Do We Need Daily Image-Guided Radiotherapy by Megavoltage Computed Tomography in Head and Neck Helical Tomotherapy? The Actual Delivered Dose to the Spinal Cord

作者：Duma Marciana Nona^*; Kampfer Severin; Schuster Tibor; Aswathanarayana Nandana; Fromm Laura Sophie; Molls Michael; Andratschke Nicolaus; Geinitz Hans

来源：International Journal of Radiation Oncology, Biology, Physics, 2012, 84(1): 283-288.

DOI：10.1016/j.ijrobp.2011.10.073

• Head and neck
• Helical tomotherapy
• IGRT
• IMRT
• Spinal cord

Purpose: To quantify the actual delivered dose to the cervical spinal cord with different image-guided radiotherapy (IGRT) approaches during head and neck (HN) cancer helical tomotherapy.
Methods and Materials: Twenty HN patients (HNpts) treated with bilateral nodal irradiation were analyzed. Daily megavoltage computed tomography MVCT) scans were performed for setup purposes. The maximum dose on the planning CT scan (plan-Dmax) and the magnitude and localization of the actual delivered Dmax (a-Dmax) were analyzed for four scenarios: daily image-guided radiotherapy (dIGRT), twice weekly IGRT (2xWkIGRT), once weekly IGRT (1xWkIGRT), and no IGRT at all (non-IGRT). The spinal cord was recontoured on 236 MVCTs for each scenario (total, 944 fractions), and the delivered dose was recalculated for each fraction (fx) separately.
Results: Fifty-one percent of the analyzed fx for dIGRT, 56% of the analyzed fx for the 2xWkIGRT, 62% of the analyzed fx for the 1xWkIGRT, and 63% of the analyzed fx for the non-IGRT scenarios received a higher a-Dmax than the plan-Dmax. The median increase of dose in these fx was 3.3% more for dIGRT, 5.8% more for 2xWkIGRT, 10.0% more for 1xWkIGRT, and 9.5% more for non-IGRT than the plan-Dmax. The median spinal cord volumes receiving a higher dose than the plan-Dmax were 0.02 cm(3) for dIGRT, 0.11 cm(3) for 2xWkIGRT, 0.31 cm(3) for 1xWkIGRT, and 0.22 cm(3) for non-IGRT. Differences between the dIGRT and all other scenarios were statistically significant (p < 0.05).
Conclusions: Compared to the Dmax of the initial plan, daily IGRT had the smallest increase in dose. Furthermore, daily IGRT had the lowest proportion of fractions and the smallest volumes affected by a dose that was higher than the planned dose. For patients treated with doses close to the tolerance dose of the spinal cord, we recommend daily IGRT. For all other cases, twice weekly IGRT is sufficient.

• 出版日期2012-9-1
• 单位河北医科大学