Comparison of radiotherapy techniques to reduce hematologic toxicity in whole pelvic radiation therapy

Introduction: Concurrent chemoradiotherapy (CRT) is a standard treatment method for patients with carcinoma of cervix. Despite admirable therapeutic results, acute hematologic toxicity (HT) is common with this regimen. Many studies evaluate the relationship between the bone marrow dosimetric parameters and the severity of HT and result shown that the low dose of bone marrow would decrease the incidence of HT in patient undergoing concomitant CRT. In this study the dosimetric parameters of two radiotherapy plans in managing of cervix cancer has been evaluated to investigate the best plan on the way of reducing bone marrow dose.   Materials and Methods: Computed tomography scans of 18 patients with carcinoma of cervix were acquired and transferred to the 3D treatment planning system. The corePlan3D treatment planning system was used to contour all of the structures and to compute the dose distribution for plans based on collapsed cone convolution (CCC). For each patient, two different treatment plan were prepared using 15 MV photon energies. The minimum dose (Dmin), maximum dose (Dmax) and mean dose (Dmean) to target (PTV) and femoral head were compared for each plan.   Results: Result shown that our manipulated four-field plan which use anterior oblique beams seemed to deliver a lower mean dose to femoral head against conventional box fields (Dmean=66.7±3.1 cGy, 98.8±7.3 cGy, Dmax=117.5±3.0 cGy, 126.9±4.3 cGy, respectively) and deliver sufficient dose to PTV (Dmax=213.5±4.2 cGy, 194.6±2.0 cGy, respectively).   Conclusion: With suspicious planning in respect to choice of beam angles, beam weighting, and appreciation of potential exposure of normal tissues to exit dose, this study revealed that compared with conventional box fields, anterior oblique beams can achieve significant reductions in the dose to BM with adequate dose coverage to the PTV with an accurate beam arrangement