Left Anterior Descending Artery Dose Research Articles

P090 Dosimetric Evaluation of the Heart and Left Anterior Descending Artery Dose in Radiotherapy for Japanese patients with Breast Cancer

P090 Dosimetric Evaluation of the Heart and Left Anterior Descending Artery Dose in Radiotherapy for Japanese patients with Breast Cancer

Dosimetric evaluation of cardiac and left anterior descending artery dose in patients with left-sided breast cancer treated by different techniques of hypofractionated adjuvant radiotherapy after breast conservative surgery

The aims: to dosimetrically evaluate the dose to the heart and left anterior descending artery in left-sided early breast cases using different techniques.
 Materials and methods: Prospective observational/analytical study done in cases of left-sided BCS referred for adjuvant RT in 54 patients. Patients who underwent left-sided BCS (breast conservative surgery), patients aged between 18- and 75 years performance status ECOG 0-2, histological confirmed DCIS, Invasive Breast Cancer-Stage 1, 2, 3, patients without any evidence of metastatic disease Irrespective of hormonal receptor and HER-2 neu status are included in the study.
 Results: All the 3 parameters for LAD showed the highest doses with 3DCRT and lowest with VMAT. Thus our study favoured VMAT (p<0.01) as the planning technique to achieve the least doses of LAD. However, for the heart, there was no statistically significant difference between 3DCRT and IMRT (p=0.349) for the average mean dose (Gy). On the other hand, there was a statistically significant difference between 3DCRT Vs VMAT and IMRT Vs VMAT (95 % CI, p<0.01), again favouring VMAT as the choice of planning technique. The average heart max dose(Gy) and average heart V20(%) showed statistically significant benefits with VMAT (p<0.01). There was a statistically significant benefit (p<0.000) with VMAT for both LV parameters. At the same time, there was a statistically significant benefit in terms of ipsilateral lung dose with VMAT(p<0.000), the dose to the right lung, right breast and favoured 3DCRT (p<0.01). PTV95 % (Gy) by 3DCRT, IMRT, and VMAT in our study is 41.01, 41.96, and 41.76, respectively. Though the difference between the 3 techniques seems meagre, there was a statistically significant difference (p<0.012) favouring IMRT.
 Conclusion: We conclude that using the VMAT technique in radiotherapy for left-sided breast cancer can significantly reduce radiation doses to the heart and LAD, potentially reducing cardiac risk. For all patients, the cardiac doses are considerably decreased for all dose levels without compromising the dose coverage to PTV, which is an advantage over IMRT and 3DCRT

Impact of lung block shape on cardiac dose for total body irradiation.

Evaluating cardiac dose during total body irradiation (TBI) is of increasing interest. A three-dimensional beam model for TBI was commissioned and lung shielding was simulated in a treatment planning system with the cardiac silhouette partially blocked and unblocked. When blocked, the median heart dose decreased by 6% (IQR=6%) and the median cardiac V12Gy decreased by 27% (IQR=17%). The median left anterior descending artery dose decreased 20% (IQR=12%) for blocked cases. Because using partial heart shielding may result in considerable changes in dose to cardiac structures, TBI protocols should explicitly consider lung block design parameters and their potential effects.

Cardiac dose reduction using deep inspiratory breath hold (DIBH) in radiation treatment of left sided breast cancer patients with breast conservation surgery and modified radical mastectomy

PurposeDeep inspiration breath hold (DIBH) reduces heart and pulmonary doses during left-sided breast radiation therapy (RT); however, there is limited information whether the reduction in doses is similar in patients with modified radical MRM (MRM) and breast conservation surgery (BCS). The primary objective was to determine whether DIBH offers greater dosimetric reduction in cardiac doses in patients with MRM as compared to BCS with secondary objectives of documenting time consumed in counseling, simulation and planning such techniques. MethodsThirty patients with diagnosis of left sided breast cancer underwent CT simulation both free breathing (FB) and DIBH. Patients were grouped into two cohorts: MRM (n = 20) and BCS (n = 10). 3D-conformal plans were developed and FB was compared to DIBH for entire group (n = 30) and each cohort using Wilcoxon signed-rank tests for continuous variables and McNemar's test for discrete variables. The percent relative reduction conferred by DIBH in mean heart (Dmean heart) and left anterior descending artery dose (LADmean and LADmax), heart V25,V10, V2 and ipsilateral DmeanLung,V20, V12 were compared between the two cohorts using Wilcox rank-sum testing. A two-tailed p-value ≤ 0.05 was considered statistically significant. Time consumed during FB and DIBH from patient counseling to planning was documented. ResultsPatients undergoing BCS had comparable boost target coverage on DIBH and FB. For the overall group (n = 30), DIBH reduced Dmean heart and LAD dose, V25, V10 and V2 doses for the heart and Ipsilateral DmeanLung, V20, V12 which was statistically significant. For individual cohorts DIBH did not significantly reduce the lung (Ipsilateral DmeanLung, V20, V12) and LAD (LADmean and LADmax) doses for BCS while significant reduction in all cardiopulmonary doses was seen in MRM cohort. Despite significant reductions with DIBH in MRM, ipsilateral lung constraint of V12 < 15% was less commonly achieved in MRM (n = 11, 55%) requiring nodal radiation as compared to BCS (n = 3, 30%). Percent reduction in all cardiac and pulmonary dosimetric parameters with DIBH was similar in the MRM cohort as compared to BCS cohort. In total 73.1 ± 2.6 min was required for FB as compared to 108.1 ± 4.1 min in DIBH. ConclusionDIBH led to significant reduction of cardiac doses in both MRM and BCS. Reduction of lung and LAD doses were significant in MRM cohort. All cardiac constraints were met with DIBH in both cohorts, lung constraints were less frequently met in MRM cohort requiring nodal radiation.

Comparison of heart dose in early-stage left-sided breast cancers treated with intraoperative radiation therapy or whole-breast irradiation with deep inspiratory breath hold

PURPOSETo compare heart dose between patients treated with lumpectomy and either intraoperative radiation therapy (IORT) with CT-guided high-dose-rate brachytherapy (precision breast IORT [PB-IORT]) or whole-breast irradiation with deep inspiratory breath hold (WBI-DIBH) for early-stage left-sided breast cancers. METHODS AND MATERIALSWe retrospectively identified the 17 patients with left-sided breast cancers treated with PB-IORT on a phase I clinical trial and 17 patients with left-sided tumors who had undergone lumpectomy and adjuvant WBI-DIBH. Dosimetric data were obtained. T-testing was performed and biologically effective doses (BEDs) were calculated using an α/β ratio of 2 Gy. ResultsMean heart dose was significantly lower with WBI-DIBH compared with PB-IORT (0.61 vs. 0.87 Gy, p = 0.006). Mean heart BED was lower with WBI-DIBH (0.62 vs. 1.3 Gy2, p = 0.0001). Nominal maximum heart dose was higher with WBI-DIBH (11.37 vs. 4.81 Gy, p = 0.004). Maximum heart dose BED was similar between WBI-DIBH and IORT, 16.63 vs. 19.36 Gy (p = 0.64), respectively. No difference was found in mean left anterior descending artery dose: 2.18 Gy with WBI-DIBH and 1.89 Gy with IORT (p = 0.446). The maximum left anterior descending doses were 9.63 Gy and 3.62 Gy with WBI-DIBH and IORT, respectively (p = 0.016). Distance from the heart to the lumpectomy cavity was inversely associated with heart dose for PB-IORT, but not for WBI-IORT. CONCLUSIONSHeart doses were low in both groups. Expected increase in cardiac risk at these doses is minimal. It is unlikely that there will be a clinically significant difference in cardiac toxicity in patients treated with WBI-DIBH or PB-IORT. Further research is needed to evaluate the actual clinical impact of the observed cardiac doses delivered with these modalities.

Postmastectomy radiation therapy technique and cardiopulmonary sparing: A dosimetric comparative analysis between photons and protons with free breathing versus deep inspiration breath hold

PurposeDosimetric studies have suggested greater cardiopulmonary sparing with protons over photons for left-sided postmastectomy radiation therapy (PMRT). Modern techniques such as deep inspiration breath hold (DIBH) can help spare the heart. This analysis compares photon and proton delivery with and without DIBH. Methods and materialsTen women with left breast cancer referred for PMRT on a prospective clinical trial with unfavorable cardiac anatomy underwent free breathing (FB) and DIBH computed tomography simulation. A partially wide tangent photon (PWTF) during DIBH, passively scattered proton during FB, pencil-beam scanning (PBS) proton during FB, and PBS proton during DIBH plan was completed for each patient. Plans were designed to achieve 95% prescription dose coverage to 95% of chest wall and regional lymphatics while maximally sparing heart and lungs. ResultsAll techniques resulted in similar target coverage, although protons improved homogeneity indices and cardiopulmonary sparing (omnibus P < .0001 for each metric). Heart/lung metrics for PWTF with DIBH, scattered protons with FB, PBS protons with FB, and PBS protons with DIBH, respectively, were as follows: mean heart dose (2.09, 0.39, 0.98, 0.71 Gy relative biological effectiveness [RBE]), mean left ventricle dose (3.72, 0.08, 0.19, 0.21 GyRBE), V20 left ventricle (2.73, 0.03, 0, 0%), maximum left anterior descending artery dose (46.14, 8.28, 4.58, 4.63 GyRBE), mean lung dose (13.30, 5.74, 7.63, 7.49 GyRBE), and V20 lung (26.04, 12.04, 15.18, 14.43 %). Pairwise testing confirmed an improvement in each metric with all proton plans compared with PWTF with DIBH; there were no differences in homogeneity indices or cardiopulmonary sparing between passively scattered and PBS protons, regardless of addition of DIBH. ConclusionsFor left-sided PMRT, passively scattered or PBS protons with or without DIBH improves homogeneity and cardiopulmonary sparing without compromise in target coverage compared with PWTF photons with DIBH. Furthermore, the addition of DIBH to proton therapy did not provide a significant dosimetric benefit.

Hybrid intensity-modulated radiation therapy (IMRT) simultaneous integrated boost (SIB) technique versus three-dimensional (3D) conformal radiotherapy with SIB for breast radiotherapy: a planning comparison

AbstractAimThis study aims to compare conventional simultaneous integrated boost (SIB) planning technique with a hybrid SIB intensity-modulated radiation therapy (IMRT) technique with varying open tangent to IMRT field dose ratios. Furthermore, we investigated which of the dose ratios proves the most favourable as a class solution across a sample.MethodsIn total, 15 patients with conventional SIB treatment plans were re-planned with hybrid SIB IMRT technique using three differing open field:IMRT dose ratios, that is, 80:20, 70:30 and 60:40. Plans were compared using dosimetric comparison of organs at risk (OARs) and homogeneity and conformity indexes across target structures.ResultsAll hybrid plans reduced dose maximums and showed a reduction of high doses to both lungs but increased lower doses, that is, V5, with similar results discovered for the heart. Contralateral breast dose was shown to decrease V5 and V1 measures by hybrid arms, whereas increasing the V2. Left anterior descending artery dose and non-irradiated structures were reduced by all hybrid arms. The homogeneity and conformity increased across all hybrid arms. Qualitative assessment of all plans also favoured hybrid plans.FindingsHybrid plans produced superior dose conformity, homogeneity, reduced dose maximums and showed an improvement in most OAR parameters. The 70:30 hybrid technique exhibited greater benefits as a class solution to the sample than conventional plans due to superior dose conformity and homogeneity to target volumes.

Assessment of Intrafraction Breathing Motion on Left Anterior Descending Artery Dose During Left-Sided Breast Radiation Therapy

Touse 4-dimensional computed tomography (4D-CT) imaging to predict the level of uncertainty in cardiac dose estimates of the left anterior descending artery that arises due to breathing motion during radiation therapy for left-sided breast cancer. The fast helical CT (FH-CT) and 4D-CT of 30 left-sided breast cancer patients were retrospectively analyzed. Treatment plans were created on the FH-CT. The original treatment plan was then superimposed onto all 10 phases of the 4D-CT to quantify the dosimetric impact of respiratory motion through 4D dose accumulation (4D-dose). Dose-volume histograms for the heart, left ventricle (LV), and left anterior descending (LAD) artery obtained from the FH-CT were compared with those obtained from the 4D-dose. The 95% confidence interval of 4D-dose and FH-CT differences in mean dose estimates for the heart, LV, and LAD were ±0.5Gy, ±1.0Gy, and ±8.7Gy, respectively. Fast helical CT is a good approximation for doses to the heart and LV; however, dose estimates for the LAD are susceptible to uncertainties that arise due to intrafraction breathing motion that cannot be ascertained without the additional information obtained from 4D-CT and dose accumulation. For future clinical studies, we suggest the use of 4D-CT-derived dose-volume histograms for estimating the dose to the LAD.

Potential benefits of using cardiac gated images to reduce the dose to the left anterior descending coronary during radiotherapy of left breast and internal mammary nodes

PurposeTo assess the benefits of using cardiac gated images for treatment planning of breast and internal mammary nodes. Patients and methodsInspiration breath hold computed tomography (CT) series acquired at prospectively gated diastolic phase were used for planning. Three different techniques were compared. Technique A used tangents and an internal mammary nodes field covering the three first inter-rib spaces; technique B used an extended internal mammary nodes including part of the medial breast in junction with tangential fields; the 3rd technique used helical tomotherapy. For each technique, two treatment plans were performed: one plan (plan-01) where mean dose and V25 to the heart were considered for plan evaluation and a second plan (plan-02) where the irradiation of the left anterior descending artery was minimized. ResultsV25 to the heart was found to be less than 5% for all six plans. Mean doses to the heart were within 4.8 to 7.2Gy. By attempting to lower the dose to the left anterior descending artery, heart Dmean was decreased by 20–30% for the two techniques A and B while being unchanged for tomotherapy. Regarding target coverage, there was no marked difference between plans where only heart dose was considered (plans-01) and plans where the left anterior descending artery dose was minimized (plans-02). When the left anterior descending artery dose was part of plan evaluation, Dmean to the left anterior descending artery could be decreased by 24, 19 and 9% for techniques A, B and tomotherapy respectively. The three techniques exposed segments of the left coronary to different levels of dose. ConclusionThis study showed that evaluation of the dose to the left anterior descending artery coronary may change the treatment strategy. Cardiac gated images without IV contrast permitted a good visualization of the coronaries in order to optimize the dose on these structures. In addition to heart V25, the dose to the coronaries should be included in prospective studies on radiotherapy related heart toxicity in association with all additional risk factors.

Accelerated Partial Breast Irradiation: What is Dosimetric Effect of Advanced Technology Approaches?

The present treatment planning study compared whole breast radiotherapy (WBRT) to accelerated partial breast irradiation (APBI) for different external beam techniques and geometries (e.g., free breathing [FB] and deep inspiration breath hold [DIBH]). After approval by our institutional review board, a treatment planning study was performed of 10 patients with left-sided Stage 0-I breast cancer enrolled in a Phase I-II study of APBI using intensity-modulated radiotherapy (IMRT). After lumpectomy, patients underwent planning computed tomography scans during FB and using an active breathing control device at DIBH. For the FB geometry, standard WBRT and three-dimensional conformal radiotherapy (3D-CRT) APBI plans were created. For the DIBH geometry with active breathing control, WBRT, 3D-CRT, and IMRT APBI plans were created. All APBI techniques had excellent planning target volume coverage. The maximal planning target volume dose was reduced from 116% of the prescription dose to 108% with the IMRT(DIBH) APBI plan. The maximal heart dose was >30 Gy for the WBRT techniques, 8.2 Gy for 3D-CRT(FB), and <5.0 Gy for 3D-CRT(DIBH) and IMRT(DIBH) techniques. The mean left anterior descending artery dose was significantly reduced from 11.4 Gy with WBRT(FB) to 4.2 with WBRT(DIBH) and <2.0 Gy with all APBI techniques. Although planning target volume coverage was acceptable with all techniques, the plans using the DIBH geometry resulted in a marked reduction in the normal tissue dose compared with WBRT planned in the absence of cardiac blocking. Additional study is needed to determine whether these techniques result in clinical benefits.