Strontium-89 Chloride Delivery for Painful Bone Metastasis in Patients with History of Previous Radiation

Abstract

Re-irradiation of previously irradiated site must be done with careful consideration to minimizing dose to organs at risk. In particular, re-irradiation of the spine carries significant morbidity due to risk of myelitis. Strontium-89 chloride (Sr-89) is widely used for treatment of painful bone metastasis. The purpose of this study is to evaluate pain response and safety of Sr-89 administration for painful bone metastasis in the setting of prior radiation. After institutional review board approval, records of patients who received Sr-89 injection for painful bone metastasis in previously irradiated sites were retrospectively reviewed. Patients with follow-up of less than 1 month were excluded from analysis. Efficacy of pain control was evaluated with the verbal rating scale (VRS), documentation of the analgesic dose employing the World Health Organization (WHO) pain relief ladder. Adverse events were measured using CTCAE v4.0. Twenty-three patients met study inclusion criteria, of which 12 were male and 11 were female. Median age at treatment was 69 years (50-83). Primary sites were lung (n=11), prostate (n=3), breast (n=2), uterine cervix (n=2), kidney (n=1), and other (n=4). Median follow-up was 8 (1-49) months. Twelve patients treated with SR-89 had prior history of palliative radiation therapy for bone metastasis. The remainder had received radiation for non-bony metastasis as follows: concurrent chemo-radiotherapy (CCRT) for lung cancer (n=7), post-operative radiotherapy to regional lymph nodes of breast cancer (n=1), pre-operative CCRT for rectal cancer (n=1), radical CCRT for cervical cancer (n=1), and radiotherapy to tumor bed for recurrent prostate cancer (n=1). Prior to administration of Sr-89, the VRS grade of 0/1/2/3 was n=1/5/12/5, respectively. Analgesic score 0/1/2/3/4/5/6 was n=3/9/2/4/3/1/1, respectively. After administration of Sr-89, VRS grade didn’t change in 3 patients, and improved in 20; 17 occurred after 1 month, 2 after 2 months, and 1 after 3 months. Analgesic score didn’t change in 15 but improved in 8 patients; 4 after 1 month, 2 after 2 months, 2 after 3 months. In two patients neither the VRS nor the analgesic score improved and in two patients the VRS improved but the analgesic score increased, hence difficult to evaluate efficacy of SR-89. This made the response rate of evaluable patients 90.1%. Flare phenomenon was observed in 3 patients, but all were controlled with analgesic and improved within one week. No grade 2 or worse adverse events was observed. Administration of strontium-89 chloride to patients with painful bone metastasis at previously irradiated sites is an effective and safe treatment options for palliation of symptoms at the end of life.