Radiation dose-volume effects in the heart

Impact of Ionizing Radiation on the Cardiovascular System: A Review

Radiation therapy has become one of the main forms of treatment for various types of cancers. Cancer patients previously treated with high doses of radiation are at a greater risk to develop cardiovascular complications later in life. The heart can receive varying doses of radiation depending on the type of therapy and can even reach doses in the range of 17 Gy. Multiple studies have highlighted the role of oxidative stress and inflammation in radiation-induced cardiovascular damage. Doses of ionizing radiation below 200 mGy, however, have been shown to have beneficial effects in some experimental models of radiation-induced damage, but low-dose effects in the heart is still debated. Low-dose radiation may promote heart health and reduce damage from oxidative stress and inflammation, however there are few studies focusing on the impact of low-dose radiation on the heart. In this review, we summarize recent studies from animal models and human data focusing on the effects and mechanism(s) of action of radiation-induced damage to the heart, as well as the effects of high and low doses of radiation and dose rates.

The feasibility of a heart block with an electron compensation as an alternative whole breast radiotherapy technique in patients with underlying cardiac or pulmonary disease

PURPOSE

We aimed to evaluate the feasibility of the heart block with electron compensation (HBE) technique, based on three-dimensional conformal radiotherapy (3D-CRT) in left-sided breast cancer patients with underlying cardiac or pulmonary disease.

METHODS

Twenty patients with left-sided breast cancer who were treated with whole breast radiotherapy (WBRT) were included in this study. Intensity-modulated radiotherapy (IMRT), 3D-CRT, and HBE treatment plans were generated for each patient. Based on the 3D-CRT plan, the HBE plan included a heart block from the medial tangential field to shield the heart and added an electron beam to compensate for the loss in target volume coverage. The dosimetric parameters for the heart and lung and the target volume between the three treatment types were compared.

RESULTS

Of the three plans, the HBE plan yielded the most significant reduction in the doses received by the heart and lung (heart Dmean: 5.1 Gy vs. 12.9 Gy vs. 4.0 Gy and lung Dmean: 11.4 Gy vs. 13.2 Gy vs. 10.5 Gy, for 3D-CRT, IMRT, and HBE, respectively). Target coverage with all three techniques was within the acceptable range (Dmean 51.0 Gy vs. 51.2 Gy vs. 50.6 Gy, for 3D-CRT, IMRT, and HBE, respectively).

CONCLUSIONS

The HBE plan effectively reduced the amount of radiation exposure to the heart and lung. It could be beneficial for patients who are vulnerable to radiation-related cardiac or pulmonary toxicities.

Radiation injury to cardiac arteries and myocardium is reduced by soy isoflavones

OBJECTIVE

The negative effects of incidental radiation on the heart and its vessels, particularly in the treatment of locally advanced non-small cell lung cancer, esophageal cancer, left-sided breast cancer, and lymphoma, are known. Late cardiac events induced by radiotherapy including coronary artery disease, ischemia, congestive heart failure, and myocardial infarction can manifest months to years after radiotherapy. We have previously demonstrated that soy isoflavones mitigate inflammatory responses induced in lungs by thoracic irradiation resulting in decreased vascular damage, inflammation, and fibrosis. In the current study, we investigate the use of soy isoflavones to protect cardiac vessels and myocardium from radiation injury.

METHODS

Mice received a single dose of 10-Gy thoracic irradiation and daily oral treatment with soy isoflavones. At different time points, hearts were processed for histopathology studies to evaluate the effect of soy isoflavones on radiation-induced damage to cardiac vessels and myocardium.

RESULTS

Radiation damage to arteries and myocardium was detected by 16 weeks after radiation. Soy isoflavones given in conjunction with thoracic irradiation were found to reduce damage to the artery walls and radiation-induced fibrosis in the myocardium.

CONCLUSION

Our histopathological findings suggest a radioprotective role of soy isoflavones to prevent cardiac injury. This approach could translate to the use of soy isoflavones as a safe complement to thoracic radiotherapy with the goal of improving the overall survival in patients whose cancer has been successfully controlled by the radiotherapy but who otherwise succumb to heart toxicity.

Survival Impact of Cardiac Dose Following Lung Stereotactic Body Radiotherapy

INTRODUCTION

The purpose of this study was to determine the impact of radiation dose to substructures of the heart in lung stereotactic body radiotherapy (SBRT) patients on non-cancer-related deaths.

METHODS

Patients treated with lung SBRT at a single institution from 2005 to 2013 were included. The heart and its substructures were contoured, and dose was calculated including mean, max, and max 10 cc dose. Clinical variables including stage, histology, age, gender, Charlson comorbidity index (CCI), preexisting cardiac disease, pulmonary function (forced expiratory volume in 1 second, diffusion capacity), and smoking status were explored for association with non-cancer-related deaths in univariable (UVA) and multivariable (MVA) analyses. Heart dosimetric parameters were correlated with the risk of radiation pneumonitis (RP) using UVA and MVA.

RESULTS

A total of 189 patients were included with median age of 76 years (range, 48-93 years). Of these patients, 45.5% were female, 27.5% were T2, 16.9% were current smokers, 64% had preexisting cardiac risk factors, and 34.5% had CCI score of ≥ 3. Mean lung dose ± SD was 456 ± 231 cGy. Heart max, mean, and 10 cc doses were 1867 ± 1712 cGy, 265 ± 269 cGy, and 1150 ± 1075 cGy, respectively. There were 14 (7.4%) ≥ Grade 2 RP and 3 (1.6%) were ≥ Grade 3. The median overall survival was 37.3 months (95% confidence interval, 29.8-45.3 months). On UVA, female gender (P < .01), higher Eastern Cooperative Oncology Group (P = .01), cardiac risk (P < .01), CCI (P < .01), and bilateral ventricles max dose (P = .02) were associated with non-cancer-related deaths; on MVA, bilateral ventricles max dose was significant (P = .05). No heart parameters were associated with RP.

CONCLUSIONS

Higher bilateral ventricles max dose is associated with poorer survival. Heart dose parameters should be considered when planning patients for SBRT.

Cardiac-sparing radiation therapy using positioning breast shell for patients with left-sided breast cancer who are ineligible for breath-hold techniques

Purpose

Patients with left-sided breast cancer (LSBC) are at increased risk of cardiac morbidity from adjuvant breast radiation therapy (ABRT). Breath-hold (BH) techniques substantially reduce the radiation received by heart during radiation therapy for LSBC. However, a subset of patients with LSBC are ineligible for BH techniques due to an inability to breath-hold or because of other comorbidities. To reduce radiation to the heart, we routinely use a custom-made breast shell for the treatment of patients with LSBC who are ineligible for BH techniques. This study evaluates the dosimetric impact of using a breast shell for patients with LSBC undergoing ABRT.

Methods and materials

Sixteen consecutive patients with LSBC who failed BH and underwent ABRT using a breast shell during the period of 2014 to 2016 were identified. Treatment was planned using field-in-field tangents with a prescribed dose of 42.5 Gy in 16 fractions. Comparisons between plans with and without a shell were made for each patient using a paired t test to quantify the sparing of organs at risk (OARs) and target coverage.

Results

There was no statistically significant difference in the planning target volume of breast coverage. A statistically significant improvement was observed in sparing the heart, left ventricle (LV), and ipsilateral lung (P-value < .001). Plans with the shell spared OARs better than the no-shell plans with a mean dose of 2.15 Gy versus 5.15 Gy (58.2% reduction) to the heart, 3.27 Gy versus 9.00 Gy (63.7% reduction) to the LV, and 5.16 Gy versus 7.95 Gy (35% reduction) to the ipsilateral lung. The irradiated volumes of OARs for plans with and without shell are 13.3 cc versus 59.5 cc (77.6% reduction) for the heart, 6.2 cc versus 33.2 cc (81.2% reduction) for the LV, and 92.8 cc versus 162.5 cc (42.9% reduction) for the ipsilateral lung.

Conclusions

A positioning breast shell offers significant benefit in terms of sparing the heart for patients with LSBC who are ineligible for BH techniques. It also can be used as a simple cardiac-sparing alternative in centers without BH capability.

Heart failure following cancer treatment: characteristics, survival and mortality of a linked health data analysis

BACKGROUND

Cardiotoxicity resulting in heart failure is a devastating complication of cancer therapy. A patient may survive cancer only to develop heart failure (HF), which has a higher mortality rate than some cancers.

AIM

This study aimed to describe the characteristics and outcomes of HF in patients with blood or breast cancer after chemotherapy treatment.

METHODS

Queensland Cancer Registry, Death Registry and Hospital Administration records were linked (1996-2009). Patients were categorised as those with an index HF admission (that occurred after cancer diagnosis) and those without an index HF admission (non-HF).

RESULTS

A total of 15 987 patients was included, and 1062 (6.6%) had an index HF admission. Median age of HF patients was 67 years (interquartile range 58-75) versus 54 years (interquartile range 44-64) for non-HF patients. More men than women developed HF (48.6% vs 29.5%), and a greater proportion in the HF group had haematological cancer (83.1%) compared with breast cancer (16.9%). After covariate adjustment, HF patients had increased mortality risk compared with non-HF patients (hazard ratios 1.67 (95% confidence interval, 1.54-1.81)), and 47% of the index HF admission occurred within 1 year from cancer diagnosis and 70% within 3 years.

CONCLUSION

Cancer treatment may place patients at a greater risk of developing HF. The onset of HF occurred soon after chemotherapy, and those who developed HF had a greater mortality risk.

Anatomical contouring variability in thoracic organs at risk

The purpose of this study was to determine whether contouring thoracic organs at risk was consistent among medical dosimetrists and to identify how trends in dosimetrist׳s education and experience affected contouring accuracy. Qualitative and quantitative methods were used to contextualize the raw data that were obtained. A total of 3 different computed tomography (CT) data sets were provided to medical dosimetrists (N = 13) across 5 different institutions. The medical dosimetrists were directed to contour the lungs, heart, spinal cord, and esophagus. The medical dosimetrists were instructed to contour in line with their institutional standards and were allowed to use any contouring tool or technique that they would traditionally use. The contours from each medical dosimetrist were evaluated against "gold standard" contours drawn and validated by 2 radiation oncology physicians. The dosimetrist-derived contours were evaluated against the gold standard using both a Dice coefficient method and a penalty-based metric scoring system. A short survey was also completed by each medical dosimetrist to evaluate their individual contouring experience. There was no significant variation in the contouring consistency of the lungs and spinal cord. Intradosimetrist contouring was consistent for those who contoured the esophagus and heart correctly; however, medical dosimetrists with a poor metric score showed erratic and inconsistent methods of contouring.

Risk of major cardiac events following adjuvant proton versus photon radiation therapy for patients with thymic malignancies

BACKGROUND

While often managed with surgery alone, patients with thymic malignancies with high-risk features may benefit from adjuvant radiation therapy but are at risk for late toxicities. Previously, the risk of major cardiac events (MCEs) was reported to increase by 7% per one Gray (Gy) to the heart. In this study, we compare dose to organs at risk (OARs) with intensity-modulated (IMRT) versus proton beam therapy (PBT). We hypothesize a decrease risk of predicted MCEs with PBT.

MATERIAL AND METHODS

Patients requiring adjuvant therapy for thymic malignancies were treated with double scattered proton beam therapy (DS-PBT). Clinical backup IMRT plans were generated. Predicted MCEs were calculated based on median dose to the heart. A Wilcoxon rank sum test was used for statistical comparisons.

RESULTS

Twenty-two consecutive patients were evaluated. DS-PBT resulted in statistically significant decreases in dose to the heart, lungs, left ventricle, esophagus, and spinal cord (all p ≤ .01). The increase in risk of MCEs from 0 to ≥20 years was lower with PBT (74% versus 135%, p = .04).

DISCUSSION

DS-PBT results in decreased dose to OARs and may reduce the risk of MCEs compared with IMRT. Long-term follow-up is required to assess for clinical benefit from DS-PBT.

An individualized radiation dose escalation trial in non-small cell lung cancer based on FDG-PET imaging

AIM

The aim of the study was to assess the feasibility of an individualized 18F fluorodeoxyglucose positron emission tomography (FDG-PET)-guided dose escalation boost in non-small cell lung cancer (NSCLC) patients and to assess its impact on local tumor control and toxicity.

PATIENTS AND METHODS

A total of 13 patients with stage II-III NSCLC were enrolled to receive a dose of 62.5 Gy in 25 fractions to the CT-based planning target volume (PTV; primary turmor and affected lymph nodes). The fraction dose was increased within the individual PET-based PTV (PTV_PET) using intensity modulated radiotherapy (IMRT) with a simultaneous integrated boost (SIB) until the predefined organ-at-risk (OAR) threshold was reached. Tumor response was assessed during follow-up by means of repeat FDG-PET/computed tomography. Acute and late toxicity were recorded and classified according to the CTCAE criteria (Version 4.0). Local progression-free survival was determined using the Kaplan-Meier method.

RESULTS

The average dose to PTV_PET reached 89.17 Gy for peripheral and 75 Gy for central tumors. After a median follow-up period of 29 months, seven patients were still alive, while six had died (four due to distant progression, two due to grade 5 toxicity). Local progression was seen in two patients in association with further recurrences. One and 2-year local progression free survival rates were 76.9% and 52.8%, respectively. Three cases of acute grade 3 esophagitis were seen. Two patients with central tumors developed late toxicity and died due to severe hemoptysis.

CONCLUSION

These results suggest that a non-uniform and individualized dose escalation based on FDG-PET in IMRT delivery is feasible. The doses reached were higher in patients with peripheral compared to central tumors. This strategy enables good local control to be achieved at acceptable toxicity rates. However, dose escalation in centrally located tumors with direct invasion of mediastinal organs must be performed with great caution in order to avoid severe late toxicity.

Effect of Breast Irradiation on Cardiac Disease in Women Enrolled in BCIRG-001 at 10-Year Follow-Up

PURPOSE

To investigate cardiac toxicity associated with breast radiation therapy (RT) at 10-year follow-up in BCIRG-001, a phase 3 trial comparing adjuvant anthracycline chemotherapy (fluorouracil, doxorubicin, and cyclophosphamide) with anthracycline-taxane chemotherapy (docetaxel, doxorubicin, and cyclophosphamide) in women with lymph node-positive early breast cancer.

METHODS AND MATERIALS

Prospective data from all 746 patients in the control arm (fluorouracil, doxorubicin, and cyclophosphamide) of BCIRG-001 at 10-year follow-up were obtained from Project Data Sphere. Cardiac toxicities examined included myocardial infarction (MI), heart failure (HF), arrhythmias, and relative and absolute left ventricular ejection fraction decrease of >20% from baseline. Toxicities were compared between patients who received RT versus no RT, left-sided RT versus no RT, and internal mammary nodal RT versus no RT.

RESULTS

Of the 746 patients, 559 (75%) received RT to a median dose of 50 Gy. Myocardial infarction occurred in 3 RT patients (0.5%) versus 6 no-RT patients (3%) (P=.01). Heart failure was seen in 15 RT patients (2.7%) versus 3 no-RT patients (1.6%) (P=.6). Among these, 35 RT patients (18%) had a left ventricular ejection fraction relative decrease of >20% baseline versus 7 (10%) who did not receive RT (P=.1). Arrhythmias were more common in RT patients (3.2%) versus no-RT patients (0%) (P=.01). On univariable and multivariable analysis HF was not significantly associated with RT, and MI was negatively associated with RT.

CONCLUSIONS

In this retrospective analysis of prospective toxicity outcomes, there is an increased risk of arrhythmias but no clear evidence of significantly increased risk of MI or HF at 10 years in lymph node-positive women treated with breast RT and uniform adjuvant doxorubicin-based chemotherapy. Given the low incidence of these outcomes, studies with larger numbers are needed to confirm our findings.

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

PURPOSE

Dosimetric 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 MATERIALS

Ten 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.

RESULTS

All 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.

CONCLUSIONS

For 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.

Geometrical uncertainty of heart position in deep-inspiration breath-hold radiotherapy of left-sided breast cancer patients

BACKGROUND

This study aimed to determine the geometrical uncertainty of the position of the heart with daily cone beam computed tomography (CBCT) during deep-inspiration breath-hold (DIBH) treatment of the left breast.

MATERIAL AND METHODS

A visually guided optical respiratory monitoring system was used in DIBH treatment of 15 breast cancer patients. Heart position was determined in relation to the planning target volume (PTV) in 225 fractions in which daily low-dose CBCT images were compared with planning CT images. In addition, the position of the left lung apex and diaphragm was measured to evaluate the success of the DIBH.

RESULTS

The median shift of the heart was 1 mm to the left, 1 mm superiorly and 0 mm in the anterior-posterior (AP) direction during the treatment course when compared to the PTV position in planning CT. Based on these movements, an AP margin of 4 mm, a lateral (LR) margin of 3 mm, and a superior-inferior (SI) margin of 5 mm should be added to the heart contour to ensure avoiding the heart when planning treatment. The distance between the left lung apex and diaphragm, applied as a surrogate for lung volume, was 2mm (median) smaller during the CBCT acquisitions than during the planning CT acquisition. The correlation coefficient between the surrogate of lung volume and the distance between the heart and PTV was r = .46 in the AP, r = .72 in the LR and r = .79 in the SI directions.

CONCLUSION

Residual variation was observed in the position of the heart in comparison to PTV, even with a visually guided DIBH technique. These geometrical uncertainties should be taken into account when planning radiotherapy treatment. The success of DIBH may make a major contribution to the variation of the heart position during treatment.

Strain Imaging Detects Dose-Dependent Segmental Cardiac Dysfunction in the Acute Phase After Breast Irradiation

PURPOSE

We examined the utility of echocardiographic 2-dimensional speckle tracking strain imaging (SI) for the evaluation of segmental myocardial dysfunction before and after radiation therapy (RT) and the relationship to dose exposure.

METHODS AND MATERIALS

We prospectively recruited 40 women with left-sided breast cancer, undergoing only adjuvant RT to the left chest. Comparisons of traditional echocardiographic parameters and SI parameters at baseline and 6 weeks after RT were analyzed. Regional strain and strain rate (SR) parameters were obtained from all 18 left ventricular segments. The correlation of change in strain parameters with segmental radiation dose was examined.

RESULTS

We observed a significant reduction in global and segmental systolic strain parameters at 6 weeks after RT compared with baseline, with the largest decrement in the apical segments; this corresponded with the segments receiving the highest radiation dose exposure (apical peak systolic strain of -21.21% ± 3.49% before RT vs -18.69% ± 3.34% after RT, percentage change of 11.88%, P=.002; apical peak systolic SR of -1.17 ± 0.24 s^-1 before RT vs -1.04 ± 0.19 s^-1 after RT, percentage change of 11.11%, P=.008). There was a modest correlation between the apical segment systolic strain reduction and radiation dose exposure (apical segment Δ change and apical radiation dose, r=0.345, P=.031; apical segment percentage change and apical radiation dose, r=0.346, P=.031). A significant reduction in early diastolic SR was observed in the apical segments after treatment compared with baseline (apical early diastolic SR, 1.54 ± 0.45 s^-1 before RT vs 1.35 ± 0.33 after RT s^-1; percentage change, 12.34%; P=.034).

CONCLUSIONS

Two-dimensional SI detected dose-related regional myocardial dysfunction in the acute phase after RT in chemotherapy-naive left-sided breast cancer patients. Although the long-term effects remain unknown, this imaging modality may have a potential role in the evaluation of irradiation-related cardiotoxicity.

Dosimetric study of three-dimensional conformal radiotherapy, electronic compensator technique, intensity-modulated radiation therapy and volumetric-modulated arc therapy in whole breast irradiation

Background

Whole breast irradiation is an essential treatment after breast-conserving surgery (BCS). However, there are some adverse effects from inhomogeneity and dose to adjacent normal tissues.

Objective

Aim of this study was to compare dosimetry among standard technique, three-dimensional conformal radiotherapy (3D-CRT), and advanced techniques, electronic compensator (ECOMP), inverse intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT).

Methods

Whole breast irradiation treatment plans of patients who had underwent BCS and whole breast irradiation were re-planned with all four techniques. Clinical target volume was contoured according to the Radiation Therapy Oncology Group atlas for breast only in patients who had negative node or ductal carcinoma in situ and breast with chest wall for patients with positive node. Planning target volume was non-uniformly expanded. Dose prescription was 50 Gy in 25 fractions with 6 MV photon energy.

Results

In total, 25 patients underwent whole breast irradiation with computed tomography simulation from November 2013 to November 2014 were included. Six patients with positive nodes were re-planned for breast with chest wall irradiation and 19 patients with negative nodes were re-planned for breast only irradiation. Primary outcome, radical dose homogeneity index (HI) of 3D-CRT, ECOMP, IMRT and VMAT were 0·865, 0·889, 0·890 and 0·866, respectively. ECOMP and IMRT showed significant higher HI than 3D-CRT (p-value<0·001). Secondary outcome, conformity index (CI) of advanced technique were significantly better than 3D-CRT. Lung V20, mean ipsilateral lung dose (MILD), mean heart dose (MHD), heart V25, heart V30 of advanced techniques were also lower than 3D-CRT. ECOMP had better mean lung dose (MLD), mean contralateral lung dose (MCLD) and mean contralateral breast dose (MCBD) when compared with 3D-CRT. Monitor units of advanced techniques were significantly higher than 3D-CRT.

Conclusions

HI of ECOMP and IMRT were significantly higher than 3D-CRT technique. All advanced techniques showed statistically better in CI. Lung V20, MILD, heart V25 and heart V30 of advanced techniques were lower than 3D-CRT. However, only ECOMP showed decreased MLD, MHD, MCLD and MCBD when compared with 3D-CRT.

Cardiac Toxicity After Radiotherapy for Stage III Non-Small-Cell Lung Cancer: Pooled Analysis of Dose-Escalation Trials Delivering 70 to 90 Gy

Purpose The significance of radiotherapy (RT) -associated cardiac injury for stage III non-small-cell lung cancer (NSCLC) is unclear, but higher heart doses were associated with worse overall survival in the Radiation Therapy Oncology Group (RTOG) 0617 study. We assessed the impact of heart dose in patients treated at our institution on several prospective dose-escalation trials. Patients and Methods From 1996 to 2009, 127 patients with stage III NSCLC (Eastern Cooperative Oncology Group performance status, 0 to 1) received dose-escalated RT to 70 to 90 Gy (median, 74 Gy) in six trials. RT plans and cardiac doses were reviewed. Records were reviewed for the primary end point: symptomatic cardiac events (symptomatic pericardial effusion, acute coronary syndrome, pericarditis, significant arrhythmia, and heart failure). Cardiac risk was assessed by noting baseline coronary artery disease and calculating the WHO/International Society of Hypertension score. Competing risks analysis was used. Results In all, 112 patients were analyzed. Median follow-up for surviving patients was 8.8 years. Twenty-six patients (23%) had one or more events at a median of 26 months to first event (effusion [n = 7], myocardial infarction [n = 5], unstable angina [n = 3], pericarditis [n = 2], arrhythmia [n = 12], and heart failure [n = 1]). Heart doses (eg, heart mean dose; hazard ratio, 1.03/Gy; P = .002,), coronary artery disease ( P < .001), and WHO/International Society of Hypertension score ( P = .04) were associated with events on univariable analysis. Heart doses remained significant on multivariable analysis that accounted for baseline risk. Two-year competing risk-adjusted event rates for patients with heart mean dose < 10 Gy, 10 to 20 Gy, or ≥ 20 Gy were 4%, 7%, and 21%, respectively. Heart doses were not associated with overall survival. Conclusion Cardiac events were relatively common after high-dose thoracic RT and were independently associated with both heart dose and baseline cardiac risk. RT-associated cardiac toxicity after treatment of stage III NSCLC may occur earlier than historically understood, and heart doses should be minimized.

Effect of accurate heart delineation on cardiac dose during the CONVERT trial

OBJECTIVE

This study investigated the effect of deviation from protocol in heart delineation for the Concurrent Once-daily Versus twice-daily Radiotherapy (CONVERT) Trial ( ClinicalTrials.gov Identifier NCT00433563) quality assurance (QA) programme and the effect of that on mean cardiac dose and percentage of heart volume receiving ≥5 Gy (V5%) and percentage of heart volume receiving ≥30 Gy (V30%).

METHODS

Patients with limited-stage small-cell lung cancer in the CONVERT trial were randomized to receive 45 Gy in 30# twice daily or 66 Gy in 33# once daily radiotherapy, with concurrent chemotherapy in both arms. Of the 100 trial patient cases reviewed by the QA team [for patient selection, disease/organs at risk (OARs) outlining and treatment planning], 50 patient cases were selected, and the heart was reoutlined according to the "gold standard" trial protocol. Dose-volume histogram (DVH) data were extracted. The impact of change in heart volume on cardiac DVH is presented.

RESULTS

For gold standard cardiac outlines, an increase in V5% and V30% was seen in 77.3% and 81.8% of cases, respectively, in the control arm (45 Gy) and in 78.6% and 82.1% of cases, respectively, in the experimental arm (66 Gy). The median increase in V5% was 1.4% and in V30%, it was 3.4%. The average of the mean cardiac dose for the control arm increased by 2.1 Gy (from 15.2 Gy for the centres outline to 17.3 Gy for the gold standard outline) and for the experimental arm by 2.4 Gy (from 16.2 to 18.6 Gy).

CONCLUSION

This study demonstrates the importance of having a robust QA programme in place to ensure accuracy of cardiac delineation to facilitate future studies investigating the impact of cardiac dose on toxicity. Advances in knowledge: This study highlights the importance of ensuring accurate delineation of OARs in clinical trials, where conclusions about normal tissue toxicity are to be drawn.

Radiation dose to the left anterior descending coronary artery during interstitial pulsed-dose-rate brachytherapy used as a boost in breast cancer patients undergoing organ-sparing treatment

Purpose

To assess dose received by the left anterior descending (LAD) coronary artery during interstitial pulsed-dose-rate brachytherapy (PDR-BT) boost for left-sided breast cancer patients undergoing organ-sparing treatment.

Material and methods

Thirty consecutive pT1-3N0-1M0 breast cancer patients boosted between 2014 and 2015 with 10 Gy/10 pulses/hour PDR-BT following a computed tomography (CT) simulation with the multi-catheter implant were included. The most common localization of primary tumor were upper quadrants. Patients were implanted with rigid tubes following breast conserving surgery and whole breast external beam irradiation (40 Gy/15 or 50 Gy/25 fractions). Computed tomography scans were retrospectively reviewed and LADs were contoured without and with margin of 5 mm (LAD_5mm). Standard treatment plan encompassed tumor bed determined by the surgical clips with margin of 2 cm. Dosimetric parameters were extracted from the dose-volume histograms.

Results

The mean D₉₀ and V₁₀₀ were 10.3 Gy (range: 6.6-13.3), and 42.0 cc (range: 15.3-109.3), respectively. The median dose non-uniformity ratio (DNR) was 0.50 (range: 0.27-0.82). The mean doses to LAD and LAD_5mm were 1.0 Gy and 0.96 Gy, and maximal doses were 1.57 Gy and 1.99 Gy, respectively. Dose to the 0.1 cc of the LAD and LAD_5mm were 1.42 Gy and 1.85 Gy (range: 0.01-4.98 Gy and 0.1-6.89 Gy), respectively.

Conclusions

Interstitial multi-catheter PDR-BT used as a boost for left-sided breast cancer is generally associated with low dose to the LAD. However, higher dose in individual cases may require alternative approaches.

Late Cardiac Toxicity After Mediastinal Radiation Therapy for Hodgkin Lymphoma: Contributions of Coronary Artery and Whole Heart Dose-Volume Variables to Risk Prediction

PURPOSE

Mediastinal radiation therapy (RT) for Hodgkin lymphoma (HL) is associated with late cardiotoxicity, but there are limited data to indicate which dosimetric parameters are most valuable for predicting this risk. This study investigated which whole heart dosimetric measurements provide the most information regarding late cardiotoxicity, and whether coronary artery dosimetry was more predictive of this outcome than whole heart dosimetry.

METHODS AND MATERIALS

A random sample of 125 HL patients treated with mediastinal RT was selected, and 3-dimensional cardiac dose-volume data were generated from historical plans using validated methods. Cardiac events were determined by linking patients to population-based datasets of inpatient and same-day hospitalizations and same-day procedures. Variables collected for the whole heart and 3 coronary arteries included the following: Dmean, Dmax, Dmin, dose homogeneity, V5, V10, V20, and V30. Multivariable competing risk regression models were generated for the whole heart and coronary arteries.

RESULTS

There were 44 cardiac events documented, of which 70% were ischemic. The best multivariable model included the following covariates: whole heart Dmean (hazard ratio [HR] 1.09, P=.0083), dose homogeneity (HR 0.94, P=.0034), male sex (HR 2.31, P=.014), and age (HR 1.03, P=.0049). When any adverse cardiac event was the outcome, models using coronary artery variables did not perform better than models using whole heart variables. However, in a subanalysis of ischemic cardiac events only, the model using coronary artery variables was superior to the whole heart model and included the following covariates: age (HR 1.05, P<.001), volume of left anterior descending artery receiving 5 Gy (HR 0.98, P=.003), and volume of left circumflex artery receiving 20 Gy (HR 1.03, P<.001).

CONCLUSION

In addition to higher mean heart dose, increasing inhomogeneity in cardiac dose was associated with a greater risk of late cardiac effects. When all types of cardiotoxicity were evaluated, the whole heart variable model outperformed the coronary artery models. However, when events were limited to ischemic cardiotoxicity, the coronary artery-based model was superior.

Prevention and Monitoring of Cardiac Dysfunction in Survivors of Adult Cancers: American Society of Clinical Oncology Clinical Practice Guideline

Purpose

Cardiac dysfunction is a serious adverse effect of certain cancer-directed therapies that can interfere with the efficacy of treatment, decrease quality of life, or impact the actual survival of the patient with cancer. The purpose of this effort was to develop recommendations for prevention and monitoring of cardiac dysfunction in survivors of adult-onset cancers.

Methods

Recommendations were developed by an expert panel with multidisciplinary representation using a systematic review (1996 to 2016) of meta-analyses, randomized clinical trials, observational studies, and clinical experience. Study quality was assessed using established methods, per study design. The guideline recommendations were crafted in part using the Guidelines Into Decision Support methodology.

Results

A total of 104 studies met eligibility criteria and compose the evidentiary basis for the recommendations. The strength of the recommendations in these guidelines is based on the quality, amount, and consistency of the evidence and the balance between benefits and harms.

Recommendations

It is important for health care providers to initiate the discussion regarding the potential for cardiac dysfunction in individuals in whom the risk is sufficiently high before beginning therapy. Certain higher risk populations of survivors of cancer may benefit from prevention and screening strategies implemented during cancer-directed therapies. Clinical suspicion for cardiac disease should be high and threshold for cardiac evaluation should be low in any survivor who has received potentially cardiotoxic therapy. For certain higher risk survivors of cancer, routine surveillance with cardiac imaging may be warranted after completion of cancer-directed therapy, so that appropriate interventions can be initiated to halt or even reverse the progression of cardiac dysfunction.

Dosimetric comparison of simultaneous integrated boost with whole-breast irradiation for early breast cancer

Purpose

The purpose of this study was to identify a more suitable boost plan for simultaneously integrated boost scheme in patients with breast cancer by comparing among 3 types of whole-breast irradiation plus tumor bed boost plans.

Methods

Twenty patients who received radiotherapy following breast-conserving surgery for early breast cancer were enrolled in this study. We performed 1 type of electron plan (E1P plan) and 2 types of 3-dimensional conformal plans using a photon (P3P and P5P plans). The dosimetric parameters for the heart, total lung and the target volume between the 3 treatment types were compared.

Results

For the tumor bed, the difference in the mean dose between the 3 plans was maximally 0.1 Gy. For normal breast parenchyma, the difference in the mean dose between the 3 plans was maximally 1.1 Gy. In the dose range over the prescribed dose of 51 Gy, V₅₅ and V₆₀ in the E1P plan were lower than those in the P3P and P5P plans, which indicated that the E1P plan was more suitable than the P3P and P5P plans. In case of the heart and total lung, the values of clinically important parameters were slightly higher in the E1P plan than in the P3P and P5P plans. However, these differences were less than 2%.

Conclusion

We observed that a simple electron plan for tumor bed boost is preferable over multi-field photon plans in terms of the target volume coverage and normal tissue sparing.

Risks and benefits of reducing target volume margins in breast tangent radiotherapy

This study investigates the potential benefits of planning target volume (PTV) margin reduction for whole breast radiotherapy in relation to dose received by organs at risk (OARs), as well as reductions in radiation-induced secondary cancer risk. Such benefits were compared to the increased radiation-induced secondary cancer risk attributed from increased ionizing radiation imaging doses. Ten retrospective patients' computed tomography datasets were considered. Three computerized treatment plans with varied PTV margins (0, 5 and 10 mm) were created for each patient complying with the Radiation Therapy Oncology Group (RTOG) 1005 protocol requirements. The BEIR VII lifetime attributable risk (LAR) model was used to estimate secondary cancer risk to OARs. The LAR was assessed for all treatment plans considering (a) doses from PTV margin variation and (b) doses from two (daily and weekly) kilovoltage cone beam computed tomography (kV CBCT) imaging protocols during the course of treatment. We found PTV margins from largest to smallest resulted in a mean OAR relative dose reduction of 31% (heart), 28% (lung) and 23% (contralateral breast) and the risk of radiation-induced secondary cancer by a relative 23% (contralateral breast) and 22% (contralateral lung). Daily image-guidance using kV CBCT increased the risk of radiation induced secondary cancer to the contralateral breast and contralateral lung by a relative 1.6-1.9% and 1.9-2.5% respectively. Despite the additional dose from kV CBCT for the two considered imaging protocols, smaller PTV margins would still result in an overall reduction in secondary cancer risk.

A cardiac contouring atlas for radiotherapy

BACKGROUND AND PURPOSE

The heart is a complex anatomical organ and contouring the cardiac substructures is challenging. This study presents a reproducible method for contouring left ventricular and coronary arterial segments on radiotherapy CT-planning scans.

MATERIAL AND METHODS

Segments were defined from cardiology models and agreed by two cardiologists. Reference atlas contours were delineated and written guidelines prepared. Six radiation oncologists tested the atlas. Spatial variation was assessed using the DICE similarity coefficient (DSC) and the directed Hausdorff average distance (d→H,avg). The effect of spatial variation on doses was assessed using six different breast cancer regimens.

RESULTS

The atlas enabled contouring of 15 cardiac segments. Inter-observer contour overlap (mean DSC) was 0.60-0.73 for five left ventricular segments and 0.10-0.53 for ten coronary arterial segments. Inter-observer contour separation (mean d→H,avg) was 1.5-2.2mm for left ventricular segments and 1.3-5.1mm for coronary artery segments. This spatial variation resulted in <1Gy dose variation for most regimens and segments, but 1.2-21.8Gy variation for segments close to a field edge.

CONCLUSIONS

This cardiac atlas enables reproducible contouring of segments of the left ventricle and main coronary arteries to facilitate future studies relating cardiac radiation doses to clinical outcomes.

Synchronous bilateral breast cancer irradiation: clinical and dosimetrical issues using volumetric modulated arc therapy and simultaneous integrated boost

OBJECTIVES

The aim of the present retrospective analysis was to evaluate dosimetric parameters, feasibility and outcome for Synchronous Bilateral Breast Cancer (SBBC) patients treated with adjuvant radiotherapy (RT) by Volumetric Modulated Arc Therapy (VMAT).

METHODS

From September 2011 to April 2016, 1100 Breast Cancer (BC) patients were referred to our institution to receive adjuvant breast RT, and those with SBBC were selected for the present analysis. A total of 16 patients were identified. A total dose of 50 Gy in 25 fractions was prescribed to the Planning Target Volume of the whole bilateral breast (PTV_BN) with or without the supraclavicular and infraclavicular nodes, while a total dose of 60 Gy in 25 fractions was prescribed to the surgical bed (PTV_boost). Several V _xGy and Dx% parameters were analyzed for the PTVs, together with Conformity and Homogeneity indexes (CI, HI), and for the critical Organs at risk (OARs), lungs and heart first.

RESULTS

With a median follow-up of 24 months, no acute or late side effects more than grade 2 were observed. All patients are alive without any sign of disease. For target dose coverage, our observed inter-patients averages (±1 sd) were V _{95% Dp} = 96.7 ± 1.6% (96.3 ± 1.8%) to the left (right) PTV_BN, V _{95% Dp} = 98.6 ± 2.7% (99.4 ± 0.9%) to the left (right) PTV_boost, and D _2% = 64.4 ± 1.8 Gy (65.0 ± 2.0 Gy) to the left (right) PTV_boost, respectively. With regard to the heart, the inter-patient average of D _mean was 8.3 ± 3.3 Gy. For the lungs, the inter-patient average of D _mean, V _5 Gy and V _20 Gy were 11.8 ± 2.3 Gy, 78.9 ± 15.3% and 15.7 ± 5%, respectively.

CONCLUSIONS

The present retrospective analysis showed the feasibility, tolerability and safety of VMAT in the treatment of SBBC patients. Further studies are necessary to confirm these preliminary data.

A case study evaluating deep inspiration breath-hold and intensity-modulated radiotherapy to minimise long-term toxicity in a young patient with bulky mediastinal Hodgkin lymphoma

Radiotherapy plays an important role in the treatment of early-stage Hodgkin lymphoma, but late toxicities such as cardiovascular disease and second malignancy are a major concern. Our aim was to evaluate the potential of deep inspiration breath-hold (DIBH) and intensity-modulated radiotherapy (IMRT) to reduce cardiac dose from mediastinal radiotherapy. A 24 year-old male with early-stage bulky mediastinal Hodgkin lymphoma received involved-site radiotherapy as part of a combined modality programme. Simulation was performed in free breathing (FB) and DIBH. The target and organs at risk were contoured on both datasets. Free breathing-3D conformal (FB-3DCRT), DIBH-3DCRT, FB-IMRT and DIBH-IMRT were compared with respect to target coverage and doses to organs at risk. A 'butterfly' IMRT technique was used to minimise the low-dose bath. In our patient, both DIBH (regardless of mode of delivery) and IMRT (in both FB and DIBH) achieved reductions in mean heart dose. DIBH improved all lung parameters. IMRT reduced high dose (V20), but increased low dose (V5) to lung. DIBH-IMRT was chosen for treatment delivery. Advanced radiotherapy techniques have the potential to further optimise the therapeutic ratio in patients with mediastinal lymphoma. Benefits should be assessed on an individualised basis.

Information Needs of Older Women With Early-Stage Breast Cancer When Making Radiation Therapy Decisions

PURPOSE

To identify the information older women with early-stage breast cancer need when making radiation therapy decisions, and who patients identify as the main decision maker.

METHODS AND MATERIALS

We surveyed (through face-to-face interview, telephone, or mail) women aged ≥65 years who received lumpectomy and were considering or receiving adjuvant radiation therapy for early-stage breast cancer. The survey instrument was constructed with input from patient and professional advisory committees, including breast cancer survivors, advocates of breast cancer care and aging, clinicians, and researchers. Participants rated the importance (on a 4-point scale) of 24 statements describing the benefits, side effects, impact on daily life, and other issues of radiation therapy in relation to radiation therapy decision making. Participants also designated who was considered the key decision maker.

RESULTS

The response rate was 56.4% (93 of 165). Mean age was 72.5 years, ranging from 65 to 93 years. More than 96% of participants indicated they were the main decision maker on receiving radiation therapy. There was wide variation in information needs regarding radiation therapy decision making. Participants rated a mean of 18 (range, 3-24) items as "essential." Participants rated items related to benefits highest, followed by side effects. Participants who were older than 75 years rated 13.9 questions as essential, whereas participants aged ≤74 years rated 18.7 as essential (P=.018).

CONCLUSIONS

Older women desire information and have more agency and input in the decision-making process than prior literature would suggest. The variation in information needs indicates that future decision support tools should provide options to select what information would be of interest to the participants.

Development of delineation for the left anterior descending coronary artery region in left breast cancer radiotherapy: An optimized organ at risk

BACKGROUND AND PURPOSE

The left anterior descending coronary artery (LAD) and diagonal branches (DBs) are blurred on computed tomography (CT). We aimed to define the LAD region (LADR) with adequate inclusion of the LAD and DBs and contouring consistency.

METHODS AND MATERIALS

The LADR was defined using coronary CT angiograms. The inclusion ratio was used to assess the LAD and DBs inclusion by the LADR. Four radiation oncologists delineated the LAD and LADR, using contrast-enhanced CT of 15 patients undergoing left breast radiotherapy. The Sørensen-Dice similarity index (DSI), Jaccard similarity index (JSI), and Hausdorff distance (HD) were calculated to assess similarity. The mean dose (D_mean) and maximum dose (D_max) to the LAD and LADR were calculated to compare consistency. Correlations were evaluated using Pearson's correlation coefficient.

RESULTS

The inclusion ratio of the LAD by the LADR was 96%. The mean DSI, JSI, and HD values were respectively 27.9%, 16.7%, and 0.42mm for the LAD, and 83.1%, 73.0%, and 0.18mm for the LADR. The D_mean between the LAD and LADR were strongly correlated (r=0.93).

CONCLUSION

Delineation of the LADR significantly improved contouring similarity and consistency for dose reporting. This could optimize dose estimation for breast radiotherapy.

The numerical stability of transformation-based CT ventilation

Abstract

Computed tomography (CT)-derived ventilation imaging utilizes deformable image registration (DIR) to recover respiratory-induced tissue volume changes from inhale/exhale 4DCT phases. While current strategies for validating CT ventilation rely on analyzing its correlation with existing functional imaging modalities, the numerical stability of the CT ventilation calculation has not been characterized.

Purpose

The purpose of this study is to examine how small changes in the DIR displacement field can affect the calculation of transformation-based CT ventilation.

Methods

First, we derive a mathematical theorem, which states that the change in ventilation metric induced by a perturbation to single displacement vector is bounded by the perturbation magnitude. Second, we introduce a novel Jacobian constrained optimization method for computing user-defined CT ventilation images.

Results

Using the Jacobian constrained method, we demonstrate that for the same inhale/exhale CT pair, it is possible to compute two DIR transformations that have similar spatial accuracies, but generate ventilation images with significantly different physical characteristics. In particular, we compute a CT ventilation image that perfectly correlates with a single-photon emission CT perfusion scan.

Conclusion

The analysis and experiments indicate that while transformation-based CT ventilation is a promising modality, small changes in the DIR displacement field can result in large relative changes in the ventilation image. As such, approaches for improving the reproducibility of CT ventilation are still needed.

Cardiac Dose and Survival After Stereotactic Body Radiotherapy for Early-stage Non-Small-cell Lung Cancer

INTRODUCTION

Recent analyses have identified cardiac dose as an important predictor of overall survival (OS) after chemoradiation for locally advanced non-small-cell lung cancer (NSCLC). However, the survival influence of the cardiac dose after stereotactic body radiotherapy (SBRT) is unknown. We performed a dose-volume histogram (DVH) analysis of patients treated with SBRT for early stage NSCLC to examine survival and cardiac toxicity.

MATERIALS AND METHODS

We reviewed the medical records of patients who had undergone SBRT for early-stage NSCLC from June 2007 to June 2015 and documented the cardiac DVH parameters, including the maximum and mean dose and percentage of volume receiving >5, >10, >20, and >30 Gy (V5, V10, V20, and V30, respectively). The biologically effective doses and 2-Gy equivalent doses were also calculated. The DVH parameters were assessed as predictors of OS using Cox regression analysis.

RESULTS

We identified 102 patients with 118 treated tumors. At a median follow-up period of 27.2 months (range, 9.8-72.5 months), the 2-year OS estimate was 70.4%. The cardiac DVH parameters were as follows: maximum dose, median, 14.2 Gy (range, 0.3-77.8 Gy); mean dose, median, 1.6 Gy (range, 0-12.6 Gy); and V5, median, 8.7% (range, 0%-96.4%). We identified no correlation between OS and any cardiac dose parameter. No patient developed acute (within 3 months) cardiac toxicity. Four patients died of cardiac causes; all had had preexisting heart disease.

CONCLUSION

In our cohort, cardiac dose was not a predictor of OS after lung SBRT, despite a subset of patients receiving high maximum cardiac doses. The findings from our limited cohort showed that high doses to small volumes of the heart appear safe. Analyses of larger patient cohorts with longer follow-up durations are needed to better delineate the safe cardiac DVH constraints for SBRT.

Cardiac risk index as a simple geometric indicator to select patients for the heart-sparing radiotherapy of left-sided breast cancer

INTRODUCTION

This is a dosimetric study to identify a simple geometric indicator to discriminate patients who meet the selection criterion for heart-sparing radiotherapy (RT). The authors proposed a cardiac risk index (CRI), directly measurable from the CT images at the time of scanning.

METHODS

Treatment plans were regenerated using the CT data of 312 consecutive patients with left-sided breast cancer. Dosimetric analysis was performed to estimate the risk of cardiac mortality using cardiac dosimetric parameters, such as the relative heart volumes receiving ≥25 Gy (heart V₂₅ ). For each CT data set, in-field heart depth (HD) and in-field heart width (HW) were measured to generate the geometric parameters, including maximum HW (HW_max ) and maximum HD (HD_max ). Seven geometric parameters were evaluated as candidates for CRI. Receiver operating characteristic (ROC) curve analyses were used to examine the overall discriminatory power of the geometric parameters to select high-risk patients (heart V₂₅  ≥ 10%).

RESULTS

Seventy-one high-risk (22.8%) and 241 low-risk patients (77.2%) were identified by dosimetric analysis. The geometric and dosimetric parameters were significantly higher in the high-risk group. Heart V₂₅ showed the strong positive correlations with all geometric parameters examined (r > 0.8, p < 0.001). The product of HD_max and HW_max (CRI) revealed the largest area under the curve (AUC) value (0.969) and maintained 100% sensitivity and 88% specificity at the optimal cut-off value of 14.58 cm² .

CONCLUSIONS

Cardiac risk index proposed as a simple geometric indicator to select high-risk patients provides useful guidance for clinicians considering optimal implementation of heart-sparing RT.

Radio(chemo)therapy in locally advanced nonsmall cell lung cancer

Definitive radiochemotherapy is the standard treatment for many patients with locally advanced nonsmall cell lung cancer (NSCLC). Treatment outcomes have improved over the last decades. Several treatment regimens have been shown effective and safe. This review summarises the results of significant studies between 1996 and 2015 on concomitant and sequential radiochemotherapy regimens and radiation dose per fraction. Beside therapy regimens, optimised radiotherapy planning is indispensable to improve outcome and minimise radiation-induced toxicity. An insight into the rationale of radiotherapy planning for stage III NSCLC is also provided.

Concomitant radiochemotherapy is an established standard treatment for locally advanced nonsmall cell lung cancerhttp://ow.ly/TTkkc

Cardiac atlas development and validation for automatic segmentation of cardiac substructures

PURPOSE

To develop and validate a set of atlases for auto-contouring cardiac substructures.

METHODS

Eight radiation oncologists manually and independently delineated 15 cardiac substructures from noncontrast CT images of 6 patients by referring to their respective fused contrast CT images. Individual contours were fused together for each structure, edited by 2 physicians, and became atlases to delineate other 6 patients. The auto-delineated contours of the 6 additional patients became templates for manual contouring. These 12 patients with well-defined contours composed the final atlases for multi-atlas segmentation.

RESULTS

The average time for manually contouring the 15 cardiac substructures was about 40min. Inter-observer variability was small for the heart, the chambers, and the aorta compared with that for other structures that were not clearly distinguishable in CT images. The mean dice similarity coefficient and mean surface distance of auto-segmented contours were within one standard deviation of expert contouring variability. Good agreement between auto-segmented and manual contours was observed for the heart, the chambers, and the great vessels. Independent validation on other 19 patients showed reasonable agreement for the heart chambers.

CONCLUSIONS

A set of cardiac atlases was created for auto-contouring from noncontrast CT images. The accuracy of auto-contouring for the heart, chambers, and great vessels was validated for potential clinical use.

Evaluation of the radiobiological gamma index with motion interplay in tangential IMRT breast treatment

The purpose of this study was to evaluate the impact of the motion interplay effect in early-stage left-sided breast cancer intensity-modulated radiation therapy (IMRT), incorporating the radiobiological gamma index (RGI). The IMRT dosimetry for various breathing amplitudes and cycles was investigated in 10 patients. The predicted dose was calculated using the convolution of segmented measured doses. The physical gamma index (PGI) of the planning target volume (PTV) and the organs at risk (OAR) was calculated by comparing the original with the predicted dose distributions. The RGI was calculated from the PGI using the tumor control probability (TCP) and the normal tissue complication probability (NTCP). The predicted mean dose and the generalized equivalent uniform dose (gEUD) to the target with various breathing amplitudes were lower than the original dose (P < 0.01). The predicted mean dose and gEUD to the OARs with motion were higher than for the original dose to the OARs (P < 0.01). However, the predicted data did not differ significantly between the various breathing cycles for either the PTV or the OARs. The mean RGI gamma passing rate for the PTV was higher than that for the PGI (P < 0.01), and for OARs, the RGI values were higher than those for the PGI (P < 0.01). The gamma passing rates of the RGI for the target and the OARs other than the contralateral lung differed significantly from those of the PGI under organ motion. Provided an NTCP value <0.05 is considered acceptable, it may be possible, by taking breathing motion into consideration, to escalate the dose to achieve the PTV coverage without compromising the TCP.

Radiation-induced heart disease in lung cancer radiotherapy: A dosimetric update

BACKGROUND

Radiation-induced heart disease (RIHD), which affects the patients' prognosis with both acute and late side effects, has been published extensively in the radiotherapy of breast cancer, lymphoma and other benign diseases. Studies on RIHD in lung cancer radiotherapy, however, are less extensive and clear even though the patients with lung cancer are delivered with higher doses to the heart during radiation treatment.

METHODS

In this article, after extensive literature search and analysis, we reviewed the current evidence on RIHD in lung cancer patients after their radiation treatments and investigated the potential risk factors for RIHD as compared to other types of cancers.

RESULT

Cardiac toxicity has been found highly relevant in lung cancer radiotherapy. So far, the crude incidence of cardiac complications in the lung cancer patients after radiotherapy has been up to 33%.

CONCLUSION

The dose to the heart, the lobar location of tumor, the treatment modality, the history of heart and pulmonary disease and smoking were considered as potential risk factors for RIHD in lung cancer radiotherapy. As treatment techniques improve over the time with better prognosis for lung cancer survivors, an improved prediction model can be established to further reduce the cardiac toxicity in lung cancer radiotherapy.

Multibeam inverse intensity-modulated radiotherapy (IMRT) for whole breast irradiation: a single center experience in China

Purpose

To present the clinical experience in our cancer center with multibeam inverse intensity-modulated radiotherapy (IMRT) for early stage breast cancer (BC) patients with whole breast irradiation (WBI).

Methods

We retrospectively analyzed 622 patients with Stage 0 to III BC treated from 2008 to 2011 with wide local excision and WBI, using an inverse IMRT technique. All of the patients were prescribed a total dose of 50 Gy to the whole breast in 2-Gy fractions, followed by a tumor bed boost of 10 Gy in 5 fractions using an electron beam.

Results

Of all of the patients, 132 (21.2%) received whole breast plus regional lymph node (RLN) irradiation. 438 of 622 patients had records of acute skin toxicity based on common terminology criteria (CTC) for adverse events. Two hundred eighty (64%) patients had Grade 0/1 toxicity, 153 (35%) had Grade 2 and only 4 patients experienced grade 3 toxicity. Seventy patients (16%) had moist desquamation. Univariate analysis revealed that breast planning target volume was the only predictive factor for Grade ≥2 acute dermatitis (P = 0.002). After 4 years, 170 patients reported cosmetic results by self-assessment, of whom 151 (89%) patients reported good/excellent cosmetic results, and 17 (11%) patients reported fair assessments. For invasive cancer, the four-year rate of freedom from locoregional recurrence survival was 98.3%. Regarding carcinoma in situ, no patients experienced recurrence.

Conclusion

BC patients who underwent conservative surgery followed by inverse IMRT plan exhibited acceptable acute toxicities and clinical outcomes. Longer follow-up is needed.

Dosimetric comparison between proton beam therapy and photon radiation therapy for locally advanced non-small cell lung cancer

OBJECTIVE

To assess the feasibility of proton beam therapy for the patients with locally advanced non-small lung cancer.

METHODS

The dosimetry was analyzed retrospectively to calculate the doses to organs at risk, such as the lung, heart, esophagus and spinal cord. A dosimetric comparison between proton beam therapy and dummy photon radiotherapy (three-dimensional conformal radiotherapy) plans was performed. Dummy intensity-modulated radiotherapy plans were also generated for the patients for whom curative three-dimensional conformal radiotherapy plans could not be generated.

RESULTS

Overall, 33 patients with stage III non-small cell lung cancer were treated with proton beam therapy between December 2011 and August 2014. The median age of the eligible patients was 67 years (range: 44-87 years). All the patients were treated with chemotherapy consisting of cisplatin/vinorelbine or carboplatin. The median prescribed dose was 60 GyE (range: 60-66 GyE). The mean normal lung V20 GyE was 23.6% (range: 14.9-32%), and the mean normal lung dose was 11.9 GyE (range: 6.0-19 GyE). The mean esophageal V50 GyE was 25.5% (range: 0.01-63.6%), the mean heart V40 GyE was 13.4% (range: 1.4-29.3%) and the mean maximum spinal cord dose was 40.7 GyE (range: 22.9-48 GyE). Based on dummy three-dimensional conformal radiotherapy planning, 12 patients were regarded as not being suitable for radical thoracic three-dimensional conformal radiotherapy. All the dose parameters of proton beam therapy, except for the esophageal dose, were lower than those for the dummy three-dimensional conformal radiotherapy plans. In comparison to the intensity-modulated radiotherapy plan, proton beam therapy also achieved dose reduction in the normal lung. None of the patients experienced grade 4 or worse non-hematological toxicities.

CONCLUSIONS

Proton beam therapy for patients with stage III non-small cell lung cancer was feasible and was superior to three-dimensional conformal radiotherapy for several dosimetric parameters.

Cardio-Oncology: An Update on Cardiotoxicity of Cancer-Related Treatment

Through the success of basic and disease-specific research, cancer survivors are one of the largest growing subsets of individuals accessing the healthcare system. Interestingly, cardiovascular disease is the second leading cause of morbidity and mortality in cancer survivors after recurrent malignancy. This recognition has helped stimulate a collaboration between oncology and cardiology practitioners and researchers, and the portmanteau cardio-oncology (also known as onco-cardiology) can now be found in many medical centers. This collaboration promises new insights into how cancer therapies impact cardiovascular homeostasis and long-term effects on cancer survivors. In this review, we will discuss the most recent views on the cardiotoxicity related to various classes of chemotherapy agents and radiation. We will also discuss broadly the current strategies for treating and preventing cardiovascular effects of cancer therapy.

Treatment Planning Considerations for Robotic Guided Cardiac Radiosurgery for Atrial Fibrillation

Purpose

Robotic guided stereotactic radiosurgery has recently been investigated for the treatment of atrial fibrillation (AF). Before moving into human treatments, multiple implications for treatment planning given a potential target tracking approach have to be considered.   

Materials & Methods

Theoretical AF radiosurgery treatment plans for twenty-four patients were generated for baseline comparison. Eighteen patients were investigated under ideal tracking conditions, twelve patients under regional dose rate (RDR = applied dose over a certain time window) optimized conditions (beam delivery sequence sorting according to regional beam targeting), four patients under ultrasound tracking conditions (beam block of the ultrasound probe) and four patients with temporary single fiducial tracking conditions (differential surrogate-to-target respiratory and cardiac motion).  

Results

With currently known guidelines on dose limitations of critical structures, treatment planning for AF radiosurgery with 25 Gy under ideal tracking conditions with a 3 mm safety margin may only be feasible in less than 40% of the patients due to the unfavorable esophagus and bronchial tree location relative to the left atrial antrum (target area). Beam delivery sequence sorting showed a large increase in RDR coverage (% of voxels having a larger dose rate for a given time window) of 10.8-92.4% (median, 38.0%) for a 40-50 min time window, which may be significant for non-malignant targets. For ultrasound tracking, blocking beams through the ultrasound probe was found to have no visible impact on plan quality given previous optimal ultrasound window estimation for the planning CT. For fiducial tracking in the right atrial septum, the differential motion may reduce target coverage by up to -24.9% which could be reduced to a median of -0.8% (maximum, -12.0%) by using 4D dose optimization. The cardiac motion was also found to have an impact on the dose distribution, at the anterior left atrial wall; however, the results need to be verified.

Conclusion

Robotic AF radiosurgery with 25 Gy may be feasible in a subgroup of patients under ideal tracking conditions. Ultrasound tracking was found to have the lowest impact on treatment planning and given its real-time imaging capability should be considered for AF robotic radiosurgery. Nevertheless, advanced treatment planning using RDR or 4D respiratory and cardiac dose optimization may be still advised despite using ideal tracking methods.