|Year : 2016 | Volume
| Issue : 2 | Page : 59-62
Evaluation of distant metastasis in treated thyroid cancers: Study of radioiodine scans in a tertiary care center
US Vishal Rao1, Srinidhi Koya2, Sataksi Chatterjee3, Ashutosh A Patil4, Ravi C Nayar5, KG Kallur6
1 Department of Surgical Oncology, Senior Consultant Surgical Oncologist (Head and Neck), Health Care Global Enterprises Ltd., Bengaluru, Karnataka, India
2 Department of Academics, Health Care Global Enterprises Ltd., Bengaluru, Karnataka, India
3 Department of Surgical Oncology (Head and Neck), Health Care Global Enterprises Ltd., Bengaluru, Karnataka, India
4 Department of Surgical Oncology (Head and Neck), Associate Consultant, Health Care Global Enterprises Ltd., Bengaluru, Karnataka, India
5 Department of Surgical Oncology, Consultant Surgical Oncologist (Head and Neck), Health Care Global Enterprises Ltd., Bengaluru, Karnataka, India
6 Department of Nuclear Medicine, Head of the Department, Health Care Global Enterprises Ltd., Bengaluru, Karnataka, India
|Date of Web Publication||20-Dec-2016|
U S Vishal Rao
Department of Surgical Oncology, Health Care Global Enterprises Ltd., Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
The presence of distant metastases is one of the most important predictive factors of poor outcomes in thyroid cancer patients. Apart from distant metastasis, sex, age, histopathological subtypes, and completeness of surgical resection are the other prognostic indicators of survival. Our attempt in this study is to analyze the presence of distant metastasis in operated patients of thyroid malignancy and evaluate these prognostic indicators in the metastatic subgroup. Objective: The objective of this study was to retrospectively analyze the presence and extent of distant metastasis among treated thyroid cancer patients. Materials and Methods: The postoperative radioiodine scan reports of the patients who presented to Health Care Global Enterprises Ltd., Bengaluru over a period of 8 years (January 2008 to December 2015) were analyzed. Results: Sixty-six patients out of the 499 patients evaluated (13.22%) had distant metastasis. Most of the patients with distant metastasis were females, aged 45 years and above and had papillary carcinoma of thyroid. Percentage of skeletal and pulmonary metastasis was almost equal in the study group. Conclusion: The patterns of distant metastasis were similar to the trends in literature, except for increased incidence of skeletal metastasis, more so in a follicular subtype of papillary carcinomas.
Keywords: Distant metastasis, follicular variant of papillary carcinoma, thyroid malignancy
|How to cite this article:|
Vishal Rao U S, Koya S, Chatterjee S, Patil AA, Nayar RC, Kallur K G. Evaluation of distant metastasis in treated thyroid cancers: Study of radioiodine scans in a tertiary care center. J Head Neck Physicians Surg 2016;4:59-62
|How to cite this URL:|
Vishal Rao U S, Koya S, Chatterjee S, Patil AA, Nayar RC, Kallur K G. Evaluation of distant metastasis in treated thyroid cancers: Study of radioiodine scans in a tertiary care center. J Head Neck Physicians Surg [serial online] 2016 [cited 2019 Jul 21];4:59-62. Available from: http://www.jhnps.org/text.asp?2016/4/2/59/196222
| Introduction|| |
The detection of distant metastasis in thyroid cancer is important since it is a poor prognostic indicator of survival.  The overall incidence of distant metastases among different histopathological subtype of the thyroid malignancy varies between 10 and 35%.  The survival rates of these patients are reduced by 50%.  Multi-site metastases are associated with a high mortality rate of 92% at 5 years. The incidence is found to be highest in Hürthle cell carcinomas (33%) and least in papillary thyroid carcinoma (10%). 
The objective of this study was to retrospectively analyze the extent and site of distant metastasis among thyroid cancer patients and to evaluate the other prognostic indicators (age, sex, histopathological subtypes, and completeness of surgical resection) in relation to the metastatic subgroup.
| Materials and Methods|| |
After Institutional Ethical Review Board clearance was obtained, the case records of patients who were treated for thyroid cancer at the Department of Head and Neck Surgery, Health Care Global Enterprises Ltd., Bengaluru, from January 2008 to December 2015 were studied. The postoperative radioiodine scan reports of these patients were evaluated for the presence of distant metastasis. The following parameters were documented and analyzed:
- Presence of metastasis (nodal and distant) in the patients and the age, sex, histopathological subtypes, and completeness of surgical resection in the metastatic subgroup
- Percentage of distant metastasis to lung, skeletal organ, and multi-site metastasis
- The treatment dose of radioiodine for the patients with distant metastasis.
| Results|| |
Postoperative radioiodine scan of 499 thyroid cancer patients was analyzed. Among them, 66 patients (13.22%) had distant metastasis, 62 patients (12.42%) had nodal metastasis. Among these, 12 patients (2.4%) had both distant as well as nodal metastasis.
Majority of the patients with distant metastasis were female (40/66 patients [60.60%]) and aged 45 years and above (55/66 patients, [83%]) [Figure 1].
|Figure 1: Age and sex distribution of the patients with distant metastasis with thyroid malignancy|
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Forty patients had papillary carcinoma of the thyroid (40/66 cases [59.09%]) and 22 (33.33%) patients had follicular carcinoma. Anaplastic and poorly differentiated subtypes were observed in one and three patients, respectively [Figure 2]. Out of the forty patients of papillary carcinoma thyroid, 19 patients had lung metastasis, 15 patients had skeletal metastasis, 3 patients had multiple organ metastasis (most commonly lung, bone, and others), and 3 patients had other organ metastasis. On the other hand, out of 22 cases of follicular carcinoma, skeletal metastasis predominated (11 cases). There were 11 patients who had follicular variant of papillary carcinoma of the thyroid. Out of these 11 patients of follicular variant of papillary carcinomas, the majority had skeletal metastasis (5/11 patients [45.45%]).
|Figure 2: Histopathological subtypes of thyroid malignancies with distant metastasis|
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Organ-specific analysis of the metastatic subgroup revealed that the skeletal metastasis (39%) and lung metastasis (38%) was almost equal in the study group [Figure 3] and [Chart 1].
The postoperative thyroglobulin level was evaluated before the radioiodine scans in all patients. The average thyroglobulin level for patients with skeletal and pulmonary metastasis was 2004 ng/dl and 4465 ng/dl, respectively. Seventeen patients out of 66 required a second radioiodine treatment.
Thirty-three out of 66 patients had evidence of postoperative residual thyroid tissue in the radioiodine scan reports. The treatment dose of radioiodine was 200 mCi in most of the patients with distant metastasis (62%).
To summarize, most of the patients with distant metastasis were females, aged 45 years and above and had papillary carcinoma of the thyroid. Patients having skeletal and pulmonary metastasis were almost equal in number.
| Discussion|| |
Metastasis from thyroid cancer varies from 4 to 15%. ,,, The most common site of metastasis is the lungs, followed by the bone with the former having a better prognosis.  Twenty percent of the thyroid malignancies have bone metastasis. ,, In this study, distant metastasis was present in 13.22% of the total number of patients. The percentage of skeletal metastasis (39% of the metastasis) was almost the same as lung metastasis (38% of the metastasis).
Eighty-three percent of these patients with metastasis in our study group were aged 45 years and above implicating that the distant metastatic disease is commonly encountered among the older patients. Most of the patients with distant metastasis were female (60.60%). However, the study population of 499 patients had more number of female patients (331 females, 168 males). Considering the above fact, the distant metastasis rate was not found to be statistically significant in male patients (25 out of 168 male patients, [14.88%]) than in females which was 12.08% (40 out of 331 female patients).
Multi-site metastases in thyroid cancer are associated with a high mortality rate, reaching 92% at 5 years necessitating early diagnosis and treatment of the same.  Multi-site metastasis was high (40.9%) in follicular histopathological subtype in this study.
Even though papillary carcinomas were most predominant in the distant metastasis group in our study, analysis revealed that the metastasis rate overall was 9% from papillary histopathological type (39/430 = 9%). The anaplastic and poorly differentiated carcinomas were found to be more aggressive with 100% distant metastasis rate.
The subtype "follicular variant" of papillary carcinoma has follicular patterned cells with nuclear features of papillary carcinoma. They metastasized hematogenously to the bone and are more aggressive compared to their classical papillary counterpart.  Similarly, in this study, the follicular variant of papillary carcinomas was found to be behaving more aggressively. The metastasis rate was more in bone than in lung (45.45% vs. 18.18%) in this subtype of tumors reiterating the fact that this group of tumors is histologically similar to papillary counterpart, but biological behavior mimics the follicular variety.
Seventy-one percent cases of pulmonary metastasis from thyroid malignancy require a cumulative iodine-131 dosage of 200-250 mCi.  Approximately, 62% of the patients with distant metastasis in our study were given a cumulative iodine-131 dosage of 150-250 mCi. High iodine dosage continues to be the preferred choice for treating distant metastasis irrespective of age. ,
Survival analysis was not performed in this study owing to the short duration of follow-up. This is a potential shortcoming of this study.
| Conclusion|| |
This study findings bring out the patterns of distant metastasis in Indian population. Distant metastasis rate in the patients above 45 years of age and patients with follicular variant of papillary carcinomas clearly shows the needs for aggressive treatments in this subgroup of patients to improve outcomes in thyroid cancers.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]