Abstract

Nikunj Patil¹, Shirley Lewis¹, Umesh V², Anusha Reddy¹, Anshul Singh¹, Priyanka Augustine¹, Sachi Chauhan¹, Krishna Sharan¹

¹Kasturba Medical College, Department of Radiotherapy and Oncology, Manipal, India; ²Kasturba Medical College,, Department of Radiotherapy and Oncology, Manipal, India

Tobacco chewing is the most common form of tobacco use in India and patients majority present in advanced-stage disease. Achieving parotid sparing with IMRT in these patients is a challenge. We aimed to correlate parotid volume with the type of tobacco use and document dose received by superficial parotids in head and cancer patients treated with radical radiotherapy.

This is a retrospective study that included patients with histological confirmation, treated with curative intent radiotherapy in our center from Jan 2017 to March 2020.  The patient's target volume encompassed bilateral neck were included in the study. Patients with Stage I laryngeal cancer, metastatic at presentation, and receiving reirradiation were excluded from the analysis. The medical records of all patients were retrieved and the demographic variables along with physician-assessed Radiation Therapy Oncology Group (RTOG) xerostomia toxicity grades were collected. The delineation of the superficial and deep lobe of the parotid was done retrospectively. All patients were treated with IMRT to a dose of 60-70Gy/30-35 fractions. The Parotids individually and superficial and deep parotids were considered to be spared if the mean dose was less than 26 Gy. Using the dosimetric information we divided our patients into 4 groups. Group 1 includes patients where we achieved bilateral parotid sparing,Group 2 consists of contralateral parotid sparing, Group 3 consists of bilateral or contralateral superficial parotid sparing, while in Group 4 no parotid gland sparing was achieved. The data was analyzed using SPSS 21. A chi-square test will be used to compare the groups. 

One seventy-four patients were included in the study. The median age of the patients was 59 years (IQR 51-66) and 84% were males. Tobacco chewing was the most common form of use (51%) followed by smoking (35%) and other forms (6%). 81% were locally advanced with stage III and IV. The oropharynx (30%) and hypopharynx (28%) were the most common sites involved.  Bilateral parotid sparing was achieved in 37% and contralateral in 25%. Superficial parotid sparing was achieved in 27%. The mean dose to parotids in these patients was 25 Gy and V26 Gy was 39%. The median parotid volume was 53cc (range 18-130cc). The parotid volume was smaller in patients with tobacco chewing compared to smokers (51% vs 38%) however p-value was not significant (p=0.3). The parotid volumes were significantly larger in patients who could achieve bilateral/contralateral sparing compared to no sparing or only superficial sparing (60-63% vs 29-37%, p=0.009). the median follow-up of these patients was 18 months (Range: 6-36 months). The patients with RTOG scores (0/1) in superficial parotid sparing at 6,12 and 18 months was 55%, 49%, and 24%. 

Tobacco chewers have smaller parotids and the volume of parotid correlates with the sparing achieved with IMRT in head and neck cancers. The patients whose even superficial parotids were spared had low xerostomia rates.