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Dosimetric Correlation of Acute and Late Xerostomia with Patients Treated with IMRT and Chemotherapy

Reviewer: Chika Madu, MD
Abramson Cancer Center of the University of Pennsylvania
Ultima Vez Modificado: 18 de octubre del 2005

Presenter: A.K. Bhatnagar
Presenter's Affiliation: Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA
Type of Session: Scientific

Background

One of the greatest determinants of quality of life following radiation for head and neck cancer is xerostomia. There are limited data for dose-volume relationships of the parotid gland in patients treated with radiation for head and neck cancer. This study was then designed to evaluate the severity of acute and "early" late xerostomia and its relationship to parotid dose during radiation for head and neck cancers

Materials and Methods

• This study evaluated 333 patients treated with intensity modulated radiation therapy (IMRT) for head and neck cancer (HNC)
• Most of the patients had squamous cell carcinoma
• 63% of the patients were treated with concurrent chemo-radiation, while 37% received radiation alone
• All patients were immobilized during the simulation
• Dose constraint for the contralateral parotid gland was 50%vol ≤ 26Gy
• Most of the IMRT plans had 7-9 fields
• Mean dose received by the parotid gland was obtained
• The RTOG toxicity scoring system was used to evaluate acute and late xerostomia and the maximum obtained scores were used for analysis
• Patients were divided into 2 groups, mean parotid dose <26Gy in group 1, mean parotid dose >26Gy in group 2
• Non-parametric correlation and Chi square analysis was used to evaluate relationships

Results

• Median follow up after completion of radiation was 8 months
• Median mean parotid dose was similar in patients treated with radiation alone or chemo-radiation (25Gy vs. 26.5Gy)
• Group 1 patients had a 20% and 3% rate of Grade 2 and 3 acute salivary toxicities respectively compared to group 2 patients, where Grade 2 and 3 early xerostomia occurred 33% and 9% of the time (p=0.005)
• There was also a statistical significant difference when grade 2 and 3 late xerostomia in group 1 patients (8% and 0%) was compared to grade 2 and 3 late xerostomia in group 2 patients (23% and 5%) [p<0.0001]
• Acute and late toxicities for patients receiving chemo-radiation was higher than acute and late xerostomia in patients receiving radiation alone, this was also statistically significant

Author's Conclusions

• There likely is a distinct dose volume relationship for head and neck cancer patients treated with chemoradiation vs. radiation alone
• A mean parotid dose >26Gy increases the incidence of xerostomia
• Incidence of xerostomia increases with the addition of chemotherapy, regardless of the mean parotid dose
• If chemoradiation is combined with a high parotid dose, xerostomia is amplified

Clinical/Scientific Implications

This study illustrates the impact of parotid radiation dose and chemotherapy on xerostomia and ultimately, on quality of life issues. This study has shown that sparing the parotid when possible decreases the incidence of xerostomia. However, the addition of chemotherapy, which is usually the case in a signifiant number of head and neck cancer patients, increases the incidence of xerostomia. This study did not evaluate for correlation between different chemotherapies and the incidence of xerostomia, but a majority of the patients received a platinum based agent. A limiting factor of this study is the short follow-up time for late xerostomia. There was also no information available on the use of radioprotectors in this population.  Further follow up is needed to determine if these early results will indeed hold up. Future directions in this area include better radiation delivery/parotid sparing, the use of radio-protectants to decreases xerostomia and defining specific dose-volume constraints for patients treated with concurrent chemo-radiation.