Treating Thyroid Treating Thyroid Cancer using Cancer using I I - - 131 Maximum 131 Maximum Tolerable Dose Tolerable Dose Method Method Christopher Martel, M.Sc., CHP Christopher Martel, M.Sc., CHP Lisa Lisa Thornhill Thornhill , NRRPT, RT(NM) , NRRPT, RT(NM) Boston University Medical Center Boston University Medical Center
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Treating Thyroid Treating Thyroid Cancer using Cancer using
II--131 Maximum 131 Maximum Tolerable Dose Tolerable Dose
Method Method Christopher Martel, M.Sc., CHPChristopher Martel, M.Sc., CHPLisa Lisa ThornhillThornhill, NRRPT, RT(NM), NRRPT, RT(NM)Boston University Medical CenterBoston University Medical Center
Thyroid CarcinomaThyroid Carcinoma
New cases and deaths in the U.S., 2007New cases and deaths in the U.S., 2007New Cases New Cases –– 33,55033,550Deaths Deaths -- 1,5301,530
Risk factors that increase chances Risk factors that increase chances 1) White female, over 40 y.o. 1) White female, over 40 y.o. 2) Genetic (for 2) Genetic (for medullarymedullary thyroid carcinoma)thyroid carcinoma)3) Not enough iodine in the diet3) Not enough iodine in the diet4) Radiation and/or radioactive fallout4) Radiation and/or radioactive fallout
National Cancer Institute, http://www.cancer.gov/
Thyroid Cancer Incidence Rates
Thyroid Cancer Incidence RatesThyroid Cancer Incidence Rates
National Cancer Institute, http://www.cancer.gov/
Methods of TreatmentMethods of Treatment
Depending on type and stage of the cancer:Depending on type and stage of the cancer:1) surgery1) surgery2) radioactive iodine2) radioactive iodine3) hormone therapy 3) hormone therapy 4) external radiation4) external radiation5) chemotherapy5) chemotherapy
Maxon,HR J Nuclear Med, 1992; 33:1132-1136
1.1. post surgery for thyroid removalpost surgery for thyroid removal2.2. related to tumor’s future capacity to concentrate iodinerelated to tumor’s future capacity to concentrate iodine3.3. positive relationship between total Ipositive relationship between total I--131 uptake per 131 uptake per
tumor mass and outcome tumor mass and outcome –– but not proven for maximal but not proven for maximal dosesdoses
** doses < 35 ** doses < 35 GyGy to tumor likely will not respond to to tumor likely will not respond to II--131 therapy need 300 131 therapy need 300 GyGy to thyroid remnant, 120 to thyroid remnant, 120 GyGyto to metastaticmetastatic focifoci
Radioiodine is used to Radioiodine is used to determine thyroid determine thyroid uptake.uptake.Isotopes used include Isotopes used include II--123 and I123 and I--131.131.Normal uptake 15Normal uptake 15--25%25%Hypo Hypo –– <10%<10%Hyper Hyper -- >30%>30%
physical halfphysical half--life of 8..06 dayslife of 8..06 daysBeta emitterBeta emittermax energy 610 max energy 610 KeVKeV; ; avgavg energy 193 energy 193 KeVKeVtissue range of 0.8 mmtissue range of 0.8 mmGamma emitterGamma emitterprincipal energy 365 principal energy 365 KeVKeV (81%)(81%)
94% of radiation dose is from the beta emissions94% of radiation dose is from the beta emissions
IodineIodine--131 Decay Data131 Decay DataHalf life:Half life: 8.06 days8.06 days
SNM: Dose Selection SNM: Dose Selection General Guidelines for Thyroid
Cancer patientsFor postoperative ablation of thyroid bed remnants For postoperative ablation of thyroid bed remnants depending on the amount of functioning tissue presentdepending on the amount of functioning tissue present
(75 (75 –– 150 150 mCimCi))
For treatment of presumed thyroid cancer in the neck or For treatment of presumed thyroid cancer in the neck or mediastinalmediastinal lymph nodeslymph nodes
(150 (150 –– 200 200 mCimCi))
For treatment of distant metastases For treatment of distant metastases
(> 200 (> 200 mCimCi) *Candidate for MTD*) *Candidate for MTD*
Maximal Dose Therapy Maximal Dose Therapy Considered When Considered When
Patients with lifePatients with life--threatening diseasethreatening diseasePatients with progressive disease but little Patients with progressive disease but little response to previous treatmentsresponse to previous treatmentsPatients with bone Patients with bone mets mets Patients with nodal diseasePatients with nodal disease
Goal is to treat but not to cure diseaseGoal is to treat but not to cure disease
Standard treatment using empiric guidelines is only a “best Standard treatment using empiric guidelines is only a “best guess”guess”and not truly tailored for each patientand not truly tailored for each patient
Better outcome if treated with one rather than multipleBetter outcome if treated with one rather than multipleII--131 treatments131 treatments
Common Side Effects from Common Side Effects from >200 >200 mCimCi Dose IDose I--131 Therapy131 Therapy
6060--70% radiation sickness70% radiation sickness1010--15% 15% sialoadenitissialoadenitis10% 10% leukopenialeukopenia for up to one yearfor up to one year70% transient 70% transient azoospermiaazoospermiaCystitis, radiation Cystitis, radiation thyroiditisthyroiditis, gastritis, transient , gastritis, transient loss of tasteloss of taste
Absorbed Dose Calculations Absorbed Dose Calculations Uses Modification to the MIRD Uses Modification to the MIRD
SystemSystem
“Practical Determination of Patient“Practical Determination of Patient--Specific Marrow Specific Marrow Dose Using Radioactivity Concentration in Blood Dose Using Radioactivity Concentration in Blood and Body”and Body”
ShenShen, , DenardoDenardo SgourosSgouros, et. al, et. alUC Davis/Memorial SloanUC Davis/Memorial Sloan--Kettering Cancer InstituteKettering Cancer InstituteJournal of Nuclear Medicine, Journal of Nuclear Medicine, VolVol 40, No. 12 December 199940, No. 12 December 1999
Critical Factors in Calculating Patient Dose
Dose to red marrow– Red marrow self dose– Total body to red marrow dose
Dose to lungs– Whole body retention at 48 hours
Limiting Factors for Limiting Factors for Maximal IMaximal I--131 Dose Therapy131 Dose Therapy
Whole Body Retention at 48 hoursWhole Body Retention at 48 hours–– 80 80 mCimCi if lung metastases are presentif lung metastases are present–– 120 120 mCimCi if lung if lung metsmets not presentnot present
Requires: WB counting using dual head Gamma CameraRequires: WB counting using dual head Gamma Camera
200 200 cGycGy (200 (200 RadsRads) absorbed dose to the red BM) absorbed dose to the red BM
Give amount of radioactivity which will reside in a particular oGive amount of radioactivity which will reside in a particular organrgan
Must determine total # nuclear transformations that occur withinMust determine total # nuclear transformations that occur within that organthat organ1) activity (transition rate or decay rate) 1) activity (transition rate or decay rate) Physical characteristicsPhysical characteristics2) time that nuclide is resident in that organ 2) time that nuclide is resident in that organ Biologic characteristicsBiologic characteristics
Cumulated Activity (Cumulated Activity (mCimCi--hrs)hrs) = Activity (= Activity (mCimCi) in organ x time = () in organ x time = (mCimCi--hrs)hrs)
Divide the Cumulated Activity in the organ / Total given ActivitDivide the Cumulated Activity in the organ / Total given Activity to bodyy to body= total # nuclear transitions in organ per unit activity= total # nuclear transitions in organ per unit activity
This is also known as the This is also known as the Residence TimeResidence Time in the organ of interestin the organ of interest
Phantom Models in OLINDAPhantom Models in OLINDA--EXMEXM
70 kg adult (reference male)70 kg adult (reference male)57 kg (reference female)57 kg (reference female)57 kg 15 year old57 kg 15 year old32 kg 10 year old32 kg 10 year old19 kg 5 year old19 kg 5 year old9.2 kg 1 year old9.2 kg 1 year old3.4 kg newborn3.4 kg newborn
Biodistribution of I-131
For most radiopharmaceuticals, the activity in a For most radiopharmaceuticals, the activity in a given organ does not remain constant given organ does not remain constant throughout the period of interest throughout the period of interest –– radioactive (physical) decayradioactive (physical) decay–– ongoing biologic processes of uptake and removal of ongoing biologic processes of uptake and removal of
metabolitesmetabolites
Problems with Biodistribution
Patients have very different rates of metabolism, especially older or sicker patients
Patients with Thyroid Cancer have had their thyroids removed
Each lesion will have its own uptake and biological removal rate
Administer tracer dose of IAdminister tracer dose of I--131 (~2131 (~2--3 3 mCimCi))Obtain blood samples at specific time Obtain blood samples at specific time intervalsintervalsObtain whole body images (gamma Obtain whole body images (gamma camera) at specific time intervalscamera) at specific time intervals
Both patients are doing very wellBoth patients are doing very wellNo recurrence of cancerous cellsNo recurrence of cancerous cells
AcknowledgmentsAcknowledgments
Stephanie Lee, M.D., Ph.D.Stephanie Lee, M.D., Ph.D.Dept. Endocrine / DiabetesDept. Endocrine / DiabetesBoston University Medical CenterBoston University Medical Center
Richard H. Behrman, Ph.D.Richard H. Behrman, Ph.D.Head Medical Physicist, Diagnostic RadiologyHead Medical Physicist, Diagnostic RadiologyBoston University Medical CenterBoston University Medical Center