MOLECULAR-DETECTION OF ACUTE LYMPHOBLASTIC-LEUKEMIA IN BOYS WITH TESTICULAR RELAPSE

Aims-To determine the role of polymerase chain reaction (PCR) based mi nimal residual disease (MRD) detection of leukaemia specific DNA in te sticular relapse in childhood acute lymphoblastic leukaemia. Methods-D NA was obtained from archival testicular and bone marrow samples from boys with acute lymphoblastic leukaemia who relapsed in the testes. Ov erlapping DJ, clone specific primers derived from clonal immunoglobuli n heavy chain (IgH) gene rearrangement in each case were used to analy se testicular or bone marrow DNA. Results-Histologically normal end of treatment testicular biopsies in the five patients in longterm remiss ion were all MRD negative, but MRD positive in three of six boys with subsequent testicular relapse. Histologically normal bone marrow sampl es taken at the end of treatment were MRD negative in five of seven ca ses, but MRD positive in all cases at the time of isolated testicular relapse. Three boys with unilateral testicular relapse underwent unila teral orchidectomy, rather than bilateral testicular irradiation, as p art of their treatment. Two of these boys were MRD positive in the his tologically uninvolved testes, and both had subsequent relapses either in the testes or the bone marrow, while the MRD negative patient has not had a testicular relapse. Conclusions-The presence of MRD in testi cular tissue can be assayed with a PCR based method to detect clone sp ecific antigen receptor gene rearrangements. In this setting, PCR is m ore sensitive than conventional testicular histology for predicting cl inical outcomes. MRD assays might be useful in the management of boys at the time of isolated testicular relapse, to confirm the presence of unilateral testicular disease.