Radiat Oncol J.  2018 Mar;36(1):54-62. 10.3857/roj.2017.00493.

Set-up errors in head and neck cancer treated with IMRT technique assessed by cone-beam computed tomography: a feasible protocol

• Delishaj D
• Ursino S
• Pasqualetti F
• Matteucci
• Cristaudo
• Soatti CP
• Barcellini A
• Paiar F

• KMID: 2418885
• DOI: http://doi.org/10.3857/roj.2017.00493

Abstract

PURPOSE
To investigate set-up errors, suggest the adequate planning target volume (PTV) margin and image-guided radiotherapy frequency in head and neck (H&N) cancer treated with intensity-modulated radiotherapy (IMRT) assessed by kV cone-beam computed tomography (CBCT).
METHODS
We analyzed 360 CBCTs in 60 patients with H&N cancer treated with IMRT. The target delineation was contoured according to ICRU62. PTVs were generated by adding a 3-5 mm margin in all directions to the respective clinical target volumes. The kV CBCT images were obtained at first three days of irradiation and weekly thereafter. The overall mean displacement, range, systematic (∑) and random (σ) errors were calculated. Adequate PTV margins were calculated according to the van Herk formula (2.5∑ + 0.7r).
RESULTS
The mean of set-up errors was less than 2 mm in any direction. The overall frequency of set-up displacements greater than 3 mm was 3.9% in medial-lateral (ML) direction, 8% in superior-inferior (SI) direction, and 15.5% in anterior-posterior (AP) direction. The range of translations shifts was 0-9 mm in ML direction, 0-5 mm in SI direction and 0-10 mm in AP direction, respectively. After systematic set-up errors correction, the adequate margin to overcome the problem of set-up errors was found to be less than 3 mm.
CONCLUSION
Image-guided kV CBCT was effective for the evaluation of set-up accuracy in H&N cancer. The kV CBCT at first three fractions and followed-by weekly appears adequate for reducing significantly set-up errors in H&N cancer treated with IMRT technique. Finally, 3-5 mm PTV margins appear adequate and safe to overcome the problem of set-up errors.

Keyword

Head and neck cancer; Radiotherapy; Chemotherapy; Cone-beam computed tomography; IMRT technique; Oncology

MeSH Terms

Cone-Beam Computed Tomography*
Drug Therapy
Head and Neck Neoplasms*
Head*
Humans
Neck
Radiotherapy
Radiotherapy, Image-Guided
Radiotherapy, Intensity-Modulated
Translations