Parathyroid Cancer

Diagnosis cannot be made prior to surgery.

• However, suspicion should be high if:
  • Pre-operative calcium levels are > 13 and parathyroid hormone (PTH) levels are in the 1,000’s.
  • The parathyroid adenoma can be felt on exam.
  • The parathyroid adenoma appears to be invading nearby structures such as the thyroid gland on pre-operative imaging (ultrasound, 4D CT, or Sestamibi SPECT).

Diagnosis is made based a combination of two factors:

• Intraoperative findings from the surgeon.
  • Parathyroid cancer can invade the thyroid gland and other nearby structures complicating the dissection.
  • This is very different from typical parathyroid adenomas which usually are easily dissected free from nearby structures.
• Pathology report.
  • This can be a challenging diagnosis for pathologists to distinguish pre-cancerous ‘atypical parathyroid neoplasm’ from parathyroid cancer.
    • Can consider using genetic sequencing to identify known mutations that cause parathyroid cancer if the diagnosis is in question.

Complete surgical removal of the parathyroid gland (Parathyroidectomy) is the only way to cure parathyroid cancer.

• If the cancer is invading a nearby structure or is very adherent to it, there should be a low threshold for the surgeon to consider removing the other structure (such as the thyroid gland) along with the parathyroid gland (‘en-bloc resection’) if possible.
  • The cancer can rarely spread to nearby lymph nodes in the neck, so there should be a low threshold to send atypical appearing lymph nodes encountered during the surgery for frozen pathology interpretation to rule this out.
    • If cancer spread to a lymph node is confirmed, the appropriate neck dissection should be performed at the same time as the parathyroidectomy.

There is a high rate of cancer recurrence in the neck if the cancer was not completely removed during the initial surgery (indicated by a positive margin on permanent pathology report).

Currently no adjuvant therapies (treatment used after surgery such as chemotherapy or radiation) are commonly used or recommended.

• Surgical outcomes / cure rates are the highest and complication rates are the lowest when surgery is performed by a high-volume surgeon (> 50 parathyroidectomy surgeries per year).
• To read more about the Parathyroidectomy surgery including what to expect, as well as details regarding recovery and risks see Parathyroidectomy.

Overall prognosis is good, with higher cure rates when negative margins (complete cancer removal) are achieved.

No universal cancer staging system has been established.

Recurrence rates have been reported to be as high as 50%, especially when positive margins are present.

10-year survival rates (how many patients have not died from the cancer 10 years following treatment) are 60-70%.

• If a patient dies from parathyroid cancer, it is not from the tumor invading a nearby structure in the neck, rather from uncontrollable hypercalcemia (elevated calcium levels in the blood).

Calcium and PTH levels in the blood can be used as effective tumor marker levels to check for recurrence of cancer.

• Calcium and PTH levels should be in the normal range if there is no cancer present.

Ultrasound of the neck can be considered looking for masses growing in the region of the previously located cancer.

• FNA (biopsy) with PTH washout can be considered if a suspicious mass is noted to confirm recurrence.

The preferred treatment for recurrence is surgery if possible (not invading vial structures of the neck like the trachea or carotid artery).

Medical management of the hypercalcemia (elevated calcium blood levels) is essential as this is the most common cause for death for recurrent parathyroid cancer.