TY - JOUR
T1 - Volumetric changes of the parotid gland during IMRT based on mid-treatment imaging
T2 - implications for parotid stem cell sparing strategies in head and neck cancer
AU - Gjini, Megi
AU - Ahmed, Sadia
AU - Kalnicki, Shalom
AU - Tomé, Wolfgang A.
AU - Garg, Madhur K.
AU - Kabarriti, Rafi
AU - Brodin, N. Patrik
N1 - Publisher Copyright:
© 2022 Acta Oncologica Foundation.
PY - 2022
Y1 - 2022
N2 - Background: To evaluate the change in parotid glands at mid-treatment during IMRT and the association between radiation dose to the parotid gland stem cell (PGSC) region and patient-reported xerostomia for patients with head and neck cancer (HNC). Material and Methods: Patients who were treated from 2006–2012 at our institution with patient-reported xerostomia outcomes available at least 9 months following RT were included. PG and PGSC regions were delineated and the dose was estimated from the treatment plan dose distribution, using contours from pre- and mid-treatment CT scans. The association between radiation dose and volumetric changes was assessed using linear regression. Univariable logistic regression, logistic dose-response curves, and receiver operating characteristics (ROC) were used to examine the relationship between radiation dose and patient-reported xerostomia. Results: Sixty-three patients were included, most treated with 70 Gy in 33 fractions; 34 patients had mid-treatment CT scans. Both contralateral and ipsilateral PGs had considerable volume reduction from baseline to mid-treatment (25% and 27%, respectively, both p <.001), significantly associated with mean PG dose (−0.44%/Gy, p =.008 and −0.54%/Gy, p <.001, respectively). There was a > 5 Gy difference in mean PG and PGSC dose for 8/34 patients at mid-treatment, with 6/8 (75%) reporting severe xerostomia. Xerostomia prediction based on whole PG or PGSC region dose showed similar performance (ROC AUC 0.754 and 0.749, respectively). The corresponding dose-response models also predicted similar risk of patient-reported xerostomia with mean dose to the contralateral PG (32.5%) or PGSC region (31.4%) at the 20 Gy QUANTEC-recommended sparing level. Conclusions: The radiation dose to the PGSC region did not show stronger association with patient-reported xerostomia compared to that of whole PG, possibly due to considerable anatomical changes identified at mid-treatment. This shift in the size and position of the PG warrants adaptive planning strategies to evaluate the true benefit of parotid stem cell sparing.
AB - Background: To evaluate the change in parotid glands at mid-treatment during IMRT and the association between radiation dose to the parotid gland stem cell (PGSC) region and patient-reported xerostomia for patients with head and neck cancer (HNC). Material and Methods: Patients who were treated from 2006–2012 at our institution with patient-reported xerostomia outcomes available at least 9 months following RT were included. PG and PGSC regions were delineated and the dose was estimated from the treatment plan dose distribution, using contours from pre- and mid-treatment CT scans. The association between radiation dose and volumetric changes was assessed using linear regression. Univariable logistic regression, logistic dose-response curves, and receiver operating characteristics (ROC) were used to examine the relationship between radiation dose and patient-reported xerostomia. Results: Sixty-three patients were included, most treated with 70 Gy in 33 fractions; 34 patients had mid-treatment CT scans. Both contralateral and ipsilateral PGs had considerable volume reduction from baseline to mid-treatment (25% and 27%, respectively, both p <.001), significantly associated with mean PG dose (−0.44%/Gy, p =.008 and −0.54%/Gy, p <.001, respectively). There was a > 5 Gy difference in mean PG and PGSC dose for 8/34 patients at mid-treatment, with 6/8 (75%) reporting severe xerostomia. Xerostomia prediction based on whole PG or PGSC region dose showed similar performance (ROC AUC 0.754 and 0.749, respectively). The corresponding dose-response models also predicted similar risk of patient-reported xerostomia with mean dose to the contralateral PG (32.5%) or PGSC region (31.4%) at the 20 Gy QUANTEC-recommended sparing level. Conclusions: The radiation dose to the PGSC region did not show stronger association with patient-reported xerostomia compared to that of whole PG, possibly due to considerable anatomical changes identified at mid-treatment. This shift in the size and position of the PG warrants adaptive planning strategies to evaluate the true benefit of parotid stem cell sparing.
KW - IMRT
KW - Parotid gland
KW - head and neck cancer
KW - parotid gland stem cell sparing
KW - patient-reported xerostomia
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U2 - 10.1080/0284186X.2022.2110384
DO - 10.1080/0284186X.2022.2110384
M3 - Article
C2 - 35978529
AN - SCOPUS:85136159796
SN - 0284-186X
VL - 61
SP - 1069
EP - 1074
JO - Acta Oncologica
JF - Acta Oncologica
IS - 9
ER -