DOSIMETRIC COMPARISON OF USING CONFORMAL RADIOTHERAPY VERSUS INTENSITY MODULATED RADIOTHERAPY IN THE TREATMENT OF MID ESOPHAGEAL CARCINOMA

Dr. Thamizholi. S, Dr. Hasib A. G, Dr. Athiyamaan, Dr. Sandesh, Dr. Sharaschandra

Abstract


BACKGROUND: Esophageal carcinoma accounts for 6% of all GI malignancies in the world. The treatment of cancer of the esophagus has
evolved from 2 dimensional conformal radiotherapy to the present day image guided radiotherapy .Due to the presence of many vitals organs like
the spinal cord, heart, lung which lie in close proximity to the esophagus, the treatment of this cancer has been challenging. In our setting most of the
cases usually present with tumors in the mid and distal esophagus. Over the past few years, studies based on dosimetric parameters have revealed
the efficacy of IMRT in the treatment of these cancers owing to its superior target volume coverage and conformality with decreased dose to the
normal structures.
OBJECTIVES: To compare the 3D conformal and IMRT technique with respect to conformality of target coverage and to analyze the dose
received by various structures around the esophagus.
METHODS: A prospective comparative study with purposive sampling of 25 patients of esophageal cancer being treated with radical chemo
radiation or radiation alone were included in the study .Three plans were created for all patients, one 3DCRT and two IMRT plans using 5
beam and 7 beams were made and dosimetric parameters were compared in each of these plans to analyse the structures around the esophagus
will benefit from using more advanced planning techniques.
RESULTS: Patients in our study had performance scores ranging from 70 to 90 with the mean GTV length being 8.74 cms and the mean PTV
length 18.34 cms. The percentage of PTV receiving 95% of the dose was 84.23% in 3DCRT, 93.67% in 5 beam IMRT and was 94.73% in 7 beam
IMRT plans thus showing statistically significant improvement in the IMRT plans as compared to 3DCRT plans (p<0.001). The volume of the heart
that received 40Gy in the 3DCRT plans was 67.23% whereas in the 5 beam IMRT plans was 30.77% and 30.36% in the 7 beam IMRT plans, all of
which was found to be statistically significant.(p<.001). The V20 of whole lung was 23.64% in the 3DCRT plans and 39.68 in the 5 beam IMRT
plans and 36.69 in the 7 beam IMRT plan.
CONCLUSION: In this study it was found that IMRT plans had significantly better PTV coverage as compared to 3DCRT plans. However the
lung doses were higher in the IMRT plans as compared to 3DCRT. When the 5 beam and 7 beam IMRT plans were compared it was found that the 7
beam IMRT plans had a lower lung dose as compared to the 5 beam IMRT plans. The heart doses were significantly lower in the IMRT plans as
compared to 3DCRT plans.


Keywords


Esophageal cancers; Dosimetric study; 3DCRT;IMRT

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