Internal Mammary Node Irradiation Research Articles

Modern Rotational Radiation Techniques with Volumetric Modulated Arc Therapy or Helical Tomotherapy for Optimal Sparing of the Lung and Heart in Left-Breast Cancer Radiotherapy Plus Regional Nodal Irradiation: A Comparative Dosimetric Analysis.

Simple SummaryFor advanced left-breast cancer patients, adjuvant radiotherapy (RT) with regional nodal irradiation (RNI) has been indicated to reduce cancer recurrence and mortality. Modern arc RT techniques, volumetric-modulated arc therapy (VMAT), or helical tomotherapy (HT), can minimize normal organ exposure without compromising disease control. The aim of this study is to identify which arc technique is optimal for patients receiving left-breast RT with RNI, and to explore distinct RNI volumes with or without IMN. A total of 108 eligible patients were enrolled (70 VMAT, 38 HT). VMAT reduced the mean dose and low-dose exposure to the heart, ipsilateral lung, whole lung, contralateral breast, and esophagus compared with HT. The advantage of VMAT for normal organ sparing was distinct when performing RNI with IMN irradiation. To limit normal organ exposure and reduce potential toxicities, VMAT is the optimal technique for patients with left-breast cancer who are undergoing RT with RNI.Background: For advanced breast cancer with lymph node involvement, adjuvant radiotherapy (RT) with regional nodal irradiation (RNI) has been indicated to reduce cancer recurrence and mortality. However, an extensive RT volume is associated with normal organ exposure, which increases the toxicity and affects patient outcomes. Modern arc RT techniques can improve normal organ sparing compared with conventional techniques. The aim of this study was to explore the optimal technique for left-breast RT with RNI. Methods: We retrospectively reviewed patients receiving RT with RNI for left-breast cancer. We used modern arc RT techniques with either volumetric-modulated arc therapy (VMAT) or helical tomotherapy (HT) with a novel block technique, and compared differences in dosimetry parameters between the two groups. Subgroup analysis of RNI with or without internal mammary node (IMN) volume was also performed. Results: A total of 108 eligible patients were enrolled between 2017 and 2020, of whom 70 received VMAT and 38 received HT. The median RT dose was 55 Gy. No significant differences were found regarding the surgery, RT dose, number of fractions, target volume, and RNI volume between the VMAT and HT groups. VMAT reduced the heart mean dose more than HT (3.82 vs. 5.13 Gy, p < 0.001), as well as the cardiac parameters of V5–V20, whole-lung mean dose, lung parameters of V5–V20, and contralateral-breast and esophagus mean dose. In the subgroup analysis of RNI with IMNs, the advantage of VMAT persisted in protecting the heart, lung, contralateral breast, and esophagus. HT was beneficial for lowering the thyroid mean dose. For RNI without IMN, VMAT improved the low-dose exposure of the heart and lung, but HT was similar to VMAT in terms of heart, whole-lung, and contralateral-breast mean dose. Conclusions: For patients with left-breast cancer receiving adjuvant RT with RNI, VMAT reduced the exposure dose to the heart, lung, contralateral breast, and esophagus compared with HT. VMAT was superior to HT in terms of normal organ sparing in the patients who underwent RNI with IMN irradiation. Considering the reduction in normal organ exposure and potential toxicity, VMAT is the optimal technique for patients receiving RNI when deep inspiration breath-hold is not available.

Radiation Oncologists' Approach to Internal Mammary Lymph Node Radiotherapy in Breast Cancer: The Turkish Society for Radiation Oncology Breast Cancer Study Group (TROD 06-005 Survey Study).

BackgroundThis study aimed to examine the practice patterns of radiation oncologists in Turkey regarding radiotherapy to the regional lymph nodes, including internal mammary lymph nodes (IMNs), and identify the factors influencing their clinical decisions in breast cancer patients.MethodsA nationwide, 19-point questionnaire was sent to the physician members of the Turkish Society for Radiation Oncology (TROD).ResultsIn total, 165 radiation oncologists completed the survey, corresponding to a 27% response rate. Regional radiotherapy was used in 64.2% of the patients with 1–3 axillary lymphatic involvement and unfavorable prognostic factors. In contrast, 61.2% of the respondents indicated that IMN should be included in the target volume for regional radiotherapy when the patient had one positive node after axillary lymph node dissection (ALND) in the inner quadrant and central region tumors. However, 71.5% of the respondents chose to include the IMN in the non-inner quadrant and non-central region tumors for patients with four or more positive nodes after ALND. The decision to offer internal mammary lymph node radiotherapy (IMNRT) varied widely and significantly among respondents, years in practice, and the rates of dedicating their clinical time to patients with breast cancer.ConclusionThe results of this survey revealed significant national variation in attitudes regarding the treatment of IMN. Thus, this study may also help document the impact of future studies on clinical practice.

OC-0068 Elective internal mammary node irradiation in women with node-positive breast cancer

OC-0068 Elective internal mammary node irradiation in women with node-positive breast cancer

Side Effects 15 Years After Lymph Node Irradiation in Breast Cancer: Randomized EORTC Trial 22922/10925.

Uncertainty about the benefit-risk ratio of regional lymph node irradiation led to varying clinical protocols. We investigated long-term late side effects after internal mammary and medial supraclavicular (IM-MS) lymph node irradiation to improve shared decision making. The multicenter European Organization for Research and Treatment of Cancer trial (ClinicalTrials.gov, NCT00002851) randomly assigned stage I-III breast cancer patients with involved axillary nodes and/or a medially located primary tumor. We analyzed late side effects both longitudinally at every follow-up and cross-sectionally at 5-year intervals. All statistical tests were 2-sided. Between 1996 and 2004, 46 departments from 13 countries accrued 4004 patients. Median follow-up was 15.7 years. Longitudinal follow-up data showed cumulative incidence rates at 15 years of 2.9% (95% confidence interval [CI] = 2.2% to 3.8%) vs 5.7% (95% CI = 4.7% to 6.9%) (P < .001) for lung fibrosis, 1.1% (95% CI = 0.7% to 1.7%) vs 1.9% (95% CI = 1.3% to 2.6%) (P = .07) for cardiac fibrosis, and 9.4% (95% CI = 8.0% to 10.8%) vs 11.1% (95% CI = 9.6% to 12.7%) (P = .04) for any cardiac disease when treated without or with IM-MS lymph node irradiation. There was no evidence for differences between left- and right-sided breast cancer (Wald χ2 test of treatment by breast side interaction, P = .33 and P = .35, for cardiac fibrosis and for any cardiac disease, respectively). The cumulative incidence probabilities of cross-sectionally reported side effects with a score of 2 or greater at 15 years were 0.1% (95% CI = 0.0% to 0.5%) vs 0.8% (95% CI = 0.4% to 1.4%) for pulmonary (P = .02), 1.8% (95% CI = 1.1% to 2.8%) vs 2.6% (95% CI = 1.8% to 3.7%) for cardiac (P = .15), and 0.0% (95% CI not evaluated) vs 0.1% (95% CI = 0.0% to 0.4%) for esophageal (P = .16), respectively. No difference was observed in the incidence of second malignancies, contralateral breast cancer, or cardiovascular deaths. The incidence of late pulmonary side effects was statistically significantly higher after IM-MS lymph node irradiation, as were some of the cardiac events, without a difference between left- and right-sided treatments. Absolute rates and differences were very low, without increased non-breast cancer-related mortality, even before introducing heart-sparing techniques.

What Can Proton Beam Therapy Achieve for Patients with Pectus Excavatum Requiring Left Breast, Axilla and Internal Mammary Nodal Radiotherapy?

AimsExposure of the heart to radiation increases the risk of ischaemic heart disease, proportionate to the mean heart dose (MHD). Radiotherapy techniques including proton beam therapy (PBT) can reduce MHD. The aims of this study were to quantify the MHD reduction achievable by PBT compared with volumetric modulated arc therapy in breath hold (VMAT-BH) in patients with pectus excavatum (PEx), to identify an anatomical metric from a computed tomography scan that might indicate which patients will achieve the greatest MHD reductions from PBT. Materials and methodsSixteen patients with PEx (Haller Index ≥2.7) were identified from radiotherapy planning computed tomography images. Left breast/chest wall, axilla (I–IV) and internal mammary node (IMN) volumes were delineated. VMAT and PBT plans were prepared, all satisfying target coverage constraints. Signed-rank comparisons of techniques were undertaken for the mean dose to the heart, ipsilateral lung and contralateral breast. Spearman's rho correlations were calculated for anatomical metrics against MHD reduction achieved by PBT. ResultsThe mean MHD for VMAT-BH plans was 4.1 Gy compared with 0.7 Gy for PBT plans. PBT reduced MHD by an average of 3.4 Gy (range 2.8–4.4 Gy) compared with VMAT-BH (P < 0.001). PBT significantly reduced the mean dose to the ipsilateral lung (4.7 Gy, P < 0.001) and contralateral breast (2.7 Gy, P < 0.001). The distance (mm) at the most inferomedial extent of IMN volume (IMN to heart distance) negatively correlated with MHD reduction achieved by PBT (Spearman's rho –0.88 (95% confidence interval –0.96 to –0.67, P < 0.001)). ConclusionFor patients with PEx requiring left-sided breast and IMN radiotherapy, a clinically significant MHD reduction is achievable using PBT, compared with the optimal photon technique (VMAT-BH). This is a patient group in whom PBT could have the greatest benefit.

Internal mammary node irradiation in node-positive breast cancer treated with mastectomy and taxane-based chemotherapy

BackgroundIt is important to continually reevaluate the risk/benefit calculus of internal mammary node irradiation (IMNI) in the era of modern systemic therapy. We aimed to investigate the effect of IMNI on survival in node-positive breast cancer treated with mastectomy and anthracycline plus taxane-based chemotherapy. MethodsWe analyzed 348 patients who underwent mastectomy and anthracycline plus taxane-based chemotherapy for node-positive breast cancer between January 2006 and December 2011. All patients received postoperative radiation therapy (RT) with IMNI (n = 105, 30.2%) or without IMNI (n = 243, 69.8%). The benefit of IMNI for disease-free survival (DFS) and overall survival (OS) was evaluated using multivariate analysis and inverse probability of treatment weighting (IPTW) to adjust for unbalanced covariates between the groups. ResultsAfter a median follow-up of 95 months, the 10-year locoregional recurrence-free survival rate, DFS, and OS in all patients were 94.8%, 77.4%, and 86.2%, respectively. The IPTW-adjusted hazard ratio (HR) for the association of IMNI (vs. no IMNI) with DFS and OS was 0.208 (95% confidence intervals (CI) 0.045–0.966) and 0.460 (95% CI, 0.220–0.962), respectively. In multivariate analysis, IMNI was a favorable factor for DFS (HR, 0.458; P = 0.021) and OS (HR 0.233, P = 0.018). ConclusionsIMNI was associated with improved DFS and OS in node-positive patients treated with mastectomy, post-mastectomy RT, and taxane-based chemotherapy, although the rate of locoregional recurrence was low.

Inter-institutional Variation in Intensity-modulated Radiotherapy for Breast Cancer in Korea (KROG 19-01).

To present the variations in the target delineation and the planning results of intensity-modulated radiation therapy (IMRT) for breast cancers. We requested the target volumes and organs at risk delineation for two cases of left breast cancers, and evaluated the IMRT plans including the supraclavicular and internal mammary node irradiation. Twenty-one institutions participated in this study. Differences in the planning target volume among institutions reached up to three-times for breast-conserving surgery (BCS) case and five-times for mastectomy case. Mean heart doses ranged from 3.3 to 24.1 Gy for BCS case and from 5.0 to 26.5 Gy for mastectomy case. Ipsilateral lung volumes receiving more than 20 Gy ranged from 4.7 to 57.4% for BCS case and from 16.4 to 55.5% for mastectomy case. There were large variations in the target delineation and planning results of IMRT for breast cancers among institutions. Considering the increased use of breast IMRT, more standardized protocols are needed.

Comparing complications in irradiated and non-irradiated free-flaps in patients with bilateral immediate breast reconstruction and unilateral post-mastectomy radiotherapy.

Numerous studies have evaluated the effect of post-mastectomy radiotherapy (PMRT) on autologous breast reconstruction, but the variability of PMRT regimens and inadequate controls have made results difficult to interpret. Therefore, in this study, irradiated free-flaps are compared to non-irradiated internal controls in patients who underwent immediate bilateral reconstruction followed by unilateral PMRT to better delineate the effect of PMRT. The role of regional nodal irradiation (RNI) is also specifically assessed. Appropriate patients were identified through retrospective review. Complications such as fat necrosis, fibrosis, infection, delayed healing, and flap loss, as well as revision surgeries, among the irradiated free-flaps were compared to those on the contralateral non-irradiated side. Additional analyses were performed to evaluate the effect of patient demographics and treatment characteristics, such as RNI, on complications involving the irradiated free-flaps. Seventy-three women were included. There was no significant difference between complication rates for the irradiated and non-irradiated free-flaps (39.7% vs. 38.4%, p=.78), although irradiated free-flaps were more likely to have fibrosis (17.0% vs. 0.0%; p <.0001) and multiple complications (9.6% vs. 0.0%; p=.02). Both groups underwent a similar number of revision surgeries (42.5% vs. 41.1%; p=.29). Looking at the irradiated free-flaps, internal mammary node (IMN) irradiation was the only factor predictive of complications (IRR 3.80, CI 1.32-10.97; p=.01). PMRT may contribute to free-flap fibrosis, but does not appear to affect the overall risk of complications or revision surgeries. However, additional counseling is warranted if IMN irradiation is likely, as it is potentially associated with increased complications.

Selection criteria for early breast cancer patients in the DBCG proton trial – The randomised phase III trial strategy

Background and purposeAdjuvant radiotherapy of internal mammary nodes (IMN) improves survival in high-risk early breast cancer patients but inevitably leads to more dose to heart and lung. Target coverage is often compromised to meet heart/lung dose constraints. We estimate heart and lung dose when target coverage is not compromised in consecutive patients. These estimates are used to guide the choice of selection criteria for the randomised Danish Breast Cancer Group (DBCG) Proton Trial. Materials and methods179 breast cancer patients already treated with loco-regional IMN radiotherapy from 18 European departments were included. If the clinically delivered treatment plan did not comply with defined target coverage requirements, the plan was modified retrospectively until sufficient coverage was reached. The choice of selection criteria was based on the estimated number of eligible patients for different heart and lung dose thresholds in combination with proton therapy capacity limitations and dose–response relationships for heart and lung. ResultsMedian mean heart dose was 3.0 Gy (range, 1.1–8.2 Gy) for left-sided and 1.4 Gy (0.4–11.5 Gy) for right-sided treatment plans. Median V17Gy/V20Gy (hypofractionated/normofractionated plans) for ipsilateral lung was 31% (9–57%). The DBCG Radiotherapy Committee chose mean heart dose ≥ 4 Gy and/or lung V17Gy/V20Gy ≥ 37% as thresholds for inclusion in the randomised trial. Using these thresholds, we estimate that 22% of patients requiring loco-regional IMN radiotherapy will be eligible for the trial. ConclusionThe patient selection criteria for the DBCG Proton Trial are mean heart dose ≥ 4 Gy and/or lung V17Gy/V20Gy ≥ 37%.

Internal mammary node irradiation in breast cancer: does benefit outweigh risk?

We have known for around three decades that breast radiotherapy not only reduces the risk of local relapse, but also breast cancer death,1,2 albeit potentially causing major cardiac events many years later.3 The balance of benefit versus harm is particularly relevant for internal mammary node radiotherapy, where patients are usually at greater risk of relapse by virtue of having higher stage disease, but heart doses can be higher due to the close proximity of the internal mammary chain. Uncertainties around the therapeutic ratio prompted clinical trials testing regional nodal (including internal mammary node) radiotherapy, with three studies reporting in 2015.

PD-0290: Efficacy of internal mammary nodal irradiation in T1-2N1 breast cancer in the modern era

PD-0290: Efficacy of internal mammary nodal irradiation in T1-2N1 breast cancer in the modern era

OC-0326: DBCG-IMN: Long-term survival gain with internal mammary node irradiation to breast cancer patients

OC-0326: DBCG-IMN: Long-term survival gain with internal mammary node irradiation to breast cancer patients

Outcomes of Adjuvant Radiation Therapy without Prophylaxis Internal Mammary Nodal Irradiation in Post-operative Breast Cancer Women with Regional Nodal Metastasis

Outcomes of Adjuvant Radiation Therapy without Prophylaxis Internal Mammary Nodal Irradiation in Post-operative Breast Cancer Women with Regional Nodal Metastasis

Hypofractionated radiation therapy for breast cancer: Preferences amongst radiation oncologists in Europe – Results from an international survey

Background and purposeWe aimed to assess the prescription preference about hypofractionated radiation therapy (HFRT) for breast cancer (BC) patients amongst radiation oncologists (ROs) practicing in Europe and to identify restraints on HFRT utilisation. Materials and methodsAn online survey was circulated amongst ROs in Europe through personal, RO and BC societies’ networks, from October 2019 to March 2020. The statistical analyses included descriptive statistics, chi-squared testing, and logistic regression analysis. ResultsWe received 412 responses from 44 countries. HFRT was chosen as the preferred schedule for whole breast irradiation (WBI) by 54.7% and for WBI with regional nodes irradiation (RNI) by 28.7% of the responding ROs. In the case of postmastectomy RT with or without reconstruction, HFRT was preferred by 21.1% and 29.6%, respectively. Overall, 69.2% of the responding ROs selected at least one factor influencing the decision to utilise HFRT, the most frequent of which included age (51.4%), RNI (46.9%), internal mammary lymph nodes irradiation (39.7%), BC stage (33.5%) and implant-based breast reconstruction (31.6%). ROs working in academic centres (odds ratio, (OR), 1.7; 95% confidence interval, (CI); 1.1–2.6, p = 0.019), practicing in Western Europe (OR, 4.2; 95%CI; 2.7–6.6, p < 0.0005) and/or dedicating >50% of clinical time to BC patients (OR, 2.5; 95%CI; 1.5–4.2, p = 0.001) more likely preferred HFRT. ConclusionAlthough HFRT is recognised as a new standard, its implementation in routine RT clinical practice across Europe varies for numerous reasons. Better dissemination of evidence-based recommendations is advised to improve the level of awareness about this clinical indication.

Prognostic significance of the primary tumor site and immune indexes in patients with estrogen receptor-positive, human epidermal growth factor receptor-2-negative breast cancer.

The ability to predict high risk factors for recurrence after neoadjuvant chemotherapy (NAC) is controversial. The purpose of the present study was to investigate the prognostic significance of tumor location, tumor-infiltrating lymphocyte (TIL) level, and pretreatment lymphocyte-to-monocyte ratio (LMR) in determining the survival of patients with estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative breast cancer after treatment with NAC. The clinical data of 285 ER-positive, HER2-negative patients with clinical stage II-III breast cancer were analyzed from January 2009 to January 2015. To explore the prognostic factors for ER-positive, HER2-negative patients, we combined the conventional clinicopathological prognostic factors with tumor location, pretreatment LMR, and TIL. In addition, samples from 79 patients, who did not achieve pathological complete response (pCR) testing after NAC, were selected for hematoxylin-eosin (HE) staining to analyze the effect of TIL on prognosis. An LMR >5.2 was correlated with better 5-year disease-free survival (DFS) and overall survival (OS; P<0.001 and P<0.001, respectively). Patients with lower-inner/central quadrant tumors had lower 5-year DFS and OS than patients with tumors in the other quadrants (P=0.012 and P=0.048). Patients with a lower TIL level (≤10%) had better 5-year DFS than patients with a higher TIL level (P=0.010). According to the results of the multivariate analyses, tumor location was an independent prognostic factor for 5-year DFS (P=0.021). Pretreatment LMR was associated with both 5-year DFS and OS (P<0.001 and P<0.001, respectively). In the subgroup analysis stratified by TIL level, the TIL level and the initial clinical stage were associated with 5-year DFS (P=0.027 and P<0.001, respectively). We explored the prognostic significance of the tumor site, TIL level, and pretreatment LMR level for ER-positive, HER2-negative patients. We concluded that the lower-inner/central quadrant tumors, TIL >10%, and pretreatment LMR level ≤5.2 were correlated with a poor prognosis. More aggressive NAC and/or endocrine therapy with internal mammary node radiotherapy (IMN-RT) should be administered to address the relatively poor prognosis of patients with breast carcinoma presenting the aforementioned adverse factors.

Toxicity of internal mammary irradiation in breast cancer. Are concerns still justified in times of modern treatment techniques?

Background The purpose of this study was to estimate the additional risk of side effects attributed to internal mammary node irradiation (IMNI) as part of regional lymph node irradiation (RNI) in breast cancer patients and to compare it with estimated overall survival (OS) benefit from IMNI. Material and methods Treatment plans (n = 80) with volumetric modulated arc therapy (VMAT) were calculated for 20 patients (4 plans per patient) with left-sided breast cancer from the prospective GATTUM trial in free breathing (FB) and in deep inspiration breath hold (DIBH). We assessed doses to organs at risk ((OARs) lung, contralateral breast and heart) during RNI with and without additional IMNI. Based on the OAR doses, the additional absolute risks of 10-year cardiac mortality, pneumonitis, and secondary lung and breast cancer were estimated using normal tissue complication probability (NTCP) and risk models assuming different age and risk levels. Results IMNI notably increased the mean OAR doses. The mean heart dose increased upon IMNI by 0.2–3.4 Gy (median: 1.9 Gy) in FB and 0.0–1.5 Gy (median 0.4 Gy) in DIBH. However, the estimated absolute additional 10-year cardiac mortality caused by IMNI was <0.5% for all patients studied except 70-year-old high risk patients (0.2–2.4% in FB and 0.0–1.1% in DIBH). In comparison to this, the published oncological benefit of IMNI ranges between 3.3% and 4.7%. The estimated additional 10-year risk of secondary cancer of the lung or contralateral breast ranged from 0–1.5% and 0–2.8%, respectively, depending on age and risk levels. IMNI increased the pneumonitis risk in all groups (0–2.2%). Conclusion According to our analyses, the published oncological benefit of IMNI outweighs the estimated risk of cardiac mortality even in case of (e.g., cardiac) risk factors during VMAT. The estimated risk of secondary cancer or pneumonitis attributed to IMNI is low. DIBH reduces the estimated additional risk of IMNI even further and should be strongly considered especially in patients with a high baseline risk.

The poor prognosis of lower-inner quadrant breast cancer in patients who received neoadjuvant chemotherapy.

The elevated risk for recurrence in breast cancer patients after receiving neoadjuvant chemotherapy (NAC) is still controversial. The purpose of this paper was to investigate the prognostic significance of tumor location concerning the survival of patients with breast cancer treated with NAC. The clinical information of 676 patients with stage II-III breast carcinoma who were being treated with NAC between March 2009 and 2014 was investigated. The primary tumor sites were categorized into three groups: outer quadrant, upper-inner quadrant, and lower-inner/central quadrant. According to the results of multivariate analyses, the number of tumor locations, nuclear grade, and the initial clinical stage was associated with disease-free survival (DFS), distant metastasis-free survival (DMFS), and overall survival (OS). When stratified into subgroups, tumors in the lower-inner/central quadrant were associated with a significantly worse prognosis in patients not treated with postmastectomy radiation therapy (PMRT) and in patients in the human epidermal growth factor receptor 2 (HER-2)-enriched and triple-negative subgroups. The primary tumor site is likely to be a critical feature that affects the prognosis of breast cancer tumors treated with NAC. To address the poor prognosis related to inner-quadrant participation in breast carcinoma, more aggressive NAC with internal mammary node radiotherapy (IMN-RT) should be conducted.

Does Internal Mammary Node Irradiation for Breast Cancer Make a Significant Difference to the Diameter of the Internal Mammary Artery? Correlation with Computed Tomography

Objective: Lymphatic irradiation in breast cancer improves locoregional control and has been shown to decrease distant metastasis. However, irradiation also accelerates the formation of atherosclerosis and can cause stenosis, not only in the coronary arteries but also in the internal mammary artery (IMA). The aim of this study was to investigate the effects of radiation on IMAs via computed tomography (CT). Methods: We reviewed the data of 3,612 patients with breast cancer treated with radiotherapy (RT) between January 2010 and December 2016. We included 239 patients with appropriate imaging and nodal irradiation in the study. All patients were treated with lymphatic irradiation of 46–50 Gy, and a boost dose (6–10 Gy) to the involved internal mammary nodes (IMNs) when imaging studies demonstrated pathological enlargement. Bilateral IMA diameter and the presence of calcification were assessed via thin contrast-enhanced CT and those of ipsilateral irradiated IMAs were compared with those of contralateral nonirradiated IMAs. Results: The mean diameter ofirradiated IMAs was significantly shorter than that of nonirradiated IMAs, regardless of laterality. All vascular calcifications were determined on the irradiated side. A boost dose of radiation to the IMNs and radiation technique did not significantly affect the IMA diameter or the presence of calcification. Conclusions: The diameter of the IMA is decreased due to RT regardless of laterality, radiation technique, and administration of a boost dose. Evaluation of vessels on CT before coronary artery bypass graft or flap reconstruction can help the surgeon select the most appropriate vessel.

Utilization patterns and temporal trends of internal mammary nodal irradiation at a tertiary cancer center.

The role and uptake of internal mammary nodal irradiation (IMNI) is variable. This study was designed to quantify the rates and determinants of IMNI at a tertiary cancer center. Consecutively treated breast cancer patients receiving adjuvant locoregional radiation therapy (RT) from January 1, 2012 to December 31, 2017 were sorted by IMNI receipt, disease risk and time period of RT delivery (2012-2015 vs 2016-2017). Differences between risk categories and groups were evaluated using χ2/Fisher's and Mann-Whitney test for categorical and continuous variables, respectively. Univariable and multivariable logistic regression analysis was done to determine factors associated with IMNI receipt. A total of 1566 patients were eligible, with 376 in Group 1 (IMNI), and 1190 in Group 2 (no IMNI). The proportion of patients receiving IMNI increased significantly each year (p < 0.0001), and 83% of patients receiving IMNI had pT1-2/pN1 disease. On univariable analysis, younger age, lymphovascular invasion, medial/central quadrant, higher stage, PR negative, mastectomy, axillary dissection, receipt of chemotherapy and nodal positivity had higher odds of IMNI. On multivariable analysis, younger age (p = < 0.001), medial/central quadrant (p = 0.0026), PR negative (p = 0.0011), mastectomy (p = 0.0055), increasing nodal positivity (p < 0.0001) and late cohort (p = 0.001) had increased likelihood of IMNI. The use of deep-inspiration breath hold was significantly higher in those receiving IMNI (45% vs 26%, p < 0.0001), and permitted achievement of acceptable mean heart and lung doses. There was a significant increase in IMNI utilization after 2015. Younger age, medial/central quadrant, PR-negative and node-positive disease predicted for receipt of IMNI. Modern RT techniques permit the safe delivery of IMNI.

Factors Influencing the Incidental Dose Distribution in Internal Mammary Nodes: A Comparative Study.

Objective: To investigate the effect of anatomic and technical parameters on the incidental internal mammary lymph node (IMN) irradiation (IIMNI) dose among postmastectomy patients.Methods: We retrospectively delineated the IMN on planning CT images from 138 patients who had undergone postmastectomy radiotherapy (PMRT). We analyzed the IIMNI dose coverage and its relationship with anatomic and technical parameters.Results: The IIMNI mean dose was 32.85 ± 9.49 Gy, and 10 of 138 patients (7.25%) treated with PMRT received ≥45 Gy. In univariate analysis, the body weight, body mass index, body surface area, thoracic transverse diameter (DT), ratio of DT to the thoracic anteroposterior diameter (DAP)(RT/AP), planning target volume of IMN (PTVIMN) included in PTV (IMNin) and the ratio of IMNin to PTVIMN (RIMNin) and PTV posterior border were the parameters affecting IIMNI dose. In multivariate analysis, body weight, RT/AP, and RIMNin were correlative factors that affected IIMNI dose.Conclusions: For patients who underwent PMRT without IMN irradiation (IMNI), there was a wide variety in IIMNI doses. A minority of patients had adequate IIMNI dose coverage, and the higher IIMNI doses were associated with the less body weights and more RIMNin.