Helical tomotherapy in the radiotherapy treatment of Hodgkin's disease - a feasibility study.

Maria T Vlachaki,Sanath Kumar

doi:10.1120/jacmp.v11i1.3042

Maria T Vlachaki, Sanath Kumar

Open Access

https://doi.org/10.1120/jacmp.v11i1.3042

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Abstract

Radiation therapy for advanced Hodgkin's disease often requires large fields and may result in significant exposure of normal tissues to ionizing radiation. In long‐term survivors, this may increase the risk for late toxicity including secondary malignancies. 3D CRT has been successfully used to treat this disease but treatment delivery is often complex requiring matching of photon with electron beams, and utilization of field‐in‐field techniques and of partial transmission blocks. HT is an arc‐rotational intensity modulated radiation therapy technique proven to achieve superior target dose conformality and sharp dose gradients around critical normal tissues. HT, however, has also been associated with higher volumes of low‐dose regions in normal tissues and, therefore, higher integral dose. The present study was undertaken to compare the dosimetry of 3D CRT to HT in a pediatric patient with advanced HD. Clinical target volume (CTV) included bilateral lower cervical and supraclavicular areas, mediastinum, bilateral hili, left axilla and bilateral diaphragmatic lymph nodes. The planning target volume (PTV) was derived by circumferentially expanding the CTV by 1 cm. Whole lung and heart irradiation was also planned due to bilateral pleural and pericardial effusions. The prescribed radiation dose was 21 Gy to the PTV and 10.5 Gy to the whole lung and heart. Target coverage was comparable for both plans. The minimum, maximum, and mean PTV doses were 18.61 Gy, 22.45 Gy and 21.52 Gy with 3D CRT and 19.85 Gy, 22.36 Gy and 21.39 Gy with HT, respectively. HT decreased mean normal tissue dose by 21.6% and 20.07% for right and left breast, 20.40% for lung, 30.78% for heart, and 22.74% for the thyroid gland. Integral dose also decreased with HT by 46.50%. HT results in significant dosimetric gain related to normal tissue sparing compared to 3D CRT. Further studies are warranted to evaluate clinical applications of HT in patients with HD.PACS number: 87.53.Kn

Highlights

The treatment of Hodgkin’s disease (HD) has evolved from using high-dose extended field irradiation alone to combined modality therapy
Using intensity modulated radiation therapy (IMRT) treatment planning, it generates a spiral fan beam around the patient that is further modulated by a binary multileaf collimator.[10]. This results in a highly conformal dose distribution, especially in cases of targets located in proximity to critical normal tissues
We present a dosimetric analysis comparing 3D CRT with Helical tomotherapy (HT) plans in a pediatric patient with HD

Summary

Introduction

The treatment of Hodgkin’s disease (HD) has evolved from using high-dose extended field irradiation alone to combined modality therapy. There are various long-term effects associated with the treatment of HD, especially in pediatric patients These include second malignancies, cardiac toxicity, endocrine dysfunction, pulmonary disease, and growth impairment and may become apparent after ten or more years of observation.[5] Risk factors include younger age, radiation therapy, chemotherapy, and time interval from treatment.[6,7] With regard to radiation therapy, studies have demonstrated increased incidence of late effects with higher radiation dose and larger field sizes, especially subtotal and total nodal irradiation.[6,8,9] the utilization of techniques which minimize normal tissue radiation exposure may prove to be an effective treatment strategy in order to reduce the incidence of late toxicity in long term survivors with HD. HT has been used for stereotactic treatment of small tumors as well as for the treatment of larger targets such as in cranio-spinal or total body irradiation.[11,12,13,14]

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