Radionuclide Therapy Flashcards
Administration routes
- IV injection
- infusion
- oral
- intracavitary
- intra-arterial
Dose target
Aim for max 5% deviation from prescribed activity, but relation between activity and outcome not straightforward, so more leeway in prescribing than with XRT ‘target dose’
Limitations of radio-nuclide therapies
- time and cost restriction on workload
- no agent is entirely selective to the desired target
- dose calc issues: inhomo deposition, individual physiology
- radiation is not risk free
- IRMER reqs a net positive benefit
- Prescription limited by normal tissue toxicity
Ideal imaging radiopharm
- Short T1/2 eff
- No particulate emissions EC or IT
- High target / BG ratio
Ideal therapy radipharm
- Very high target/bg ratio with rapid clearance from no target tissue
- Suitable pH, Sterile, pyrogen free, non-toxic
- Practical - kit / min prep
- Imaging emissions if possible
- T1/2p and T1/2b match up
- Particulate emissions
What are the following therapies used for ?
- P32, Sr-89, Samarium-153, Y-90 + Rhenium-186, Y90
P32 - treats polycythaemia vera Sr-89 - Bone mets Samarium-153 - Bone mets Y-90 + Rhenium-186 - Inflammation of the joints + bleeding in the joints (haemophillia treatment). Y-90 hepatocellular carcinoma
Outline thyrotoxicosis therapy
- Treatment of an overactive thyroid
- Outpatient treatment
- Follow up blood test of thyroid hormone levels
- May require second treatment or hormone tablets if below normal levels after
RP advice post thyrotoxicosis therapy
See MDGN Table 15.2
3 days careful bathroom hygiene
Stay 1m away from adults for 11 days
Stay 1m away from children under the ages of 3 for 21 days
No Blood sampling for 1 month
Carry instruction card for 1 month, 3 month if travelling.
Outline the thyroid ablation therapy pathway
- Painless lump, biopsy, histology
- Thyroidectomy
- Ablation of thyroid tissue
- Post ablation whole body scan
- Diagnostic Imaging, neck u/s, Tg blood results
? Further Therapy? Other imaging
What is the purpose of thyroid ablation ?
Eliminate residual thyroid tissue
Reduce recurrence and aid monitoring
Admin activity is based on the amount of residual tissue post surgery.
What is the purpose of post ablation imaging?
- Baseline to show residual thyroid tissue at time of treatment.
- However it cannot distinguish between thyroid tissue and well differentiated tumour.
Laws relating to therapy administration
IRMER - patient dose and jusification
IRR - Dose to Staff / Members of the public
EPR - Waste accumulation, storage, disposal.
Outline the calculation of the dose to the thyroid from thyrotox therapy.
Use the MIRD method
1. Calc Te - effective half life
(tp x tb)/(tp+tb)
- Calc acumulated activity:
A = 1.44 x A0 x Te x fh - Calc Abs dose:
D = A x s = Act under curve x S-value
Thyroid therapy patient prep
- Advise patient to avoid high Iodine foods + review meds
- Pregnancy test
- Exclude breast-feeding patients unless alt arragement can be made.
- Assess continence
- Obtain written consent
RP during thyroid treatment (inpatient)
- ID check (IRMER)
- Instruct nursing personnel of the rad risk
- Periodically monitor activity of the patient’s thyroid gland
- Review measured act against the departure limit set by their risk assessment.
- Note any other med conditions/ establish contingency plans.
- Medical necessity overrides concern about rad risk.
- Instruct patient to keep hydrated and shower regularly
- Double flush the toilet
- Display visitor restriction time on the door (set by NM staff)
Advise for departing patients post iodine therapy
- Provide a patient advise card instructing restriction times
- Provide a document the patient can display when traveling (for 6 months min)
- Instruct to keep hydrated
- Advise to hand wash dishes
- Double flush the toilet
- Advise to shower/wash hands frequently
- Advise too avoid fathering/having children for 6 months.
Risk to pregnant women from iodine therapy
Radio-iodine can easily cross the maternal placenta, leading to foetal thyroid uptake. Which risk the induction of permanent hypothyroidism.
Safe oral administration of I-131
- Administer in a controlled area
- Have a radioactive waste disposal bag ready for tissue paper or gloves ready
- Have the patient sit on a covered seat, covered floor
- If admin as a capsule use a tube to tip the capsule from a shielded vial into their mouth using a straw.
- Liquid I-131 should be sucked up from a shielded pot using a straw. The patient should be asked to drink several glasses of water.
Outline radio-immunotherapy
Cancer-cell-targeted therapy using labelled monoclonal antibodies (mAbs)
Combines radiation therapy and immunotherapy
When injected into the blood stream, the labelled (mAbs) will travel to and bind to the cancer cells.
Outline the advantage radio-immunotherapy
Advantages: The labelled antibody specifically binds to a tumour associated antigen - increasing tumour dose + decreasing dose to normal tissues.
What is radio-immunotherapy used to treat?
non-Hodgkin’s B-cell lymphoma, chronic lymphocytic leukaemia and immune diseases.
