Yan-Jun Su,Shao-Hao Cheng,Xi-Xiang Gong,Wei Zhao,Gao-Hong Zhu,Bo He,Yu-Shan Xu,Hua Zhou,Jun Qian,Ruo-Chuan Cheng＊

1Department of Thyroid Surgery,The First Affiliated Hospital of Kunming Medical University,Kunming 650032,China;2Department of Otolaryngology,The Sixth Affiliated Hospital of Kunming Medical University,Yuxi 650032,China;3Department of Thoracic Surgery,The First Affiliated Hospital of Kunming Medical University,Kunming 650032,China;4Department of Nuclear Medicine,The First Affiliated Hospital of Kunming Medical University,Kunming 650032,China;5Department of Medical Imaging,The First Affiliated Hospital of Kunming Medical University,Kunming 650032,China;6Department of Endocrine,The First Affiliated Hospital of Kunming Medical University,Kunming 650032,China;7Department of Radiology Oncology,The First Affiliated Hospital of Kunming Medical University,Kunming 650032,China

Parathyroid carcinoma is an extremely rare malignant tumor,composed primarily of vacuolated principal cells,but may also be composed of eosinophils.The exact etiology and pathogenesis of parathyroid carcinoma is unknown,and head and neck radiation exposure,chronic stimulation from renal failure,and familial syndromes can lead to the development of parathyroid carcinoma.Most parathyroid carcinoma is difficult to distinguish from benign HPT and is often diagnosed only when there is a recurrence of hypercalcemia several years later,which can manifest as weight loss,extreme fatigue,anorexia,and muscle atrophy.At present,surgical resection remains the primary treatment.In this case,the patient underwent initial surgery for primary hyperparathyroidism and was subsequently diagnosed with parathyroid carcinoma.During the 8 years of follow-up,the patient underwent 7 surgeries in combination with radiation therapy,chemotherapy and targeted medications.Although the neck tumor was cured,the patient died of complications related to hypercalcemia.We will review the literature on the combination of surgery,radiotherapy,chemotherapy,and targeted drug therapy in order to improve the diagnosis and treatment of parathyroid carcinoma.

Key words:Parathyroid carcinoma,Hypercalcemia,Surgery,Radiotherapy,Chemotherapy

Background

Parathyroid carcinoma (PC) is a rare endocrine neoplasm of unknown etiology that accounts for 0.005% of systemic malignancies and up to 0.5%-5%of primary hyperparathyroidism [1-3].The annual incidence of PC in Europe has been reported in the literature to be 3/10,000,000 [4],while James et al.[5]used the National Cancer Institute’s Surveillance,Epidemiology and End Result data analyzed for 2000-2012 reported an incidence rate of 3.6/10,000,000.PC is mostly sporadic and may be familial;the majority of PC is functional tumor.

Surgery is the only effective treatment for PC,but due to the lack of reliable tumor morphological features and serological markers for PC,even intraoperative frozen section examination is difficult to distinguish PC from parathyroid adenoma or parathyroid hyperplasia,resulting in the majority of patients diagnosed with PC postoperatively or at recurrence [2,3].Moreover,due to lack of treatment experience with PC,it often leads to inadequate initial treatment and resulting in local recurrence rates of 24% [6] and distant metastasis rates of 21% [1].Recurrence rates remain high after reoperation,there is no effective treatment for distant metastases,unless completely resection of metastatic tumors is possible,radiotherapy (RT) and chemotherapy are not effective in controlling tumor regression,and patients often die of metabolic complications of hypercalcemia due to high serum PTH,rather than from the tumor itself.The 5-year and 10-year overall survival(OS) rates for PC patients have been reported to be approximately 80%-91% [7,8] and 65.4%-72% [8,9],respectively;the 20-year OS rate is 39%,and the 5-year OS rate after the occurrence of distant metastasis is only 16% [10].

We now report a case of PC who was followed up for 8 years and underwent 7 operations,combined with RT,chemotherapy and sorafenib treatment.Although the tumor in the neck was cured,the patient still died of hypercalcemia related complication,and it is worthwhile to learn lessons from the treatment of this case.

Case presentation

The patient was a farmer,male,who had initial surgery for primary hyperparathyroidism at the age of 36 years(June 2013),after which he was diagnosed with PC.He underwent 6 subsequent operations until January 2019 due to local recurrence or distant metastasis;external radiation therapy to the neck in February 2016;and 1 course of chemotherapy with a combination of pyroxasin and oxaliplatin in December 2018.After 3 courses of sorafenib treatment from February to May 2019 and 1 course of chemotherapy with epirubicin and cyclophosphamide in May 2019,the patient abandoned treatment due to increased serum total calcium and PTH level and severe adverse effects,and subsequently three episodes of acute severe pancreatitis developed and the patient died in April 2020.A detailed treatment history is given below.

Treatment

Surgical treatment,RT,chemotherapy and sorafenib treatment are summarized in table below (Table 1).

Management of hypercalcemia

Hypercalcemia or hypercalcemia crisis (total serum calcium ＞ 3.75 mmol/L) occurred when tumor relapsed,symptoms include fatigue,poor appetite,nausea and vomiting.Intravenous rehydration solution,2,500 mL(sodium chloride 4.5 g + potassium chloride 4 g) along with loop diuretic (furosemide 20 mg/day,intravenous push) and salmon calcitonin (50 IU,iH,Tid) or zoledronic acid were applied to control hypercalcemia.It was not until the sixth surgery that 25-hydroxyvitamin D levels were measured,suggesting vitamin D deficiency (16.57 ng/mL) and 0.5 μg of calcitriol was administered daily.

Imaging examination

CT or MRI of the neck and/or chest have been performed prior to each surgery,and the positive findings are shown in the figure below (Figure 1).

99mTc-sestamibi parathyroid scintigraphy

Dual-phase99mTc-sestamibi parathyroid scintigraphy was not performed prior to the first surgery,which was performed prior to the subsequent re-operations for six times,and no MiBi uptake foci were found in the neck.Dual-phase99mTc-MiBi whole-body scintigraphy was performed in December 2018 prior to 6thoperation,a MiBi uptake foci (1.4 × 0.98 cm) was found in anterior superior mediastinal space,but no abnormalities were found in the neck,and multiple pulmonary grinded glass-like micro-nodules are also incompatible with MiBi.

Laboratory examination

Serum PTH and serum total calcium level

Serum PTH and serum total calcium levels showed a consistent trend over the whole course,and the changes in serum PTH and serum total calcium levels available before and after each operation are shown in the following figure (Figure 2),with the lowest serum PTH level (＜ 3 ng/L) after the third surgery,and the highest serum total calcium and PTH levels before the sixth surgery.

Pathology

PC was confirmed pathologically following each surgery.Tumor excised from the 7thoperation was also confirmed to be metastatic PC by HE staining and PTHimmunohistochemical staining (Figure 3A-D),with a 25% positive rate of Ki67 (Figure 3E) and strong expression of CD31and CD34molecules (Figure 3F-G).

Table 1 The summary of treatment history

Gene mutation test

Tumor-specific genetic changes using next-generation sequencing panel covers more than 300 genes associated with common oncology drugs,including partial exon and partial intron regions of targeted drugrelated genes,chemotherapy drug-related genes,and drug pathway-related genes.No gene mutations associated with targeted drugs and immunotherapy were revealed,and 22 gene mutations associated with chemotherapy were detected (Table 2);5 gene mutations of unspecified clinical therapeutic relevance were also found (Table 3).

Treatment outcome

Prior to the sixth surgery in November 2018,enhanced CT,MRI,MiBi-SPECT/CT,and 18F-FDG-PET-CT were all performed and no structural diseases were found in the neck (Figure 4).Meanwhile,highresolution ultrasound of the neck was performed by an experienced sonographer,FNAB was performed on suspicious structures and no malignant cells were detected,and the PTH assay from FNA washout was ＜1 ng/L.A whole body bone scan,gastroscopy,and laryngoscopy were performed,and no positive findings were found.All of those evidence proved the curative status of the neck tumor.

Due to limited therapeutic options and severe gastrointestinal symptoms caused by chemotherapy(epirubicin combined with cyclophosphamide)following sorafenib treatment,and the patient abandoned any treatment,resulting in the highest levels of PTH and serum total calcium 1 month later,1289.8 ng/L and 4.67 mmol/L,respectively,and subsequently hypercalcemia induced three episodes of acute severe pancreatitis and the patient died in April 2020.

Table 2 Gene mutations associated with chemotherapy

Figure 1 Preoperative CT/MRI of the neck or chest (Figures 1A-F,H-I:CT;Figure 1G:MRI).A:neck CT prior to the 1st surgery have been showed a 1.8 × 2.4 cm mass behind the right thyroid lobe;B:neck CT prior to the 2nd surgery have been showed a mildly enhanced recurrent tumor in right thyroid bed;C:neck CT prior to the 3rd surgery have been showed a mildly enhanced recurrent tumor in right thyroid bed;D:neck CT prior to the 4th surgery have been showed a mildly enhanced recurrent tumor in left level IV;E-F:chest CT prior to the 5th surgery have been showed a 1.2 × 0.8 cm nodule in the outer basal segment of the left lower lobe of the lung;G:chest MRI prior to the 6th surgery have been showed a 1.5 × 1 cm mass in the anterior superior mediastinal;H-I:chest CT prior to the 7th surgery have been showed recurrent tumor on the left diaphragmatic and left mural layer.

Figure 2 Serum total calcium and serum PTH levels trends during the course of the disease.A:1st operation(2d for calcium;4d for PTH);B:2nd operation;C:3rd operation;D:4th and 5th operation;E:6th operation;F:7th operation.(Normal range of serum total calcium:A:2.09-2.54 mmol/L,B-F:2.2-2.55 mmol/L.Normal range of serum PTH:A:6-80 ng/L,B-F:12-88 ng/L.)

Discussion

The case we report is not a successfully treated PC,nor is the case with the longest follow-up or the highest number of surgeries,but rather a case of locally cured and systemic failed in combination with RT,chemotherapy and targeted drugs after seven surgeries.It is worthwhile to draw lessons from this case in light of the literature review on surgery,RT,chemotherapy and targeted drug therapy.

Surgical treatment

Figure 3 Histopathology of PC from the 7th operation.A:intraoperative findings (black arrow:tumor implanted on the left diaphragm;yellow arrow:left lower lobe of the lung);B:cross appearance of the tumor resected;C:microscopic pathology of parathyroid carcinoma (HE stain,× 200);D:PTH staining (immunohistochemical stain,×200);E:proliferation assay (Ki67 immunohistochemical stain,25% positive rate);F:CD31 staining(immunohistochemical stain,× 200);G:CD34 staining (immunohistochemical stain,× 200).PC,parathyroid carcinoma.

Figure 4 Multiple imaging evaluation of the neck.A-B:enhanced MRI scan of the neck;C-D:enhanced CT scan of the neck;E:MiBi-SPECT/CT scan of the neck (fusion image);F:18F-FDG-PET-CT scan of the neck (fusion image).

Table 3 Gene mutations of unspecified clinical therapeutic relevance

PC is rare in clinical practice and the clinical features are usually similar to those of parathyroid adenoma.The lack of reliable tumor markers and the difficulty in identifying benign or malignant parathyroid tumors by preoperative imaging modalities or even intraoperative frozen section examination has resulted in approximately 50% of PC being diagnosed only when metastasis or recurrence occurs.Complete surgical resection is the main modality for the treatment of PC,especially in the initial surgery [11].A number of researchers have done statistical correlation between different treatment modalities (Table 4) and found that radical surgery has a lower recurrence rate than simple parathyroidectomy.The standard radical surgery is a cystic resection of the parathyroid tumor,the ipsilateral thyroid lobe and the surrounding infiltrating tissue(tracheal and/or esophageal wall),using R0 resection whenever possible,and should avoid tumor rupture leading to tumor cell spread [16-19].Unfortunately,about 35-90% of patients undergo local resection instead of en-bloc resection at initial treatment [7-8,20-21],resulting in a high recurrence rate in patients.In the present study,the biggest lesson learned was the result of the initial surgery without en-bloc resection and the high intraoperative suspicion of PC,but the inability to perform en-bloc resection of the surrounding infiltrating tissue along with it.Once any clinical evidence of suspected PC is present,en-bloc resection should be performed [22],and timely further surgery may provide a second chance to cure PC [20].The missed good timing of the initial surgery resulted in frequent postoperative recurrences in patients.In this regard,we should perform standard radical tumor resection in future surgeries once the tumor is preoperatively suspected or intraoperatively characterized as greater than 3 cm,grayish,lobulated,stony and hard,adherent or infiltrated with surrounding tissues,and for PC without en-bloc resection after initial surgery or postoperative diagnosis,completion of ipsilateral thyroid lobe and surrounding tissues should be promptly performed excision.

Surgical treatment of recurrence

Studies have shown that PC has an overall recurrence rate of up to 51% [1] and a local recurrence rate of up to 24% [6].Although some studies have concluded that reoperation after recurrence does not improve outcome[21],most studies have concluded that reoperation should be performed at the time of recurrence,and one study found that reoperation at the time of recurrence should improve prognosis by removing the ipsilateral recurrent laryngeal nerve,internal jugular vein,carotid sheath lymph nodes,and pre-tracheal lymphatic fat tissue [23].In this regard,at the first recurrence,we resected both the recurrent tumor,the infiltrating esophageal wall and the recurrent laryngeal nerve,and prophylactically performed unilateral CND and selective LND (grade III-IV).On postoperative day 1,serum PTH decreased to less than 3 ng/L,and the tumor was considered cured without further treatment,as detailed in Table 1.Unfortunately,biochemical recurrence occurred 1 month after surgery and structural recurrence occurred 6 months later.In this regard,we suggest that after reoperation at the time of recurrence,although the tumor was controlled by biochemical manifestations,adjuvant therapy such as:control of hypercalcemia,RT,Chemotherapy and target therapy,especially for hypercalcemia;secondly,PC metastasizes through both lymphatic and hematological routes,and the most common site of spread is regional lymph nodes.After controlling hypercalcemia,imaging should be performed to localize and assess the extent of the disease,and regular follow-up should be performed to prevent the possibility of recurrence.the recurrent laryngeal nerve.Preoperative hoarseness suggests involvement of the recurrent laryngeal nerve.There is no doubt that the loss of laryngeal nerve function caused by the tumor should be removed.However,it is often a dilemma for the inexperienced surgeon to remove the infiltrated but functional recurrent laryngeal recurrent nerve,as removal of the recurrent laryngeal recurrent nerve will inevitably lead to permanent hoarseness and decreased quality of life.It has been found that the recurrent laryngeal recurrent nerve without significant tumor infiltration should be protected,whereas the recurrent laryngeal recurrent nerve with significant infiltration should be resected[24-25].In the present case,it can be seen that the recurrent laryngeal recurrent nerve on the right side of the initial surgery was tightly wrapped by the tumor and should have been removed,but inexperience led to the failure to remove the laryngeal recurrent nerve infiltrated by the tumor,which became a potential source of tumor recurrence.In this regard,we suggest that removing the recurrent laryngeal nerve that is infiltrated by the tumor but is functioning normally may be more beneficial to the patient’s prognosis.

Table 4 Prognostic impact of different treatment modalities

CND

Lymph node metastases rarely occur at the time of initial diagnosis of PC,and whether prophylactic CND is performed remains controversial [1,21,26-31].Lee et al.[28] found that lymph node metastases were not associated with death (HR = 2.84;P= 0.227);Hundahl et al.[29] found that lymph node involvement did not affect the 5-year survival rate (82.6 and 83.3%).However,Talat et al.[1] found that central compartment lymph node metastasis was associated with poor prognosis in PC (HR = 6.16,95%CI:0.88-42.85,P=0.01) and a large sample study (n = 1022) by Sadler et al.[21] found that central compartment lymph node metastasis was associated with poor prognosis in PC(HR = 6.47 ,95%CI:1.81-23.11,P= 0.004) and concluded that standard radical surgery should also include ipsilateral central zone lymph node dissection[16-17].

To date,there is no evidence that prophylactic central neck dissection improves survival due to the lack of prospective studies.Therefore,it is generally accepted that clinically involved lymph nodes should be dissected,but there is no consensus on prophylactic CND.Although this study performed bilateral CND and bilateral elective LND (grades III-IV) in the 2nd,3rd,and 4th surgeries without lymph node involvement,we found an implantation tumor lesion,which certainly increases the risk of identifying potential malignancy by clinicians.In this regard,we recommend prophylactic CND in patients with a high risk of lymph node metastasis (tumors ＞ 3 cm).

Nonsurgical treatment

Radiation therapy.Traditionally,PC is considered a tumor insensitive to RT,and the literature reports that RT does not significantly improve local tumor control and survival [6,27].Asare et al.[30] analyzed data from 733 PC patients in the National Cancer Database and found that RT did not improve OS (HR = 1.24,95 %CI:0.75-2.05,P= 0.4),but the study did not analyze tumor severity with and without RT.Sadler et al.[21] applied RT in 13% of PC patients and found that patients treated with RT had shorter survival (129.72 m vs 132.25 m),lower 5-year survival (RR= 2.08,95%CI:1.13-3.81,P= 0.021),suggesting that RT should be performed in PC patients with severe disease.As these were nonprospective studies,Prof.Shaha agreed that the conclusion that RT treatment has no significant effect on prognosis should be viewed with caution,which needs to be confirmed by data from more prospective studies with larger samples.

Christakis et al.[32] of MD Anderson reported that RT was applied in 11% of PC patients and good local control rates were obtained in those who received RT(total dose of 42-66 Gy) postoperatively [33].Munson et al.[34] showed that four patients received RT (dose of 66-70 Gy) postoperatively and no local recurrence was observed in any of them.Our patient was treated with RT at a total dose of 70 Gy 1 month after palliative surgery for the 3rd recurrent tumor in the neck,and from the follow-up results,neck recurrence was effectively controlled.There is no consensus on which patients need RT treatment;when to start;and how to proceed,and these issues need to be addressed in future work.Until these issues are resolved,based on the high rate of local recurrence (50%) and poor prognosis of PC,we recommend prompt postoperative RT for patients with high risk of recurrence or WITH positive surgical margins status,rather than waiting for recurrence or palliative surgery before RT treatment,which may allow more PC patients to benefit from adjuvant RT therapy.The prognosis may not be as poor if that patient receives RT after the initial surgery or the first reoperation.

Chemotherapy and target therapy.Due to the rarity of PC and individual variability,chemotherapy has not proven effective in the treatment of PC,and most treatment regimens are derived from personal experience and case reports,although successes have been reported with monotherapy with dacarbazine and with the combination of fluorouracil,cyclophosphamide,and dacarbazine,as well as with the combination of methotrexate,adriamycin,cyclophosphamide,and lomustine [35-37],but there is no consensus on an effective chemotherapy regimen for PC.In the present case,after the 6th surgery,calcium and PTH did not fall into the normal range,and imaging suggested the presence of pulmonary metastases,for which the patient was willing to try chemotherapy with a regimen of pirofloxacin (40 mg/m2,ivgtt) combined with oxaliplatin (85 mg/m2,ivgtt).Unfortunately,instead of a decrease in serum PTH and calcium,an increase was observed after 3 weeks of treatment(Figure 2),presumably making this chemotherapy regimen ineffective for treatment.However,after 4 weeks,serum PTH and calcium decreased by 21.45%and 13.37%,respectively,and we considered that the inhibitory effect of osteopontin may be caused by osteopontin rather than chemotherapy.In addition,we identified 22 genetic mutations associated with chemotherapy (Table 3) and reviewed the literature on the association between these mutations and efficacy and adverse effects,combined with the success of cyclophosphamide combined with other drugs for PC[37-38],we tried epirubicin (90 mg/m2) combined with cyclophosphamide (500 mg) after failure of sorafenib/m2) for chemotherapy.Due to severe digestive adverse effects such as nausea,vomiting and loss of appetite,the patient refused further treatment after 1 month when peak serum PTH and total serum calcium reached 1289.8 ng/L and 4.67 mmol/L,respectively.Unfortunately,it is difficult to assess the efficacy of this regimen with only 1 cycle of chemotherapy,and such severe chemotherapy-related adverse effects may be related to the chemotherapy drug dose or to the overlap of adverse effects caused by chemotherapy immediately after sorafenib discontinuation.In this regard,we believe that the emergence of new treatment systems may improve the future response to drug therapy with a large number of prospective studies to determine personalized adjuvant.

Recently,Rozhinskaya et al.[12] treated a PC patient with aCDC73mutation and unresectable lung metastases with sorafenib with good results.Kutahyalioglu et al.[39] reported a case of aTSC1mutation with Vandetanib and everolimus (mTOR inhibitor) with short-term (2.5 months) of stable disease and well-controlled calcium levels.Sorafenib is a tyrosine kinase inhibitors (TKIs) with anti-angiogenic,cell proliferation and survival effects.We found that the patient had aCDC73gene mutation by next-generation sequencing(64.04%),for which we administered sorafenib for 3 weeks (400 mg,bid),but no tumor suppression was seen.We believe that theCDC73gene may be the causative gene in this case of sporadic PC and is not a target of sorafenib.Despite the lack of effect of our treatment,targeted therapy plays an important role in the treatment of PC [24,39

41].Although there is no unanimous agreement on chemotherapy and targeted therapy,the emergence of new drugs and the understanding of PC pathogenesis may change this difficulty in the future.In this regard,we need more studies to better understand PC tumorigenesis and to explore the use of TKIs and/or immunotherapy or other targeted therapies.Based on limited clinical data,we can use epigenetic analysis as well as precise oncological methods of tumor immunoassays that can be used to guide targeted therapies and/or immunotherapies.The choice of targeted therapy or immunotherapy can be driven by the discovery of precise molecular alterations based on the mutation and characteristics of the tumor,while patients without targeted mutations can be considered for the use of multi-targeted TKIs such as anti-angiogenic agents like sorafenib/lenvatinib/cabozantinib.

Conclusion

In the discussion of this case,we have reported and reviewed the literature and we have gained many insights into the challenging diagnosis and treatment of PC.Standard radical surgery is the mainstay of treatment for PC,including complete excision of PC and the ipsilateral thyroid lobe,together with central neck dissection and removal of the infiltrating recurrent laryngeal nerve.Adjuvant postoperative external RT helps to control local recurrence.Surgical approaches should also be sought for resectable recurrent or metastatic tumours,and even palliative resection can be helpful in the management of hypercalcaemia.There is no effective chemotherapy regimens available.With the increasing importance of targeted drugs,we believe that the emergence of new therapeutic systems may improve the future response to drug therapy.