Radiation Oncology

Question 1

Finely Fractionated therapy - Curative Intent

Answer 1

Generally for microscopic disease

Spares tissue by delivering multiple small doses

4 R’s:
1) Redistribution (redistribute to more sensitive phases of cell cycle)

2) Reoxygenation (allows time for reoxygenation between fractions - hypoxic cells are less sensitive)
3) Repair (late responding tissues preferentially spared with small dose/fraction)
4) Repopulation (allows time for normal acutely responding cells to repopulate, dec the severity of acute effects & prob of tumor control - prolonging therapy not a good thing for tumor control)

Question 2

Stereotatic Radiation therapy - Curative Intent

Answer 2

Treatment for gross disease

Large doses of radiation delivered in a precise conformal manner

**Spares tissues by geographical avoidance rather than be delivering many small fractions - MUST confirm location!!

OSA responds great to this

Acromegaly felines do well with this
- some developed hypothyroidism

Question 3

Palliative Radiation Therapy

What patients benefit from this?

Answer 3

Used to decrease pain and improve function or hygiene in animals with advanced disease

Hypofractionated - like stereotactic, but NOT conformal

*dose delivery varies, because goal is NOT to cure tumor, and in most cases almost one palliative regimen works as well as the next

Question 4

What is Radiation? What kind of radiation to we use?

Answer 4

Radiation = Energy in transit

• energy or elementary particles that can propagate through air and transfer energy to matter
• electrons don’t penetrate as deep as protons

Ionizing radiation: radiation is of sufficient energy to eject electron

• Electromagnetic
• X rays

Question 5

Management of Acute Effects of XRT

Answer 5

straightforward… Stay ahead of the pain! and keep patient comfortable and treatment area clean)

Question 6

IMRT

Answer 6

Intensity Modulated, Fractionated Radiation Therapy (IMRT)

• Major difference is development of inverse treatment planning
• Delivery of radiation via fields that have non-uniform radiation fluence
• collimation/compensation
• temporal modulation of fluence

Spares healthy tissue while targeting tumor cells

Can use this technology with SRT or FFRT

Question 7

Fractionated IMRT Indications (Vetmed)

Answer 7

• nasal
• head/neck
• brain/spinal cord
• bladder/prostate

Question 8

Oral melanoma

Answer 8

Melanomas are aggressive and most patient die soon from metastasis

• 30-40% of oral tumors
• older dogs
• small breed > large
• anywhere on mouth/lip = aggressive

Question 9

Most important criteria when referring to a radiation center

Answer 9

Having an on-site radiation oncologist whom you can speak with and who will be available in the future to help you manage any acute or late side effects