Anatomical and Dose Changes of Gross Tumour Volume and Parotid Glands for Head and Neck Cancer Patients during Intensity-modulated Radiotherapy: Effect on the Probability of Xerostomia Incidence

Anatomic and dosimetric changes in patients with head and neck cancer treated with an integrated MRI-tri-60Co teletherapy device

“…The wide ranges indicate that tumour response is not uniform and subject to unpredictable patterns of regression. 4,8,10,22 Using daily CT scans, Barker et al observed a median rate of loss for primary tumours of 1.7% per day, 4 and Chen et al 22 found a mean % volume reduction for human papilloma virus positive oropharyngeal GTVs of 57.5%. Although limited by sample size, our study Table 1. included two patients who were human papilloma virus positive with base of tongue tumours and mean percentage reduction of 50.1%, indicating similar findings.…”

“…Overall, the medial shift of the parotid glands correlated with weight loss, confirming the findings of Barker et al 4 Other studies have attempted to correlate anatomic changes with dosimetric analysis and discussed the potential benefits of replanning in head and neck cancers. [7][8][9][10][11][12][13]15,17,19 As the parotid glands shift medially during IMRT, they may be exposed to higher than expected levels of radiation and consequently an increased probability of xerostomia. 8,[10][11][12]14 Although several studies have found that adaptive replanning may potentially reduce dosage to the parotids, the appropriate means of selection remain elusive.…”

“…[7][8][9][10][11][12][13]15,17,19 As the parotid glands shift medially during IMRT, they may be exposed to higher than expected levels of radiation and consequently an increased probability of xerostomia. 8,[10][11][12]14 Although several studies have found that adaptive replanning may potentially reduce dosage to the parotids, the appropriate means of selection remain elusive. 11,13,15,17,19 While our results did not identify any significant changes in parotid dose over the course of IMRT, this conclusion is limited by the heterogeneous patient population and the lack of cumulative dosage data.…”

“…2,3 Several studies have documented anatomical changes during the course of IMRT in patients with head and neck cancer, quantifying regression and spatial shifts of tumours and organ at risk (OAR). [4][5][6][7][8][9][10] Interfractional anatomical changes, in turn, can substantially alter dose deposition, suggesting a benefit to adaptive replanning. [7][8][9][10][11][12][13][14][15][16][17][18][19] However, adaptive replanning remains to be widely adopted owing to its time-intensive nature and an unclear threshold of anatomical changes required for its posited benefit.…”

“…[4][5][6][7][8][9][10] Interfractional anatomical changes, in turn, can substantially alter dose deposition, suggesting a benefit to adaptive replanning. [7][8][9][10][11][12][13][14][15][16][17][18][19] However, adaptive replanning remains to be widely adopted owing to its time-intensive nature and an unclear threshold of anatomical changes required for its posited benefit. 10,11,16,20 The aforementioned studies of anatomical alteration during IMRT relied on CT imaging, which might not provide optimal soft-tissue contrast/ resolution, leading to possible interobserver variability.…”