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Study of volumetric and dosimetric changes during fractionated radiotherapy in head and neck cancers: A single centre
Viney Kumar1, Vipul Nautiyal1, Ravi Kant1
1Department of Radiation Oncology, Cancer Research Institute, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Dehradun, Uttarakhand, India.
Aims And Objective:
The assessment of volumetric and dosimetric changes in the head-and-neck cancer during fractionated radiotherapy by intensity-modulated radiotherapy (IMRT) technique.
Materials And Methods:
A single-center prospective observational hospital-based study with a sample size of 20 cases of the head-and--neck squamous cell carcinoma over 1 year treated with chemoradiotherapy 66-70 Gy/33-35#@2 Gy/fraction with weekly cisplatin 35 mg/m2. After contouring of target volumes (TVs) and organs at risk (OARs) in initial computed tomography (CT) scan, all patients were planned and treated by the IMRT technique. We re-delineated the TVs and OARs in the second (CT15#) and third (CT30#) planning CT scan, and the initial plan was implemented in the re-CT scan dataset with the same optimization and doses. The volumetric and dosimetric changes during fractionated radiotherapy of TVs and OARs were evaluated and compared. Nonparametric Wilcoxon-signed-rank test was used to compare the means between each plan.
Results:
For all 20 patients, plans were compared for volumetric and dosimetric parameters on repeat CT scans. The mean variation in gross tumor volume (GTV) and planning TV (PTV) was significant after 15 and 30 fractions of radiotherapy. On dosimetric evaluation, there was a significant increase in doses to GTV and OARs (parotid, spinal cord, and cochlea) with a significant P value. However, doses to the OARs were not exceeded the maximum tolerance limit.
Conclusion:
This prospective single-center study concluded that two repeat imaging, along with re-planning improved TV coverage and decreased doses to the normal tissue. Larger studies with more sample sizes are required to set the criteria for replanning.
