A robust treatment planning approach for chest motion in postmastectomy chest wall intensity modulated radiation therapy.

PURPOSE: Chest wall postmastectomy radiation therapy (PMRT) should consider the effects of chest wall respiratory motion. The purpose of this study is to evaluate the effectiveness of robustness planning intensity modulated radiation therapy (IMRT) for respiratory movement, considering respiratory motion as a setup error. MATERIAL AND METHODS: This study analyzed 20 patients who underwent PMRT (10 left and 10 right chest walls). The following three treatment plans were created for each case and compared. The treatment plans are a planning target volume (PTV) plan (PP) that covers the PTV within the body contour with the prescribed dose, a virtual bolus plan (VP) that sets a virtual bolus in contact with the body surface and prescribing the dose that includes the PTV outside the body contour, and a robust plan (RP) that considers respiratory movement as a setup uncertainty and performs robust optimization. The isocenter was shifted to reproduce the chest wall motion pattern and the doses were recalculated for comparison for each treatment plan. RESULT: No significant difference was found between the PP and the RP in terms of the tumor dose in the treatment plan. In contrast, VP had 3.5% higher PTV Dmax and 5.5% lower PTV V95% than RP (p < 0.001). The RP demonstrated significantly higher lung V20Gy and Dmean by 1.4% and 0.4 Gy, respectively, than the PP. The RP showed smaller changes in dose distribution affected by chest wall motion and significantly higher tumor dose coverage than the PP and VP. CONCLUSION: We revealed that the RP demonstrated comparable tumor doses to the PP in treatment planning and was robust for respiratory motion compared to both the PP and the VP. However, the organ at risk dose in the RP was slightly higher; therefore, its clinical use should be carefully considered.

Utilization and predictors of postmastectomy radiation receipt in an Oncology Center in Zimbabwe.

PURPOSE: Few sub-Saharan African studies have ascertained utilization for postmastectomy radiation (PMRT) for breast cancer, the second most common cancer among African women. We estimated PMRT utilization and identified predictors of PMRT receipt in Zimbabwe. METHODS: Retrospective patient cohort included non-metastatic breast cancer patients treated from 2014 to 2019. PMRT eligibility was assigned per NCCN guidelines. Patients receiving chemotherapy for non-metastatic disease were also included. The primary endpoint was receipt of PMRT, defined as chest wall with/without regional nodal radiation. Predictors of receiving PMRT were identified using logistic regression. Model performance was evaluated using the c statistic and Hosmer-Lemeshow test for goodness-of-fit. RESULTS: 201 women with localized disease and median follow-up of 11.4 months (IQR 3.3-17.9) were analyzed. PMRT was indicated in 177 women and utilized in 59(33.3%). Insurance coverage, clinical nodal involvement, higher grade, positive margins, and hormone therapy receipt were associated with higher odds of PMRT receipt. In adjusted models, no hormone therapy (aOR 0.12, 95% CI 0.043, 0.35) and missing grade (aOR 0.07, 95% CI 0.01, 0.38) were associated with lower odds of PMRT receipt. The resulting c statistic was 0.84, with Hosmer-Lemeshow p-value of 0.93 indicating good model fit. CONCLUSION: PMRT was utilized in 33% of those meeting NCCN criteria. Missing grade and no endocrine therapy receipt were associated with reduced likelihood of PMRT utilization. In addition to practice adjustments such as increasing hypofractionation and increasing patient access to standard oncologic testing at diagnosis could increase postmastectomy utilization.

Impact of clinical-pathological factors on locoregional recurrence in mastectomy patients with T1-2N1 breast cancer: who can omit adjuvant radiotherapy?

PURPOSE: Postmastectomy radiation therapy (PMRT) in T1-T2 tumors with 1-3 positive axillary lymph nodes (ALNs) is controversial. This study was to identify prognostic factors of locoregional control (LRC) following mastectomy with or without PMRT for patients with T1-2N1 breast cancer and to discuss the selection of patients who might omit PMRT. MATERIALS AND METHODS: Between January 2006 and December 2012, the data of 1474 postmastectomy patients staged pT1-2N1 were analyzed. PMRT was applied in 663 patients. LRC and disease-free survival (DFS) were calculated using the Kaplan-Meier method. Cox regression model was applied in the univariate and multivariate analyses to recognize the recurrence risk factors. RESULTS: With the median follow-up duration of 93 months (range, 5-168 months), 78 patients (5.3%) failed to secure LRC and 220 patients (14.9%) experienced any recurrence. The 7.7-year LRC and DFS was 94.9% and 85.4% respectively in the entire cohort. PMRT significantly improved 7.7-year LRC from 93.4% to 96.6% (p = 0.005), but not the DFS (p = 0.335). Multivariate analysis revealed that PMRT was an independent prognostic factor of LRC (p < 0.001), meanwhile, age ≤ 40 years (p = 0.012), histological grade 3 (p = 0.004), 2-3 positive nodes (p < 0.001) and tumor size of 3-5 cm (p = 0.045) were significantly associated with decreased LRC. The 7.7-year LRC for patients with 0, 1, and 2-4 risk factors was 97.7% / 98.9% (p = 0.233), 95.3% / 98.0% (p = 0.092), and 80.3% / 94.8% (p < 0.001) in the non-PMRT and PMRT group, respectively. CONCLUSIONS: In patients with T1-2N1 breast cancer, clinical-pathological factors including young age, histological grade 3, 2-3 positive nodes, and tumor size of 3-5 cm were identified to be predictors of a poorer LRC following mastectomy. Patients with 0-1 risk factor might consider the omission of PMRT.

A retrospective analysis on safety and effectiveness of hypofractioned post-mastectomy radiotherapy.

The data supporting hypofractionated post-mastectomy radiotherapy is limited. The purpose of this study is to present the experience from Tarnów of hypofractionated PMRT over 20 fractions with respect to toxicity and effectiveness. We delivered post-mastectomy radiotherapy at the dose of 45 Gy in 20 fractions to the chest wall and the draining regional lymph nodes. The primary outcome of interest was to ensure that the rate of grade 3 or greater toxicity from the hypofractionation, at any time point, was non-inferior to standard post-mastectomy radiotherapy. We conducted a retrospective analysis of 211 women with stages I-IV breast cancer. After a median follow-up of 30 months, there were four reported grade 3 toxicities, with grade 3 lymphedema being the most frequent (1.5%). There were 134 reported grade 2 toxicities, with grade 2 fatigue being the most frequent (18%). There were six instances of isolated locoregional (6 of 211; 2.8%). Three-year estimated local recurrence-free survival was 96.4% (95% CI 0.921-0.984). The 3-year estimated distant recurrence-free survival was 77.8% (95% CI 0.699-0.838). To our knowledge, the results presented here are the largest single institution experience of hypofractionated post-mastectomy radiotherapy published in the literature to date. Our fractionation scheme, 45 Gy in 20 fractions, seems to be safe and effective with low toxicity.

Single stage immediate breast reconstruction with acellular dermal matrix and implant: Defining the risks and outcomes of post-mastectomy radiotherapy.

INTRODUCTION: The objective of this study is to evaluate outcomes and complications in patients with single-stage ADM-implant based immediate breast reconstruction with and without radiotherapy (RT), highlighting the effects of RT on the reconstruction. MATERIALS AND METHODS: This prospective study recruited 91 consecutive patients who underwent skin-sparing, nipple-sparing or wise-pattern skin reduction mastectomy with direct-to-implant breast reconstruction with ADMs using sub-pectoral or pre-pectoral approach at the two breast units. Early and late complications like seroma, delayed wound healing, wound breakdown, infection, capsular contracture, implant loss and revision surgery were evaluated in the RT and non-RT groups. RESULTS: In the total cohort of 91 patients, 29 received adjuvant RT and 62 did not need RT. In the RT group, 3-7% of them had early complications like seroma, wound infections and delayed healing. 20.7% had post-RT capsular contractures which either required revision surgery with autologous flap (6.9%) or capsulotomy with exchange of implant (6.9%). In the non-RT group, 7-9% cases had seroma & wound infections, 3.06% had delayed wound healing and 7.25% had capsular contracture. 13.04% required revision surgery due to infection, implant loss or failure to achieve expectations. The total loss of implants in the cohort was 7.14% (RT group 6.9% and non-RT group 7.25%). The need for PMRT could have been predicted pre-operatively in the RT group in 55.17% cases based on the extent of disease, multifocality, tumour grade and positive LN status on imaging. CONCLUSION: ADM based reconstruction in patients anticipated to receive adjuvant RT is always debatable. Though there is no significant difference in the revision surgeries in our study of the 2 groups, the rate of capsular contracture as expected, was higher in the RT group. Hence, pre-operative discussion on the need for RT highlighting the risks and complications will help patients make a better-informed choice.

Post-mastectomy immediate breast reconstruction and adjuvant radiotherapy: long term results of a mono institutional experience.

INTRODUCTION: The aim of this paper is to investigate the outcome of patients treated with mastectomy, immediate breast reconstruction (IBR) and post-mastectomy radiotherapy (PMRT) and the risk of late complications. MATERIAL AND METHOD: All patients had post-mastectomy, immediate reconstructive surgical procedure by using autologous abdominal implant; tissue expander (TE)/permanent prosthesis (PP); or even combined procedures. Adjuvant external beam radiotherapy treatment (EBRT) was delivered to the reconstructed chest wall and supraclavicular nodes, for a total dose of 50 Gy in 25 fractions. The Kaplan-Meyer analysis evaluates patients' rate of late side effects, Overall Survival (OS), Progression Free survival (PFS), Local-regional free survival (LRFS) and Metastasis Free Survival (MFS). The univariate analysis investigates the correlation between late toxicity and related factors. RESULTS: Between November 2003 and October 2016, 91 breast cancer patients were treated with IBR and PMRT. Twenty-three (25.3%) patients experimented late toxicity. Overall, 16 (17.6%) patients experienced late complications which required a surgical approach. The 1- 2- 5- years late toxicity rates were 96.6%, 87.1% and 77.9%, respectively. The type of reconstruction was not statistically related with late toxicity rate (P = 0.35). The median follow-up period was 59 months (range 6-142 months). Median OS was not reached, the 1- 2- 5-years OS rates were 100%, 95.4% and 81% respectively. CONCLUSION: This study underlines that the type of reconstruction does not influence late toxicity rate. Moreover, IBR followed by adjuvant radiotherapy, has showed acceptable late toxicity profile and no influence on OS.

Evolution in practice patterns of axillary management following mastectomy in patients with 1-2 positive sentinel nodes.

PURPOSE: The optimal management of breast cancer patients with a positive sentinel lymph node (SLN) who undergo mastectomy remains controversial. This study aimed to describe treatment patterns of patients with positive SLNs who undergo mastectomy using a large population-based database. METHODS: The NCDB was queried for cT1-2N0 breast cancer patients treated with mastectomy between 2006 and 2014 who had 1-2 positive SLNs. Patients receiving neoadjuvant chemotherapy were excluded. Axillary management included SLN dissection (SLND) alone, axillary lymph node dissection (ALND), post-mastectomy radiation (PMRT) alone, and ALND + PMRT. Trends of axillary management and patient characteristics were examined. RESULTS: Among 12,190 patients who met study criteria, the use of ALND dropped with a corresponding increase in other approaches. In 2006, 34% of patients had SLND alone, 47% ALND, 8% PMRT and 11% ALND + PMRT. By 2014, 37% had SLND, 23% ALND, 27% PMRT and 13% ALND + PMRT. Patients who underwent SLND alone were older (mean 60.6 years) with more comorbidities (Charlson-Deyo score > 2), smaller primary tumors (mean 2.1 cm), well-differentiated histology, hormone receptor-positive, HER2-negative tumors, without lymphovascular invasion (all P values < 0.01). Treatment with SLND alone was more likely if patients had only one positive SLN (P < 0.001) or micrometastatic disease (P < 0.001), and were treated at community centers compared with academic centers (P < 0.001). CONCLUSIONS: The management of breast cancer patients undergoing mastectomy with positive SLNs has evolved over time with decreased use of ALND and increased use of radiation. Some patient subsets are underrepresented in recent clinical trials, and therefore, future trials should focus on these patients.

Radiotherapy after skin-sparing mastectomy with immediate breast reconstruction in intermediate-risk breast cancer : Indication and technical considerations.

BACKGROUND: Skin-sparing (SSME) and nipple-sparing mastectomy (NSME) were developed to improve the cosmetic results for breast cancer (BC) patients, both allowing for immediate breast reconstruction. Recommendations for post-mastectomy radiotherapy (PMRT) are primarily derived from trials where patients were treated by standard mastectomies. Due to their more conservative character, SSME and especially NSME potentially leave more glandular tissue at risk for subclinical disease. METHODS: Rates and sites of locoregional failures following SSME and NSME plus/minus reconstruction were analyzed regarding tumor stage and biological risk factors. In particular, the role of PMRT in "intermediate"-risk and early stage high-risk breast cancer patients was revisited. Implications on targeting and dose delivery of PMRT were critically reviewed. RESULTS: The value of PMRT in stage III BC remains undisputed. For node-negative BC patients, the majority of reports classify clinical and biological features such as tumor size, close surgical margins, premenopausal status, multicentricity, lymphangiosis, triple-negativity, HER2-overexpression, and poor tumor grading as associated with higher rates of locoregional relapse, thus, building an "intermediate" risk group. Surveys revealed that the majority of radiation oncologists use risk-adaptive models also considering the number of coinciding factors for the estimation of recurrence probability following SSME and NSME. Constellations with a 10-year locoregional recurrence risk of >10% are usually triggering the indication for PMRT. There was no common belief that the amount of residual tissue, e.g., tissue thickness over flaps, serves as additional decision aid. Modern treatment planning can ensure optimal dose distribution for PMRT in almost all patients with SSME. There are no reliable data supporting a reduction of the treatment volume from the CTV chest wall, e.g., to the nipple-areola complex, to the dorsal aspect behind the implant volume, the pectoralis muscle, nor the regional interpectoral, axillary, or complete regional lymph nodes only. The omission of a skin bolus in intermediate-risk BC does not compromise oncological safety. CONCLUSIONS: For intermediate-risk as well as early stage high-risk BC patients, the DEGRO Breast Cancer Expert Panel recommends the use of PMRT following SSME and NSME when a 10-year locoregional recurrence risk is likely to be greater than 10%, as estimated by clinical and biological risk factors. Subvolume-only radiation is discouraged outside of trials. The impact of adequate systemic treatment and the value of radiotherapy on optimal locoregional tumor control, with the goal of less than 5% LRR at 10-years follow-up, has to be verified in prospective trials.

Postmastectomy Radiation Therapy (PMRT) before and after 2-Stage Expander-Implant Breast Reconstruction: A Systematic Review.

Background: In those undergoing treatment for breast cancer, evidence has demonstrated a significant improvement in survival, and a reduction in the risk of local recurrence in patients who undergo postmastectomy radiation therapy (PMRT). There is uncertainty about the optimal timing of PMRT, whether it should be before or after tissue expander or permanent implant placement. This study aimed to summarize the data reported in the literature on the effect of the timing of PMRT, both preceding and following 2-stage expander-implant breast reconstruction (IBR), and to statistically analyze the impact of timing on infection rates and the need for explantation. Methods: A comprehensive systematic review of the literature was conducted using the PubMed/Medline, Ovid, and Cochrane databases without timeframe limitations. Articles included in the analysis were those reporting outcomes data of PMRT in IBR published from 2009 to 2017. Chi-square statistical analysis was performed to compare infection and explantation rates between the two subgroups at p < 0.05. Results: A total of 11 studies met the inclusion criteria for this study. These studies reported outcomes data for 1565 total 2-stage expander-IBR procedures, where PMRT was used (1145 before, and 420 after, implant placement). There was a statistically significant higher likelihood of infection following pre-implant placement PMRT (21.03%, p = 0.000079), compared to PMRT after implant placement (9.69%). There was no difference in the rate of explantation between pre-implant placement PMRT (12.93%) and postimplant placement PMRT (11.43%). Conclusion: This study suggests that patients receiving PMRT before implant placement in 2-stage expander-implant based reconstruction may have a higher risk of developing an infection.

Breast Reconstruction and Radiation Therapy.

PURPOSE: The optimal approach to the integration of postmastectomy reconstruction and radiation therapy is not well-established. This review will summarize current literature pertaining to the most common types of reconstruction in the setting of postmastectomy radiation therapy (PMRT). DATA SOURCES: Literature from PubMed was reviewed from 2000 to 2016. STUDY SELECTION: Studies were selected with relevance to "postmastectomy breast reconstruction," "breast reconstruction," and "breast reconstructive methods and PMRT." Surgical outcomes, patient satisfaction, and cost-effectiveness were examined. DATA EXTRACTION: Data from publications was extracted, summarized, and converted to a table. RESULTS OF DATA SYNTHESIS: Implant-based techniques are on the rise, in the setting of PMRT. Implant-based methods are more affordable in the short term and result in immediate breast-mound formation compared to autologous methods. When compared to implant-based reconstruction with PMRT, autologous reconstruction with PMRT results in better quality of life (QoL) and sensory recovery as well as fewer complications and failures. Among autologous flaps, deep inferior epigastric perforator flaps are considered superior to transverse rectus abdominal muscle (TRAM) pedicled flaps and may be more suitable for PMRT. Latissimus dorsi and muscle-sparing free TRAM flaps are also viable options. In delayed autologous, which may be advantageous for high-risk patients, the optimal timing to delay surgery after radiation therapy is unknown. Reconstruction with a 2-stage tissue expander-implant technique offers good to excellent cosmetic outcomes in the setting of PMRT, although there may be complications in this 2-stage process. CONCLUSION: Surgical, cosmetic, quality of life, and life expectancy must be taken into account when selecting the way to integrate breast reconstruction and PMRT.

Immediate tissue expander or implant-based breast reconstruction does not compromise the oncologic delivery of post-mastectomy radiotherapy (PMRT).

PURPOSE: Increasingly, women are choosing immediate breast reconstruction (IBR) following mastectomy. Reports have indicated IBR may compromise post-mastectomy radiotherapy (PMRT). We investigated the impact of IBR on timing of PMRT, target coverage, and doses to organs at risk in a modern radiotherapy practice using advanced planning techniques. METHODS: Between 2013 and 2015, PMRT was delivered to 116 patients (66 mastectomy alone, 50 IBR). PMRT was delivered with a median dose of 50 Gy in 25 fractions. Left-sided patients were treated in breath-hold under image guidance. Differences in dosimetric parameters and time to the initiation of PMRT were assessed between patients with and without reconstruction. RESULTS: Reconstructed patients were younger and had lower clinical stage disease. Reconstruction did not significantly increase the mean time to PMRT initiation (51 days reconstructed vs. 45 days non-reconstructed, p = 0.14) or the number of patients who initiated PMRT within 12 weeks of the last therapeutic intervention (48/50 [96.0] vs. 61/66 [92.4%], p = 0.41). There was no significant difference in the percentage of patients in whom the internal mammary lymph nodes (IMNs) were targeted (72 vs. 80%, p = 0.29) or in IMN target coverage (mean IMN V40.5 Gy 92.6 vs. 94.1%, p = 0.62). Reconstruction did not significantly affect the mean ipsilateral lung V20 (25.4 vs. 26.4%, p = 0.37) or the mean heart dose (2.2 vs. 2.1 Gy, p = 0.63). CONCLUSIONS: In a specialized breast multidisciplinary practice, immediate breast reconstruction did not significantly delay PMRT, compromise target coverage, or increase dose to organs at risk.

Postoperative Radiation Therapy after Nipple-Sparing or Skin-Sparing Mastectomy: A Survey of European, North American, and South American Practices.

Skin sparing mastectomy, a surgical procedure sparing a large portion of the overlying skin of the breast, and nipple-sparing mastectomy, sparing the whole nipple-areolar complex, are increasingly used, although their oncologic efficacy remains unclear. The aim of this study was to assess the radiation oncologists' opinions regarding the indications of radiation therapy (RT) after skin-sparing mastectomy and nipple-sparing mastectomy. Radiation oncology members of four national and international societies were invited to complete a questionnaire comprising of 22 questions to assess their opinions regarding RT indications in the context of skin-sparing and nipple-sparing mastectomy. A total of 298 radiation oncologists answered the questionnaire. 90.9% of respondents affirmed that breast cancer is one of their specializations. The majority declared that post-mastectomy RT is indicated for early-stage (stages I and II) breast cancer patients who present with risk factors for recurrence after skin-sparing or nipple-sparing mastectomy (87.2% and 80.2%, respectively). All suggested risk factors (tumor size, lymph node involvement, extracapsular extension, lymphovascular space invasion, positive surgical margins, triple negative tumor, multicentric tumor, and age) were considered as major elements (important or very important). There is no consensus regarding the necessity of evaluating residual breast tissue or the definition of residual breast tissue after mastectomy. All classic factors were considered as major elements, potentially influencing the decision to advice or not postoperative RT. Many uncertainties remain about the indications for RT after skin-sparing mastectomy or nipple-sparing mastectomy.

The impact of postmastectomy and regional nodal radiation after neoadjuvant chemotherapy for clinically lymph node-positive breast cancer: a National Cancer Database (NCDB) analysis.

BACKGROUND: Following neoadjuvant chemotherapy (NAC), the optimal strategies for postmastectomy radiotherapy (PMRT) and regional nodal irradiation (RNI) after breast-conserving surgery (BCS) are controversial. In this analysis, we evaluate the impact of these radiotherapy (RT) approaches for women with clinically node-positive breast cancer treated with NAC in the National Cancer Database (NCDB). PATIENTS AND METHODS: Women with cT1-3 cN1 M0 breast cancer treated with NAC were divided into four cohorts by surgery [Mastectomy (Mast) versus BCS] and post-chemotherapy pathologic nodal status (ypN0 versus ypN+). Overall survival (OS) was estimated using the Kaplan-Meier method and RT approaches were analyzed using the log-rank test, multivariate Cox models, and propensity score-matched analyses. RESULTS: From 2003 to 2011, 15 315 cases were identified including 3040 Mast-ypN0, 7243 Mast-ypN+, 2070 BCS-ypN0, and 2962 BCS-ypN+ patients. On univariate analysis, PMRT was associated with improved OS for both Mast-ypN0 (P = 0.019) and Mast-ypN+ (P < 0.001) patients. On multivariate analyses adjusted for factors including age, comorbidity score, cT stage, in-breast pathologic complete response, axillary surgery, ypN stage, estrogen receptor status and hormone therapy, PMRT remained independently associated with improved OS among Mast-ypN0 [hazard ratio (HR) = 0.729, 95% confidence interval (CI) 0.566-0.939, P = 0.015] and Mast-ypN+ patients (HR = 0.772, 95% CI 0.689-0.866, P < 0.001). No differences in OS were observed with the addition of RNI to breast RT for BCS-ypN0 or BCS-ypN+ patients. Propensity score-matched analyses demonstrated identical patterns of significance. On subset analysis, OS was improved with PMRT in each pathologic nodal subgroup (ypN0, ypN1, and ypN2-3) (all P < 0.05). CONCLUSIONS: In the largest reported analysis of RT for cN1 patients treated with NAC, PMRT was associated with improved OS for all pathologic nodal subgroups. No OS differences were observed with the addition of RNI to breast RT.

Assessment of Postmastectomy Radiation Therapy Receipt by Age and Association With Outcomes in Women With Breast Cancer.

PURPOSE: Postmastectomy radiation therapy (PMRT) reduces locoregional recurrence (LRR) and improves overall survival (OS) in patients with breast cancer. Young age has been recognized as a risk factor for LRR. The primary objective of this study was to determine if recommendations for PMRT differed among patients younger than 50 years as compared to women aged 50 years or older. METHODS: We reviewed medical records of patients with breast cancer who underwent mastectomy with or without PMRT from 2010 through 2018. Univariable and multivariable models were used to estimate the association of age with PMRT. RESULTS: Of 2471 patients, 839 (34%) were <50 years; 1632 (66%) were ≥50 years. Patients <50 years had a higher percentage of grade 3 tumors, hormone receptor (HR) negative and/or Her-2/neu positive tumors, clinical stage T2/T3 tumors, and nodal involvement. Compared with patients ≥50 years, patients <50 years were more likely to undergo PMRT (OR 1.57; P = .001) and regional node irradiation (RNI) to the internal mammary nodes. Advanced clinical and pathologic stage, invasive tumor histology, the presence of lymphovascular invasion, and treatment with systemic chemotherapy were predictors of PMRT receipt for patients <50 years (P < .05). PMRT was associated with improved OS and recurrence free survival (RFS) among all patients (P < .01). CONCLUSION: Patients <50 years were more likely to undergo PMRT and to receive RNI to the internal mammary nodes but were also more likely to have other risk factors for recurrence that would warrant a PMRT recommendation. PMRT improved OS and RFS for all patients.

Who can benefit from postmastectomy radiotherapy among HR+/HER2- T1-2 N1M0 breast cancer patients? An explainable machine learning mortality prediction based approach.

Objective: The necessity of postmastectomy radiotherapy(PMRT) for patients with HR+/HER2 T1-2 N1M0 breast cancer remains controversial. We want to use explainable machine learning to learn the feature importance of the patients and identify the subgroup of the patients who may benefit from the PMRT. Additionally, develop tools to provide guidance to the doctors. Methods: In this study, we trained and validated 2 machine learning survival models: deep learning neural network and Cox proportional hazard model. The training dataset consisted of 35,347 patients with HR+/HER2- T1-2 N1M0 breast cancer who received mastectomies from the SEER database from 2013 to 2018. The performance of survival models were assessed using a concordance index (c-index).Then we did subgroup analysis to identify the subgroup who could benefit from PMRT. We also analyzed the global feature importance for the model and individual feature importance for individual survival prediction. Finally, we developed a Cloud-based recommendation system for PMRT to visualize the survival curve of each treatment plan and deployed it on the Internet. Results: A total of 35,347 patients were included in this study. We identified that radiotherapy improved the OS in patients with tumor size >14mm and age older than 54: 5-year OS rates of 91.9 versus 87.2% (radio vs. nonradio, P <0.001) and cohort with tumor size >14mm and grade worse than well-differentiated, 5-year OS rates of 90.8 versus 82.3% (radio vs. nonradio, P <0.001).The deep learning network performed more stably and accurately in predicting patients survival than the random survival forest and Cox proportional hazard model on the internal test dataset (C-index=0.776 vs 0.641) and in the external validation(C-index=0.769 vs 0.650).Besides, the deep learning model identified several key factors that significantly influence patient survival, including tumor size, examined regional nodes, age at 45-49 years old and positive regional nodes (PRN). Conclusion: Patients with tumor size >14mm and age older than 54 and cohort with tumor size >14mm and grade worse than well-differentiated could benefit from the PMRT. The deep learning network performed more stably and accurately in predicting patients survival than Cox proportional hazard model on the internal test. Besides, tumor size, examined regional nodes, age at 45-49 years old and PRN are the most significant factors to the overall survival (OS).

Post-mastectomy radiation therapy after breast reconstruction: from historic dogmas to practical expert agreements based on a large literature review of surgical and radiation therapy considerations.

Breast reconstruction (BR) after mastectomy is important to consider for a woman's body image enhancement and psychological well-being. Although post-mastectomy radiation (PMRT) significantly improves the outcome of patients with high-risk breast cancer (BC), PMRT after BR may affect cosmetic outcomes and may compromise the original goal of improving quality of life (QoL). With the lack of practical guidelines, it seems essential to work on a consensus and provide some "expert agreements" to offer patients the best option for PMRT after BR. We report a global "expert agreement" that results from a critical review of the literature on BR and PMRT during the 6th international multidisciplinary breast conference in March 2023.

Randomized clinical trial of tissue equivalent bolus prescription in postmastectomy radiotherapy stratified by skin involvement status.

Purpose: To assess the impact and optimize the prescription of tissue-equivalent bolus in postmastectomy radiotherapy (PMRT), we compared the use of different bolus regimens tailored by skin involvement status. Methods: Patients with breast cancer who required PMRT were recruited (NCT01925651) and classified into two groups: standard-risk (SR, without skin involvement) and high-risk (HR, with skin involvement). SR was randomized between no bolus or 5 mm-bolus on alternate days and HR between 5 mm-bolus on alternate days or daily. Conventional fractionation (50.4 Gy; 1.8 Gy/daily) was used. Acute skin toxicity was evaluated blindly and the radiodermatitis-specific toxicity index [rads-TI] calculated. Subsequently, patients were followed up to assess oncologic outcomes, focusing on chest wall (CW) local control. Results: Fifty-eight patients were enrolled (34 SR and 24 HR). Baseline characteristics were similar between arms within the same risk group. Overall, maximal radiodermatitis rates were 29.4 % (G2) and 15.7 % (G3). In the SR group, no difference existed in G2 radiodermatitis incidence between the subgroups (p = 0.70) and no G3 events occurred. In the HR group, incidences of G2 (100 % vs 44.5 %, p = 0.01) and G3 radiodermatitis (70 % vs 11.1 %, p = 0.02) were higher with daily bolus. After adjusting for confounders, the daily bolus had a higher incidence of G2 (p = 0.03), G3 radiodermatitis (p = 0.04), and worse rads-TI (p < 0.01). After a median follow-up of 6.2 years, the 5-year local control was 95.8 % (95 %CI: 88.2 %-100 %) in the SR and 91.7 % (95 %CI: 77.3 %-100 %) in the HR groups. Per risk group, there was no difference in local control between the SR (p = 0.90) or the HR bolus regimens (p = 0.70). Conclusion: Daily 5 mm bolus prescription significantly increased the overall toxicity burden. In this preliminary study, within the same risk group, no detriment in CW local control was detected with less intense bolus regimens (SR: no bolus; HR: alternate-days bolus). Additionally, the rads-TI was able to distinguish overall radiodermatitis burden.

Performance evaluation of buildup bolus during external radiotherapy of mastectomy patients: treatment planning and film dosimetry.

A buildup bolus is used during the post-mastectomy radiotherapy (PMRT) to overcome under-dosage issues in the chest wall. The current study is aimed at evaluating the performance of a bolus in dose enhancement through both film dosimetry and treatment planning approaches. Twenty patients were enrolled in current research. The received dose by the skin at the lateral and medial regions of the chest wall in the presence and absence bolus was evaluated. Film dosimetry results showed that the presence of the bolus can averagely increase the skin dose by about 80% (P value < 0.001) and 92% (P value < 0.001) in lateral and medial regions, respectively. No significant difference was observed between the measured and treatment planning system (TPS)-calculated dose values in the presence of bolus. The presence of the bolus can considerably increase the absorbed dose by superficial chest wall regions. The TPS shows a favorable performance in superficial dose calculations in the presence of the buildup bolus. Hosseini et al.: demonstration of implemented research in the current study.

Radiation and free flaps: what is the optimal timing?

The debate over when to perform flaps in patients undergoing radiation remains an ongoing dilemma without definitive resolution. Classically, reconstructive surgeons recommended avoiding exposure of autologous flaps to radiotherapy due to concerns over surgical complications and poor aesthetic outcomes. However, delayed reconstruction carries its own risk profile and aesthetic limitations, given the irreversible changes to the breast envelope. Immediate reconstruction not only confers psychosocial benefits but allows for preservation of the native breast skin and footprint. In recent years, a growing body of evidence suggests that with modern radiation techniques, long-term outcomes of immediate vs. delayed autologous reconstruction may be more similar than previously thought. This review examines the advantages and disadvantages of each treatment algorithm and critically evaluates the existing literature on autologous breast reconstruction in the setting of post-mastectomy radiotherapy. Importantly, radiation regimens have varied widely over time and between institutions, introducing significant heterogeneity in published outcomes of flap contracture or fat necrosis after immediate reconstruction. While delayed autologous reconstruction remains a reasonable pathway, the benefits of immediate reconstruction should not be dismissed. Our findings ultimately corroborate the view that immediate flap reconstruction is a sound treatment option that can be safely offered to patients. The decision regarding which pathway to pursue should ultimately be patient-centric and driven by multidisciplinary consensus, rather than by prior dogma.

Dosimetric characterization of single- and dual-port temporary tissue expanders for postmastectomy radiotherapy using Monte Carlo methods.

Purpose: The aim of this work was two-fold: a) to assess two treatment planning strategies for accounting CT artifacts introduced by temporary tissue-expanders (TTEs); b) to evaluate the dosimetric impact of two commercially available and one novel TTE. Methods: The CT artifacts were managed using two strategies. 1) Identifying the metal in the RayStation treatment planning software (TPS) using image window-level adjustments, delineate a contour enclosing the artifact, and setting the density of the surrounding voxels to unity (RS1). 2) Registering a geometry template with dimensions and materials from the TTEs (RS2). Both strategies were compared for DermaSpan, AlloX2, and AlloX2-Pro TTEs using Collapsed Cone Convolution (CCC) in RayStation TPS, Monte Carlo simulations (MC) using TOPAS, and film measurements. Wax slab phantoms with metallic ports and breast phantoms with TTEs balloons were made and irradiated with a 6 MV AP beam and partial arc, respectively. Dose values along the AP direction calculated with CCC (RS2) and TOPAS (RS1 and RS2) were compared with film measurements. The impact in dose distributions was evaluated with RS2 by comparing TOPAS simulations with and without the metal port. Results: For the wax slab phantoms, the dose differences between RS1 and RS2 were 0.5% for DermaSpan and AlloX2 but 3% for AlloX2-Pro. From TOPAS simulations of RS2, the impact in dose distributions caused by the magnet attenuation was (6.4 ± 0.4) %, (4.9 ± 0.7)%, and (2.0 ± 0.9)% for DermaSpan, AlloX2, and AlloX2-Pro, respectively. With breast phantoms, maximum differences in DVH parameters between RS1 and RS2 were as follows. For AlloX2 at the posterior region: (2.1 ± 1.0)%, (1.9 ± 1.0)% and (1.4 ± 1.0)% for D1, D10, and average dose, respectively. For AlloX2-Pro at the anterior region (-1.0 ± 1.0)%, (-0.6 ± 1.0)% and (-0.6 ± 1.0)% for D1, D10 and average dose, respectively. The impact in D10 caused by the magnet was at most (5.5 ± 1.0)% and (-0.8 ± 1.0)% for AlloX2 and AlloX2-Pro, respectively. Conclusion: Two strategies for accounting for CT artifacts from three breast TTEs were assessed using CCC, MC, and film measurements. This study showed that the highest differences with respect to measurements occurred with RS1 and can be mitigated if a template with the actual port geometry and materials is used.