|Year : 2016 | Volume
| Issue : 1 | Page : 25-27
A comparison between intensity-modulated radiotherapy and three-dimensional conformal radiotherapy in a case of retinoblastoma
Om Prakash Gurjar, Mehlam Kausar, Virendra Bhandari, Desh Deepak Ladia
Roentgen-SAIMS Radiation Oncology Centre, Sri Aurobindo Institute of Medical Sciences, Indore, Madhya Pradesh, India
|Date of Web Publication||29-Feb-2016|
Dr. Om Prakash Gurjar
Roentgen-SAIMS Radiation Oncology Centre, Sri Aurobindo Institute of Medical Sciences, Indore - 453 555, Madhya Pradesh
Source of Support: Equipment support of Roentgen Oncologic Solutions
Pvt. Ltd. and Sri Aurobindo Institute of Medical Sciences, Indore (India)., Conflict of Interest: None
Retinoblastoma (Rb) is highly a radiosensitive tumor. Radiotherapy has an important role in salvage, consolidative treatment, and that are nonresponding to chemotherapy and other local therapies. A 2-year-old girl known case of Rb, with enucleation of right eye was treated with three-dimensional conformal radiotherapy (3DCRT). Ketamine (1 mg/kg) was used for sedation during radiotherapy. For study purpose, intensity-modulated radiotherapy (IMRT) plan was created and compared with 3DCRT. The 95 and 99% of PTV was covered with 99 and 96% and 97.7 and 92% of the prescribed dose in 3DCRT and IMRT, respectively. Maximum doses to left (Lt) eye was 1.4 and 17.9 Gy, Lt lens was 0.3 and 6.2 Gy, Lt optic nerve was 2.3 and 25.97 Gy, brainstem was 34.99 and 30.08 Gy, optic chiasm was 46.1 and 49.1 Gy, pituitary gland was 45.24 and 46.48 Gy, and the mean doses of brain was 7.24 and 7.02 Gy in 3DCRT and IMRT, respectively. The homogeneity indices were 1.10 and 1.11, conformity indices were 1.54 and 1.40, and total integral dose to brain was 12.6 and 12.9 J in 3DCRT and IMRT, respectively. 3DCRT has decreased dose to OARs as compared to IMRT with better target coverage and also the treatment time in 3DCRT was much less. So 3DCRT in such cases can be considered as a good option, especially when the patient is financially incapable.
Keywords: Enucleation, radiotherapy, retinoblastoma
|How to cite this article:|
Gurjar OP, Kausar M, Bhandari V, Ladia DD. A comparison between intensity-modulated radiotherapy and three-dimensional conformal radiotherapy in a case of retinoblastoma. Sifa Med J 2016;3:25-7
|How to cite this URL:|
Gurjar OP, Kausar M, Bhandari V, Ladia DD. A comparison between intensity-modulated radiotherapy and three-dimensional conformal radiotherapy in a case of retinoblastoma. Sifa Med J [serial online] 2016 [cited 2021 Jun 19];3:25-7. Available from: https://www.imjsu.org/text.asp?2016/3/1/25/177693
| Introduction|| |
Retinoblastoma (Rb) is one of the most common ocular malignancies in childhood. The incidence is higher in developing countries, may be due to lower socioeconomic status and the presence of certain human papilloma virus.  Rb can be presented as unilateral disease, bilateral disease, or rarely with tumor in both eyes and the pineal gland, which is known as trilateral disease. Rb is diagnosed before the age of 3 years in about 80% of cases. Unilateral cases diagnosed at an earlier age (14-16 months) than those with bilateral presentations (29-30 months). The most common presentation of Rb is leukokoria.  External beam radiotherapy (EBRT) has a very important role in the management of Rb, particularly as salvage, or as a consolidative treatment in tumors that are nonresponding to chemotherapy and other local therapies. Other indications for EBRT are lesions that are too large, numerous, or close to the optic disc or fovea and has a special role in treating eyes with vitreous seeds.
| Case Report|| |
A 2-year-old girl presented with proptosis of right eye diagnosed with right side Rb on ophthalmological examination on July 2013. She underwent complete enucleation of right eyeball on February 2014. Microscopically it showed poorly differentiated Rb, there was choroidal invasion more than 3 mm, scleral invasion seen, iris stroma showed tumor cells, presented Homer Wright and Flexner-Wright rosettes, and optic nerve showed invasion by tumor cells. The patient was planned for local radiotherapy of the right eye. A dose of 54 Gy in 30 fractions (54 Gy/30 #) was planned using three-dimensional conformal radiotherapy (3DCRT) technique.
Thermoplastic sheet (Orfit) was molded in required shape for immobilization of head. Computed tomography (CT) simulation of the patient was done on Siemens SOMATOM Definition AS scanner (Siemens Medical Systems, Germany). CT images of 3 mm slice thickness were obtained. The images were transferred to treatment planning system (TPS) Eclipse vs 8.9 (Varian Medical Systems, Palo Alto, CA) for radiotherapy planning. Clinical target volume (CTV), planning target volume (PTV), and various organs at risk (OARs) were delineated. Patient was treated under short anesthesia, that is, ketamine (1 mg/kg).
Comparison of 3DCRT and IMRT
The 3DCRT plan with three coplanar fields (Gantry (G) = 30° with enhanced dynamic wedge (EDW)60OUT, 0° with EDW25IN, and 330° with EDW60IN) with couch angle 90° as shown in [Figure 1]a was done by using 6 MV photon energy. Dose was calculated by using anisotropic analytical algorithm (AAA) with 0.25 cc grid size. While for the study purpose, intensity-modulated radiotherapy (IMRT) plan with six coplanar (G = 153°, 115°, 40°, 0°, 306°, and 204°) fields with couch angle 0° as shown in [Figure 1]b was done with 6 MV photon energy and dose volume optimizer (DVO) was used for plan optimization. Anisotropic analytical algorithm (AAA) was used to calculate doses with grid size of 0.25 cc. While the target coverage and doses to OARs were compared; and are given in [Table 1]. It can be clearly seen that the target coverage in 3DCRT is much better than in IMRT and the doses to OARs is much better than in IMRT except the mean dose (Dmean) of brain which is 0.22 Gy more in 3DCRT than in IMRT. Moreover, the treatment time required in this case by IMRT (including imaging) was about 12-15 min, while in 3DCRT it was 6-7 min.
|Figure 1: Field arrangements in (a) 3DCRT and in (b) IMRT. 3DCRT = Three-dimensional conformal radiotherapy, IMRT = intensity-modulated radiotherapy|
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|Table 1: Dosimetric parameters of three dimensional conformal radiotherapy and intensity modulated radiotherapy plans |
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[Figure 2] shows the combined dose-volume histogram (DVH) of both the plans and [Figure 3] shows the color dose wash slices.
| Discussion|| |
There are many techniques available for treatment of Rb like anterior lens sparing technique, multiple noncoplanar arcs, single anterior electron fields, stereotactic radiotherapy, 3DCRT, and IMRT.  Krasin et al.,  and Reisner et al.,  did the comparative analysis of external radiotherapy techniques with IMRT in Rb cases. As per their studies, the IMRT planning has greater sparing of the surrounding OARs, bony orbit, and lacrimal gland. However in the studies quoted above, enucleation was not performed. But when radiation is indicated after enucleation of eye in a case of unilateral Rb as in our case report, it shows 3DCRT has near to or better coverage along with greater sparing of surrounding normal structures. As it is difficult to immobilize children and IMRT takes at least 12-15 min, the required dose of sedation for this much time is at least 1.5 mg/kg, while 1 mg/kg is able to sedate only for 8-10 min. 3DCRT takes only 5-7 min only. So the above given dose was sufficient and also the dosimetric parameters in this case shows that 3DCRT is much better than IMRT.
| Conclusion|| |
In this case, 3DCRT has decreased dose to OARs as compared to IMRT with better target coverage and also the treatment time in 3DCRT was much less. So treating with 3DCRT in such cases can be considered as a good option, especially when the patient is financially incapable.
| Acknowledgement|| |
We thank to Managing Director, Roentgen Oncologic Solutions Pvt. Ltd. And Chairman, Sri Aurobindo Medical College and P. G. Institute, Indore for their positive support in conducting this study.
| References|| |
Orjuela M, Castaneda VP, Ridaura C, Lecona E, Leal C, Abramson DH, et al
. Presence of human papilloma virus in tumor tissue from children with retinoblastoma: An alternative mechanism for tumor development. Clin Cancer Res 2000;6:4010-6.
Kachanov DY, Dobrenkov KV, Shamanskaya TV, Abdullaev RT, Inushkina EV, Varfolomeeva SR, et al
. Solid tumors in young children in Moscow region of Russian federation. Radiol Oncol 2008;42:39-44.
McDaid C, Hartley S, Bagnall AM, Ritchie G, Light K, Riemsma R. Systematic review of effectiveness of different treatments for childhood retinoblastoma. Health Technol Assess 2005;9:iii, ix-x, 1-145.
Krasin MJ, Crawford BT, Zhu Y, Evans ES, Sontag MR, Kun LE, et al
. Intensity-modulated radiation therapy for children with intraocular retinoblastoma: Potential sparing of the bony orbit. Clin Oncol (R Coll Radiol) 2004;16:215-22.
Reisner ML, Viégas CM, Grazziotin RZ, Santos Batista DV, Carneiro TM, Mendonça de Araújo CM, et al
. Retinoblastoma - comparative analysis of external radiotherapy techniques, including an IMRT technique. Int J Radiat Oncol Biol Phys 2007;67:933-41.
[Figure 1], [Figure 2], [Figure 3]