The role of postmastectomy radiotherapy in clinically node-positive, stage II-III breast cancer patients with pathological negative nodes after neoadjuvant chemotherapy: an analysis from the NCDB

Purpose

The role of postmastectomy radiotherapy (PMRT) in clinically node-positive, stage II-III breast cancer patients with pathological negative nodes (ypN0) after neoadjuvant chemotherapy (NAC) remains controversial.

Methods

A total of 1560 clinically node-positive, stage II-III breast cancer patients treated with NAC and mastectomy who achieved ypN0 between 1998 and 2009 in the National Cancer Database were analyzed. The effects of PMRT on overall survival (OS) for the entire cohort and multiple subgroups were evaluated. Imputation and propensity score matching were used as sensitivity analyses to minimize biases.

Results

Of the entire 1560 eligible patients, 903 (57.9%) received PMRT and 657 (42.1%) didn’t. At a median follow-up of 56.0 months, no statistical difference was observed for OS between two groups by univariate and multivariate analyses (P = 0.120; HR 1.571, 95% CI 0.839-2.943). On subgroup analyses, PMRT significantly improved OS in patients with clinical stage IIIB/IIIC disease, T3/T4 tumor, or residual invasive breast cancer after NAC (P < 0.05). This improvement in OS remained significant after sensitivity analyses for the propensity score-matched patients.

Conclusions

This study demonstrated that PMRT showed a heterogeneous effect in clinically node-positive, stage II-III breast cancer patients with ypN0 following NAC. PMRT improved OS for patients with clinical stage IIIB/IIIC disease, T3/T4 tumor, or residual invasive breast tumor after NAC. In the absence of definitive conclusions from prospective studies, including the ongoing NSABP B-51 trial, our findings may help identify specific groups of women with clinically node-positive, stage II-III breast cancers who could benefit from PMRT after NAC.

Patterns and risk factors for locoregional failures after mastectomy for breast cancer: an International Breast Cancer Study Group report

BACKGROUND

Rates and risk factors of local, axillary and supraclavicular recurrences can guide patient selection and target for postmastectomy radiotherapy (PMRT).

PATIENTS AND METHODS

Local, axillary and supraclavicular recurrences were evaluated in 8106 patients enrolled in 13 randomized trials. Patients received chemotherapy and/or endocrine therapy and mastectomy without radiotherapy. Median follow-up was 15.2 years.

RESULTS

Ten-year cumulative incidence for chest wall recurrence of >15% was seen in patients aged <40 years (16.1%), with ≥4 positive nodes (16.5%) or 0-7 uninvolved nodes (15.1%); for supraclavicular failures >10%: ≥4 positive nodes (10.2%); for axillary failures of >5%: aged <40 years (5.1%), unknown primary tumor size (5.2%), 0-7 uninvolved nodes (5.2%). In patients with 1-3 positive nodes, 10-year cumulative incidence for chest wall recurrence of >15% were age <40, peritumoral vessel invasion or 0-7 uninvolved nodes. Age, number of positive nodes and number of uninvolved nodes were significant parameters for each locoregional relapse site.

CONCLUSION

PMRT to the chest wall and supraclavicular fossa is supported in patients with ≥4 positive nodes. With 1-3 positive nodes, chest wall PMRT may be considered in patients aged <40 years, with 0-7 uninvolved nodes or with vascular invasion. The findings do not support PMRT to the dissected axilla.

Post-mastectomy radiotherapy benefits subgroups of breast cancer patients with T1-2 tumor and 1-3 axillary lymph node(s) metastasis

Background

To determine the role of postmastectomy radiotherapy (PMRT) in breast cancer patients with T1–2 and N1 disease.

Patients and methods.

A total of 207 postmastectomy women were enrolled. The 5-year Kaplan-Meier estimates of locoregional recurrence rate (LRR), distant recurrence rate (DRR) and overall survival (OS) were analyzed by different tumor characteristics. Multivariate analyses were performed using Cox proportional hazards modeling.

Results

With median follow-up 59.5 months, the 5-year LRR, DRR and OS were 9.1%, 20.3% and 84.4%, respectively. On univariate analysis, age < 40 years old (p = 0.003) and Her-2/neu over-expression (p = 0.016) were associated with higher LRR, whereas presence of LVI significantly predicted higher DRR (p = 0.026). Negative estrogen status (p = 0.033), Her-2/neu overexpression (p = 0.001) and LVI (p = 0.01) were significantly correlated with worse OS. PMRT didn’t prove to reduce 5-year LRR (p = 0.107), as well as 5-year OS (p = 0.918). In subgroup analysis, PMRT showed significant benefits of improvement LRR and OS in patients with positive LVI.

Conclusions

For patients with T1–2 and N1 stage breast cancer, PMRT can decrease locoregional recurrence and increase overall survival only in patients with lymphovascular invasion.

A Comparative Study of Hypofractionated and Conventional Radiotherapy in Postmastectomy Breast Cancer Patients

Objective

The aim of this study was to compare toxicity and locoregional control of short duration hypofractionated (HF) radiotherapy (RT) with conventional RT in breast cancer patients.

Methods

A total of 100 postmastectomy breast cancer patients were randomized for adjuvant RT in control group (comprising fifty patients who received the standard conventional dose of 50 Gy in 25 fractions with 2 Gy per fraction) and study group (comprising fifty patients who received HF RT with dose of 42.72 Gy in 16 fractions with 2.67 Gy per fraction). All patients were treated on linear accelerator with 3-dimensional conformal RT technique. Outcome was analyzed in terms of toxicity, tolerability, and locoregional control.

Results

In the present study, at a median follow-up of 20 months, almost similar results were seen in both the groups in terms of toxicity, tolerability, and locoregional control. Adjuvant postmastectomy HF RT was found to be well tolerated with mild-to-moderate side effects that neither reached statistical significance nor warranted any treatment interruption/hospitalization.

Conclusions

HF postmastectomy RT is comparable to conventional RT without evidence of higher adverse effects or inferior locoregional tumor control and has an added advantage of increased compliance because of short duration; hence, it can help in accommodating more breast cancer patients in a calendar year, ultimately resulting in decreased waiting list, increased turnover, and reduced cost of treatment.

Automated treatment planning of postmastectomy radiotherapy

Purpose

Breast cancer is the most common cancer in women globally and radiation therapy is a cornerstone of its treatment. However, there is an enormous shortage of radiotherapy staff, especially in low‐ and middle‐income countries. This shortage could be ameliorated through increased automation in the radiation treatment planning process, which may reduce the workload on radiotherapy staff and improve efficiency in preparing radiotherapy treatments for patients. To this end, we sought to create an automated treatment planning tool for postmastectomy radiotherapy (PMRT).

Methods

Algorithms to automate every step of PMRT planning were developed and integrated into a commercial treatment planning system. The only required inputs for automated PMRT planning are a planning computed tomography scan, a plan directive, and selection of the inferior border of the tangential fields. With no other human input, the planning tool automatically creates a treatment plan and presents it for review. The major automated steps are (a) segmentation of relevant structures (targets, normal tissues, and other planning structures), (b) setup of the beams (tangential fields matched with a supraclavicular field), and (c) optimization of the dose distribution by using a mix of high‐ and low‐energy photon beams and field‐in‐field modulation for the tangential fields. This automated PMRT planning tool was tested with ten computed tomography scans of patients with breast cancer who had received irradiation of the left chest wall. These plans were assessed quantitatively using their dose distributions and were reviewed by two physicians who rated them on a three‐tiered scale: use as is, minor changes, or major changes. The accuracy of the automated segmentation of the heart and ipsilateral lung was also assessed. Finally, a plan quality verification tool was tested to alert the user to any possible deviations in the quality of the automatically created treatment plans.

Results

The automatically created PMRT plans met the acceptable dose objectives, including target coverage, maximum plan dose, and dose to organs at risk, for all but one patient for whom the heart objectives were exceeded. Physicians accepted 50% of the treatment plans as is and required only minor changes for the remaining 50%, which included the one patient whose plan had a high heart dose. Furthermore, the automatically segmented contours of the heart and ipsilateral lung agreed well with manually edited contours. Finally, the automated plan quality verification tool detected 92% of the changes requested by physicians in this review.

Conclusions

We developed a new tool for automatically planning PMRT for breast cancer, including irradiation of the chest wall and ipsilateral lymph nodes (supraclavicular and level III axillary). In this initial testing, we found that the plans created by this tool are clinically viable, and the tool can alert the user to possible deviations in plan quality. The next step is to subject this tool to prospective testing, in which automatically planned treatments will be compared with manually planned treatments.

Improvement of survival with postmastectomy radiotherapy in patients with 1-3 positive axillary lymph nodes: A systematic review and meta-analysis of the current literature

In breast cancer with >4 positive axillary lymph nodes, it is common practice to deliver radiotherapy to the affected site following mastectomy. However, less is known regarding the benefits this may confer on women with 1-3 positive lymph nodes. In this meta-analysis, we aimed to assess whether post-mastectomy radiotherapy (PMRT) was beneficial for such patients. A literature review was conducted using the PubMed and Ovid databases. Selected studies were analysed and data regarding overall survival (OS) and locoregional recurrence (LRR) rates were extracted. Statistical analysis was then conducted in order to develop a combined risk ratio (RR) for both OS and LRR in the setting of PMRT in women with breast cancer with 1-3 positive lymph nodes. PMRT in women with 1-3 positive lymph nodes significantly reduced the risk of LRR, with a RR of 0.3 [95% confidence interval (CI): 0.23-0.38] and also showed a minor benefit in terms of OS (RR=1.03, 95% CI: 1.00-1.07). Therefore, in breast cancer patients with 1-3 positive lymph nodes, PMRT significantly reduced the risk of LRR and was associated with a minor OS benefit. Until the results of ongoing randomised controlled trials are published, PMRT should be recommended in this group of patients following a careful multidisciplinary discussion.

Modeling of the metallic port in breast tissue expanders for photon radiotherapy

The purpose of this study was to model the metallic port in breast tissue expanders and to improve the accuracy of dose calculations in a commercial photon treatment planning system (TPS). The density of the model was determined by comparing TPS calculations and ion chamber (IC) measurements. The model was further validated and compared with two widely used clinical models by using a simplified anthropomorphic phantom and thermoluminescent dosimeters (TLD) measurements. Dose perturbations and target coverage for a single postmastectomy radiotherapy (PMRT) patient were also evaluated. The dimensions of the metallic port model were determined to be 1.75 cm in diameter and 5 mm in thickness. The density of the port was adjusted to be 7.5 g/cm³ which minimized the differences between IC measurements and TPS calculations. Using the simplified anthropomorphic phantom, we found the TPS calculated point doses based on the new model were in agreement with TLD measurements within 5.0% and were more accurate than doses calculated based on the clinical models. Based on the photon treatment plans for a real patient, we found that the metallic port has a negligible dosimetric impact on chest wall, while the port introduced significant dose shadow in skin area. The current clinical port models either overestimate or underestimate the attenuation from the metallic port, and the dose perturbation depends on the plan and the model in a complex way. TPS calculations based on our model of the metallic port showed good agreement with measurements for all cases. This new model could improve the accuracy of dose calculations for PMRT patients who have temporary tissue expanders implanted during radiotherapy and could potentially reduce the risk of complications after the treatment.

Locoregional recurrence-associated factors and risk-adapted postmastectomy radiotherapy for breast cancer staged in cT1-2N0-1 after neoadjuvant chemotherapy

Objective

In order to identify risk factors associated with locoregional recurrence (LRR) and assess the role of postmastectomy radiotherapy (PMRT) in early breast cancer (BC), managed with neoadjuvant chemotherapy (NAC) and mastectomy, a retrospective analysis of BC diagnosed with clinical stage T1-2N0-1 was conducted.

Patients and methods

A total of 217 patients were included in this analysis. The median age was 50 years (24-72 years). The clinical stage distributions were cT1 in 15 cases, cT2 in 202, cN0 in 53, and cN1 in 161 cases. All patients were treated with NAC and mastectomy, and 128 patients received PMRT.

Results

With a median follow-up time of 61 months, the 5-year cumulative LRR rate was 12%. Multivariate analysis demonstrated that pathological N stage, lymph-vascular invasion, and histological grade were independent prognostic factors associated with LRR. A nomogram model based on these factors was established, based on which the patients were deeply stratified into low- and high-risk group. In the low-risk group, radiotherapy did not decrease LRR (3.3% in PMRT group, 1.7% in no PMRT group, P=0.192). While in the high-risk group, PMRT significantly decreased LRR (21.8% in PMRT group, 42.2% in no PMRT group, P=0.031).

Conclusion

Lymph-vascular invasion, histological grade, as well as pathological N stage were important prognostic factors associated with LRR in BC patients staged in cT1-2N0-1, who were managed with NAC and mastectomy. In our cohort, not only clinical and pathological stage information but also other risk factors were taken into consideration when adjuvant PMRT was recommended. In the high-risk subgroup, PMRT significantly improved the prognosis.

Evaluation of a mixed beam therapy for postmastectomy breast cancer patients: Bolus electron conformal therapy combined with intensity modulated photon radiotherapy and volumetric modulated photon arc therapy

PURPOSE

The purpose of this study was to assess the potential benefits and limitations of a mixed beam therapy, which combined bolus electron conformal therapy (BECT) with intensity modulated photon radiotherapy (IMRT) and volumetric modulated photon arc therapy (VMAT), for left-sided postmastectomy breast cancer patients.

METHODS

Mixed beam treatment plans were produced for nine postmastectomy radiotherapy (PMRT) patients previously treated at our clinic with VMAT alone. The mixed beam plans consisted of 40 Gy to the chest wall area using BECT, 40 Gy to the supraclavicular area using parallel opposed IMRT, and 10 Gy to the total planning target volume (PTV) by optimizing VMAT on top of the BECT + IMRT dose distribution. The treatment plans were created in a commercial treatment planning system (TPS), and all plans were evaluated based on PTV coverage, dose homogeneity index (DHI), conformity index (CI), dose to organs at risk (OARs), normal tissue complication probability (NTCP), and secondary cancer complication probability (SCCP). The standard VMAT alone planning technique was used as the reference for comparison.

RESULTS

Both techniques produced clinically acceptable PMRT plans but with a few significant differences: VMAT showed significantly better CI (0.70 vs 0.53, P < 0.001) and DHI (0.12 vs 0.20, P < 0.001) over mixed beam therapy. For normal tissues, mixed beam therapy showed better OAR sparing and significantly reduced NTCP for cardiac mortality (0.23% vs 0.80%, P = 0.01) and SCCP for contralateral breast (1.7% vs 3.1% based on linear model, and 1.2% vs 1.9% based on linear-exponential model, P < 0.001 in both cases), but showed significantly higher mean (50.8 Gy vs 49.3 Gy, P < 0.001) and maximum skin doses (59.7 Gy vs 53.3 Gy, P < 0.001) compared with VMAT. Patients with more tissue (minimum distance between the distal PTV surface and lung approximately > 0.5 cm and volume of tissue between the distal PTV surface and heart or lung approximately > 250 cm³ ) between distal PTV surface and lung may benefit the most from mixed beam therapy.

CONCLUSION

This work has demonstrated that mixed beam therapy (BECT + IMRT:VMAT = 4:1) produces clinically acceptable plans having reduced OAR doses and risks of side effects compared with VMAT. Even though VMAT alone produces more homogenous and conformal dose distributions, mixed beam therapy remains as a viable option for treating postmastectomy patients, possibly leading to reduced normal tissue complications.

A clinical trial to compare a 3D-printed bolus with a conventional bolus with the aim of reducing cardiopulmonary exposure in postmastectomy patients with volumetric modulated arc therapy

BACKGROUND

We compared the dosimetry, application, and acute toxicity of a 3D-printed and a conventional bolus for postmastectomy radiotherapy (PMRT) with volumetric modulated arc therapy (VMAT). Materials and Methods Eligible patients (n = 75) with PMRT breast cancer were randomly selected to receive VMAT with a conventional bolus or a 3D-printed bolus. The primary endpoint was a 10% decrease in the mean heart dose to left-sided breast cancer patients. The secondary endpoint was a 5% decrease in the mean ipsilateral lung dose to all patients. A comparative analysis was carried out of the dosimetry, normal tissue complication probability (NTCP), acute skin toxicity, and radiation pneumonitis.

RESULTS

Compared to a conventional bolus, the mean heart dose in left-sided breast cancer was reduced by an average of 0.8 Gy (5.5 ± 1.3 Gy vs. 4.7 ± 0.8 Gy, p = 0.035) and the mean dose to the ipsilateral lung was also reduced by an average of 0.8 Gy (12.4 ± 1.0 Gy vs. 11.6 ± 0.8 Gy, p < 0.001). The values for V_50Gy of the PTV of the chest wall for the 3D-printed and conventional boluses were 95.4 ± 0.6% and 94.8 ± 0.8% (p = 0.026) and the values for the CI of the entire PTV were 0.83 ± 0.02 and 0.80 ± 0.03 (p < 0.001), respectively. The NTCP for the 3D-printed bolus was also reduced to an average of 0.14% (0.32 ± 0.19% vs. 0.18 ± 0.11%, p = 0.017) for the heart and 0.45% (3.70 ± 0.67% vs. 3.25 ± 0.18%, p < 0.001) for the ipsilateral lung. Grade 2 and Grade 1 radiation pneumonitis were 0.0% versus 7.5% and 14.3% versus 20.0%, respectively (p = 0.184).

CONCLUSIONS

The 3D-printed bolus may reduce cardiopulmonary exposure in postmastectomy patients with volumetric modulated arc therapy.

Real-world outcomes of postmastectomy radiotherapy in breast cancer patients with 1-3 positive lymph nodes: a retrospective study

OBJECTIVE

To assess the treatment outcomes and to explore the determinants of clinical outcome in breast cancer patients with 1-3 positive nodes who did or did not receive postmastectomy radiotherapy (PMRT) in a tertiary care referral cancer center in Northern Thailand.

METHODS

We investigated a retrospective cohort of registered breast cancer patients at the Faculty of Medicine, Chiang Mai University, Thailand from 2001-2007. Analysis was performed using Cox regression models to identify factors affecting the overall survival (OS) and relapse-free survival (RFS) rates. Comparisons were made between two cohorts: women who received adjuvant PMRT (74 patients) and women who did not receive adjuvant PMRT (81 patients).

RESULTS

A total of 155 patients were included with a median follow-up period of 4.45 years. There was a statistically significant 4-year OS difference between the two groups of patients: 100% for the PMRT group and 93.1% for the non-PMRT group (P = 0.044). The 4-year RFS was 85.9% for patients receiving PMRT and 78.3% for patients who did not receive PMRT (P = 0.291). On multivariate analysis of OS, using hormonal treatment was the only significant independent factor associated with improved OS. On multivariate analysis of RFS, none of the variables were significantly associated with improved RFS. PMRT was notfound to be a prognostic variable related to the outcome of patients using a logistic regression model.

CONCLUSION

Our retrospective, hospital-based analysis demonstrated that PMRT improved the treatment outcome in terms of OS for women with 1-3 node positive early-stage breast cancer.

Is it beneficial for patients with pT1-2N1M0 breast cancer to receive postmastectomy radiotherapy? An analysis based on RecurIndex assay

The benefit of postmastectomy radiotherapy (PMRT) for pT1-2N1M0 breast cancer patients currently remains controversial. This study was conducted to investigate whether pT1-2N1M0 breast cancer patients could benefit from PMRT based on RecurIndex assay. The clinical data of 213 pT1-2N1M0 breast cancer patients were retrospectively analyzed. Through RecurIndex assay, 81 cases were assessed as the low risk, and 132 as the high risk. Compared to low-risk patients, high-risk patients especially those not receiving PMRT had a significantly increased risk of recurrence and metastasis, and worse 7-year local-regional recurrence-free interval (LRFI), distance recurrence-free interval (DRFI) and recurrence-free survival (RFS) rates. PMRT-based subgroup analysis indicated no significant differences between the low-risk patients with and without PMRT in 7-year LRFI, DRFI, RFS and overall survival (OS) rates, but apparent differences were all shown between the high-risk patients with and without PMRT in 7-year LRFI, DRFI, RFS and OS rates. Overall, for pT1-2N1M0 breast cancer patients at low risk of recurrence and metastasis stratified by RecurIndex assay, there may be a phenomenon of no PMRT benefits, while for those at high risk, use of PMRT may produce survival benefits.

Postmastectomy radiotherapy using three different techniques: a retrospective evaluation of the incidental dose distribution in the internal mammary nodes

Objective

To evaluate the incidental coverage dose to the internal mammary nodes (IMN) in patients treated with postmastectomy radiotherapy (PMRT) and its relationship with the treatment plan.

Patients and methods

We retrospectively analyzed 138 patients undergoing PMRT and divided them into three groups: three-dimensional conformal radiotherapy (3D-CRT), field-in-field forward intensity-modulated radiotherapy (F-IMRT), and inverse intensity-modulated radiotherapy (I-IMRT). The IMN were contoured according to the Radiation Therapy Oncology Group consensus and not included in the planning target volume. We analyzed incidental IMN dose coverage and its relationship with the lung and heart.

Results

The mean dose (Dmean) to the IMN was 32.85 Gy for all patients, and the dose delivered to the IMN showed no differences in 3D-CRT, F-IMRT, and I-IMRT (33.80, 29.65, and 32.95 Gy, respectively). In addition, 10.42%, 2.04%, and 9.76% of patients achieved ≥45 Gy with 3D-CRT, F-IMRT, and I-IMRT, respectively. No differences were evident among the three treatment plans regarding IMN dose in the first three intercostal spaces (ICS1-3). The Dmean, V20, V30, V40, and V50 of ICS2 and ICS3 were superior to those of ICS1 for all three plans. For 3D-CRT, a moderate positive correlation was evident between the Dmean to the IMN and the Dmean to the heart. For F-IMRT and I-IMRT, positive correlations were evident between the Dmean of the IMN and the Dmean and V20 of the lung.

Conclusion

The mean incidental dose to the IMN for IMRT (F-IMRT and I-IMRT) and 3D-CRT after modified radical mastectomy was insufficient to treat subclinical disease. A substantial dose was delivered to the IMN in some patients. Higher incidental doses to the IMN were associated with a higher heart mean dose for 3D-CRT and a higher dose to the lung for IMRT. Future prospective studies should further explore subgroups that do not require IMN irradiation.

Effect of postmastectomy radiotherapy on triple-negative breast cancer with T1-2 and 1-3 positive axillary lymph nodes: a population-based study using the SEER 18 database

There is consensus on the routine use of postmastectomy radiotherapy (PMRT) in patients with four or more positive axillary lymph nodes. However, the benefits of PMRT in patients with T1-2 and 1-3 involved lymph nodes still remain controversial. Data from the Surveillance, Epidemiology, and End Results Program (SEER) of the United States between 2010 and 2012 were used to analyze the outcomes of 675 triple-negative breast cancer (TNBC) patients with T1-2 and 1-3 lymph nodes involved. Those patients were subdivided into radiotherapy (RT) (312) and no-RT groups (363). After a median follow-up time of 37 months, Kaplan-Meier analysis showed that PMRT significantly improved overall survival (OS) but not breast cancer-specific survival (BCSS) in the total cohort of 675 patients (P=0.033 and P=0.063). And it was demonstrated that PMRT were independently associated with increased OS according to univariate and multivariate analyses. However, no significant differences in BCSS or OS were observed between the groups stratified by the number of positive lymph nodes. In conclusion, PMRT significantly improved OS for TNBC patients with T1-2 and 1-3 lymph nodes involved. Additional prospective studies are needed to provide a stronger evidence base for choosing patients for PMRT.

Clinical implementation of brass mesh bolus for chest wall postmastectomy radiotherapy and film dosimetry for surface dose estimates

Objective

This study presents the dosimetric data taken with radiochromic EBT3 film with brass mesh bolus using solid water and semi-breast phantoms, and its clinical implementation to analyze the surface dose estimates to the chest wall in postmastectomy radiotherapy (PMRT) patients.

Materials and Methods

Water-equivalent thickness of brass bolus was estimated with solid water phantom under 6 megavoltage photon beam. Following measurements with film were taken with no bolus, 1, 2, and 3 layers of brass bolus: (a) surface doses on solid water phantom with normal incidence and on curved surface of a locally fabricated cylindrical semi-breast phantom for tangential field irradiation, (b) depth doses (in solid phantom), and (c) surface dose measurements around the scar area in six patients undergoing PMRT with prescribed dose of 50 Gy in 25 fractions.

Results

Water-equivalent thickness (per layer) of brass bolus 2.09 ± 0.13 mm was calculated. Surface dose measured by film under the bolus with solid water phantom increased from 25.2% ±0.9% without bolus to 62.5% ± 3.1%, 80.1% ± 1.5%, and 104.4% ± 1.7% with 1, 2, and 3 layers of bolus, respectively. Corresponding observations with semi-breast phantom were 32.6% ± 5.3% without bolus to 96.7% ± 9.1%, 107.3% ± 9.0%, and 110.2% ± 8.7%, respectively. A film measurement shows that the dose at depths of 3, 5, and 10 cm is nearly same with or without brass bolus and the percentage difference is <1.5% at these depths. Mean surface doses from 6 patients treated with brass bolus ranged from 79.5% to 84.9%. The bolus application was discontinued between 18^th and 23^rd fractions on the development of Grade 2 skin toxicity for different patients. The total skin dose to chest wall for a patient was 3699 cGy from overall treatment with and without bolus.

Conclusions

Brass mesh bolus does not significantly change dose at depths, and the surface dose is increased. This may be used as a substitute for tissue-equivalent bolus to improve surface conformity in PMRT.

Verification using in vivo optically stimulated luminescent dosimetry of the predicted skin surface dose in patients receiving postmastectomy radiotherapy

The purpose of this study was to evaluate whether dose to the skin surface underneath bolus, was accurately predicted by a 3D treatment planning system (TPS) in patients receiving 50 Gy/25# postmastectomy radiotherapy (PMRT) using optically stimulated luminescent dosimetry (OSLD) for verification. In vivo dosimetry using OSLDs was performed in 20 consecutive patients receiving PMRT. An array of 9 OSLDs were applied to the chest wall or neobreast in a grid arrangement. Dosimetry data were recorded on 3 separate treatment fractions, averaged, and extrapolated to 25 fractions. On the 3D TPS, the predicted dose was calculated using the departmental planning algorithm at points corresponding to the OSLDs. The mean within patient difference between the planned and measured dose at each of the 9 points was calculated and Bland-Altman limits of agreement used to quantify the extent of agreement. Paired t-tests were used to test for evidence of systematic bias at each point. The coefficient of variation of the 3 OSLD readings per patient at each of the 9 points was low for 8 points (≤4.4%) demonstrating comparable dose received per fraction at these points. The mean ratio between the in vivo measured extrapolated OSLD (IVME OSLD) dose and the planned TPS dose ranged between 0.97 and 0.99 across all points (standard deviation range 0.05 to 0.08). The mean within patient difference between the IVME OSLD and planned TPS was <1 Gy at 7 of the 9 points and the t-test for evidence of systematic bias was significant (p = 0.03) at only 1 of the 9 points. Our commercially available 3D TPS closely predicted PMRT skin surface dose underneath bolus as verified by OSLDs. At all sites, the average ratio of delivered to predicted dose was >0.97 but <1. This practical and feasible OSLD assessment of only 3 of 25 fractions facilitates quality assurance of a TPS in predicting skin surface dose under bolus.

Role of postmastectomy radiotherapy in early-stage (T1-2N0-1M0) triple-negative breast cancer: a systematic review

Triple-negative breast cancer (TNBC), which represents 15%–20% of all breast cancers, is defined by the absence of estrogen receptor (ER) and progesterone receptor (PR) and overexpression of human epidermal growth factor receptor 2 (HER2). Owing to the absence of specific therapeutic targets and its aggressive biologic characteristics, TNBC patients often experience a high risk of disease progression and poor overall survival. Furthermore, TNBC exhibits an early pattern of recurrence with a peak recurrence risk at 2–3 years after surgery. Currently, chemotherapy continues to be the mainstay in TNBC patients; however, such treatment leaves them associated with a high rate of local and systemic relapses even in early-stage (T1–2N0–1M0). Therefore, in early-stage disease, greater emphasis is placed on locoregional treatments, based on radiation therapy (RT) after surgery, to reduce local and systemic relapses. However, there are no specific treatment guidelines for early-stage (T1–2N0–1M0) TNBC patients. In this review, we discuss the type of surgery received and the relevant adverse clinicopathologic factors and underlying BRCA1 mutation status regarding the influence of tailing postmastectomy radiotherapy (PMRT). In addition, we assess the role of PMRT in early-stage (T1–2N0–1M0) TNBC patients.

Surface Dose Measurements in Chest Wall Postmastectomy Radiotherapy to Achieve Optimal Dose Delivery with 6 MV Photon Beam

Aim

A tissue-equivalent bolus of sufficient thickness is used to overcome build up effect to the chest wall region of postmastectomy radiotherapy (PMRT) patients with tangential technique till Radiation Therapy Oncology Group (RTOG) Grade 2 (dry desquamation) skin reaction is observed. The aim of this study is to optimize surface dose delivered to chest wall in three-dimensional radiotherapy using EBT3 film.

Materials and Methods

Measurements were conducted with calibrated EBT3 films with thorax phantom under "open beam, Superflab gel (0.5 cm) and brass bolus conditions to check correlation against TPS planned doses. Eighty-two patients who received 50 Gy in 25# were randomly assigned to Group A (Superflab 0.5 cm gel bolus for first 15 fractions followed by no bolus in remaining 10 fractions), Group B or Group C (Superflab 0.5 cm gel or single layer brass bolus, respectively, till reaching RTOG Grade 2 skin toxicity).

Results

Phantom measured and TPS calculated surface doses were within - 5.5%, 4.7%, and 8.6% under open beam, 0.5 cm gel, and single layer of brass bolus applications, respectively. The overall surface doses (OSD) were 80.1% ±2.9% (n = 28), 92.6% ±4.6% (n = 28), and 87.4% ±4.7% (n = 26) in Group A, B, and C, respectively. At the end of treatment, 7 out of 28; 13 out of 28; and 9 out of 26 patients developed Grade 2 skin toxicity having the OSD value of 83.0% ±1.6% (n = 7); 93.7% ±3.2% (n = 13); and 89.9% ±5.6% (n = 9) in Groups A, B, and C, respectively. At the 20^th-23^rd fraction, 2 out of 7; 6 out of 13; and 4 out of 9 patients in Groups A, B, and C developed a Grade 2 skin toxicity, while the remaining patients in each group developed at the end of treatment.

Conclusions

Our objective to estimate the occurrence of optimal dose limit for bolus applications in PMRT could be achieved using clinical EBT3 film dosimetry. This study ensured correct dose to scar area to protect cosmetic effects. This may also serve as quality assurance on optimal dose delivery for expected local control in these patients.

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 (D_T), ratio of D_T to the thoracic anteroposterior diameter (D_AP)(R_T/AP), planning target volume of IMN (PTV_IMN) included in PTV (IMNin) and the ratio of IMNin to PTV_IMN (R_IMNin) and PTV posterior border were the parameters affecting IIMNI dose. In multivariate analysis, body weight, R_T/AP, and R_IMNin 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 R_IMNin.

A Prognostic Risk Stratification Model to Identify Potential Population Benefiting From Postmastectomy Radiotherapy in T1-2 Breast Cancer With 1-3 Positive Axillary Lymph Nodes

Background and Objectives

To establish a prognostic stratification nomogram for T1–2 breast cancer with 1–3 positive lymph nodes to determine which patients can benefit from postmastectomy radiotherapy (PMRT).

Methods

A population-based study was conducted utilizing data collected from the Surveillance, Epidemiology, and End Results database. Chi-square test or Fisher exact test was used to compare the distribution of characteristics. Cox analysis identified significant prognostic factors for survival. A prognostic stratification model was constructed by R software. Propensity score matching was applied to balance characteristics between PMRT cohort and control cohort. Kaplan-Meier method was performed to evaluate the performance of stratification and the benefits of PMRT in the total population and three risk groups.

Results

The overall performance of the nomogram was good (3-year, 5-year, 10-year AUC were 0.75, 0.72 and 0.67, respectively). The nomogram was performed to excellently distinguish low-risk, moderate-risk, and high-risk groups with 10-year overall survival (OS) of 86.9%, 73.7%, and 62.7%, respectively (P<0.001). In the high-risk group, PMRT can significantly better OS with 10-year all-cause mortality reduced by 6.7% (P = 0.027). However, there was no significant survival difference between PMRT cohort and control cohort in low-risk (P=0.49) and moderate-risk groups (P = 0.35).

Conclusion

The current study developed the first prognostic stratification nomogram for T1–2 breast cancer with 1–3 positive axillary lymph nodes and found that patients in the high-risk group may be easier to benefit from PMRT.

Helical Tomotherapy for Postmastectomy Radiotherapy after Immediate Left Breast Reconstruction: A Case Study

A 43-year-old premenopausal female presented with a multicentric infiltrating lobular carcinoma of the left breast with axillary nodes metastasis. She underwent modified radical mastectomy with axillary lymph node dissection (level I and II) followed by a mixed autologous latissimus dorsi flap reconstruction with the addition of prosthesis. The final pathological analysis revealed a 6 cm invasive lobular carcinoma pT3N2aM0, grade III/III, estrogen and progesterone positive, human epidermal growth factor receptor 2 (HER2) negative, with 5/16 positive lymph nodes. She received neoadjuvant chemotherapy with doxorubicin and cyclophosphamide followed by paclitaxel. Post-mastectomy radiotherapy with axillary, supraclavicular and internal mammary lymph nodes (IMLN) irradiation was delivered to a dose of 50 Gy/25 fx. In this case with multiple risk factors for radiation-induced cardiac toxicity (left-sided lesion, internal mammary lymph nodes (IMLN) irradiation), we discuss the role of helical tomotherapy as a treatment alternative to conventional tangential radiotherapy.

Clinical decision making in postmastectomy radiotherapy in node negative breast cancer

For decades, postmastectomy radiotherapy (PMRT) has been recommended for node positive [N(+)] breast cancer patients; nevertheless, the beneficial effect of PMRT for treatment of node negative [N(−)] disease remains under discussion. Nowadays, the biology of breast cancer and the risk factors (RFs) for locoregional failure (LRF) must be included in the decision on whether or not to carry out PMRT. For these reasons, the present review aims to evaluate the rationale use of PMRT in N(−) patients and discuss which subgroups may further benefit from the treatment in present times where the decision must be personalised, according to the RFs of locoregional recurrence (LRR). To perform the analysis, we ponder that LRR of over 10% should be considered unacceptable due to the fact that LRRs generate great morbidity in patients. For this purpose, we consider that routine RT in these patients is not recommended, although there are subgroups of patients with high LRR, in which PMRT could be beneficial.

Locoregional therapy in breast cancer patients treated with neoadjuvant chemotherapy

Introduction: Neoadjuvant chemotherapy (NAC) is increasingly used preoperatively in breast cancer patients to achieve disease downstaging, reduce distant dissemination, and assess chemosensitivity. While NAC indications are expanding, knowledge of its impact on subsequent locoregional treatment with surgery and radiation therapy (RT) decisions is evolving. Radiation oncologists are often called upon to estimate locoregional recurrence (LRR) risks and provide recommendations for adjuvant RT to the breast/chest wall and regional lymph nodes postoperatively. In the non-NAC setting, adjuvant RT decisions are guided by the pathology findings after definitive surgery. In the NAC setting, decisions for or against adjuvant RT are complex, particularly in patients who achieve complete pathologic response (pCR).Areas covered: This review will examine contemporary data on NAC in patients with breast cancer and discuss its impact on surgical and RT decisions. We will also evaluate controversies in the role of LRRT for these patients, focussing on prognostic factors that include biological subtypes and pCR after NAC.Expert opinion: Advances in personalized medicine and diagnostic techniques have shifted paradigms and increased complexities in locoregional treatment decisions, particularly in the setting of NAC. Despite the challenges, our goals while we await prospective data remain focused on improving survival, minimizing toxicity, and optimizing function and cosmesis.

[Effect of postmastectomy radiotherapy on survival outcomes of patients with metaplastic breast cancer]

OBJECTIVE

To evaluate the effect of postmastectomy radiotherapy (PMRT) on the overall survival (OS) and breast cancer-specific survival (BCSS) of patients with metaplastic breast cancer (MpBC) in comparison with those of patients with invasive ductal breast carcinoma (IDC).

METHODS

We selected the patients with pathologically confirmed MpBC and IDC who either received PMRT or not from the archived cases (from January, 1998 to December, 2016) in the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database. In total, 31 982 patients were selected, including 308 patients with MpBC and PMRT, 629 with MpBC and PMRT, and 31 045 with IDC and PMRT. All the included patients were above 18 years of age without distant metastases or a second primary cancer and underwent radical surgery. Baseline characteristics of the patients were compared among the 3 subgroups, and multivariate Cox regression and Kaplan-Meier analyses were performed for analyzing the prognostic factors of MpBC, OS, and BCSS.

RESULTS

The majority (81.2%) of patients with MpBC were older than 50 years, had pathological grade III (68%), and were negative for ER (75.9%) and PR (79.8%) and in stage T2-3 (71.3%) and N0-1 (85.6%). Multivariate Cox regression analysis showed that age, T stage, N stage, PMRT, and chemotherapy were significantly associated with the prognosis of patients with MpBC (P < 0.05), while pathological grade, ER status, or PR status did not significantly affect the prognosis (P>0.05). Kaplan-Meier analysis showed that the patients with MpBC and PMRT had better OS (HR=1.394, 95% CI: 1.125-1.727; P < 0.05) and BCSS (HR=1.390, 95% CI: 1.074-1.800; P < 0.05) than those with MpBC who did not receive PMRT; but after PMRT, the patients with MpBC had worse OS (HR=1.626, 95%CI: 1.386-1.908; P < 0.001) and BCSS (HR=1.710, 95% CI: 1.418-2.062; P < 0.001) as compared with those with IDC.

CONCLUSION

MpBC has unique clinicopathological features. In patients with MpBC, age, T stage, N stage, radiotherapy and chemotherapy are all the prognostic factors affecting the survival outcomes, and PMRT can improve the OS and BCSS of the patients.

Effect of internal port on dose distribution in post-mastectomy radiotherapy for breast cancer patients after expander breast reconstruction

Background

In patients with expander-based reconstruction a few dosimetric analyses detected radiation therapy dose perturbation due to the internal port of an expander, potentially leading to toxicity or loss of local control. This study aimed at adding data on this field.

Materials and methods

A dosimetric analysis was conducted in 30 chest wall treatment planning without and with correction for port artifact. In plans with artifact correction density was overwritten as 1 g/cm³. Medium, minimum and maximum chest wall doses were compared in the two plans. Both plans, with and without correction, were compared on an anthropomorphic phantom with a tissue expander on the chest covered by a bolus simulating the skin. Ex vivo dosimetry was carried out on the phantom and in vivo dosimetry in three patients by using film strips during one treatment fraction. Estimated doses and measured film doses were compared.

Results

No significant differences emerged in the minimum, medium and maximum doses in the two plans, without and with correction for port artifacts. Ex vivo and in vivo analyses showed a good correspondence between detected and calculated doses without and with correction.

Conclusions

The port did not significantly affect dose distribution in patients who will receive post-mastectomy radiation therapy.