Prognostic value of serum β-2 microglobulin in low-grade lymphoma

Objective: To evaluate serum beta-2 microglobulin (β-2M) and other prognostic indicators in previously untreated low-grade lymphoma. Design: Cohort study of 80 patients with uniformly treated low-grade lymphoma, followed for a median of 21 months. These 80 patients, all of whom had serum β-2M drawn within 2 weeks before starting therapy, were derived from a cohort of 119 previously untreated patients entered into one of three clinical trials. Setting: Tertiary referral cancer center. Patients: Eighty previously untreated stage I to IV patients (mean age, 55 years). Intervention: Treatment was given according to Ann Arbor stage: Patients in stage IV were treated with CHOP-bleomycin and maintained on Interferon therapy; those in stage III received CHOP-bleomycin and radiotherapy; and those in stages I and II received COP-bleomycin and radiotherapy. Measurements: Outcome was determined by assessing complete remission rate and time to treatment failure. Univariate and multivariate analyses were used. Results: The complete remission rate for patients with a β-2M level of 3.0 mg/L or greater was 36% compared with 71% for those with a level of less than 3.0 mg/L. Using multivariate analysis that tested β-2M as a continuous variable, it was selected as the most significant factor for complete response. The adjusted odds ratio was 0.285 (95% CI, 0.101 to 0.809). The Ann Arbor stage had marginal significance (adjusted odds ratio, 0.435; CI, 0.150 to 1.263). For time to treatment failure, β-2M was the only variable retained in the multivariate model. At 42 months, no patient with a β-2M level of 3.0 mg/L or greater was projected to be in remission as compared with 85% of patients with a β-2M level of less than 3.0 mg/L. Conclusions: The serum β-2M level is a good predictor of complete response and time to treatment failure. A larger number of patients should be studied to clarify the role of other potentially independent variables such as stage and age.