Radiation Therapy Exam With Verified Answers A+ Pass

Radiation Therapy Exam With Verified Answers A+ Pass What are some indications for radiation therapy in companion animals? - Answer- -Incompletely resected tumors (treatment of choice for these) -Non resectable tumors (results depend on tumor type) -Pain control (bone cancer/bone mets) What are some different types of radiation used in veterinary medicine? - Answer- X-rays (photons) Gamma rays (photons) Particles (beta-particles in radioisotopes) What type of cell does radiation target? - Answer- Cells/tissues with a high proliferation rate express radiation damage relatively quickly. What are the most radiation sensitive cells in the body? - Answer- -Undifferentiated -High mitotic rate (bone marrow, intestinal crypt cells, germinal layer of epidermis, tumors) -Cells with long mitotic future What is different in DNA repair in tumor cells vs normal cells? - Answer- Tumoral mechanisms of DNA repair are not as efficient as in normal cells, so it is harder for them to repair quickly. What is fractionation? - Answer- This is the practice of spreading radiation treatments over a period of time. Why use fractionation? - Answer- -Allows reassortment of tumor cells within the active phases of the cell cycle; as tumoral cells die, the cells that are hypoxic are allowed to achieve a more oxygenated status, which makes them more susceptible to be killed with further radiation fractions. -Also allows time for normal cells killed by radiation to be repopulated by surviving cells; occurs in tumor cells but to a lesser degree. -Normal cells are more efficient at repairing the radiation therapy to DNA than tumor cells when radiation is delivered in multiple small doses. Describe the four R's of radiation therapy (fractionation). - Answer- 1. Repair of sublethal damage 2. Repopulation of normal tissues 3. Reoxygenation and 4. Reassortment of cells into radiosensitive phases of cell cycle increases the damage to the tumor. What are two types of radiation treatment machines in use in veterinary practice? - Answer- -Cobalt 60 therapy unit -Linear accelerator Describe the features of electron beam in radiation therapy. - Answer- -Various energies are possible -Rapid dose reduction (depending on energy used) -Therapeutically useful depth (1.5-5.6 cm) -Single fields, simple dose calculation Describe the features of photon beam in radiation therapy. - Answer- -High penetration into tissues -Slow dose reduction -Field arrangements are necessary -Penetration of normal tissue -Need to do CT-based treatment planning What are the goals of radiation therapy? - Answer- -Curative/definitive (cure or long term tumor control) -Palliative (palliation, stabilization of disease, pain reduction/relief) For what types of tumors is radiation therapy used as a post-surgery adjuvant? - Answer- Mast cell tumor Soft tissue sarcoma Feline vaccine-associated sarcoma etc When is radiation used as a primary treatment modality? - Answer- Brain tumor Tumor of head and neck (oral, nasal) MCT Epulis What is the median survival of nasal tumors without treatment? With surgery alone? With radiation therapy alone? With RT and sx? - Answer- -Median survival: around 3 months -Surgery alone: around 3-6 months -Radiation therapy alone: 8-20 months -RT and sx: up to 47 months