Evolution of Parathyroid Surgery Using Sestamibi

Imaging Guidance

David R. Byrd, MD

Department of Surgery

University of Washington

Disorders of Parathyroid Glands• hypoparathyroidism -rare. Almost always caused

by excessive surgical removal of parathyroid tissue (iatrogenic) during thyroid or parathyroid surgery

• hyperparathyroidism (HPT): – primary - hi Ca++, hi PTH - usually due to single

adenoma (90%), cured by removal of adenoma

– secondary - lo Ca++, hi PTH, seen in chronic renal failure - not a surgical problem

– tertiary - hi Ca++, hi PTH, seen after renal transplant - hyperplasia of all 4 glands

Traditional Surgery for Hyperparathyroidism

• primary HPT - 4 gland exploration, remove adenoma, biopsy 3+ normal glands

• tertiary HPT (after renal transplantation) - 3 1/2 gland removal +/- forearm autotransplant

Complications of Parathyroid Surgery

• persistent HPT - 1-20% (experience dependent)• temporary or permanent hypocalcemia - 1-

20%• nerve injury - recurrent or superior laryngeal -

1-10%• bleeding - <5%

Unilateral Exploration for Primary HPT

• if: one abnormal, hypercellular gland and one normal gland found on one side, no contralateral exploration

• occasional use of preop thallium-technetium scan

• results of 5 studies - cure 93-100%

Indications for Operation in Asymptomatic Patient w/ Primary

HPT - NIH Consensus(1990)

• markedly elevated serum Ca++• episode of life-threatening hyperCa++• reduced creatinine clearance• renal stones• markedly elevated 24 hr urinary Ca++• substantially reduced bone mass (by DEXA

scan)• age <50 (relative indication for surgery)

Parathyroid Imaging

• Tc-99m sestamibi scan (Cardiolyte)• ultrasound• initially thought useful only in persistent or

recurrent disease• thallium-technetium subtraction scan - now

rarely used

Tc-99m Sestamibi Scan

• taken up by actively metabolizing tissues - salivary glands, thyroid, parathyroid glands

• over time, blood flow causes washout from thyroid and normal parathyroid glands

• delayed images show a discrete “hot spot” in 75-80% patients with primary HPT

• can be used to direct minimally invasive surgical approaches

Parathyroid Imaging - Tc-99m Sestamibi45 min Anterior 45 min LAO

2 HR 2 HR

submandibulargland

thyroid lobe

adenoma

Delayedviews

Right inferior pole parathyroid adenoma

15 min Ant 1 hr Ant 1 hr RAO

adenoma

15 min Ant 1 hr Ant

Right superior parathyroid adenoma

adenoma

Advances Enabling Localized Exploration

• Tc-99m sestamibi radioguided exploration

• rapid IOPTH assay - 1/2 life = 3-5 minutes

Rapid IOPTH Assay

• exploits short half life (3-5 minutes) of PTH• serum baseline level #1 prior to exploration• level #2 after exploration but before removal

adenoma• levels 5 & 10 minutes after adenoma removal• 5 minute level > 50% second baseline level =

high prediction of success-Irvin G, et al, 1993

Studies of IOPTH Measurement in HPT

solitary/ Uni/bilat. Cure rate # pts MGD exploration ( %)

Nussbaum 1988 12 12/0 8/4 100Chapuis 1996 173 -- 160/13 94Irvin 1993 61 -- -- 90Sofferman 1998 40 31/9 -- 100Carty 1997 67 58/9 42/25 99Irvin 1994 18 18/0 -- 89Starr 2001 50 38/12 0/50 92

Minimally Invasive Radioguided Parathyroidectomy (MIRP)

• only in patients who localize by pre-op sestamibi scan (75% with primary HPT)

• sestamibi scan performed 2-3 hours before exploration - timing crucial

• gamma probe used to find the “hottest” spot• ex vivo adenoma counts >20% background• no further dissection and no frozen section• if no adenoma found, 4 gland exploration

-Norman J, et al, 1997

MIRP - results

• 2 cm incision• local w/ sedation, out-patient procedure• 100% cure rate• no complications• mean operating time = 25 minutes• re-operative cure rate = 100%

-Norman J, 1997

Studies of MIRP in HPT

solitary/ Uni/bilat. Cure rate # pts MGD exploration ( %)

Martinez 3 2/1 -- --Gallowitsch 12 -- -- --Bonjer 62 49/10 -- 95Norman 15 15/0 14/1 --Norman 24 21/0 21/1 --Flynn 39 32/6 30/9 100

Evolution of Surgery for Primary HPT

• Preoperative sestamibi in all patients with primary HPT:– help decision whether to operate in selected patients

– localize adenoma to plan localized exploration

• Minimally invasive parathyroidectomy (MIP):– 2-4 cm incision

– often w/ local + sedation

– out-patient procedure

– +/- IOPTH testing - biochemical confirmation

• Endoscopic removal of parathyroid gland(s)

Right inferior parathyroid adenoma - 54F

15 min Ant 1 hr Ant 1 hr RAO

adenoma

IOPTH Testing and Results

Baseline #1 214

Baseline #2 157

5 minute post 32

10 minutes post 20

MIP findings - 500mg L inferior pole adenoma

F/U levels 3 mos: Ca++ = 9.5, PTH = 55 (both normal)

Case # 3

50M, asymptomatic:- serum Ca++ = 13.4- preop iPTH = 750- concern for carcinoma

Tc-99m sestamibi positive for intense uptake LIP

Immed Ant Delay Ant

IOPTH Testing and Results

Baseline #1 1259

Baseline #2 764

5 minute post 129

10 minutes post 93

Case #3: 50M, 4.2 LIP gm adenoma

Early F/U: Ca++ =8.8, PTH = 138 (low calcium, sl. elevated PTH)

Operation for Tertiary HPT

• standard operation remains 3 1/2 gland removal or total parathyroidectomy w/ auto transplant dorsal forearm

• Imaging not standard at present• selected patients may benefit from Tc-99m

sestamibi preop scan• role of IOPTH testing evolving