The prognostic value of testicular biopsy in childhood acute lymphoblastic leukemia: a report from the Childrens Cancer Study Group.

One of the objectives of Childrens Cancer Study Group (CCSG) study 141 (CCG-141) was to determine the frequency of occult testicular leukemia (TL) after 3 years of disease-free survival (DFS) and to retreat boys with occult TL to prolong their subsequent DFS. Of the 494 boys entered on study, 255 (51.6%) were in complete continuous remission (CCR) 3 years after entering remission and an additional eight were in CCR 3 years after localized extramedullary relapse and retreatment; 263 boys were eligible for testicular biopsy. Elective testicular biopsy was performed on 235 (89.4%) boys. Of the 204 (86.8%) boys with negative biopsies, 175 (85.8%) remained in CCR 10 to 12 years after diagnosis and 25 (12.3%) relapsed, 11 (44%) of whom died. Isolated overt TL occurred in four (2.0%) and all remained in CCR 22+ to 60+ months after re-treatment. Of the 26 boys with occult TL, 16 (62%) remained in CCR. Ten (38%) relapsed despite local testicular irradiation and systemic re-treatment; six of the 10 died. Of the 26 boys who did not undergo biopsy, 21 (80.8%) remained in CCR; two (7.7%) developed isolated overt TL. DFS after testicular biopsy was significantly better in boys without occult TL (P = .001). Occult TL after 3 years of CCR represents aggressive minimal-residual disease and carries a worse prognosis than absence of TL. Initial treatment should be directed at obviating occult and overt testicular relapse. Conventional therapy as used in this study was suboptimal in preventing subsequent bone marrow (BM) relapse and death. If occult TR is identified during or at the end of planned therapy, a higher salvage rate may require intensified alternate therapy. As such, testicular biopsies may be clinically useful. Further investigation is limited by the relative rarity of, and the lack of identifying features in boys with occult TL.