9 Radionuclide therapy

Phosphrous-32 P-32 therapy in myeloproliferativediseases -Polycythaemia rubra vera -Essential thrombocythaemia

P-32 therapy in Polycythameia vera(PV) - PV is characterized by an increased production of red blood cell but not an increased blood cell survival - The production of red blood cells can be as high as 2-3 times the normal production rate - Transitions from PV to myeloid metaplasia and acute Leukemia are common -The median survival of patients with an untreated PV is approximately 1.5 years Treatment modalities *Phlebotomy *Chemotherapy with chlorambucil, busulfan *Radiophosphorus

P-32 - Pure beta emitter - Mean range in tissue is about 3mm - Suppress hyperproliferative cell - It is taken up primarily in the bone, spleen and liver - The high radiation dose delivered to the bone marrow account for the treatment effect in PV

P-32 Bio-distribution a. I t concentrates as phosphate within the DNA of rapidly dividing hematopoietic cells in the treatment of polycythaemia rubra vera and as phosphate in areas of increased bone formation. b. Decay mode: by β c. Physical half - life: 14 days Administration and dosage Polycythaemia rubra vera: IV, 3 mCi (111 MBq)

Strontium-89 ( Sr-89 ) chloride *It is indicated for the alleviation of bone pain arising from metastatic bone disease. *As a metabolic analog of calcium, Sr-89 concentrates selectively in areas of increased osteogenesis, thus delivering a radiation dose sufficient to provide a palliative effect. *Reduction in patient analgesic usage occurs in up to 75% of patients treated. *Bone marrow suppression effects limit Sr-89 use to patients with initial low WBC count.

Bio-distribution * After administration, Sr-89 clears rapidly from blood and localizes in the bone hydroxyapatite. *Initial biological half -life in normal bone is 14 days; longer retention is seen in metastatic bone lesions. * Elimination is primarily renal. Decay mode: by β Pure beta emitter Physical half -life: 50 days Administration and dosage. IV, 4 mCi (148 MBq)

Samarium-153 ( Sm-153) lexidronam Sm-153 is indicated for the relief of pain in patients who have confirmed metastatic cancer of the bone Sm-153 concentrates in areas of high bone turnover and accumulates more in osteoblastic lesions than in the normal bone. The goal of Sm-153 therapy is for patients to be able to reduce the amount of narcotic analgesics needed to control their pain.

*The lesion to normal bone ratio is 5:1. Bio-distribution *The lesion to normal bone ratio is 5:1. *The percentage of uptake of Sm-153 is directly proportional to the number and severity of lesions the patient has. *Sm-153 is 100% renally excreted over 12 hr . *Decay mode: by β and γ decay *Physical half - life: 46 hr *Precautions. Sm-153 may cause bone marrow suppression. Administration and dosage. IV, 1 mCi/kg (37 MBq/kg)

Targeted Radionuclide Therapy Radiation therapy uses ionizing radiation to kill cancer cells and shrink tumours by damaging the cells’ DNA, thereby stopping these cells from continuing to grow and divide. The most common way of exposing cancer patients to radiation is through external radiation therapy. With this approach, only a limited area of the body is irradiated by delivering a beam of high-energy x rays to the main tumour.

Targeted radionuclide therapy, on the other hand, is like chemotherapy, because it is a systemic treatment; it uses a molecule labelled with a radionuclide to deliver a toxic level of radiation to disease sites. Targeted radionuclide therapy attack specific tumour-associated antigen or receptor. In addition, a systemically administered targeted radio therapeutic that combines the specificity of cancer cell targeting with the known antitumor effects of ionizing radiation has the potential to simultaneously eliminate both a primary tumour site and cancer that has spread throughout the body (metastases), including malignant cell populations undetectable by diagnostic imaging.

The most commercially approved radio-immunotherapy agents, yttrium-90 ibritumomab tiuxetan (Zevalin), which is used to treat resistant B-cell lymphoma and related cancers. It target a B-cell surface antigen expressed on B-cells, and produces excellent clinical results. . the patient is given a therapeutic dose of the monoclonal antibody radiolabel with a beta-emitting radionuclide (yttrium-90) intravenously.

Targeted Radionuclide Therapy: curing tumours while avoiding damage of healthy organs

Prof. Dr. Omar Shebl Zahra Thank you and Good Luck Prof. Dr. Omar Shebl Zahra