Changes in the Levels of CD4 + and CD8 + T-Lymphocytes After Strontium-89 Chloride Therapy for Painful Bone Metastases in Patients Correlate with Treatment Efficacy

The aim of this study was to evaluate changes in the peripheral blood CD₄ ⁺ and CD₈ ⁺ T-lymphocyte populations following strontium-89 chloride (⁸⁹SrCl₂) therapy for painful bone metastases and to relate these changes to a therapeutic response. Forty-two (42) patients with painful bone metastases were treated with 148 MBq (4 mCi) of ⁸⁹SrCl₂. Blood samples were drawn before and monthly for 6 months after the treatment. CD₄ ⁺ and CD₈ ⁺ T-lymphocyte levels were measured using flow cytometry. The number of bone metastases and the pain score were used to assess the effect of therapy. Before the administration of ⁸⁹SrCl₂, the ratio of CD₄ ⁺ to CD₈ ⁺ T-lymphocytes was lower in patients with bone metastases than in the control subjects (p < 0.01); after therapy, the ratio increased up to the fourth month and then gradually declined to pretreatment levels. Responders had higher post-therapeutic ratios of CD₄ ⁺ to CD₈ ⁺ than nonresponders. There was a good correlation between the ratio of CD₄ ⁺ to CD₈ ⁺ and both the number of bone metastases and the pain score. The ratio of CD₄ ⁺ to CD₈ ⁺ T-lymphocytes correlated strongly with the response of bone metastases to ⁸⁹SrCl₂, and therefore, may be used as an indicator of ⁸⁹SrCl₂ efficacy.