H Vulpe1, J Y Y Kwan1, A McNiven1, J D Brierley1, R Tsang1, B Chan2, D P Goldstein3, L W Le4, A Hope1, M Giuliani1. 1. Department of Radiation Oncology, Princess Margaret Cancer Centre. 2. Radiation Medicine Program, Princess Margaret Cancer Centre. 3. Department of Otolaryngology-Head and Neck Surgery; and. 4. Department of Biostatistics, Princess Margaret Cancer Centre, University of Toronto, Toronto, ON.
Abstract
BACKGROUND: The radiotherapy (rt) volumes in anaplastic (atc) and differentiated thyroid carcinoma (dtc) are controversial. METHODS: We retrospectively examined the patterns of failure after postoperative intensity-modulated rt for atc and dtc. Computed tomography images were rigidly registered with the original rt plans. Recurrences were considered in-field if more than 95% of the recurrence volume received 95% of the prescribed dose, out-of-field if less than 20% received 95% of the dose, and marginal otherwise. RESULTS: Of 30 dtc patients, 4 developed regional recurrence: 1 being in-field (level iii), and 3 being out-of-field (all level ii). Of 5 atc patients, all 5 recurred at 7 sites: 2 recurrences being local, and 5 being regional [2 marginal (intramuscular to the digastric and sternocleidomastoid), 3 out-of-field (retropharyngeal, soft tissues near the manubrium, and lateral to the sternocleidomastoid)]. CONCLUSIONS: In dtc, locoregional recurrence is unusual after rt. Out-of-field dtc recurrences infrequently occurred in level ii. Enlarged treatment volumes to level ii must be balanced against a potentially greater risk of toxicity.
BACKGROUND: The radiotherapy (rt) volumes in anaplastic (atc) and differentiated thyroid carcinoma (dtc) are controversial. METHODS: We retrospectively examined the patterns of failure after postoperative intensity-modulated rt for atc and dtc. Computed tomography images were rigidly registered with the original rt plans. Recurrences were considered in-field if more than 95% of the recurrence volume received 95% of the prescribed dose, out-of-field if less than 20% received 95% of the dose, and marginal otherwise. RESULTS: Of 30 dtc patients, 4 developed regional recurrence: 1 being in-field (level iii), and 3 being out-of-field (all level ii). Of 5 atc patients, all 5 recurred at 7 sites: 2 recurrences being local, and 5 being regional [2 marginal (intramuscular to the digastric and sternocleidomastoid), 3 out-of-field (retropharyngeal, soft tissues near the manubrium, and lateral to the sternocleidomastoid)]. CONCLUSIONS: In dtc, locoregional recurrence is unusual after rt. Out-of-field dtc recurrences infrequently occurred in level ii. Enlarged treatment volumes to level ii must be balanced against a potentially greater risk of toxicity.
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