Introduction:
Thyroid malignancy is the fifth most common in women worldwide and it is
expected to become the second most common malignancy in women and the
ninth most common in men by
20301. The incidence of
thyroid cancers has been rising over the past few decades. Unlike most
head and neck cancers, the presence of distant metastasis (DM) does not
preclude curative intent treatment and surgical interventions are common
in metastatic disease. DM has an adverse impact on survival and lends
considerable morbidity to the patient. Based on the histopathology,
thyroid cancers are divided into various subtypes which include
differentiated thyroid carcinoma (DTC), medullary and anaplastic thyroid
carcinomas. DTCs are derived from thyrocytes, express the sodium
transporter and represent 90% of all thyroid cancers and the
terminology encompasses papillary thyroid cancer, follicular carcinoma
and poorly differentiated thyroid
cancers2.
Genetic determinants of clinical behaviour in DTC are being investigated
and find applications in the assessment of the risk of malignancy in
indeterminate thyroid
nodules3 .Notable among
these markers has been theBRAFV600E mutation present
in 45-59% of papillary thyroid cancer and associated with a higher
incidence of extra thyroidal extension, nodal metastasis, refractoriness
to RAI treatment and decreased
survival4.
Four percent of all patients are diagnosed with or develop distant
metastasis. Metastasis develops in 7-15% of patients following thyroid
surgery for DTC5. Poorly
differentiated thyroid cancers account for 5-10% of all thyroid cancers
and the mean survival after diagnosis is 3.2
years6. Bone metastasis
have been observed to occur in 2-13% of patients diagnosed with
differentiated thyroid cancers. In thyroid cancer, the overall 10 year
survival had been declined to 13-21% in the presence bone
metastasis7.
Skeletal survey with whole body bone scan, CT/MRI and whole body MRI in
patients with spinal cord involvement is warranted whenever there is a
suspicion of metastasis. Biopsy from the metastatic site may be required
to confirm the
histology8.
I131 therapy is the first choice of treatment for
papillary and follicular thyroid cancers with distant metastasis, unless
they lose the ability to trap
iodine9. RAI
(Radioactive iodine) therapy has shown to be effective in improving the
disease free survival in patients diagnosed with locally advanced or
metastatic diseases10.
According to the guidelines published by the American Thyroid
Association (ATA), complete removal of bony metastasis has been seen to
exert a beneficial effect on survival and it is recommended particularly
in younger patients with spinal metastases with neurological
deficits11. Hence,
completely resectable lesion of bony metastases should be attempted
wherever feasible12.
Lung metastases respond well to radioactive iodine therapy than any
other organ metastases but surgical resection of the lung is undertaken
only in selected patients, especially with anatomically limited
disease13.
Tyrosine kinase inhibitors are effective and promising drugs for the
treatment of poorly differentiated thyroid
cancers14. Newer
treatment options to treat the locally recurrent and metastatic
progressive differentiated thyroid cancers include small molecule oral
multi-targeted kinase inhibitors, namely Vandetanib and Sorafenib.
Sorafenib works on VEGFR (Vascular endothelial growth factor) 1, 2, and
3 and PDGFR (Platelet derived growth factor).
The role and administration of external beam radiation therapy (EBRT) is
not well characterized in differentiated thyroid cancers due to the lack
of homogeneity of protocols and conflicting outcomes. In a study done by
Lin et al and Benker et
al15. They showed that
EBRT is not routinely recommended in PTC as there is no significant
improvement in overall survival. In fact the higher survival is observed
in patients who did not receive EBRT. Despite these drawbacks, in some
studies administration of EBRT has improved loco-regional control in
invasive disease, unresectable/gross residual tumours and in disease
resistant to RAI
therapy16.
Unlike cancer at other head and neck sites, patients with metastatic DTC
frequently undergo surgery during the course of their protracted
treatment. There is no available data on the clinical characteristics
and patterns of surgical care received by this rare subset of patients
leading us to conduct this study.