Cancer Therapy

Biography

Biography: Sakshi Chauhan

Abstract

Extracorporeal irradiation therapy (ECRT) and re-implantation is now an established technique for limb salvage surgery of malignant bone tumor. ECRT is a biological reconstruction method with several advantages including no risk of immunological reaction or diseases transmission, cost-effective, absence of heavy implants, no need for subsequent surgeries in growing-age patients, and others. Bone is a natural composite in which mineral (hydroxyl-apatite) crystals are embedded between end to end gaps of 40nm collagen fibrils. The ratios in which both the component co-exist have direct co-relation with mechanical properties of bone. Several studies have focused on clinical outcome of the procedure, whereas no compositional and mechanical aspects have been looked into to examine the changes occurring in human bone under heavy dose of radiation (50 Gy). In this study a correlation is established between compositional and biomechanical property in resected bone for patients with malignant bone tumors (osteo-sarcoma and Ewing’s sarcoma) pre and post ECRT. So far four males and one female patient, with mean age of 18 years has been examined with Malignant bone tumor (MBT) undergoing ECRT at All India Institute for Medical Sciences (AIIMS, Delhi), and subsequent compositional study has been performed at Indian Institute of Technology Delhi (IIT-Delhi). The humerus, forearm and tibia are the concern locations. From each subject two bone samples are resected, one from the non irradiated section called pre irradiated sample and other from 50 Gy irradiated section called post irradiated sample. Both the samples are delivered in physiologically saline solution to IIT Delhi where, initially they are cleared of bone marrow (defatting) and excess of soft tissue using jet of de-ionized water followed by ultrasonic bath and then kept in desiccators for an hour. The sample is embedding epoxy and subsequently polished for concerned testing. For investigating the change in ratio of amount of phosphate (143−) to the amount of collagen amide present in both the sample, the technique of inVia confocal Raman spectroscopy is performed. Excitation laser of 785 nm with 50% laser power is used to scan 110 X 110 µm2 areas at two positions in each sample with two accumulations at every position. The compositional changes are correlated with biomechanical property of the same sample via Nano-Indentation study. Set of data revealed that bone undergoes significant compositional changes as a result of high-dose (50 Gy) radiation. Amount of mineralization, ratio of 959 cm-1 to amide I at 1660 cm-1 is reduced as an effect of irradiation, making the bone softer in nature. There is slight decrease in amount of calcium and carbonate substitution while crystallinity in all the samples remained almost same which is calculated as the inverse of band width at half maxima of phosphate band at 959 cm-1. Average indentation curve obtained by series of indentation at the location of secondary osteon revealed loss of modulus for all the five specimens. Such data can help clinicians in selection of suitable external support mechanism (such as locking plates, intra-medullary nails, simple K wires, or pins) during re-implantation and in deciding post-operative care.