Incidence and prognostic significance of blood lymphocyte clonal excess in localized non-Hodgkin's lymphoma.

Despite elaborate staging procedures, a substantial number of patients with localized NHL experience dissemination after local therapy, indicating that current routine methods are insufficient to detect tumour spread. We have used flow cytometric clonal excess (CE) analysis of peripheral blood in conjunction with routine staging procedures to study the occurrence of occult leukaemic spread in patients with localized NHL stages I, IE and IIE. CE in peripheral blood was a rare finding, identified in only 11% (14/130), and slightly more frequent in low-grade NHL, 20% compared to high-grade NHL, 7%. There was no correlation to any of the other major prognostic factors studied. Occult tumour spread would suggest an increased risk of relapse and possibly a decreased survival after local therapy. Among 93 patients given only local treatment there was an increased risk of relapse in those with low-grade malignant lymphomas and CE, which was not found in patients with high-grade malignant lymphomas and CE. CE in peripheral blood had no influence on survival in either of the histologic groups. A tentative explanation is that circulating lymphoma cells represent indolent populations irrespective of the histology of the primary tumour. The malignant nature of such a lymphoma spread might not be obvious during this rather limited follow-up of a median 34 months. The clinical interpretation is that the existence of CE in peripheral blood in patients with localized high-grade NHL should have no influence on the choice of therapy. In localized low-grade lymphoma the same therapeutic attitude which applies to widespread disease might be considered.