Diagnosis of Leukemia or Lymphoma in the Central Nervous System by Beta₂-Microglobulin Determination

To detect early relapse in the central nervous systems (CNS) of patients with acute leukemia or lymphoma, we measured levels of beta₂-microglobulin (β₂m) in serum and cerebrospinal fluid (CSF). CSF levels were significantly higher in patients with leukemia (P<0.001) or lymphoma (P<0.02) with clinical evidence of CNS involvement than in those without this complication. When serum and CSF levels were measured simultaneously, the CSF level of β₂m was significantly higher than the serum level in patients with acute leukemia and lymphoma with CNS involvement (P = 0.05), but not in patients without CNS involvement. Serial determination of CSF β₂m correlated well with the clinical appearance and disappearance of CNS involvement. These data suggest that serial and simultaneous determination of β₂m in serum and CSF may be useful in early diagnosis of CNS involvement and in monitoring intrathecal therapy in patients with acute leukemia or lymphoma. (N Engl J Med. 1980; 303:718–22.) THE current treatment of patients with acute leukemia or advanced lymphoma uses improved drug regimens and supportive care, and routinely produces a high incidence of complete remissions and notably prolongs survival.^{1 2 3 4 5} Unfortunately, many patients who have complete clinical remissions subsequently have relapses. Although not very common, one of the more unfavorable sites for relapse is the central nervous system (CNS).^{6 7 8 9 10 11 12 13 14} Protected by the blood–brain barrier, residual tumor cells evade destruction by systemic chemotherapy and multiply in the CNS. They ultimately produce overt relapse and often death. In approximately 20 to 40 per cent of CNS relapses, the patient may still.