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Core > Nuclear: Therapy > Flashcards

Nuclear: Therapy Flashcards

1
Q

What radiopharmaceuticals have been approved for treating bone pain associated with metastatic disease from breast and prostate cancer?

A
  • Strontium-89 chloride (Sr-89)
  • Samarium-153 EDTMP (Sm-153)
  • Radium-223 dichloride (Ra-223)
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2
Q

Can pts receive radiopharmaceuticals to treat bone pain while receiving external radiation treatment?

A

Yes, external radiation is not a contraindication

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3
Q

Absolute contraindications for Sm-153 EDTMP treatment of bone pain

A
  • Pregnancy
  • Breastfeeding
  • Renal failure (GFR < 30)

Note: These are contraindications for bone pain treatment with either Sr-89 or Sm-153.

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4
Q

How does strontium-89 chloride (Metastron) work?

A

It complexes with the hydroxyapatite in areas of high bone turnover and is a pure beta emitter

Note: It has high bone marrow toxicity and isn’t used as much as the newer agents (Sm-153 and Ra-223).

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5
Q

Which is better for treating bone pain: Sr-89 or Sm-153 EDTMP?

A

Sm-153 EDTMP (less bone marrow toxicity and also emits gamma rays that can be used for imaging)

Note: “Samarium is a Good Samaritan”.

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6
Q

Side effects of Sm-153 EDTMP

A

Myelosuppression (mostly thrombocytopenia and leukopenia)

Note: This is transient and goes away faster than with Sr-89.

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7
Q

How does Samarium-153 EDTMP (Quadramet) work?

A

It complexes with the hydroxyapatite in areas of high bone turnover and is a beta and gamma emitter (allowing for imaging)

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8
Q

What is the mechanism of excretion of Sm-153?

A

Renal (primarily)

Note: This is why renal failure (GFR < 30) is an absolute contraindication.

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9
Q

What is the best radiopharmaceutical to use for bone pain?

A

Radium-223 (Xofigo)

Note: It has the least bone marrow toxicity (as an alpha emitter it has a shorter range of damage) and a long half life that makes shipping easy.

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10
Q

How does radium-223 work?

A

It behaves like calcium and gets absorbed into the bone matrix at sites of active bone mineralization, where it emits alpha particles

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11
Q

Side effects of radium-223 therapy

A
  • Diarrhea
  • Fatigue
  • Nasea/vomiting
  • Bone pain

Note: These are more significant than the minimal bone marrow suppression (due to the short range of alpha particles).

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12
Q

What is the route of excretion for radium-223?

A

Gastrointestinal

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13
Q

What precautions should be taken for a pt taking radium-223?

A
  • Soiled clothing and boldly fluids should be handled with gloves
  • Clothes should be laundered seperately

Note: The general population is safe due to the low gamma radiation (Radium-223 is mostly an alpha emitter).

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14
Q

How long after taking radium-223 should a pt use contraception?

A

For at least 6 months

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15
Q

Does radiopharmaceutical therapy for bone mets improve survival?

A

Generally no

Note: The exception is using Radium-223 to treat prostate cancer bone mets, which does seem to improve survival.

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16
Q

How does Yttrium-90 work?

A

It is a beta emitter, destroying tissue near where it is injected

17
Q

What is the maximum tissue penetration of Y-90?

A

10 mm

Note: This is why Y-90 treatment spares most of the surrounding healthy liver tissue.

18
Q

Why is it important to do a Tc-99m MAA hepatic arterial injection prior to treatment with Y-90?

A

To identify a lung shunt fraction (should be less than 10% ideally, not more than 20%)

Note: If the lung shunt fraction is > 20%, the risk of radiation pneumonitis is too high.

19
Q

What does the lung shunt fraction need to be in order to do Y-90?

A

Less than 20% (less than 10% is ideal, but 10-20% is ok you just have to reduce the Y-90 dose)

Note: If > 20%, the risk of radiation pneumonitis is too high.

20
Q

What is the optimal particle size for Y-90 embolization?

A

20-40 micrometers

Note: This size allows particles to get stuck in tumor nodules without fully obstructing blood flow (some blood flow is needed to help generate free radicals).

21
Q

What is the typical dose used for Y-90 embolization?

A

100-1000 Gy

22
Q

What are the Y-90 photopeaks that can be used for imaging?

A
  • 175 keV
  • 185 keV
23
Q

What is the half life of Y-90?

A

2.67 days

24
Q

What is radioimmune therapy?

A

The use of Y-90 labeled monoclonal antibodies to treat cancer

Note: This is mostly used for refractory non-Hodgkin lymphoma.

25
Q

How do you perform radioimmune therapy?

A

First, In-111 labeled monoclonal antibodies are given for imaging (to ensure the biodistribution is good, that the antibodies only go where you want them to go)

Then, you give Y-90 labeled monoclonal antibodies to treat that distribution

26
Q

Which monoclonal antibody is often used for radioimmune therapy of refractory non-Hodgkins lymphoma?

A

Ibritumomab tiuxetan (Zevalin)

Note: This antibody binds to the CD-20 receptors on B-cells.

27
Q

What does platelet level need to be to receive radioimmune therapy for non-Hodgkins lymphoma?

A

Greater than 100,000

28
Q

What is the most common side effect of radioimmune therapy for non-Hodgkins lymphoma?

A

Thrombocytopenia and neutropenia (90% of cases)

29
Q

What is considered altered distribution of In-111 Zevalin (meaning that you should not treat with Y-90 Zevalin)?

A
  • Bone marrow uptake > 25%
  • Fixed uptake in the bowel (or bowel uptake greater than liver)
  • Uptake in the kidneys greater than the liver on day 3
  • Uptake in the lungs greater than the heart on day 1
  • Uptake in the lungs greater than the liver on days 2 or 3
30
Q

Does radioimune therapy for non-Hodgkin lymphoma need to occur as an inpatient? Or can the pt be released home?

A

They can be released home (dose to the general population is low enough)

Note: They should sleep alone and take other precautions for the first week or so.

31
Q

Protocol for radioimmune therapy for non-Hodgkins lymphoma

A
  1. Give rituximab (to block the CD20 receptors on circulating B cells and in the spleen)
  2. Give In-111 Zevalin to see if there is altered biodistribution (get delayed images at 90-120 hours if you think it might be altered)
  3. If normal biodistribution, give Y-90 Zevalin

Core (98 decks)

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