ANALYSIS OF DOSE AT 3D-CRT AND IMRT TECHNIQUES IN LEFT BREAST CANCER CASE WITH HYPOFRACTIONATION USING DEEP INSPIRATION BREATH-HOLD (DIBH)

In terms of breast cancer radiation treatment, it has radiation using the 3D-Conformal Radiotherapy (3D-CRT) technique and the continuation of the 3D-CRT technique, namely the Intensity Modulated Radiation Therapy (IMRT) technique. This study aims to evaluate the dosage aspects of PTV and OAR between the 3D-CRT and IMRT techniques in cases of left breast cancer with hypofractionation using the Deep Inspiration Breath Hold (DIBH) method using the Conformity Index (CI) and Homogeneity Index (H.I.) and H.I. organ at risk uses tolerance limits. This type of research is comparative quantitative with ten samples with primary data conducted at Siloam T.B. Hospital. Simatupang from November 2019 to April 2020. The research was carried out in the form of radiation planning with 3D-CRT techniques and IMRT techniques, and the results of planning both techniques were evaluated between 3D-CRT techniques and IMRT techniques through PTV evaluations using CI and H.I. values. Furthermore, the organs at risk use tolerance limits on each organ. results showed the assessment between 3D-CRT and IMRT on PTV and organs at risk received different doses. The PTV shows the CI value, which is almost the same as the difference of 0.034, and there is a slight difference in H.I. with an average value in the IMRT technique of 0.07 and 3D-CRT of 0.11, and it can be seen that the IMRT is slightly superior because the excellent H.I. value is the closest to 0. Then at the dose of organ at risk received by the sample, the 3D-CRT technique is slightly superior by obtaining a lower dose that obtains the difference in the heart by 0.53%, lung by 3.46%, spinal cord by 6.51 Gy, esophagus at 4.5 Gy, and larynx at 5.18 Gy.


Introduction
Breast cancer was initially treated with conventional fractionation, which associated administering a total dose of 45 -50 Gy (1.8 -2 Gy per fraction) in 25 -28 times fractions, but this can now be accomplished with hypofraction. Hypofractionation is administering a total dose of 40.5 -42.5 Gy (2.66 -2.67 Gy per fraction) in 15-16 times the fraction in breast cancer irradiation. Radiotherapy has been shown to accomplish this goal in several experiments conducted abroad. This trial compared hypofractionated Radiotherapy to conventional fractionation as postoperative adjunctive treatment. These findings suggest that the acute and chronic effects of each type of breast cancer irradiation are not significantly different. (4,5) A method known as the Deep Inspiration Breath Hold (DIBH) method delivers a lower dose to the heart and lungs to minimize acute and chronic effects. This method focuses on reducing the dose to the cardiac substructure during radiation treatment for left breast cancer.
While the 3D-CRT technique is the most frequently used for breast cancer radiation treatment, other techniques may be used, one of which is developing the 3D-CRT technique, namely the IMRT technique. 3D Conformal Radiation Therapy (3D-CRT) is a technique for irradiating breast cancer expected to reduce radiation doses delivered to healthy organs. The tumor location can be determined more precisely by using Computed Tomography (C.T.) to simulate and plan radiotherapy treatment. (3). The 3D-CRT technique is widely regarded as the industry standard for treatment planning. However, compared to 3D-CRT, IMRT can provide more excellent target coverage and lower radiation doses to surrounding vital organs.
Among the efforts is using the DIBH method for breast cancer irradiation and cutting-edge radiotherapy technology, specifically the 3D-CRT and IMRT techniques. The goal is similar to Radiotherapy, which delivers the maximum dose possible to the target while sparing the surrounding organs at risk. Additionally, both techniques apply to cases of breast cancer.
The Deep Inspiration Breath Hold (DIBH) method was used to determine the dose of 3D-CRT and IMRT techniques in hypofractionated left breast cancer cases.

METHODS OF RESEARCH
The data collection method used in this study was a discussion with radiotherapists and medical physicists to obtain the necessary information regarding sample selection, analysis of organs at risk to be studied, and processing of CI and H.I. data. Then, using experimental experiments at TPS, we obtained 3D-CRT and IMRT techniques in one patient who met the research inclusion criteria, with a sample size often, and we observed and recorded data from the results of TPS calculation planning, specifically DVH 3D-CRT and IMRT techniques in cases of left breast cancer treated with hypofractionation using the DIBH method. Following data processing in this study, the results of TPS planning for each patient will be compared using the DVH diagram. The dose value on the PTV and organ at risk is determined using DVH. At PTV, the data will be processed using CI and H.I. and then compared to the tolerance limit for the organ at risk. After evaluating and comparing the dose values for PTV and organ at risk for each patient using 3D-CRT and IMRT techniques, conclusions will be drawn regarding which technique is the most optimal for CI and H.I. values and organ at risk in cancer patients. Hypofractionation of the left breast using the DIBH method.

RESULTS AND DISCUSSION
The results obtained in the form of DVH result from treatment planning performed by Medical Physicists in the TPS room. DVH indicates the dose and volume values for PTV and organs at risk, which correspond to the dose tolerance limit, and the quality of the dose distribution in the target being evaluated by examining the CI and H.I. parameters.
The radiation planning results were evaluated for their suitability for the target shape, homogeneity of the target volume, and dose to at-risk organs nearby the target. The CI and H.I. values were used to determine the dose distribution's suitability for the target tumor or PTV. The conformity index is defined in ICRU report 83 as the degree to which the prescribed dose covers the tumor target and is expressed in equation 1.

= (Persamaan 1)
Where PTV Volume is 95 percent of Treated Volume and Treated Volume is PTV Volume The ideal conformity index value is 1, which indicates that the isodose curve for the prescribed dose fits the PTV perfectly.
The homogeneity index, defined in equation 2, is a ratio between the maximum and minimum doses in the target volume; a lower value indicates a more homogeneous dose distribution.

= (Persamaan 2)
Where D2% is the dose that covers 2% of the PTV volume, D98% is the dose that covers Additionally, the IMRT technique achieves an H.I. value that is closer to zero than the 3D-CRT technique.
The IMRT technique's homogeneity is due to optimization in the treatment planning process, which ensures that the dose received by the PTV is the same in each direction of the beam.
Based on the study results, different tolerance limits for each organ, namely the heart, lung, spinal cord, esophagus, and larynx, will be used in cases of left breast cancer treated with hypofractionation using the DIBH method, as illustrated in Fig. Table 3. And the results of the study on ten samples examined indicated that all organs at risk, namely the heart, lung, spinal cord, esophagus, and larynx, received a lower dose in the 3D-CRT technique than in the IMRT technique, with a difference of 0.53 percent for the heart, 3.46 percent for the lung, 6.51 Gy for the spinal cord, 4.5 Gy for the esophagus, and 5.18 Gy for the larynx. Additionally, the entire organ is within the tolerance dose limit.