Parathyroid Cancer: Patient Guide

Parathyroid cancer has an estimated incidence of 0.015 per 100,000 people. Estimated prevalence in the United States is 0.005%. The NCI calls it one of the rarest of all human cancers.

Parathyroid adenomas are common. These are noncancerous growths on the same glands. Cancer accounts for under 1% of primary hyperparathyroidism cases in most series.

Two details set it apart from benign disease. The median age at diagnosis in most series is 45 to 51. And it strikes women and men equally, at a ratio of 1 to 1. Benign primary hyperparathyroidism hits women 3 to 4 times as often as men.

This cancer behaves unlike almost every other. Most endocrine tumors become less hormonally active when they turn malignant. Parathyroid cancers stay hyperfunctional.

The gland pumps out parathyroid hormone, or PTH. PTH pulls calcium out of bone and into the blood. Serum PTH can run three to ten times above the upper limit of normal. In ordinary primary hyperparathyroidism it is usually under twice normal.

Everything that follows comes from high calcium. In a series of 43 patients, 56% had kidney stones and 84% had kidney impairment. Bone disease appears in up to 70%, with bone pain and thinning bone.

The combination is the tell. Having both kidney and skeletal disease at the same time happens in up to half of parathyroid cancer patients. In benign primary hyperparathyroidism it is distinctly unusual.

Other findings at diagnosis fall into groups. Bones: thinning at the edge of the bone, breaks from little force, bone pain. Kidneys: stones and renal colic. Gut: peptic ulcer, repeated pancreatitis, nausea and vomiting, poor appetite. Whole body: fatigue, muscle weakness, weight loss, heavy urination, extreme thirst, and dehydration.

Suspicion before surgery matters, because it changes the operation. The NCI lists specific features that should raise it:

• Calcium above 14 milligrams per deciliter
• PTH more than twice the normal level
• A neck mass you can feel in a person with high calcium
• High calcium together with paralysis of one vocal cord
• Kidney and bone disease at the same time with a markedly raised PTH

That vocal cord clue means tumor has reached the recurrent laryngeal nerve. That nerve controls the voice box.

Several tests can locate the tumor before an operation. They include a technetium Tc 99m sestamibi scan and single photon emission computed tomography. CT images can be fused with the sestamibi images. Ultrasound, plain CT, a selective angiogram, and selective venous sampling for PTH are also used.

Surgery is the only effective therapy here. How it is done matters more than almost anything else.

The right operation is en bloc resection. The tumor comes out in one piece, with all tissue it might have invaded, at the first operation. One review of the literature reported a local recurrence rate of 8% after en bloc resection. After a standard parathyroidectomy it was 51%.

That gap is the whole argument. En bloc surgery may mean removing the recurrent laryngeal nerve if tumor has reached it. That leaves one vocal cord paralyzed. The NCI judges the gain in long-term control worth the cost. It also notes the voice can be improved later, with methods such as injection into the paralyzed cord.

Lymph node dissection is not routine. It is performed only for enlarged or firm nodes, particularly level VI paratracheal nodes and level III and IV internal jugular nodes.

Some patients are never suspected before or during surgery. They get an operation designed for an adenoma. The real diagnosis only surfaces when the pathology comes back, or when the disease returns.

Telling a benign parathyroid tumor from a malignant one under the microscope is genuinely difficult. The NCI notes that capsular and vascular invasion track closely with recurrence and spread. So those two findings are treated as the defining markers of cancer.

Surgeons also use appearance. Cancers tend to be firm, stony-hard, and lobulated. Adenomas are soft, round or oval, and reddish-brown. Median maximum diameter is 3.0 to 3.5 cm for cancer. For adenomas it is roughly 1.5 cm. In about half of cases the tumor sits inside a dense grayish-white capsule. That capsule grows into nearby tissue.

For anyone whose disease cannot be fully removed, lowering calcium is the first goal, not a side task.

Standard measures include fluids by vein and diuretics. Bisphosphonates are added as well. These drugs slow the release of calcium from bone.

Calcimimetics work another way. They act on the calcium sensing receptor and cut PTH release directly. Cinacalcet carries an FDA label for high calcium in adults with parathyroid cancer. It is started low and stepped up in stages over weeks, guided by repeated blood tests, until serum calcium comes down to normal. Only your team sets and changes that dose. Tablets are swallowed whole, with food or just after a meal.

The label carries real cautions. Treatment must not be started if serum calcium is below the lower limit of normal. Low calcium from overtreatment has caused life-threatening events and deaths. It can stretch the QT interval on the heart tracing. It can lower the seizure threshold. It can also cause low blood pressure, worse heart failure, or an abnormal heart rhythm. Bleeding in the upper gut is a separate warning. Once a maintenance dose is set, calcium is checked about every 2 months.

Roughly 40% to 60% of patients have a recurrence after surgery, typically 2 to 5 years after the first resection.

In most cases rising calcium comes first, before anything shows on exam or scan. About two-thirds of recurrences are regional, in neck tissue or neck lymph nodes. They can be small, scattered, and hidden in scar tissue.

Older studies reported distant spread in 25% of patients, mostly to the lungs, and also to bone and liver. Because the disease is indolent, management of recurrence is still primarily surgical. Removing even very small deposits in the neck, nodes, lungs, or liver can produce significant benefit.

Monitoring is lifelong. Multiple relapses over long periods are expected rather than exceptional.

In a National Cancer Database series of 286 patients, 10-year survival was about 49%. A smaller series reported 77%. That may reflect better supportive care and better control of dangerous high calcium.

The NCI states the point plainly: patients rarely die of the tumor itself. They die of the metabolic consequences of uncontrolled hyperparathyroidism. That single sentence explains why calcium control is treated as urgent rather than supportive.

• Was parathyroid cancer suspected before surgery, and was en bloc resection done
• Does the pathology report describe capsular or vascular invasion
• What are my calcium and PTH values now, and what are the targets
• How often will calcium be checked, and who reviews the result
• Is a calcimimetic appropriate for me, and what are my kidney numbers
• Who is coordinating long-term follow-up, since monitoring is for life

Calcium is what makes this disease dangerous, so the warning signs are the signs of calcium swinging too far in either direction.

• Call 911 or go to an emergency department if you or the person you care for becomes confused, drowsy and hard to wake, or unresponsive, has a seizure, or develops a racing, pounding or irregular heartbeat with faintness. These point to a calcium crisis, high or low, and they can move fast.
• Call your care team the same day if vomiting stops you keeping fluids down, you are passing very little urine, or severe thirst and weakness set in. Losing fluid drives blood calcium higher. Also call the same day for tingling round the mouth, numb fingers, or muscle cramps and twitching, which suggest calcium has fallen too low on treatment.
• Call your care team within a day or two if thirst, heavy urination, constipation or bone pain creep back after treatment, or a neck lump or hoarse voice is new. Returning calcium is usually the first sign of recurrence.

https://www.cancer.gov/types/parathyroid/hp/parathyroid-treatment-pdq https://medlineplus.gov/ency/article/000365.htm https://medlineplus.gov/ency/article/000311.htm https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ff0b9500-085a-4e1e-a2e4-fd918ed70b2e