Slackers Radiation Oncology Fact Stack

Mike Ori

Disclaimer

• These represent my understanding of the subject and have not been vetted or reviewed by faculty. Use at your own peril.

• I can’t type so below are common missing letters you may need to supply

• e r l• I didn’t use greek letters because they are a pain

to cut and paste in.

• What are the five stages of cancer diagnosis and therapy

• Screening• Diagnosis• Staging• Therapy• Follow-up

• What is the most successful use of radiology for screening

• Mammography

• What is one area where radiology techniques have not been successful in screening

• Ultrasound screening of the prostate

• Explain the role of contrast kinetics in MRI

• Wash-in and wash-out times help differentiate benign and malignant

• Normal tissue tends to have slower wash-in and wash-out kinetics than tumor.

• What is a sestamibi scan

• Use of 99mTc-sestamibi to identify areas of angiogenesis and tumor.

• Compare sestamibi scans to MRI

• Uses ionizing radiation• Not as available as MR• Faster• Cheaper

• What is octreotide scanning

• A somatostatin-like compound that can interact wit somatostatin receptors on the surface of cells. Some types of cancer (neuro-endocrine mostly) are notable for such receptors.

• Compare octreotide scanning to MRI/CT

• Sometimes shows mets when other modalities don’t

• Poorer anatomic localization than other modalities

• Can be used to indicate treatment with yttrium 90-octrotide

• What is MRI spectroscopy

• The use of the MRI machine to perform spectroscopic analysis of tissue to look for marker compounds that indicate growth or abnormal metabolism.

• Rarely used capability due to reimbursement

• What radiographic techniques can be used to stage cancer

• CT– The workhorse

• PET– Especially when combine with CT

• MRI– Increasing in use. Dominant in some areas

• Radionucleotide bone scans– For skeletal mets

• Ultrasound– Rarely

• How does PET scanning work

• Fluoro-D-Glucose is injected into the body. Hot spots appear in any tissue actively metabolizing glucose. This includes tumors but also inflammed and regnerating areas.

• For what cancers is PET scanning approved

• Non-small cell lung cancer• Colorectal cancer• Melanoma• Lymphoma• Head and neck cancer (not thyroid or CNS)• Esophageal• Cervical• Breast monitoring and restaging• Thyroid restaging

• Explain radionucleotide bone scans

• 99mTC-methylene diphosphonate is injected into the body and incorporated into hydroxyapatite in the bone by osteoblasts. Thus areas of bone growth are visible.

• Needs follow-up anatomic imaging

• What is the role of radioactive iodine in the treatment of thyroid neoplasia

• RAI is used post surgery to destroy remaining thyroid tissue.

• What is image guided therapy

• The use of radiology techniques in the performance of treatment

• Intra arterial chemo catheter• Embolization– Simple– Chemo

• Alcohol ablation/cryotherapy• RF ablation• Focused ultrasound

• What is RECIST

• Response evaluation criteria in solid tumors is an heuristic used to quantify the change in a solid tumor over time.– CR = complete response– PR = partial response, 30% decrease– PD = progressive disease, 20% increase– SD = stable disease

• What type of radiation is used in radiotherapy

• Ionizing radiation such as x-rays, gamma rays, electrons, protons

• What device produces the radiation used most predominantly in the US

• The linear accelerator or linac

• How many linacs can fit on the head of a pin?

• None.

• Differentiate teletherapy from brachytherapy

• Teletherapy uses a radiation beam generated by source remote to the patient. This is your classic sci-fi death ray.

• Brachytherapy places an intrinsically radioactive substance in close approximation to the target tissue.

• What is linear energy transfer

• The amount of energy transferred per unit length of track

• What is the bragg peak

• The point of maximum energy release along a track.

• Differentiate directly ionizing from indirectly ionizing radiation

• Directly ionizing radiation has sufficient energy to directly disrupt the atomic structure of DNA. Protons.

• Indirectly ionizing radiation creates free radicals that damage DNA. X-rays.

• What is the primary method of cell killing caused by radiation

• Double stand DNA breaks that are improperly repaired.

• Why are oxygenated cells more susceptible to radiation than are hypoxic cells

• The ionizing process generates free electrons which are taken up by oxygen to generate oxygen radicals which attack DNA. In hypoxic conditions, less oxygen is available to generate free radicals.

• Which phase of the cell cycle is sensitive to radiation? Which is resistant?

• G1/M are sensitive• S is resistant

• What factors influence the survival of a radiated cell?

• Position in the mitotic cycle• Molecular checkpoint activation• Hypoxia• Repopulation

• Describe how a 50Gy dose of radiation is delivered to patients

• The dose is usually fractionated into multiple doses of ~2Gy. These are then delivered over the course of many days until the total prescription is delivered.

• Describe image modulated radiation therapy

• IMRT uses a multi-leaf collimator shape a radiation beam to limit exposure of adjacent structures.

• List several benign diseases for which radiotherapy can be prescribed

• Omas of the CNS– Schwanoma– Chordoma– Meningioma– Pituitary adenoma

• AVM• Trigeminal neuralgia• Pterygium• Heterotopic ossification• Trigeminal neuralgia