Background and purpose: 3-dimensional conformal therapy (3DCRT) is widely employed radiation therapy technique for breast cancer, but there is still need to minimize the doses to organ at risk (OAR) using 3DCRT. A few clinical studies have discussed using intensity modulated radiation therapy (IMRT) to address this shortfall. Simultaneous integrated boost (SIB) has been used in head and neck and prostate cancer, and there is a growing interest in using SIB for breast cancer too. This study aimed to compare SIB-IMRT versus SIB-3DCRT for breast cancer patients. Materials and Methods: SIB-3DCRT treatment plans were created for 36 consecutive patients. Dose was prescribed as 45 Gy in 25 fractions to the planning target volume (PTV)-1 and 60 Gy in 25 fractions to PTV-2. Treatment plans were normalized to 95% of PTV volume receiving 95% of the prescription dose. The conformity index (CI), homogeneity index (HI), lung dose, heart dose, left anterior descending artery(LAD) dose, and low dose volume and integral dose of normal healthy tissue were recorded and analyzed. Results: With the use of IMRT technique, there was an improvement in CI (0.14) when compared to CI of 3DCRT (0.18; p = 0.01). However, there was no significant difference in the HI (p = 0.45). On average, the V20Gy of ipsilateral lung was 37.9 % for 3DCRT and 22.4 % (p < 0.01) for IMRT, whereas the V20Gy of total lung (ipsilateral + contralateral) was 21.8% for 3DCRT and 12.14 (p < 0.01) for IMRT. Similarly, average V40Gy of heart was 7.5 % for 3DCRT and 2.13 % (p = 0.01) for IMRT. The LAD maximum dose to left side breast patients, on average, was 39.5 Gy for 3DCRT and 29.17 Gy (p = 0.03) for IMRT. The average number of monitor units was about 180 for 3DCRT and 1441 (p < 0.01) for IMRT. Conclusion: IMRT for breast cancer treatment is feasible. In comparison to 3DCRT, IMRT can reduce the maximum dose to the target volume, and dose to the OAR. However, 3DCRT technique is superior in terms of low dose volume, integral dose, and treatment time. With the use of breath-hold gated technique in IMRT, it can further improve the target coverage and reduction of doses to the heart, lung, and LAD. SIB technique could reduce the overall treatment duration by about one week.
Dosimetrically, IMRT-APBI provided best target coverage with less dose to normal tissues compared with 3DCRT-APBI.
Purpose: Whole breast irradiation is part of breast conservative management for early breast cancer; addition of boost dose to tumor bed improves local recurrence rates and is currently the standard of care. Randomized trials reported low a/b ratio for breast cancer that predict a radiobiological advantage for hypofractionation. Simultaneous boost radiation as a method of hypofractionation proved safe and effective for head and neck tumors. In this study we attempt to compare and analyze the dosimetric aspects of adding Simultaneous Integrated Boost (SIB) over Sequential Boost (SB) to a hypofractionated treatment schedule in breast cancer patients after BCS. Materials and methods:CT simulation data sets for 23 patients were selected for this planning study; Targets and OAR were delineated as per RTOG guidelines. Multiple dynamic field IMRT plans were generated for each patient. The prescribed dose was 40 Gy/15 fractions to whole breast (2.67 Gy/fraction) and 48 Gy/15fractions to lumpectomy cavity (3.2 Gy/fraction) for SIB, and 40 Gy/15 fractions followed by 10Gy/5 fractions for SB. Generated Treatment plans were evaluated by experienced radiation oncologist, and the best plan was selected for the dosimetric analysis. Results:The pre specified target coverage criteria were met for the lumpectomy cavity as well as whole breast in all plans. All quality indices for PTV coverage showed to be significantly improved with SIB for both whole breast and tumor bed volumes. SB technique showed more dose spillage outside the boost volume. SIB-IMRT was better in sparing OAR ,the volume of the ipsilateral lung V20 Gy was 19.8 % compared to 22.8 % (p = 0.04), maximum dose to LAD was 17.6 Gy Vs. 21.6 (p= 0.01) and contralateral breast mean dose was 0.36 Gy Vs. 1.27 Gy (p = 0.01) for SIB and SB respectively. Conclusions:Hypofractionated breast SIB is feasible with better PTV coverage and OAR. Along with further reduction of the overall period which may increase patient convenience and resource utilization benefit.
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