Cellular and molecular approaches are being explored to find a biomarker which can predict the development of radiation induced acute toxicity prior to radiation therapy. SNPs in radiation responsive genes may be considered as an approach to develop tools for finding the inherited basis of clinical radiosensitivity. The current study attempts to screen single nucleotide polymorphisms/deletions in DNA damage response, DNA repair, profibrotic cytokine as well as antioxidant response genes and its predictive potential with the normal tissue adverse reactions from 183 head and neck cancer patients undergoing platinum based chemoradiotherapy or radiotherapy alone. We analysed 22 polymorphisms in 17 genes having functional relevance to radiation response. Radiation therapy induced oral mucositis and skin erythema was considered as end point for clinical radiosensitivity. Direct correlation of heterozygous and mutant alleles with acute reactions as well as haplotype correlation revealed NBN variants to be of predictive significance in analysing oral mucositis prior to radiotherapy. In addition, genetic linkage disequilibrium existed in XRCC1 polymorphisms for >grade 2 oral mucositis and skin reaction indicating the complex inheritance pattern. The current study indicates an association for polymorphism in NBN with normal tissue radiosensitivity and further warrants the replication of such studies in a large set of samples.

The purpose of this study was to conduct quality assurance of a three dimensional conformal radiotherapy (3DCRT) of two targets in pelvis region planned with single isocenter technique. Methods: A treatment plan was generated with two identical water phantoms with ionization chamber (IC) sleeves (IC-1 & IC-2), simulated as if targets are in pelvis region, simultaneously irradiated with single isocenter technique with a dose prescription of 300 cGy for point dose verification. A two dimensional ion chamber array detector was used for fluence verification. Results: Calculated minimum, mean and maximum dose (in cGy) for IC-1 & IC-2 were 295, 303 and 307 as per dose volume histogram. The global dose maximum was found to be 307.4 cGy. Measured point doses to both lesions were within ±2.5% of the computed dose. A pass percentage of 97% was obtained with the set of criteria 3 mm distance to agreement and 3% dose difference for fluence verification. Conclusion: Treatment execution of two targets simultaneously with single isocenter can reduce positional errors and delivery time.