A Dosimetric Study Comparing 3D-CRT vs. IMRT vs. VMAT in Left-Sided Breast Cancer Patients After Mastectomy at a Tertiary Care Centre in Eastern India

Abstract

Introduction Post-mastectomy radiation in left-sided breast cancer in women continues to pose a significant risk to the underlying lungs and heart. This study analyzed the difference in planning target volume (PTV) coverage and dose to the organs at risk (OAR) by using three different planning methods for the same patient - three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and volumetric-modulated arc therapy (VMAT). Material and methods Thirty-five left-sided breast cancer patients’ post-mastectomy were included in this study, and three different plans for adjuvant radiation were created using 3D-CRT, IMRT, and VMAT. The prescribed dose was 50Gy in 25 fractions. Kruskal-Wallis analysis of variance (ANOVA) was done, followed by a pairwise t-test to establish a hierarchy of plan quality and dosimetric benefits. The plans were compared with PTV 95 , homogeneity index (HI), conformity index (CI), hotspot (V 107% ), left lung V 20Gy , mean lung dose, heart V 25Gy , mean heart dose, and integral dose (ID) to the body. Results Both VMAT and IMRT led to improved PTV 95% coverage (95.63±1.82%, p=0.000 in VMAT; 93.70±2.16 %, p=0.000; 81.40±6.27% in 3D-CRT arm) and improved CI (0.91±0.06 in IMRT [p<0.05] and 0.96±0.02 for VMAT plans [p<0.05]) as compared to 3D-CRT (0.66±0.11), which was statistically significant on pairwise analysis. In contrast, the difference in HI and reduction in hotspots were not significantly different. Left lung V 20 was statistically very different between the three arms with the highest values in IMRT (36.64±4.45) followed by 3D-CRT (34.80±2.24) and the most negligible value in VMAT (33.03±4.20). Mean lung dose was also statistically different between the three arms. There was a statistically significant difference in mean heart dose between the three arms on pairwise analysis. Both the inverse planning methods led to a statistically significant increase in low dose volume (V 5 and V 10 ) of the ipsilateral lung, opposite lung, and heart, and increased ID to the body excluding the PTV. Conclusion While both the inverse planning modalities led to increased coverage, better CI, and better HI and decreased high dose volumes in OARs, there was increased low volume irradiation of heart, lungs, and body with VMAT faring marginally better than IMRT in coverage and decreasing lung irradiation with comparable heart irradiation.

Dosimetric Study Comparing 3D Conformal Radiotherapy (3D-CRT), Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) in Hypofractionated One-Week Radiotherapy Regimen in Breast Cancer

“…The conformity index for the hypofractionated regimen used in our study was better for IMRT compared to VMAT or 3D-CRT (p<0.05). A similar result was reported in previous studies for other hypofractionated regimens [5][6][7]. In the multicentric randomized trial protocol (HYPORT-Adjuvant) treatment planning achieving breast/chest wall coverage with 95% of the prescribed dose and limiting the maximum dose to less than 107% of the prescribed dose was allowed [9].…”

“…The same was reported by Sudha et al, who found PTV coverage was better in VMAT [5]. A study by Das Majumdar et al showed improved PTV coverage with VMAT and IMRT compared to 3D-CRT [7]. In a study by Liu et al, IMRT has shown better V 95 coverage compared to VMAT (p-value <0.05) [8].…”

“…In view of fewer comparative dosimetric studies for the one-week regimen, the pattern was compared with more protracted hypofractionated regimens. The V 25 value for lung reported by Das Majumdar et al were 13.46, 13.15, and 12.12 for 3D-CRT, IMRT and VMAT, respectively, with no statistically significant difference [7]. V 20 Gy reported by Sudha et al were 29.88 and 12.79 for 3D-CRT and VMAT, respectively [5].…”

A Dosimetric Study Comparing Different Radiotherapy Planning Techniques With and Without Deep Inspiratory Breath Hold for Breast Cancer

“… 1 3D-Conformal radiotherapy (3DCRT) is the most common technique of adjuvant RT by virtue of its simplicity, but more recent treatment techniques such as intensity modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), tomotherapy, etc offer the potential to reduce volumes of organs-at-risk (OARs) exposed to high doses. 2 , 3 These techniques are more likely to be considered in more complex cases such as patients requiring internal mammary node radiation. Cardiotoxicity resulting from radiotherapy for breast cancers has been associated with morbidity and mortality.…”

“…Even though offering higher conformity and superior target coverage, advanced techniques such as IMRT and VMAT are invariably associated with increased low-dose exposure to OARs. 3 In this particular scenario, respiratory immobilization plays a vital role in reducing the heart as well as the lung dose to a lesser extent. This can be achieved using gating, tracking, and optimized free breathing modules.…”