A bioactive glass composition for use in treating bone cancer includes 0.5-10 mol % gallium oxide or 1.0-20 mol % gallium nitrate/halide; 25 to 75 mol % silicon dioxide; 10 to 30 mol % calcium oxide and/or strontium oxide; up to 30 mol % sodium oxide; and up to 15 mol % phosphorous pentoxide. It may further comprise magnesium and/or potassium oxide. The bioactive glass composition may be positioned within a patient's bone post-surgery to promote apatite formation and to release gallium ions having a toxic effect on any remaining cancerous cells.