Anatomical change during radiotherapy for head and neck cancer, and its effect on delivered dose to the spinal cord

David J Noble; Ping-Lin Yeap; Shannon Y K Seah; Karl Harrison; Leila E A Shelley; Marina Romanchikova; Amy M Bates; Yaolin Zheng; Gillian C Barnett; Richard J Benson; Sarah J Jefferies; Simon J Thomas; Raj Jena; Neil G Burnet

doi:10.1016/j.radonc.2018.07.009

Anatomical change during radiotherapy for head and neck cancer, and its effect on delivered dose to the spinal cord

Radiother Oncol. 2019 Jan:130:32-38. doi: 10.1016/j.radonc.2018.07.009. Epub 2018 Jul 23.

Authors

Affiliations

¹ Cancer Research UK VoxTox Research Group, University of Cambridge Department of Oncology, Cambridge Biomedical Campus, Addenbrooke's Hospital, UK; Oncology Centre, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, UK. Electronic address: david.noble@addenbrookes.nhs.uk.
² Cancer Research UK VoxTox Research Group, University of Cambridge Department of Oncology, Cambridge Biomedical Campus, Addenbrooke's Hospital, UK; Cavendish Laboratory, University of Cambridge, UK.
³ Cancer Research UK VoxTox Research Group, University of Cambridge Department of Oncology, Cambridge Biomedical Campus, Addenbrooke's Hospital, UK; Department of Engineering, University of Cambridge, UK; Department of Medical Physics and Clinical Engineering, Addenbrooke's Hospital, Cambridge, UK.
⁴ Cancer Research UK VoxTox Research Group, University of Cambridge Department of Oncology, Cambridge Biomedical Campus, Addenbrooke's Hospital, UK; Department of Medical Physics and Clinical Engineering, Addenbrooke's Hospital, Cambridge, UK.
⁵ Cancer Research UK VoxTox Research Group, University of Cambridge Department of Oncology, Cambridge Biomedical Campus, Addenbrooke's Hospital, UK; Cambridge Clinical Trials Unit, Box 401, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, UK.
⁶ University of Cambridge School of Clinical Medicine, UK; Department of Medicine, Cheltenham General Hospital, UK.
⁷ Cancer Research UK VoxTox Research Group, University of Cambridge Department of Oncology, Cambridge Biomedical Campus, Addenbrooke's Hospital, UK; Oncology Centre, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, UK.
⁸ Oncology Centre, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, UK.
⁹ University of Manchester, Manchester Academic Health Science Centre and The Christie NHS Foundation Trust, Manchester, UK.

Abstract

Background and purpose: The impact of weight loss and anatomical change during head and neck (H&N) radiotherapy on spinal cord dosimetry is poorly understood, limiting evidence-based adaptive management strategies.

Materials and methods: 133 H&N patients treated with daily mega-voltage CT image-guidance (MVCT-IG) on TomoTherapy, were selected. Elastix software was used to deform planning scan SC contours to MVCT-IG scans, and accumulate dose. Planned (D_P) and delivered (D_A) spinal cord D_2% (SCD_2%) were compared. Univariate relationships between neck irradiation strategy (unilateral vs bilateral), T-stage, N-stage, weight loss, and changes in lateral separation (LND) and CT slice surface area (SSA) at C1 and the superior thyroid notch (TN), and ΔSCD_2% [(D_A - D_P) D_2%] were examined.

Results: The mean value for (D_A - D_P) D_2% was -0.07 Gy (95%CI -0.28 to 0.14, range -5.7 Gy to 3.8 Gy), and the mean absolute difference between D_P and D_A (independent of difference direction) was 0.9 Gy (95%CI 0.76-1.04 Gy). Neck treatment strategy (p = 0.39) and T-stage (p = 0.56) did not affect ΔSCD_2%. Borderline significance (p = 0.09) was seen for higher N-stage (N2-3) and higher ΔSCD_2%. Mean reductions in anatomical metrics were substantial: weight loss 6.8 kg; C1LND 12.9 mm; C1SSA 12.1 cm²; TNLND 5.3 mm; TNSSA 11.2 cm², but no relationship between weight loss or anatomical change and ΔSCD_2% was observed (all r² < 0.1).

Conclusions: Differences between delivered and planned spinal cord D_2% are small in patients treated with daily IG. Even patients experiencing substantial weight loss or anatomical change during treatment do not require adaptive replanning for spinal cord safety.

Keywords: Head & neck neoplasm; Radiation dosage; Radiotherapy, Image-guided; Radiotherapy, Intensity-modulated; Spinal cord; Weight loss.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Female
Head and Neck Neoplasms / diagnostic imaging
Head and Neck Neoplasms / pathology
Head and Neck Neoplasms / radiotherapy*
Humans
Male
Middle Aged
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted / methods*
Radiotherapy, Image-Guided
Radiotherapy, Intensity-Modulated
Spinal Cord / radiation effects*
Tomography, X-Ray Computed

Abstract

Publication types

MeSH terms

Grants and funding