Thyroid Cancer Progression Slowed With Dose Escalation of IMRT

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Patients with gross disease were most likely to experience local-regional failure.
Patients with gross disease were most likely to experience local-regional failure.

(HealthDay News) — Local-regional failure (LRF) in patients with well-differentiated thyroid cancer is mostly seen in patients with gross disease at the time of intensity-modulated radiation therapy (IMRT), according to a review published in the Journal of Medical Imaging and Radiation Oncology.

Erin Shugard, from the University of California, San Francisco, and colleagues retrospectively reviewed records of well-differentiated thyroid cancer patients treated with IMRT from 1998 to 2011 to assess the effect of IMRT dose escalation on preventing LRF of microscopic and macroscopic well-differentiated thyroid cancer.

The researchers found that over a median of 56 months of follow-up, 17 of 30 patients (57%) had gross residual, 5 (17%) had microscopic residual, and 8 (27%) had clear margins at the time of IMRT. At a median time of 44 months, 9 patients (30%) developed LRF. Two-thirds of these 9 patients had been radiated to gross disease and 1 patient had microscopic residual. 

In the 7 analyzable cases, only 1 LRF occurred within the 70 Gy isodose volume. Of marginal LRFs cases, 4 were outside 70 Gy, 1 outside 60 Gy, and 1 outside 50 Gy. 

The majority of recurrence (86%) occurred in the periesophageal region.

"Meticulous surgical dissection, especially in the periesophageal region, should be prioritized to prevent long-term LRF," the researchers wrote.

Reference

  1. Shugard E, Chen J, Quivey JM, et al. Does radiation dose matter in thyroid cancer?: Patterns of local-regional failure in recurrent and metastatic well-differentiated thyroid cancers treated with dose-painted intensity-modulated radiation therapy. J Med Imaging Radiat Oncol. 2016. doi:10.1111/1754-9485.12452.
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