Parotid gland-recovery after radiotherapy in the head and neck region - 36 months follow-up of a prospective clinical study

Abstract

BackgroundThe aim of the present study was to evaluate the recovery potential of the parotid glands after using either 3D-conformal-radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT) by sparing one single parotid gland.MethodsBetween 06/2002 and 10/2008, 117 patients with head and neck cancer were included in this prospective, non-randomised clinical study. All patients were treated with curative intent. Salivary gland function was assessed by measuring stimulated salivary flow at the beginning, during and at the end of radiotherapy as well as 1, 6, 12, 24, and 36 months after treatment. Measurements were converted to flow rates and normalized relative to rates before treatment. Mean doses (Dmean) were calculated from dose-volume histograms based on computed tomographies of the parotid glands.ResultsPatients were grouped according to the Dmean of the spared parotid gland having the lowest radiation exposure: Group I - Dmean < 26 Gy (n = 36), group II - Dmean 26-40 Gy (n = 45), and group III - Dmean > 40 Gy (n = 36). 15/117 (13%) patients received IMRT. By using IMRT as compared to 3D-CRT the Dmean of the spared parotid gland could be significantly reduced (Dmean IMRT vs. 3D-CRT: 21.7 vs. 34.4 Gy, p < 0.001). The relative salivary flow rates (RFSR) as a function of the mean parotid dose after 24 and 36 months was in group I 66% and 74%, in group II 56% and 49%, and in group III 31% and 24%, respectively. Multiple linear regression analyses revealed that the parotid gland dose and the tumor site were the independent determinants 12 and 36 months after the end of RT. Patients of group I and II parotid gland function did recover at 12, 24, and 36 months after the end of RT.ConclusionsIf a Dmean < 26 Gy for at least one parotid gland can be achieved then this is sufficient to reach complete recovery of pre-RT salivary flow rates. The radiation volume which depends on tumor site did significantly impact on the Dmean of the parotids, and thus on the saliva flow and recovery of parotid gland.

PSMA-Targeted Radionuclide Therapy of Metastatic Castration-Resistant Prostate Cancer with 177Lu-Labeled PSMA-617

“…Thus, the sporadic incidence of reversible xerostomia, which was mainly observed after the third cycle, is reasonable, taking into account published radiation tolerance limits (22). However, if mild xerostomia is considered to be an annoying but harmless side effect, kidneys are the only essential dose-limiting organs and their tolerance limits would permit about twice the cumulative dose-that is, 36 GBq of 177 Lu-PSMA-617 (23)-which conversely would still stay below the limits to provoke severe and irreversible xerostomia (22). Additionally, recent attempts to reduce kidney uptake of PSMA ligands raise hope to further increase the therapeutic index (24).…”

Radiation Dosimetry for177Lu-PSMA I&T in Metastatic Castration-Resistant Prostate Cancer: Absorbed Dose in Normal Organs and Tumor Lesions

“…In our experience, despite the application of up to 30 GBq of 177 Lu-PSMA I&T, so far only sporadic cases of reversible xerostomia and no considerable complaints on dry eyes were noted (10). Hey et al, for example, using external-beam radiation therapy, reported that a dose to the parotid glands below 26 Gy allowed complete recovery of pretherapeutic salivary flow rates (23).…”

Analysis of Factors Associated with Weight Loss After Esophagectomy for Esophageal Cancer

“…Intensitymodulated radiotherapy (IMRT) for head and neck cancer can spare PGs, leading to significant reductions in the incidence and severity of xerostomia, at a mean dose to PGs of approximately 26 Gy (11)(12)(13)(14)(15). Moreover, salivary function tends to recover within 2 years of IMRT if the mean dose to the PG is 30 Gy or less (12).…”