients was 11 (range 1–73) vs. 20 (range 0.5–100) in B0 patients. There was no significant difference in progression to the advanced stage between B0 and B1 (P = 0.112) patients or overall survival between B0 and B1 patients during median follow-ups of 49 months and 45 months, respectively. These results suggest that blood tumour burden in early-stage MF, measured by the percentage aberrancy in CD4+CD7– and CD4+CD26– cell counts, does not correlate with clinical stage, skin tumour burden or stage progression. This suggests that in B1 involvement, atypical lymphocytes may lose their skin-homing properties. Interestingly, levels of CD4+7– and CD26– are similar in B1 involvement, despite the ISCL criteria defining B2 involvement as a lower relative loss of CD26–. Identifying B1 patients is important as certain therapeutic options such as extracorporeal photopheresis and mogamulizumab may be indicated in patients with early-stage MF, refractory to skin-directed therapies.