Radiation Oncology/Thyroid/Medullary
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Front Page: Radiation Oncology | RTOG Trials |
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Thyroid: Main Page | Workup | Staging | Papillary and follicular | Medullary | Hurthle cell | Anaplastic |
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Contents |
[edit] Epidemiology
- About 5% of thyroid cancers.
- Present in 5th decade.
- 80% are sporadic, but some can result from MEN 2 syndrome.
- There is also a Familial (non MEN 2-related) medullary thyroid cancer syndrome
[edit] Genetics
- Medullary thyroid CA associated w/ MEN 2 syndrome results from a mutation in RET gene.
- MEN 2 w/ ~70% penetrance
[edit] Pathophysiology
- Neuroendocrine tumor that derive from parafollicular C cells
- C cells secrete can secrete calcitonin (which can therefore be used as a tumour marker)
- Non iodine avid therefore no role for I-131 ablation after surgery
[edit] Staging
UICC/AJCC Staging
- see Staging for details
- Stage I - <2cm, confined to thyroid
- Stage II - 2-4cm, confined to thyroid
- Stage III - >4cm, N+ in level IV, or microscopic extrathyroid extension
- Stage IV - M+, N+ outside of level IV, gross soft tissue extension
[edit] Treatment
- Treatment includes total thyroidectomy with central neck lymph node dissection.
- Indications for adjuvant radiation: microscopic residual dz, extensive nodal involvement, extrathyroid extension.
[edit] Adjuvant Radiation
- University of Toronto, 1996 (1954-92) PMID 8875751 -- "Medullary thyroid cancer: analyses of survival and prognostic factors and the role of radiation therapy in local control." Thyroid. 1996 Aug;6(4):305-10.
- 73 pts w/ medullary thyroid CA. 46 pts received xrt (median dose 40 Gy).
- On multi-variate analysis, factors that predicted for lower CSS were extraglandular invasion and postop gross residual dz.
- Pts w/ high risk for locoregional relapse (microscopic residual dz, extraglandular invasion, N+) benefited from RT.
- Conclusion: external beam RT recommended if high risk
- FFCI, 1992 (1971-89) PMID 1736326 -- "Results of postoperative radiation therapy in medullary carcinoma of the thyroid: a retrospective study by the French Federation of Cancer Institutes--the Radiotherapy Cooperative Group." Radiother Oncol. 1992 Jan;23(1):1-5.
- 59 pts w/ medullary thyroid CA receiving EBRT w/ curative intent. Total thyroidectomy in 55 pts. 11 pts w/ residual tumor, 44 pts w/ N+. Mean dose 54 Gy.
- 70% local control, with failures mostly occurring in RT field.
- MDACC, 1988 (1943-87) PMID 2807151 -- "Medullary thyroid carcinoma: prognosis of familial versus nonfamilial disease and the role of radiotherapy." Samaan NA et al. Horm Metab Res Suppl. 1989;21:21-5.
- 202 pts w/ medullary thyroid CA
- Pts w/ MEN2 had longer survival rates than sporadic medullary thyroid CA
- When pts who were matched for age, extent of dz, and surgery were compared for effect of radiation therapy, pts who had no radiotherapy were found to live significantly longer.
