Parathyroid Carcinoma: Incidence, Survival Analysis, and Management: A Study from the SEER Database and Insights into Future Therapeutic Perspectives

Advances in the management of parathyroid carcinoma

Parathyroid carcinoma (PCA) is a rare malignancy accounting for approximately 1% of all patients with primary hyperparathyroidism. It is characterised by excessive parathyroid hormone (PTH) production. This manuscript reviews recent advances in the management of parathyroid carcinoma, focusing on molecular insights, diagnostic modalities, surgical innovations, adjuvant therapies, and emerging targeted treatments. Recently published manuscripts (between 2022 and 2023) were obtained from Medical Literature Analysis and Retrieval System Online (Medline), Excerpta Medica (Embase), Cochrane Central Register of Controlled Trials (CENTRAL), and European Union Drug Regulating Authorities Clinical Trials (EudraCT). These were assessed for their relevance in terms of the diagnosis and management of patients with PCA. This manuscript explores the role of genetic profiling and presents case studies illustrating successful management strategies. The manuscript also discusses the ongoing challenges in the management of parathyroid carcinoma, suggesting future research directions and potential therapeutic avenues.

Risk Factors of Distant Metastatic Parathyroid Carcinoma and Insights into Therapeutic Perspectives

BACKGROUND

Distant metastatic parathyroid carcinoma (DM-PC) is a rare but often lethal entity with limited data about prognostic indicators. We sought to investigate the risk factors, patterns, and outcomes of DM-PC.

METHODS

In this observational cohort study, 126 patients who underwent surgery for PC at a tertiary referral center from 2010 to 2023 were enrolled, among whom 38 had DMs. Univariate and multivariate Cox regression analyses were used to assess the effects of prognostic factors on DM.

RESULTS

The cumulative incidence of DM was 14.1%, 33.8%, and 66.9% at 5, 10, and 20 years in the duration of disease course, respectively. DM-PC patients suffered a worse 5-year overall survival of 37.1% compared with 89.8% in the non-DM patients (p < 0.001). DM-PC patients also suffered more previous operations (p < 0.001), higher preoperative serum calcium (p<0.001) and parathyroid hormone (PTH) levels (p < 0.001), lower frequencies of R0 resection (p < 0.001), higher rates of pathological vascular invasion (p = 0.020), thyroid infiltration (p = 0.027), extraglandular extension (p = 0.001), upper aerodigestive tract (UAT) invasion (p < 0.001), and lymph node metastasis (p < 0.001). Multivariate Cox regression revealed that non-R0 resection (HR 6.144, 95% CI 2.881-13.106, p < 0.001), UAT invasion (HR 3.718, 95% CI 1.782-7.756, p < 0.001), and higher preoperative PTH levels (HR 1.001, 95% CI 1.000-1.001, p = 0.012) were independent risk factors of DM.

CONCLUSIONS

Upper aerodigestive tract invasion and higher preoperative PTH levels might be risk factors for possible metastatic involvement of PC. R0 resection and closer surveillance should be considered in such cases to minimize the risk of DM and to optimize patient care.

The prognostic value of lymph node dissection in patients with parathyroid carcinoma

Background

Surgery is the only curative treatment strategy for parathyroid carcinoma (PC). However, the optimal extent of surgery remains uncertain, particularly regarding whether routine central lymph node dissection (LND) confers a survival advantage to patients with PC. This study aimed to evaluate the prognostic value of LND in PC patients.

Methods

Patients diagnosed with PC between 2004 and 2018 were identified in the Surveillance, Epidemiology, and End Results (SEER)-18 registries. With inclusion and exclusion criteria, a total of 338 patients were included as cohort 1 to describe the characteristics of PC, while 215 patients were selected as cohort 2 to assess the effect of LND on cancer-specific survival (CSS). Univariate and multivariate Cox proportional hazards regression models were used to identify independent risk factors associated with CSS. Propensity score matching (PSM) was performed to adjust for potential confounding variables. The prognostic value of LND was further analyzed in subgroups stratified by predictors associated with CSS.

Results

The 5- and 10-year CSS were 94.4% and 87.9% respectively in cohort 1. LND failed to significantly improve CSS in the entire cohort 2 and the PSM cohort 2. Large tumor size (>40 mm) and distant metastasis were independently associated with poor CSS. Subgroup analyses revealed that LND was not significantly associated with improved CSS in patients with aggressive PC, such as those with a tumor size greater than 40 mm. Unexpectedly, LND may compromise CSS in patients with distant disease (P=0.03).

Conclusions

PC is a rare and indolent endocrine malignancy. The presence of large tumors and distant metastases are independent predictors of poor CSS. Routine central LND as part of initial surgery does not significantly improve CSS in PC patients, even for those with large tumors, lymph node metastasis, or distant disease.

A case report of mediastinal parathyroid carcinoma in a chronic kidney disease patient: Addressing management conundrum

Parathyroid carcinoma is a rare malignancy; and it is rarer to find one located in an ectopic location. Ectopic parathyroid glands are a reported cause of failed primary surgery for hyperparathyroidism. We report here a 73-year-old male who previously had parathyroidectomy for primary hyperparathyroidism but then had recurrence of his symptoms with a diagnosis of a mediastinal parathyroid carcinoma on further evaluation. This presentation of complicated mediastinal parathyroid carcinoma posed significant diagnostic and management challenges due to comorbid stage IV chronic kidney disease (CKD). Secondly, due to the same comorbid condition, a more aggressive calcimimetic regimen could not be undertaken due to the risk of renal dysfunction with potential progression to dialysis status. Thirdly, he was a high-risk surgical candidate due to significant cardiovascular risks. Ideally, open surgical intervention would be recommended but due to the associated risks, he was managed with robotic-assisted thoracoscopic surgery. He subsequently developed hypocalcemia which normalized with supplemental calcium at follow-up.

Four-Dimensional Computed Tomography for Parathyroid Adenoma Localization: A Pre-Operative Imaging Protocol

OBJECTIVE

Primary hyperparathyroidism (PHPT) affects approximately 0.86% of the population, with surgical resection as the treatment of choice. A 4D computed tomography (CT) is a highly effective tool in localizing parathyroid adenomas; however, there is currently no defined role for 4D CT when stratified against ultrasonography (USG) and nuclear medicine Technetium Sestamibi SPECT/CT (SES) imaging.

STUDY DESIGN

Retrospective Study.

SETTING

University Hospital.

METHODS

All patients who underwent parathyroidectomy for PHPT between 2014 and 2019 at a single institution were reviewed. Patients who had a 4D CT were included. We compared outcomes of 4D CT as a second line imaging modality to those of USG and SES as first line modalities. An imaging algorithm was proposed based on these findings.

RESULTS

There were 84 patients identified who had a 4D CT after unsuccessful first line imaging. A 4D CT localized parathyroid adenoma to the correct quadrant in 64% of cases, and to the correct laterality in 75% of cases. Obese patients had significantly lower rates of adenoma localization with USG (33.4%), compared to non-obese patients (67.5%; P = .006). In determining multigland disease the sensitivity of 4D CT was 86%, while the specificity was 87%.

CONCLUSIONS

A 4D CT has impressive rates of accurate localization of parathyroid adenomas; however due to the radiation exposure involved, it should remain a second line imaging modality. PHPT patients should first be evaluated with USG, with 4D CT used if this is unsuccessful and patients are greater than 40 years old, have a high BMI, or are having revision surgery.

Parathyroid carcinoma: Imaging features of initial presentation and recurrence. A single center experience

BACKGROUND AND PURPOSE

Parathyroid carcinoma is the rarest endocrine neoplasm with very few published data discussing its imaging appearance with primary focus on ultrasound imaging features. We present our 23 years institutional experience to highlight multimodality imaging evaluation at presentation and at recurrence.

MATERIAL AND METHODS

Retrospective chart review of clinical and pathological diagnosis of parathyroid carcinoma patients presented for initial or recurrent disease management at M.D. Anderson Cancer Center between the period of January 2000 and February 2023 was performed. Imaging findings on US, CT, PET/CT, and technetium-99m sestamibi were analyzed for initial and local recurrent parathyroid carcinoma. We further assess patterns of distant recurrence and its location.

RESULTS

Twenty three patients with pathological and clinical diagnosis of initial (14 patients) or recurrent parathyroid carcinoma (14 patients) were included in this study. US findings of parathyroid carcinoma were larger lesions, increased/irregular vascularity, and non-circumscribed margins. Multiphasic CT findings of parathyroid carcinoma included an arterially enhancing lesion that is hypoenhancing relative to the thyroid and demonstrates no washout on delayed imaging. Highly suggestive findings for recurrent disease included a hypoechoic solid nodule (91.67%) with increased vascularity on ultrasound (81.8%) with corresponding enhancement on CT.

CONCLUSION

Parathyroid carcinoma is a rare malignancy often diagnosed after surgical resection. We provided CT and US imaging features that are helpful in suggesting the diagnosis of parathyroid carcinoma and detection of early local recurrence.

Overview of Thyroid and Parathyroid Disease-The Endocrinology Perspective

Thyroid and parathyroid disorders are quite common in the population and range from benign to malignant conditions that may be hormonally active or inactive. Select disorders of the thyroid and parathyroid can be managed medically, although there are a variety of circumstances that may require definitive management with surgery. Surgical intervention may be required for hormonal control, compressive symptoms, or for the removal and/or control of malignancy. The endocrinologist's perspective of the preoperative and postoperative management regarding thyroid and parathyroid surgeries will be discussed.

Approach to the Patient With Parathyroid Carcinoma

Parathyroid carcinoma (PC) is usually associated with severe symptomatic primary hyperparathyroidism (PHPT) and accounts for less than 1% of all cases of PHPT and approximately 0.005% of all cancers. PC most commonly occurs as a sporadic disease and somatic CDC73 mutations can be detected in up to 80% of cases. Approximately 30% of patients harbor a germline mutation of the CDC73 gene. Preoperative diagnosis of PC is difficult because no disease-specific markers are available, and PC should be suspected in patients with severe hypercalcemia and end-organ complications. The diagnosis is based on the evidence of invasive tumor growth at histology and/or metastases. En bloc resection of the tumor, together with the ipsilateral thyroid lobe and adjacent structures, should be performed by an experienced surgeon when PC is suspected. This surgical approach reduces the risk of recurrence and metastasis and offers the highest chance of cure. Nonetheless, PC has a recurrence rate of 40% to 60% and, if feasible, multiple surgical procedures should be performed. When surgery is no longer an option, medical treatment is aimed to reduce hypercalcemia and target organ complications. Targeted agents have been effectively used in a few cases. We describe herein a patient with severe PHPT due to PC and provide a systematic diagnostic and treatment approach. A thorough review of the medical history, a typical clinical and biochemical phenotype and, in some cases, the revision of the histological examination provide the clues for the diagnosis of PC.

Comparison of prognosis after partial and total surgical resection for parathyroid carcinoma: an inverse probability of treatment weighting analysis of the SEER database

Background

Complete resection of the tumor and the ipsilateral thyroid lobe at the primary surgery is the "gold standard" for the treatment of parathyroid carcinoma (PC). However, differences in the overall survival (OS) of patients with PC who underwent partial and total surgical resection remain to be determined.

Methods

Data on patients with PC who underwent partial and total surgical resection were extracted from the Surveillance, Epidemiology and End Results (SEER) database (2000-2018). The X-tile software (https://medicine.yale.edu/lab/rimm/research/software/) was used to define the optimal cut-off values for continuous variables. The inverse probability of treatment weighting (IPTW) method was used to reduce the selection bias. IPTW-adjusted Kaplan-Meier curves and Cox proportional hazards models were used to compare the OS of patients with PC in the partial and total surgical resection groups.

Results

A total of 334 patients with PC were included in this study (183 and 151 in the partial and total surgical resection groups, respectively). The optimal cut-off values for age at diagnosis were 53 and 73 years, respectively, while that for tumor size was 34 mm. In both the Kaplan-Meier analysis and univariable Cox proportional hazards regression analysis before IPTW, the difference in OS between the partial and total surgical resection groups was not statistically significant (p>0.05). These findings were confirmed in the IPTW-adjusted Kaplan-Meier analysis and multivariate Cox proportional hazards regression analysis (p>0.05). Subgroup analysis revealed that total surgical resection was beneficial for OS only in the subgroup with unknown tumor size.

Conclusion

There was no significant difference in the prognosis of patients who underwent partial and total surgical resection. This finding may provide a useful reference for the treatment of PC.

Parathyroid Carcinoma Presenting as Recurrent Primary Hyperparathyroidism and Neck Mass: A Case Report

Parathyroid carcinoma is a rare endocrine neoplasm that accounts for <1% of cases of primary hyperparathyroidism. The management of parathyroid carcinoma is a challenge due to the high rate of local recurrence of the tumour. We report the case of a middle-aged north Indian woman who presented with recurrent primary hyperparathyroidism due to parathyroid carcinoma. She presented with a recurrent palpable hard neck mass and underwent radical dissection of the neck six times. At the time of writing this report, she was referred for external beam radiotherapy to the neck. Parathyroid carcinoma is a rare malignancy with an indolent but tenacious course. Complete resection at the time of initial surgery determines the prognosis of the neoplasm. Chemotherapy and radiotherapy are usually ineffective. Hypercalcaemia needs to be aggressively managed. A multidisciplinary team is required to effectively manage parathyroid carcinoma.

Parathyroid carcinoma presenting as severe hypercalcaemia responding to steroids

A man in his 50s was referred with profound, symptomatic hypercalcaemia. He was diagnosed with primary hyperparathyroidism, confirmed on ^99mTc-sestamibi scan. He was treated for the hypercalcaemia and referred to ear, nose and throat (ENT) surgeons for parathyroidectomy, which was delayed due to the COVID-19 pandemic. In the ensuing 18 months, he had five hospital admissions with severe hypercalcaemia requiring intravenous fluids and bisphosphonate infusions. During the last admission, hypercalcaemia was resistant to maximal medical management. Emergency parathyroidectomy was planned, but delayed due to intervening COVID-19 infection. Due to persistent severe hypercalcaemia (serum calcium: 4.23 mmol/L), he was commenced on intravenous steroids, following which serum calcium normalised. Subsequently, he underwent emergency parathyroidectomy, which normalised his serum parathyroid and calcium levels. On histopathological examination, a diagnosis of parathyroid carcinoma was made. On follow-up, patient remained well and normocalcaemic. In patients with primary hyperparathyroidism unresponsive to standard therapy, but responsive to steroids, underlying parathyroid malignancy should be considered.

A Nomogram for Relapse/Death and Contemplating Adjuvant Therapy for Parathyroid Carcinoma

Parathyroid carcinoma (PC) is a rare endocrine malignancy with an increased incidence in the last decade. There is no reliable prognostic staging system for PC. Several hosts, tumors, and tumor microenvironment factors have been negatively correlated with survival in the last decade. Surgical resection with negative margins is still the standard of treatment in PC. Chemo and radiotherapy have no proven beneficial effect. A new promising approach with molecular profiling could lead to adjuvant therapies.

Multiple Metastases of Parathyroid and Papillary Thyroid Carcinoma in a Female Patient Treated with Long-Term Hemodialysis

Parathyroid cancer is a rare, clinically aggressive malignancy with a prevalence of approximately 0.005% relative to all carcinoma cases and 1-5% among patients with primary hyperparathyroidism. Prognosis largely depends on the extent of the primary surgery. Non-radical surgical treatment increases the risk of local and distant metastases of the parathyroid cancer associated with limited treatment options. The combination of thyroid and parathyroid disorders has been described rather well for the general population; however, cases of parathyroid and thyroid carcinoma in the same patient are extremely rare (1 case per 3000 patients with parathyroid disorders). We present a rare clinical case of combination of parathyroid and thyroid cancers with metastases of both tumors to the neck lymph nodes in a woman with a mutation in the MEN1 gene (NM_130799.2): c.658T > C p.Trp220Arg (W220R), who has been exposed to radiation for 20 years before diagnosis of thyroid cancer and received renal replacement therapy with long-term hemodialysis before the diagnosis of parathyroid cancer. The patient underwent several surgeries because of metastases of the parathyroid cancer in the neck lymph nodes. Surgeons used intraoperative navigation methods (single-channel gamma detection probe, Gamma Probe 2, and fluorescence angiography with indocyanine green (ICG)) to clarify the volume of surgery. Currently, the patient is still in laboratory remission, despite the structural recurrence of tumors.

Margin Free Resection Achieves Excellent Long Term Outcomes in Parathyroid Cancer

Long-term outcomes of parathyroid cancer remain poorly documented and unsatisfactory. This cohort includes 25 consecutive parathyroid cancer patients with median follow-up of 10.7 years (range 4.1−26.5 years). Pre-operative work-up in the center identified a suspicion of parathyroid cancer in 17 patients. En bloc resection, including the recurrent laryngeal nerve in 4/17 (23.5%), achieved cancer-free resection margins (R0) in 82.4% and lasting loco-regional disease control in 94.1%. Including patients referred after initial surgery elsewhere, R0 resection was achieved in merely 17/25 (68.0%) of patients. Cancer-positive margins (R1) in 8 patients led to local recurrence in 50%. On multivariate analysis, only margin status prevailed as independent predictor of recurrence free survival (χ2 19.5, p < 0.001). Local excision alone carried a 3.5-fold higher risk of positive margins than en bloc resection (CI95: 1.1−11.3; p = 0.03), and a 6.4-fold higher risk of locoregional recurrence (CI95: 0.8−52.1; p = 0.08). R1-status was associated with an 18.0-fold higher risk of recurrence and redo surgery (CI95: 1.1−299.0; p = 0.04), and a 22.0-fold higher probability of radiation (CI95: 1.4−355.5; p = 0.03). In patients at risk, adjuvant radiation reduced the actuarial risk of locoregional recurrence (p = 0.05). When pre-operative scrutiny resulted in upfront oncological surgery achieving cancer free margins, it afforded 100% recurrence free survival at 5- and 10-year follow-up, whilst failure to achieve clear margins caused significant burden by outpatient admissions (176 vs. 4 days; χ2 980, p < 0.001) and exposure to causes for concern (1369 vs. 0 days; χ2 11.3, p = 0.003). Although limited by cohort size, our study emphasizes the paradigm of getting it right the first time as key to improve survivorship in a cancer with excellent long-term prognosis.

Mediastinal Parathyroid Cancer

Parathyroid cancer (PC) is rare, but its pre-operative recognition is important to choose appropriate access strategies and achieve oncological clearance. This study characterizes features of mediastinal parathyroid cancer (MPC) and explores criteria aiding in the pre-operative recognition of malignancy. We assembled data from 502 patients with mediastinal parathyroid neoplasms (MPNs) from a systematic review of the literature 1968−2020 (n = 467) and our own patient cohort (n = 35). Thirty-two of the 502 MPNs (6.4%) exhibited malignancy. Only 23% of MPC patients underwent oncological surgery. Local persistence and early recurrence at a median delay of 24 months were frequent (45.8%), and associated with a 21.7-fold (95%CI 1.3−351.4; p = 0.03) higher risk of death due to disease. MPCs (n = 30) were significantly larger than cervical PC (n = 330), at 54 ± 36 mm vs. 35 ± 18 mm (χ2 = 20; p < 0.0001), and larger than mediastinal parathyroid adenomas (MPA; n = 226) at 22 ± 15 mm (χ2 = 33; p < 0.01). MPC occurred more commonly in males (60%; p < 0.01), with higher calcium (p < 0.01) and parathyroid hormone (PTH) levels (p < 0.01) than MPA. Mediastinal lesions larger than 3.0 cm and associated with a corrected calcium ≥ 3.0 mM are associated with a more than 100-fold higher odds ratio of being malignant (OR 109.2; 95%CI 1.1−346; p < 0.05). The composite 3 + 3 criterion recognized 74% of all MPC with an accuracy of 83%. Inversely, no MPN presenting with a calcium < 3.0 mM and size < 3.0 cm was malignant. When faced with pHPT in mediastinal location, consideration of the 3 + 3 rule may trigger an oncological team approach based on simple, available criteria.

Immunohistochemical Profile of Parathyroid Tumours: A Comprehensive Review

Immunohistochemistry remains an indispensable tool in diagnostic surgical pathology. In parathyroid tumours, it has four main applications: to detect (1) loss of parafibromin; (2) other manifestations of an aberrant immunophenotype hinting towards carcinoma; (3) histogenesis of a neck mass and (4) pathogenetic events, including features of tumour microenvironment and immune landscape. Parafibromin stain is mandatory to identify the new entity of parafibromin-deficient parathyroid neoplasm, defined in the WHO classification (2022). Loss of parafibromin indicates a greater probability of malignant course and should trigger the search for inherited or somatic CDC73 mutations. Aberrant immunophenotype is characterised by a set of markers that are lost (parafibromin), down-regulated (e.g., APC protein, p27 protein, calcium-sensing receptor) or up-regulated (e.g., proliferation activity by Ki-67 exceeding 5%) in parathyroid carcinoma compared to benign parathyroid disease. Aberrant immunophenotype is not the final proof of malignancy but should prompt the search for the definitive criteria for carcinoma. Histogenetic studies can be necessary for differential diagnosis between thyroid vs. parathyroid origin of cervical or intrathyroidal mass; detection of parathyroid hormone (PTH), chromogranin A, TTF-1, calcitonin or CD56 can be helpful. Finally, immunohistochemistry is useful in pathogenetic studies due to its ability to highlight both the presence and the tissue location of certain proteins. The main markers and challenges (technological variations, heterogeneity) are discussed here in the light of the current WHO classification (2022) of parathyroid tumours.