Abstract
BackgroundXerostomia is one of the most common adverse events of radiotherapy in head and neck cancer patients. There have been many reports on functional changes of the parotid gland after radiation therapy, but there have been few reports on the volume of the parotid gland and its relationship with oral quality of life (QOL) and even fewer reports on longitudinal change of the parotid gland volume. The purpose of this study was to evaluate the long-term change of the parotid gland volume after intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma and the relationship between parotid irradiation dose and xerostomia symptoms.MethodsWe retrospectively analyzed 26 patients with nasopharyngeal cancer treated by IMRT. Longitudinal changes of parotid gland volumes after IMRT were evaluated on CT images. The parotid gland volumes in each period were converted to the ratio to parotid gland volumes before radiotherapy (relative parotid volume). Dunnett’s test was used to evaluate the longitudinal changes in relative parotid volumes at 0-6, 7-18, 19-30, 31-42, 43-54 and 55-66 months after IMRT. We assessed xerostomia 3 years or more after IMRT by measuring the degree of oral moisture using a moisture-checking device (Mucus, Life Co., Ltd.) and oral QOL evaluation by GOHAI (General Oral Health Assessment Index).ResultsThe relative parotid volumes during radiotherapy and at 0-6, 7-18, 19-30, 31-42, 43-54 and 55-66 months after IMRT were 75.2 ± 14.3%, 67.2 ± 11.4%, 68.5 ± 15.9%, 72.4 ± 14.8%, 73.0 ± 13.8%, 76.2 ± 17.5%, and 77.1% ± 17.3%, respectively. The parotid volume had recovered significantly at 43-54 and 55-66 months after IMRT, especially in parotids receiving less than 40 Gy as the mean dose. The mean irradiated dose for bilateral parotids showed negative correlations with oral QOL score and oral moisture after a long period.ConclusionsThe parotid volume recovered gradually but had not reached a plateau even 3 years after radiotherapy, especially in parotids receiving less than 40 Gy as the mean dose.
Highlights
Xerostomia is one of the most common adverse events of radiotherapy in head and neck cancer patients [1]
Salivary glands are highly sensitive to radiation and they can be damaged by radiation, leading to xerostomia, which causes a decrease in patients’ quality of life after radiotherapy [2]
It is known that the parotid gland can be affected by even 10-15 Gy in conventional fractional radiotherapy [8, 9], and recovery of parotid gland function is possible with the lapse of time after irradiation with 40-50 Gy, higher doses cause irreversible and permanent xerostomia [10,11,12,13]
Summary
Xerostomia is one of the most common adverse events of radiotherapy in head and neck cancer patients [1]. There have been many reports on functional changes of the parotid gland after radiation therapy, but there has been no report on the volume of the parotid gland and its relationship with oral quality of life (QOL) and there are few reports on longterm longitudinal change of the parotid gland volume. There have been many reports on functional changes of the parotid gland after radiation therapy, but there have been few reports on the volume of the parotid gland and its relationship with oral quality of life (QOL) and even fewer reports on longitudinal change of the parotid gland volume. The purpose of this study was to evaluate the long-term change of the parotid gland volume after intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma and the relationship between parotid irradiation dose and xerostomia symptoms
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