Detection of a T Cell Clone in the Peripheral Blood at Diagnosis and in the Skin in Complete Clinical Remission after PUVA and Interferon-α Combination Therapy Is Not a Negative Prognostic Factor in Early Mycosis Fungoides.
Authors: Gaia Goteri , Serena Rupoli , Stefano Pulini , Angela Tassetti , Renzo Ranaldi , Rita Scortechini Anna , Roberta Capretti , Alessandra Filosa , Doriana Morichetti , Simonetta Mulattieri , Pietro Leoni 
Published: April 2020

Abstract
In the skin of 50–75% patients with early mycosis fungoides (MF) a dominant T-cell receptor (TCR) γ gene rearrangement can be detected. An identical T-cell clone is also detectable in the peripheral blood (PB) in 15–40% of these patients, as well as in 39–61% of skin biopsies showing histological remission after therapy. At the present time, it is still unclear if molecular analyses might be helpful to recognize an unfavourable subset of patients less responsive to skin-directed therapy or with a higher risk of disease recurrence. 89 patients (56 men, 33 women) with a median age of 60 years (range, 17–80), with a histologically confirmed diagnosis of early MF, were treated with a combination protocol of PUVA and low dose IFN-α for 14 months and then closely followed up. Only patients with a dominant clone in the affected skin at diagnosis, and in whom peripheral blood samples at diagnosis and a second tissue biopsy at the end of treatment were available, were selected for the present study. Twenty-four patients (10 men, 14 women; median age 62.5 yrs, range 17–77; 6 in stage IA, 15 IB, 3 IIA) met the inclusion criteria. PCR amplification for TCR γ gene was performed on DNA extracted from formalin-fixed and paraffin-embedded skin tissue samples and from frozen PB lymphocytes, as previously reported. Amplification products were visualised by 10% polyacrylamide gel electrophoresis at the same time, on the same gel, thereby allowing precise comparison of the dominant clonal populations. In one patient the identity of T-cell clones in the skin at diagnosis and at the end of therapy was assessed by sequencing analysis. After a mean time of 4 months (range 1–11), all 24 patients responded to the combination therapy, obtaining a clinical complete remission (CCR), even if three of them showed histological persistence of disease. During the follow-up, 11 patients had a disease recurrence (median time 70 months range 27–108). PCR analysis of TCR γ gene in the PB showed a circulating T-cell clone identical to the one detected in the skin in 9 cases (37.5%) at diagnosis. An identical T-cell clone was observed in the skin at the end of therapy in 17 cases (71%). Disease-free survival curves plotted by Kaplan-Meier method showed that patients with or without a peripheral T cell clone did not behave differently, that is, half of them would have experienced a relapse after a similar period of time in any case. The same behaviour was observed in patients showing different molecular responses after therapy. Only in one third of patients a molecular cure for the disease could be obtained by combination IFN-α and PUVA therapy, since a high rate of persistence of monoclonal PCR signals following CR was observed (71% of CR cases with a dominant clone at diagnosis); surprisingly, such a molecular outcome seems not to protect patients from subsequent disease relapses. On the other hand, our data seems to indicate that the combination of a skin-directed therapy like PUVA in addition to the systemic immunoregulatory effects of IFN-α may abolish the negative influence of a circulating clone.