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Volume 9 Issue 3 (March, 2021)

Original Articles

Estimation of tumor regression parameters from dose response relationship in patients of head and neck cancer undergoing EBRT
Rajkumar Nirban, Rajesh Kumar

Background: Head and neck carcinoma (HNC) is the sixth most common cancer worldwide. In India, it accounts for one fourth of male cancers and one tenth of female cancers. The present study estimated the tumor regression parameters from dose response relationship in patients of head and neck cancer undergoing EBRT to interpret the curvilinear L-Q curves as obtained from in vivo and in vitro studies. Also, these data were compared with α/β ratio estimated by use of Fe plot method. Materials & Methods: 60 patients of locally advanced carcinoma of head and neck were enrolled. Local examination of oral cavity was done under aseptic conditions. Primary site of malignancy was inspected for site, size, shape, surface, borders, margins, base, infiltration to surrounding structures and any signs of inflammation. Patients were divided into 2 groups. Group A (Conventional): - This group consisted of randomly selected previously untreated 30 patients of squamous cell carcinoma of oropharynx. Group B (hyper fractionated): - This group consisted of randomly selected, previously untreated 30 patients of squamous cell carcinoma of oropharynx. Results: The mode ECOG was 1 in both the groups with 80% and 66.67% patients in the hyperfractionated and conventional arms, respectively having ECOG status 1. The Fe-plot drawn for the isoeffect doses of grade 1 mucosal reactions. X-axis depicts the dose per fraction of the treatment schedule and Y-axis shows the inverse of the mean isoeffect dose. The patients of the hyperfractionated arm developed grade 1 mucosal reaction at the mean isoeffect dose of 29.840Gy, while it was 27.667Gy for the conventional arm. The intercept on the y-axis (1/33.75) obtained by extrapolating the line joining the respective isodose lines corresponds to α/logeS and the slope of the curve (3.235 × 10-3) corresponds to β/logeS. Conclusion: The virtual α/β represents the complex radiobiological phenomena taking place during fractionated radiotherapy. It incorporates the combined influence of cell loss, changing tumor kinetics, clonogen doubling, repair, reoxygenation, blood flow and clearance of the dead and necrotic tissue/debris and thus, could be more appropriate in clinical radiotherapy.

 
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