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Background: routinely, patient's planning scans are acquired after administration of iodinized contrast media but they will be treated in the absence of that. similarly, high energy photons have a better penetrating power, while low energy photons will result in tighter dose distribution and negligible neutron contamination. The aim of the study was to investigate a suitable photon beam energy in the presence of intravenous contrast medium. Materials and methods: an indigenously made original-contrast (OC) phantom was mentioned as virtual-contrast (VC) and virtual-without-contrast (VWC) phantom were generated by assigning the hounsfield Units (HU) to different structures. Intensity- modulated (IMRT) and volumetric-modulated-arc (VMAT) plans were generated as per criteria of the TG-119 protocol. Results: It was observed that the maximum dose to the spinal cord was better with 6 mega-voltage (MV) in IMRT. The coverage of prostate PTV (PR PTV) was similar with all the photon energies and was comparable with TG-119, except for original-contrast (OC) phantom using the VMAT technique. homogeneity-index (HI) was comparatively better for VMAT plans. Conclusion: The contrast CT images lower the dose to targets. IMRT or VMAT plans, generated on such CT images will be delivered with higher doses than evaluated. However, the overdose remains non-significant. [ABSTRACT FROM AUTHOR]

Aim To study and explores the feasibility and efficacy of re-irradiation (Re-RT) for locally recurrent head and neck cancer (HNC) and second primary (SP) malignancies. Background The most common form of treatment failure after radiotherapy (RT) for HNC is loco-regional recurrence (LRR), and around 20–50% of patients develop LRR. Re-irradiation (Re-RT) has been the primary standard of care in the last decade for unresectable locally recurrent/SP HNC. Materials and methods It was a retrospective analysis in which we reviewed the medical records of 51 consecutive patients who had received Re-RT to the head and neck region at our institute between 2006 and 2015. Results Forty-eight patients were included for assessment of acute and late toxicities, response evaluation at 3 months post Re-RT, and analyses of locoregional control (LRC) and overall survival (OS). The median LRC was 11.2 months, and at 2 and 5 years the LRC rates were 41% and 21.2%, respectively. A multivariate analysis revealed two factors: initial surgical resection performed prior to Re-RT, and achievement of CR at 3 months after completion of Re-RT to be significantly associated with a better median LRC. The median OS was 28.2 months, and at 1, 2, and 5 years, OS were 71.1%, 55.9% and 18%, respectively. A multivariate analysis revealed initial surgical resection performed prior to Re-RT, and achievement of CR at 3 months post completion of Re-RT being only two factors significantly associated with a better median OS. Acute toxicity reports showed that no patients developed grade 5 toxicity, and 2 patients developed grade 4 acute toxicities. Conclusion Re-RT for the treatment of recurrent/SP head and neck tumors is feasible and effective, with acceptable toxicity. However, appropriate patient selection criteria are highly important in determining survival and treatment outcomes. [ABSTRACT FROM AUTHOR]