BackgroundOmitting the placement of clips inside tumour bed during breast cancer surgery poses a challenge for delineation of lumpectomy cavity clinical target volume (CTVLC). We aimed to quantify inter-observer variation and accuracy for CT- and MRI-based segmentation of CTVLC in patients without clips.Patients and methodsCT- and MRI-simulator images of 12 breast cancer patients, treated by breast conserving surgery and radiotherapy, were included in this study. Five radiation oncologists recorded the cavity visualization score (CVS) and delineated CTVLC on both modalities. Expert-consensus (EC) contours were delineated by a senior radiation oncologist, respecting opinions of all observers. Inter-observer volumetric variation and generalized conformity index (CIgen) were calculated. Deviations from EC contour were quantified by the accuracy index (AI) and inter-delineation distances (IDD).ResultsMean CVS was 3.88 +/− 0.99 and 3.05 +/− 1.07 for MRI and CT, respectively (p = 0.001). Mean volumes of CTVLC were similar: 154 +/− 26 cm3 on CT and 152 +/− 19 cm3 on MRI. Mean CIgen and AI were superior for MRI when compared with CT (CIgen: 0.74 +/− 0.07 vs. 0.67 +/− 0.12, p = 0.007; AI: 0.81 +/− 0.04 vs. 0.76 +/− 0.07; p = 0.004). CIgen and AI increased with increasing CVS. Mean IDD was 3 mm +/− 1.5 mm and 3.6 mm +/− 2.3 mm for MRI and CT, respectively (p = 0.017).ConclusionsWhen compared with CT, MRI improved visualization of post-lumpectomy changes, reduced interobserver variation and improved the accuracy of CTVLC contouring in patients without clips in the tumour bed. Further studies with bigger sample sizes are needed to confirm our findings.

BackgroundDuring radiotherapy of left-sided breast cancer, parts of the heart are irradiated, which may lead to late toxicity. We report on the experience of single institution with cardiac-sparing radiotherapy using voluntary deep inspiration breath hold (V-DIBH) and compare its dosimetric outcome with free breathing (FB) technique.Patients and methodsLeft-sided breast cancer patients, treated at our department with postoperative radiotherapy of breast/chest wall +/– regional lymph nodes between May 2015 and January 2017, were considered for inclusion. FB-computed tomography (CT) was obtained and dose-planning performed. Cases with cardiac V25Gy ≥ 5% or risk factors for heart disease were coached for V-DIBH. Compliant patients were included. They underwent additional CT in V-DIBH for planning, followed by V-DIBH radiotherapy. Dose volume histogram parameters for heart, lung and optimized planning target volume (OPTV) were compared between FB and BH. Treatment setup shifts and systematic and random errors for V-DIBH technique were compared with FB historic control.ResultsSixty-three patients were considered for V-DIBH. Nine (14.3%) were non-compliant at coaching, leaving 54 cases for analysis. When compared with FB, V-DIBH resulted in a significant reduction of mean cardiac dose from 6.1 +/– 2.5 to 3.2 +/– 1.4 Gy (p < 0.001), maximum cardiac dose from 51.1 +/– 1.4 to 48.5 +/– 6.8 Gy (p = 0.005) and cardiac V25Gy from 8.5 +/– 4.2 to 3.2 +/– 2.5% (p < 0.001). Heart volumes receiving low (10–20 Gy) and high (30–50 Gy) doses were also significantly reduced. Mean dose to the left anterior coronary artery was 23.0 (+/– 6.7) Gy and 14.8 (+/– 7.6) Gy on FB and V-DIBH, respectively (p < 0.001). Differences between FB- and V-DIBH-derived mean lung dose (11.3 +/– 3.2 vs. 10.6 +/– 2.6 Gy), lung V20Gy (20.5 +/– 7 vs. 19.5 +/– 5.1 Gy) and V95% for the OPTV (95.6 +/– 4.1 vs. 95.2 +/– 6.3%) were non-significant. V-DIBH-derived mean shifts for initial patient setup were ≤ 2.7 mm. Random and systematic errors were ≤ 2.1 mm. These results did not differ significantly from historic FB controls.ConclusionsWhen compared with FB, V-DIBH demonstrated high setup accuracy and enabled significant reduction of cardiac doses without compromising the target volume coverage. Differences in lung doses were non-significant.

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PurposeThe purpose of our study is to determine indications for the use of an IMRT technique for large volume size left breast cancers.Materials/methodsWe ran a retrospective review of Stage 0-III left breast cancers with large volumes treated with conservation therapy from April 2011 to January 2012 at the Radiation Oncology Department at the National Center for Cancer Care and Research in Doha, Qatar. Computer tomography simulation was used to design fields. Patients were treated supine and received 2 Gray (Gy) fractions to 50 Gy to the whole breast followed by an electron or 3D boost of 16 Gy using 6, 15 or mixed 6/15 megavoltage photons. A variety of techniques including electronic compensation (E-comp), field in field (FinF), and 3D with wedges (3DW) were compared. Dosimetric evaluations were made of the breast planning target volume (PTV), lung, heart and contralateral breast for each technique. RTOG skin toxicity grades, treatment data, and breast volumes were obtained by chart and treatment plan review. We further continued dose volume data evaluation using the following dosimetric parameters: uniformity index (UI), conformity index (CI) and homogeneity index (HI) parameters and radiobiological models to further assess our results.ResultsA total of 30 patients were treated, and all patients received chemotherapy. Volumes ranged from 718–3296 cc (ave.1483.33 cc). Separations ranged from 20–35 cm (ave. 23.87 cm). During treatment there were 63% Grade 1, 37% Grade 2, 0% grade 3/ 4 RTOG skin toxicity; no treatment breaks recorded. E-comp plans resulted in better coverage of the 95% volume (V95) coverage with improved dose homogeneity of the PTV. This was seen especially in breast volumes > 2400 cc. Also, there was a reduction in V110 and V115 in the FinF and Ecomp plans compared to conventional 3DW technique. In terms of dose to the contralateral breast Ecomp had a slight advantage (1%). No significant difference seen in the LT lung V20 and Heart V25 and Contralateral Breast V5 between Ecomp and FinF which was better than 3DW. The average dose coverage values of PTV with ecomp and FinF plans were comparable, and achieved an overall better target coverage than 3D plans. Forward planning IMRT gave higher conformity index values of 0.66 ± 0.07 and 0.67 ± 0.07 for ecomp and FinF plans respectively as compared to 0.65 ± 0.07 for 3D-CRT plans. The Homogeneity (HI) and Uniformity Index (UI) values favored ecomp and FinF values compared to 3DCRT with average HI values of 0.27 ± 0.16 for ecomp, 0.31 ± 0.14 for FinF, and 0.38 ± 0.33 for 3D-CRT. And uniformity index values of 1.11 ± 0.04, 1.13 ± 0.05 and 1.26 ± 0.39 for ecomp, FinF, and 3D respectively.ConclusionsFor women with large breast size Ecomp planning significantly improved dose homogeneity decreased acute skin toxicity and less hot spot value. These factors grow more important in women with large breasts, who may experience more Grade 3/4 skin toxicity and increased pain resulting in a lower quality of life with standard tangential fields. Therefore, we suggest using an Ecomp technique for left-sided breast cancer in the following situations: 1) breast volume >1500cc 2) separation of >25 cm or 4) combination of large volume/cup size with separation > 22 cm or vice versa, 5) the use of mixed beams. For patients with large breast volumes supine IMRT treatments can provide good dose homogeneity, spare dose to critical structures, and may be preferable to the prone breast irradiation. Conformity Index, Homogeneity Index and Uniformity Index are objective tools for evaluating dose coverage for breast planning. This study showed that a better target coverage for ecomp and FinF plans over 3D-CRT with a slight advantage of ecomp over FinF with large breast volumes. Furthermore, we will assess the potential advantage of IMRT over 3D planning using radiobilogical models.

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