Adaptive radiotherapy for head and neck cancer reduces the requirement for rescans during treatment due to spinal cord dose

Abstract

BackgroundPatients treated with radiotherapy for head and neck (H&N) cancer often experience anatomical changes. The potential compromises to Planning Target Volume (PTV) coverage or Organ at Risk (OAR) sparing has prompted the use of adaptive radiotherapy (ART) for these patients. However, implementation of ART is time and resource intensive. This study seeks to define a clinical trigger for H&N re-plans based on spinal cord safety using kV Cone-Beam Computed Tomography (CBCT) verification imaging, in order to best balance clinical benefit with additional workload.MethodsThirty-one H&N patients treated with Volumetric Modulated Arc Therapy (VMAT) who had a rescan CT (rCT) during treatment were included in this study. Contour volume changes between the planning CT (pCT) and rCT were determined. The original treatment plan was calculated on the pCT, CBCT prior to the rCT, pCT deformed to the anatomy of the CBCT (dCT), and rCT (considered the gold standard). The dose to 0.1 cc (D0.1cc) spinal cord was evaluated from the Dose Volume Histograms (DVHs).ResultsThe median dose increase to D0.1cc between the pCT and rCT was 0.7 Gy (inter-quartile range 0.2–1.9 Gy, p < 0.05). No correlation was found between contour volume changes and the spinal cord dose increase. Three patients exhibited an increase of 7.0–7.2 Gy to D0.1cc, resulting in a re-plan; these patients were correctly identified using calculations on the CBCT/dCT.ConclusionsAn adaptive re-plan can be triggered using spinal cord doses calculated on the CBCT/dCT. Implementing this trigger can reduce patient appointments and radiation dose by eliminating up to 90% of additional un-necessary CT scans, reducing the workload for radiographers, physicists, dosimetrists, and clinicians.

Initial Feasibility and Clinical Implementation of Daily MR-Guided Adaptive Head and Neck Cancer Radiation Therapy on a 1.5T MR-Linac System: Prospective R-IDEAL 2a/2b Systematic Clinical Evaluation of Technical Innovation

“…ART has begun to play an increasingly prominent role in the treatment of HNC for 2 primary reasons: (1) significant tumor shrinkage, weight loss, and large anatomic deformations of OARs are often observed for HNC patients during RT, [22][23][24] and (2) treatment-related side effects from conventional RT can be particularly debilitating for patients with HNC and often persist for years after treatment. 25,26 Several studies have shown clinically significant reductions in doses to the parotid glands, [27][28][29] spinal cord, 29,30 and swallowing-related structures 31,32 with 1 or more offline plan adaptations during the course of RT. Because offline adaptive replanning is time and resource intensive, many studies have focused on identifying anatomic and dosimetric guidelines to determine when plan adaptation would be optimally effective.…”

“…Because offline adaptive replanning is time and resource intensive, many studies have focused on identifying anatomic and dosimetric guidelines to determine when plan adaptation would be optimally effective. 30,31,33 However, the clinical introduction of the 1.5T MR-linac has made daily ART for HNC a feasible clinical reality.…”

Monte Carlo as quality control tool of stereotactic body radiation therapy treatment plans

“…If the last generation of Linear accelerators like (MRI-Linac) or CBCT adaptive radiotherapy [36][37][38] is used, it implies a possible scenario where QC is without an irradiation of a real phantom, because image acquisition (MRI or CBCT), contouring, dose calculation and finally dose delivery should be done without change position of the patient. The MC as independent platform of QC of patient dosimetry could by the optimal solution since it has many advantages like most accurate dose calculations, saving linear accelerator time and performing QC of the machine by using log files as input MC dose calculations.…”

Initial Feasibility and Clinical Implementation of Daily MR-guided Adaptive Head and Neck Cancer Radiotherapy on a 1.5T MR-Linac System: Prospective R-IDEAL 2a/2b Systematic Clinical Evaluation of Technical Innovation

“…ART has begun to play an increasingly prominent role in the treatment of HNC for two primary reasons: 1) significant tumor shrinkage, weight loss, and large anatomical deformations of OARs are often observed for HNC patients during RT [16][17][18]; and 2) treatment-related side effects from conventional RT can be particularly debilitating for HNC and often persist for years after treatment [19,20]. Several studies have demonstrated clinically significant reductions in doses to the parotid glands [21][22][23], spinal cord [23,24], and swallowing-related structures [25,26] with one or more off-line plan adaptations over the course of radiotherapy. Because offline adaptive re-planning is time-and resource-intensive, many studies have focused on identifying anatomical and dosimetric guidelines to determine when plan adaptation would be optimally effective [24,25,27].…”

“…Several studies have demonstrated clinically significant reductions in doses to the parotid glands [21][22][23], spinal cord [23,24], and swallowing-related structures [25,26] with one or more off-line plan adaptations over the course of radiotherapy. Because offline adaptive re-planning is time-and resource-intensive, many studies have focused on identifying anatomical and dosimetric guidelines to determine when plan adaptation would be optimally effective [24,25,27]. However, the clinical introduction of the 1.5T MR-linac has made daily ART for HNC a feasible clinical reality.…”