Postmastectomy Radiation Research Articles

The Impact of Timing of Delayed Autologous Breast Reconstruction following Postmastectomy Radiation Therapy on Postoperative Morbidity.

The ideal time to perform reconstruction after the completion of postmastectomy radiation therapy (PMRT) in patients with locally advanced breast cancer is currently unknown. We evaluate the association between the timing of delayed autologous breast reconstruction following PMRT and postoperative complications. Patients who underwent mastectomy, PMRT, and then delayed autologous breast reconstruction from 2009 to 2016 were identified from the Truven Health MarketScan Research Databases. Timing of reconstruction following PMRT was grouped 0-3, 3-6, 6-12, 12-24, and after 24 months. Multivariable models were used to assess associations between timing of reconstruction following PMRT and key measures of morbidity. A total of 1,039 patients met inclusion criteria. The rate of any complications for the analytic cohort was 39.4%, including 13.3% of patients who experienced wound complications and 11.3% of patients requiring additional flaps. Unadjusted rates of complications increased from 23.4% between 0 and 3 months to 49.4% between 3 and 6 months and decreased thereafter. Need for additional flaps was highest within 3 to 6 months (14.0%). Multivariate analysis revealed higher rates of any complications when reconstruction was performed between 3 and 6 months (odds ratio [OR]: 3.04, p < 0.001), 6 and 12 months (OR: 2.66, p < 0.001), or 12 and 24 months (OR: 2.13, p = 0.001) after PMRT. No difference in complications were noted in reconstructions performed after 24 months compared with those performed before 3 months (p > 0.05). However, rates of wound complications were least likely in reconstructions after 24 months (OR: 0.34, p = 0.035). These findings suggest plastic surgeons may consider performing autologous breast reconstruction early for select patients, before 3 months following PMRT without increasing postoperative morbidity.

Post-Mastectomy Implant Complications in the Hispanic Breast Cancer Patient Population.

The purpose was to analyze the impact of post-mastectomy radiation therapy (PMRT) on implant-based breast reconstruction (IBR) in self-identified Hispanic patients compared to non-Hispanic counterparts. We retrospectively reviewed patients who underwent IBR between January 1, 2017 and December 31, 2019 at a single hospital system. Patients were cisgender women, assigned female at birth, 18 years or older, and underwent mastectomy with immediate IBR +/- PMRT. We compared characteristics between Hispanic and non-Hispanic patients, assessing capsular contracture and implant loss rates. Multivariable analysis was performed to identify factors associated with complications. A total of 317 patients underwent mastectomy and reconstruction. Of these patients, 302 underwent a total of 467 mastectomies with IBR, and these 467 procedures were included in the analysis of complications. Complications occurred in 175 breasts (37.5%), regardless of PMRT. Seventy-two of the 302 patients (24%) received PMRT to one breast. The overall rates of capsular contracture, implant loss, and overall complications did not vary significantly between Hispanic and non-Hispanic patients (p=0.866, 0.974, and 0.761, respectively). When comparing only irradiated patients, there was a trend towards increased implant loss and overall complication rates in Hispanic versus non-Hispanic patients (p=0.107 and 0.113, respectively). Following PMRT the rate of any complication was 71% in Hispanic women and 53% in non-Hispanic women. Our study illuminates a trend towards higher complication rates after PMRT in Hispanic versus non-Hispanic patients. Further studies are needed to understand why Hispanic patients may have more side effects from radiation therapy.

52P A comparative study to assess volumetric and dosimetric profile of heart and lung in patients undergoing left sided post mastectomy radiotherapy: Continuous positive airway pressure (CPAP) versus free breathing (FB) techniques

52P A comparative study to assess volumetric and dosimetric profile of heart and lung in patients undergoing left sided post mastectomy radiotherapy: Continuous positive airway pressure (CPAP) versus free breathing (FB) techniques

De-escalated radiotherapy for HER2-overexpressing breast cancer patients with 1-3 positive lymph nodes undergoing anti-HER2 targeted therapy.

In the era of anti-HER2 targeted therapy, the potential clinical feasibility of considering HER2-overexpressing breast cancer cases presenting with 1-3 positive axillary lymph nodes as low-risk, and thereby contemplating postoperative radiotherapy reduction, remains an important subject for in-depth examination. The aim of this retrospective study was to evaluate the effectiveness of de-escalated radiotherapy in T1-2N1M0 HER2-overexpressing breast cancer patients receiving anti-HER2 targeted therapy. Specifically, omitting regional lymph node irradiation (RNI) after breast-conserving surgery and only performing whole-breast irradiation or omitting postmastectomy radiation therapy. A retrospective analysis was conducted on 429 patients with stage T1-2N1M0 primary invasive HER2-overexpressing breast cancer from our center between 2004 and 2018. Patients who received anti-HER2 targeted therapy were divided into an RNI group and a no RNI group to assess the role of RNI. The prognostic role of RNI was investigated via the Kaplan-Meier method and Cox proportional hazards modeling. The median follow-up time was 46.8 months (range 7.1-225.8 months). In the anti-HER2 targeted therapy group RNI yielded no significant improvements in invasive disease-free survival (IDFS) (p = 0.940), local-regional recurrence-free survival (p = 0.380), distant metastases-free survival (p = 0.698), or overall survival (p = 0.403). Estrogen receptor (ER) status (hazard ratio [HR] 0.105, 95% confidence interval [CI] 0.023-0.749, p = 0.004) and lymph vascular invasion status (LVI) (HR 5.721, 95% CI 1.586-20.633, p = 0.008) were identified as independent prognostic factors for IDFS, and ER-positive and LVI-negative patients exhibited better prognoses. Omitting RNI may be a safe option in T1-2N1 HER2-overexpressing breast cancer patients receiving standardized anti-HER2 targeted therapy; particularly in ER-positive or LVI-negative subgroups.

Impact of Varying Chest Wall Target Volume Delineation on Postmastectomy Radiation Therapy Outcomes in Breast Cancer Patients with Implant-Based Reconstruction

Background: The target volume for post-mastectomy radiation therapy (PMRT) in breast cancer patients with reconstruction has been a subject of debate. Traditionally, the RT chest wall (CW) volume encompasses the entire implant. For patients with retropectoral implants, the deep lymphatic plexus dorsal part of the implant is no longer considered high risk and can be omitted. This study aimed to assess the radiation dose distribution and treatment outcomes associated with different CW delineation according to ESTRO ACROP guideline for patients who have undergone implant-based reconstruction. Methods: We conducted a retrospective review of breast cancer patients who underwent a mastectomy followed by two-stage implant-based breast reconstruction and adjuvant radiation therapy (RT) between 2007 and 2022. The expanders/implants were positioned retropectorally. The chest wall target volumes were categorized into two groups: the prepectoral group, which excluded the deep lymphatic plexus, and the whole expander group. Results: The study included 26 patients, with 15 in the prepectoral group and 11 in the whole expander group. No significant differences were observed in normal organ exposure between the two groups. There was a trend toward a lower ipsilateral lung mean dose in the prepectoral group (10.2 vs. 11.1 Gy, p = 0.06). Both groups exhibited limited instances of reconstruction failure and local recurrence. Conclusions: For patients undergoing two-stage expander/implant retropectoral breast reconstruction and PMRT, our data provided comparable outcomes and normal organ exposure for those omitting the deep lymphatic plexus.

Effect of radiation therapy during surgery on postoperative wound complications after breast reconstruction in patients with breast cancer: A meta-analysis.

Breast remodelling is a major therapeutic choice in radical mastectomy. Breast reconstruction is regarded as a promising option for the treatment of breast cancer. The purpose of this meta-analysis was to investigate the effect of Post mastectomy radiotherapy (PMRT) on postoperative wound complications in breast carcinoma. A comprehensive review of documents was conducted between the date of establishment and the 28th of August 2023. In all of the trials, patients were treated with breast cancer. The researchers chose 11 publications out of 8068 related studies. Two researchers examined these publications to satisfy the inclusion criteria. Among the 516 patients who had received radiation therapy in the course of the operation, 1772 had not received radiation therapy. The impact of radiation therapy and non-radiation therapy in breast cancer patients after breast reconstruction was reported in 8 studies, and the incidence of postoperative wound infection in non-radiation group was significantly lower (OR, 1.95; 95% CI, 1.26-3.02 p = 0.003). In nine studies, There is not considered to have achieved statistical significance between radiation therapy and non-radiation treatment for post-operation wound dehiscence in breast cancer patients who had received chemotherapy (OR, 1.61; 95% CI, 0.70-3.72 p = 0.27). The results of six trials demonstrated that radiation therapy and non-radiation therapy had no statistical significance on post-operation haemorrhage in breast cancer patients (OR, 1.02; 95% CI, 0.42-2.47 p = 0.96). The results of 7 trials demonstrated that radiation therapy and non-radiation therapy had no significant impact on the post-operation of skin necrosis (OR, 1.22; 95% CI, 0.66-2.28 p = 0.53). Two trials demonstrated that those without radiation therapy were less likely than those who received radiation therapy in skin contracture in patients (OR, 7.24; 95% CI, 1.80-29.10 p = 0.005). Regarding the incidence of wound infection and cutaneous contraction was higher in the radiation group.

Breast Reconstruction Complications After Postmastectomy Proton Radiation Therapy for Breast Cancer

Our purpose was to report complications requiring surgical intervention among patients treated with postmastectomy proton radiation therapy (PMPRT) for breast cancer in the setting of breast reconstruction (BR). Patients enrolled on a prospective proton registry who underwent BR with immediate autologous flap, tissue expander (TE), or implant in place during PMPRT (50/50.4 Gy +/- chest wall boost) were eligible. Major reconstruction complication (MRC) was defined as a complication requiring surgical intervention. Absolute reconstruction failure was an MRC requiring surgical removal of BR. A routine revision (RR) was a plastic surgery refining cosmesis of the BR. Kaplan-Meier method was used to assess disease outcomes and MRC. Cox regression was used to assess predictors of MRC. Seventy-three courses of PMPRT were delivered to 68 women with BR between 2013 and 2021. Median follow-up was 42.1 months. Median age was 47 years. Fifty-six (76.7%) courses used pencil beam scanning PMPRT. Of 73 BR, 29 were flaps (39.7%), 30 implants (41.1%), and 14 TE (19.2%) at time of irradiation. There were 20 (27.4%) RR. There were 9 (12.3%) MRC among 5 implants, 2 flaps, and 2 TE, occurring a median of 29 months from PMPRT start. Three-year freedom from MRC was 86.9%. Three (4.1%) of the MRC were absolute reconstruction failure. Complications leading to MRC included capsular contracture in 5, fat necrosis in 2, and infection in 2. On univariable analysis, BR type, boost, proton technique, age, and smoking status were not associated with MRC, whereas higher body mass index trended toward significance (hazard ratio, 1.07; 95% CI, 0.99-1.16; P = .10). Patients undergoing PMPRT to BR had a 12.3% incidence of major complications leading to surgical intervention, and total loss of BR was rare. MRC rates were similar among reconstruction types. Minor surgery for RR is common in our practice.

Patient-Reported and Toxicity Results from the FABREC Study: A Multicenter Randomized Trial of Hypofractionated vs. Conventionally-Fractionated Postmastectomy Radiation Therapy after Implant-Based Reconstruction

Patient-Reported and Toxicity Results from the FABREC Study: A Multicenter Randomized Trial of Hypofractionated vs. Conventionally-Fractionated Postmastectomy Radiation Therapy after Implant-Based Reconstruction

The trade-off of post-mastectomy radiotherapy usage for the breast cancer patients aged 70 years or older: a study based on SEER database

BackgroundThis study aimed to investigate the role of post-mastectomy radiotherapy (PMRT) in the female aged 70 years or older diagnosed with breast cancer, which is still controversial.MethodsThis retrospective study enrolled female breast cancer women aged 70 + years following mastectomy from the Surveillance, Epidemiology, and End Results (SEER) database. Propensity score matching (PSM) was performed to reduce covariable imbalance. A nomogram was created to predict the 1,3,5-years overall survival (OS) and divide patients into three risk groups.ResultsAfter matching, PMRT were associated with significant improvement in breast cancer-specific survival (BCSS) and OS (p < 0.001). By contrast, the BCSS and OS benefit from PMRT were not significant in patients with T1N1 tumor (BCSS: HR = 0.716, p = 0.249;OS:HR = 0.908, p = 0.572), and T2N1 tumor (BCSS:HR = 0.866, p = 0.289;OS:HR = 0.879, p = 0.166). Stratified by subtype, the HR+/HER-2- subtype and the HR-/HER-2- subtype (all p < 0.001) have a significant prolonged survival, yet not significant BCSS difference are shown in the HER-2 + tumor. In the low-risk group as determined by the nomogram, the use of PMRT did not significantly improve OS (p = 0.203).ConclusionsThis study demonstrated that PMRT improves the survival of females with elderly breast cancer, while for T1-2N1 breast cancer patients, the omission of PMRT could be considered. Furthermore, the nomogram we constructed could be used as a decision tool for the omission of PMRT in low-risk elderly patients.

Patient-reported health-related quality of life outcomes following mastectomy for breast cancer, with immediate, delayed or no breast reconstruction: Four-year follow-up from a prospective cohort study.

Breast reconstruction (BR) improves women's health-related quality of life (HRQOL) following mastectomy for breast cancer, yet factors contributing to improved HRQOL remain unclear. This study aimed to explore the overall impact of mastectomy with or without BR on participants' perceptions of HRQOL over time in a cohort of women with high-risk breast cancer; to examine differences in mean HRQOL scores between immediate BR, delayed BR and no BR groups; to assess the influence of patient characteristics potentially associated with HRQOL scores; and to determine the feasibility of long-term collection of patient-reported outcome measures in clinical settings. A prospective, longitudinal study of 100 women with high-risk breast cancer who underwent mastectomy with or without breast reconstruction and were likely to require post-mastectomy radiotherapy. Four validated patient-reported questionnaires, comprising 21 outcome measures relating to HRQOL, administered at baseline and up to 4 years post-mastectomy. Demographic, clinical and surgical data extracted from patient medical records. Consistently significant declines in perceptions of future health and arm symptoms, consistently significant improvements in treatment side effects, breast symptoms and fatigue, as well as significant improvements, compared to baseline, in social functioning and financial difficulties at 48 months. No significant differences in mean HRQOL scores between women given a choice of reconstructive options. Similar trajectories of HRQOL scores were found in women with high-risk breast cancer who were offered a choice of BR. Informed choice may be an independent contributing factor in long-term maintenance of most HRQOL indicators at their pre-mastectomy levels.

Post Mastectomy Radiation Therapy Impact on Clinical Outcomes of Male Breast Cancer: A Meta-Analysis of Comparative Studies

Male breast cancer accounts for less than 1 percent of all cancer diagnoses in men. Because it is rare, it does not lend itself to large, randomized trials. In general, the approach to the treatment of early, non-metastatic male breast cancer has largely been extrapolated from female breast cancer trials though it is deemed to be a different disease. Data on early-stage post mastectomy radiation therapy (PMRT) is limited, and its benefits remain unclear. We conducted this meta-analysis to determine the impact of PMRT on recurrence patterns and survival outcomes using the available male breast cancer data. A review of the medical literature was conducted using online databases. Inclusion criteria consisted of English language, diagnosis of invasive non-metastatic male breast cancer (MBC), comparative studies of PMRT versus none, and studies that reported the incidence of local and distant recurrences as well as survival data in the compared arms. A meta-analysis using the Mantel-Haenszel method for calculating the weighted pooled relative risk (RR) under the fixed effects model was conducted. Subsequently, the heterogeneity statistic was incorporated to calculate the summary RR under the random effects model. Ten retrospective comparative studies with 3912 patients were included and analyzed. Eight studies reported survival data. Six and three studies reported local and distant recurrence incidence, respectively. PMRT did not have an impact on overall survival or distant recurrences. However, PMRT significantly lowered the RR of locoregional recurrences (RR = 0.53, 95% CI 0.31-0.92). In addition, when survival was analyzed by TNM stage and N status, PMRT was found to have a significant reduction in RR of death in stage III (RR = 0.85, 95% CI 0.75-0.97), N1 (RR = 0.77, 95% CI 0.61-0.98), and N2 (RR = 0.61, 95% CI 0.49-0.78) disease. This is the first meta-analysis to show that PMRT is associated with a lower relative risk of death in stage III MBC as well as N1 and N2 disease. It also demonstrates a significant reduction in RR of locoregional recurrences. In the absence of randomized clinical trials, it represents the most compelling data supporting the use of PMRT in this MBC patient population using MBC data.

Postmastectomy Radiation in HER-2 Positive Breast Cancer after Neoadjuvant Therapy: Secondary Analysis of Two Randomized Trials

The role of postmastectomy radiation therapy (PMRT) following primary systemic therapy (PST) in HER-2 positive breast cancer (Her2+BC) remains poorly understood. The current study evaluates PMRT based on the pathological response to PST in Her2+BC. TRYPHAENA and NeoSphere are randomized phase II trials that investigated PST for Her2+BC. Our study is a pooled analysis of both trials, including 312 node-positive patients treated with HER-2 targeted PST followed by mastectomy with or without PMRT. The primary endpoint is loco-regional recurrence-free survival (LRRFS). Our analysis included 172 (55%) patients who achieved nodal pCR and 140 (45%) patients who did not. Patients with nodal pCR had a 5-year LRRFS of 97% with PMRT delivered in 98 patients (57%). Patients without nodal pCR had a 5-year LRRFS of 87% with PMRT delivered in 93 patients (66%). Patients with ypN1 (n = 62) disease who received PMRT (n = 40) had a 5-year LRRFS of 85% as compared to 89% in those who did not (n = 22); (p = 0.60). A significant LRRFS difference was noted in patients with ypN2-3 (n = 78) disease who received PMRT (n = 53) compared to those who did not (n = 25) (5-year LRRFS 92% vs. 75%; p = 0.019). On multivariate analysis, clinical nodal disease at diagnosis and nodal pCR were significantly associated with loco-regional recurrence (LRR). Her2+BC patients who achieve nodal pCR after PST have excellent loco-regional control which supports de-escalation of PMRT.

Recurrence Risk Score Model for Evaluating the Impact of Postmastectomy Radiotherapy in Breast Cancer Patients with Pathologic Nodal Negative after Neoadjuvant Chemotherapy and Mastectomy

Recurrence risk score model was established to distinguish the recurrent risk of patients with pathologic nodal negative (ypN0) after neoadjuvant chemotherapy (NACT) and mastectomy and determine the impact of postmastectomy radiotherapy (PMRT). This multicenter retrospective study reviewed 766 patients who underwent mastectomy and NACT with ypN0 from 2000 to 2014. Recurrent risk score model was assigned proportionally to the relative contribution of independent prognostic factors in the multivariate Cox model of disease-free survival (DFS). Decision tree analysis was conducted to determine two optimal cutoff points for stratification. The median follow-up time was 74 months. The 5-year locoregional control (LRC), DFS, and overall survival (OS) rates for the entire group were 96.5%, 89.1% and 95.3%, respectively. 353 (46.1%) patients received PMRT and 413 (53.9%) patients did not. Patients with PMRT have more high-risk factors, including age <40 years, clinical stage III, grade III, or ER and PR negative. Chest wall and regional nodal region were irradiated in 307 (87.0%) and chest wall only in 46 (13.0%). The median radiation dose was 50 Gy (range: 36-60 Gy) in 25 fractions (range: 15-30 fractions). There were no significant differences between the PMRT and No-PMRT groups in the LRC, DFS and OS rates. Recurrent risk score model consisted of five factors and used a range of zero to eleven scoring points: age <40 years and clinical N1 stage for one point; clinical N2, NACT ≥4 cycles, lymphovascular invasion and ypT1-2 for two points; ypT3-4 for four points. 456 (59.5%) patients scoring zero to four points, 188 (24.5%) scoring five points and 122 (15.9%) scoring six to eleven points were assigned to the low-, intermediate-, and high-risk group. LRC, DFS and OS rates in three risk groups were significantly distinct from each other (5yr-LRC: 98.6% vs. 95.5% vs. 89.8%, p < .001; 5yr-DFS: 94.4% vs. 87.4% vs. 71.5%, p < .001; 5yr-OS: 97.6% vs. 93.2% vs. 90.0%, p < .001). PMRT had no impact on the LRC, DFS and OS rates in either low-, intermediate-, or high-risk group. The recurrence risk score model can effectively distinguish patients with different recurrent risk stratification. PMRT in patients with ypN0 after NAC and mastectomy cannot improve LRC, DFS or OS. Table 1. Survival outcomes and comparison between PMRT and No-PMRT arms in different groups.

A Population-Based Assessment of Long-Term Sexual Well-Being and Patient Satisfaction after Breast Reconstruction and Post-Mastectomy Radiation

In 2016, more than 40% of women who underwent mastectomy for breast cancer went on to have breast reconstruction, but there is little data regarding long-term cosmetic outcomes past 5 years after post-mastectomy radiation (PMRT) and reconstruction. This study aims to evaluate the difference in patient breast satisfaction and sexual well-being over time by receipt of reconstruction and PMRT. The iCanCare study is a population-based, longitudinal study of women diagnosed with breast cancer in 2014-15 identified in the Los Angeles and Georgia SEER registries. Women were surveyed during initial treatment and again approximately 6 years later in survivorship (2021-2022). Participants were asked about their "Sexual well-being after mastectomy" and "Satisfaction with breasts" using the Breast-Q, which was dichotomized into "high" and "low" scores (using the median), with a high score indicating increased satisfaction. We then evaluated whether satisfaction differed by treatment characteristics, using unadjusted odds ratios (OR) for categorical variables, calculated using the Chi-square test, or the Kruskal-Wallis test for continuous variables. Adjusted odds ratios were found using multivariable logistic regression models adjusting for treatment characteristics, diagnosis, age, BMI, education, and breast cancer stage. In this preliminary sample of 1191 respondents, 445 underwent mastectomy, of which 272 (61.12%) had reconstruction, and 65 (14.61%) had PMRT. Having breast reconstruction was associated with higher long-term sexual well-being (median score 36.30 vs. 22.20, OR 1.69, 95% confidence interval [CI] 1.09 - 2.64) and breast satisfaction scores (OR 1.53, 95% CI 1.01 - 2.33) compared to not having reconstruction. However, this improvement in sexual well-being was attenuated in women who additionally had PMRT (OR 0.83, CI 0.271 - 2.51). In women who did not have reconstruction after mastectomy, there was no statistically significant difference in sexual well-being scores regardless of the use of PMRT (OR 0.68, CI 0.39 - 1.22). Among respondents in adjusted models who did not receive PMRT, those with reconstruction had higher sexual well-being scores than those with without reconstruction (aOR 2.47, CI 1.34 - 4.56), though there was no statistically significant difference in breast satisfaction scores (p = 0.16) among the groups. Sexual well-being and breast satisfaction are improved with reconstruction 6 years after mastectomy for breast cancer. However, these improvements were attenuated for women who received PMRT. To our knowledge, this is the first study to look at long term outcomes of sexual well-being and treatment satisfaction after breast reconstruction for patients who underwent mastectomy for breast cancer. These data suggest that continued work should be done to optimize patient outcomes when combining PMRT and breast reconstruction.

Comparison between Pre-Pectoral and Post-Pectoral Implant Reconstruction and Different Radiation Modalities on Breast Reconstruction Complications

Single Stage direct to implant (DTI) is a rising reconstruction approach. It has been speculated that prepectoral implant placement reduces reconstruction complications as well as using newer postmastectomy radiation (PMRT) modalities as protons. Largest series in this topic included 350 DTI patients with less than 30 patients receiving PMRT. We reviewed the charts of 2,187 patients (pts) who underwent mastectomy and reconstruction at our institution between 2000 and 2020. Pts only receiving DTI with and without PMRT were included. PMRT was delivered either with 3D conformal photon +/- chest wall electron boost (CWB) or proton therapy mainly with pencil beam scanning. All pts received conventional fractionation (50-50.4 Gy in 25-28 fractions). Patients on active protons clinical trials were excluded. Primary endpoints were reconstruction complications defined as infection/necrosis (I/N) requiring debridement; capsular contracture (CC) requiring capsulotomy and overall reconstruction failure (ORF: removal of permanent implant for any complication with and without salvage reconstruction). Subgroup analysis for pts receiving PMRT was done to explore impact of proton and photons on complications. Logistic and cox regression were used. Eight hundred nine pts received DTI, with an overall median follow-up of 6.2 years. Among the entire cohort, 78/809 (9.7%) had prepectoral implants while the rest had subpectoral implants with and without alloderm support. Of the entire cohort 391/809 (48.5%) received PMRT, among those 43/391 (11%) received protons. The 5 years cumulative incidence of CC was 8.5% and 6.6% among prepectoral vs subpectoral implants (HR = 1.2, p = 0.7). The 5 years cumulative incidence of ORF was 32.2% and 28.2% among prepectoral vs subpectoral implants (HR 1.1, p = 0.6). For pts receiving PMRT, the 5 years cumulative incidence of CC were 26.0% and 8.6% among protons vs photons (HR 3.7, p < 0.0005). The 5 years cumulative incidence of ORF were 38.2% and 30.1% among protons vs photons (HR 1.4, p = 0.2). Multivariable logistic regression analysis accounting for BMI, smoking history, diabetes, and PMRT showed no significant difference between prepectoral implants versus subpectoral coverage for CC (OR = 0.7, p = 0.5), and for ORF (OR = 0.9, p = 0.8). Subgroup multivariable analysis for those receiving PMRT only showed protons compared to photons significantly increased the risk of CC (OR = 5.3, p < 0.0001) and ORF (OR = 2.1, p = 0.03). No significant difference in I/N was noted between photons and protons or between prepectoral and subpectoral pts. For breast cancer patients receiving single stage direct to implant reconstruction with and without PMRT, prepectoral implant placement did not reduce the risk of complications. Proton therapy compared to photons significantly increased the risk of capsular contracture requiring capsulotomies and significantly increased overall reconstruction failures with implants removal.

Omission of Chest Wall/Scar Boost and Skin Bolus Does Not Increase Risk of Local Recurrence for Breast Cancer Patients

For breast cancer patients receiving postmastectomy radiation (PMRT), little is known about the value of Chest Wall Boost (CWB) and Skin Bolus (SB) across different biological subtypes and patients with high-risk features. We reviewed 2,917 charts of breast cancer patients treated with mastectomy between 2000-2020 at our institution. Only patients treated with PMRT were included. Patients with and without reconstruction were included. Reconstruction types included autologous or single-stage-direct-implant or two stages expanders/implant. PMRT was delivered with 3D conformal technique using photons and conventional fractionation (50-50.4 Gy in 25-28 fractions). CWB using enface electrons and 3-5 mm SB applied every other day were delivered at the discretion of the physician. Primary objectives were locoregional failure (LF) rates between CWB and No CWB groups; SB and No SB groups. Different subgroup analyses exploring the benefits of CWB and SB in different biological subtypes, patients with lymphovascular invasion (LVI+), positive margins (PM) and nipple sparing mastectomy (NSM) were conducted. Secondary objectives were toxicity of CWB and SB on different reconstruction outcomes and PMRT side effects. Logistic and cox regressions were used. A total of 1,103 patients with an overall median follow-up of 7.8 years were available for analysis. Among the entire cohort, 55.4% received CWB, 76% received SB, 48% had LVI, 23% with PM, 41% with NSM, 67% with Luminal A, 15% with Luminal B, 7% with HER2 enriched and 11% with triple negative. The 10 years incidence of LF was 6.5% and 4.0% for CWB and NO CWB, respectively (HR 1.6, p = 0.1); and 5.6% and 5.1% for SB and NO SB respectively (HR 0.9, p = 0.8). Multivariable analysis of LF adjusted for LVI, ECE, grade, tumor size, number of malignant nodes, and biological subtype showed no association of CWB and SB with local control (HR:1.4, p = 0.2 and HR:0.9, p = 0.8), respectively. Subgroup analyses confirmed no association of CWB or SB with improved local control across different biological subtypes, (LVI+), PM and NSM patients. On multivariable level CWB significantly increased reconstruction complications (OR 2.3, p = 0.001, OR 1.7, p = 0.008) for infection/necrosis (I/N) and overall reconstruction failure (ORF), respectively; while SB did not (OR 1.1, p = 0.8, OR 1.0, p = 0.9) for I/N and ORF, respectively. 56 patients needed treatment break, 49 of them (87%) had SB. Both CWB and SB significantly increased the risk of higher grade radiation dermatitis (2-4) in the entire cohort OR 2.1 p = 0.01, and OR 2.3, p = 0.02 for CWB and SB, respectively. CWB and SB did not improve local control across different biological subtypes, patients with LVI, Positive Margins and NSM. CWB significantly increased reconstruction complications and SB increased treatment breaks and radiation dermatitis. These findings do not support routine usage of CWB and SB.

Pattern and Complication of Reconstructed Breast Cancer Patients Who Received Postmastectomy Radiotherapy in the National Health Insurance Service Cohort

This study aimed to analyze the nationwide pattern of reconstruction after mastectomy in patients with breast cancer who received postmastectomy radiotherapy (PMRT) and to compare complications according to fractionation and reconstruction procedures. By using claim data from the National Health Insurance Service (NHIS) database, we analyzed breast cancer patients who received PMRT and underwent reconstruction between 2015 and 2020. We defined the grade ≥ 3 complications as the primary endpoint which involved hospital admission to the plastic surgery department. The complication was identified by using the procedure code for debridement and the International Classification of Diseases 10th codes for wound infections, dehiscence, necrosis, and mechanical complication of breast prosthesis and implant. The propensity score matching method was adopted to constitute the matched cohort between the hypofractionated fractionation (HF) and the conventional fractionation (CF), adjusted for age, diabetes, hypertension, obesity, smoking history, PMRT technique, use of bolus, year of PMRT delivery, and reconstruction method. Logistic regression was performed to evaluate the association between complication and variables. Altogether 4,553 patients were analyzed: 1,395 (30.6%) in the HF group and 3,158 (69.4.%) in the CF group. The use of HF has steadily increased from 20.1% in 2015 to 42.2% in 2020. Immediate implant reconstruction (36.8%) method was the most frequently used, followed by immediate autologous (33.3%) and two-stage implant reconstruction methods (19.6%). In the matched cohort (N = 2,052), the major complication rate was not significantly different between the HF group and the CF group (5.9% [60/1,026] vs. 5.4% [55/1,026], P = 0.568) with the median follow-up of 30.9 months (range, 6.0-82.1). Surgical debridement was performed in 3.3% [34/1026] of the HF group and 3.5% [36/1026] of the CF group (P = 0.808). HF was not associated with major complications (odds ratio (OR) 1.09, 95% CI 0.75-1.59, P = 0.128). In a nationwide insurance cohort, the complication rate was not significantly different between the HF group and the CF group. Our data suggest HF for reconstructed breasts is comparable to CF. However, consultation for fractionation regimen for reconstructed breast cancer patients may be still required at time of consideration of PMRT.

Proton vs. Photons for Breast Cancer Patients with Immediate, Implant-Based Reconstruction Receiving Postmastectomy Radiotherapy: A Multicenter Pooled Analysis

Proton therapy improves postmastectomy radiotherapy (PMRT) normal tissue sparing compared with photon techniques. However, little is understood about its effect on reconstruction outcomes. The primary objective was to evaluate complication rates in breast cancer patients treated with proton (PRO) versus photon (PHO) PMRT following immediate, implant-based breast reconstruction. Consecutive patients with breast cancer who underwent mastectomy and immediate reconstruction with a tissue expander (TE) or permanent implant (PI) and PRO or PHO PMRT between 2011 and 2022 were included from two institutions. Complication rate was defined as the sum of reconstruction failure (explantation without replacement), unplanned prosthesis exchange, and other unplanned revisional surgery. Each complication type was analyzed as an independent endpoint. Among 733 patients, median follow-up was 4.4 years; 36.5% (267) were treated with PRO and 63.5% (466) with PHO. There was no difference in age, BMI, or comorbidities between the two groups. PRO was more likely to have had, two-stage reconstruction and pre-pectoral implant placement (p<.01). Median dose was 50-50.4 Gy in 25-28 fractions, with only 50 receiving hypofractionation. Bolus was used in all PHO patients. Regional nodes were more likely to be included in PRO (99.6% v. 83.7% PHO, p<.01). Although there was no difference in the use of chest wall boost between groups, the axillary nodes were more frequently boosted in PRO (25.1% vs 2.8% PHO, p<.01). The overall rate of complications at 4 years was 26.7% (95% CI = 23.3-30.5). The 4-year rate of reconstruction failure, unplanned exchange, and other surgery was 8.2% (95% CI = 6.3-10.7), 17.4% (95% CI = 14.6-20.8), and 12.5% (95% CI = 10.1-15.5), respectively. On MVA, PRO did not confer an increased risk of reconstruction complications compared to PHO. Significant risk factors for reconstruction failure included TE-to-autologous approach [HR versus direct-to-implant reference: 4.05 (95% CI = 1.60-10.22)], TE-to-permanent implant approach [HR = 2.06 (95% CI = 1.12-3.79)], chest wall boost [HR = 2.20 (95% CI = 1.21-4.02)], and any lymph node boost [HR = 2.33 (95% CI = 1.10-4.97)]. Compared to direct-to-implant, two-stage reconstruction was also associated with a higher rate of unplanned exchange [HR for TE/PI = 1.49 (95% CI = 1.01-2.20)] and revisional surgery [HR for TE-to-autologous = 3.95 (95% CI = 1.64-9.52)]. Prepectoral implant placement was correlated with reduced risk of revisional surgery, relative to subpectoral placement [HR = 0.42 (95% CI = 0.22-0.81)]. This represents the largest combined series to date comparing PRO and PHO PMRT. Despite a higher rate of two-stage reconstruction, nodal irradiation, and nodal boost in PRO, there was no significant difference in the risk of complications between protons and photons. Differences in PRO delivery techniques between institutions and dosimetric details such as skin dose will be presented in person.

Interim Analysis of a Non-Randomized Prospective Trial Comparing Hypofractionated Post-Mastectomy Radiotherapy (HF-PMRT) to Conventional Post-Mastectomy Radiotherapy (CF-PMRT) for Breast Cancer (BC) Patients

The standard of care for treatment for LABC patients who have undergone modified radical mastectomy (MRM) is PMRT. Post-mastectomy RT (PMRT) for LABC patients has been established in three trials to improve locoregional control and overall survival (OS). A published trial from China showed that HF-PMRT was non-inferior to CF-PMRT. This study was conducted to determine if HF-PMRT can provide similar efficacy and toxicity. A non-randomized prospective trial design was employed to compare HF-PMRT and CF-PMRT in post-MRM BC patients. Patients with pathologically proven BC who underwent MRM without positive margins and with less than 8 positive nodes were included. Informed consent was obtained. Patients decided which treatment they will receive. They received either HF-PMRT of 43.2 Gy in 16 fractions (fx) [2.7 Gy/fx] or CF-PMRT of 50-50.4 Gy in 1.8-2.0 Gy/fx to both chest wall and regional nodes (axillary and supraclavicular) in both regimens. Primary endpoints were 2-year OS and 2-year local recurrence free survival (LRFS). Secondary endpoints include acute and late toxicities. Analysis was done as intention-to treat. An interim analysis of 2-year results is presented. A total of 37 patients were enrolled in two separate cohorts: a single-arm cohort that recruited 10 HF-PMRT patients from 2014-2015 and a two-arm prospective trial that started recruitment last 2019 and included 12 HF-PMRT and 15 CF-PMRT patients. Median follow-up was 35 months. There were more Stage IIB and Stage III for the CF-PMRT arm [p = 0.040]. Treatment interruptions were more frequent in the CF-PMRT arm (100% vs 68%, p = 0.028). The duration of interruption was also longer in CF-PMRT (median 8 vs 3 days) [p < 0.003]. Acute and late toxicities were not statistically different. There was one patient each with RTOG Grade 2 acute skin toxicity in the HF-PMRT (4.55%) and CF-PMRT arms (6.67%) [p = 0.703]. For late toxicities, the HF-PMRT arm had 6 Grade 1 late skin toxicities and 1 Grade 3 late skin toxicity vs 1 Grade 1 late skin toxicity for CF-PMRT arm [p = 0.196]. 2-year OS rate (86.3% vs 100%, p = 0.403) 2-year DFS rate (68.18% and 73.33%, p = 0.126) were both not statistically different. There were no reported locoregional recurrences (LCR). In terms of local control, both arms have showed no LCRs. 2-year OS and DFS rate were no different. As the study has not yet reached the adequate sample size, the non-inferiority of HF-PMRT cannot be definitively concluded. Acute and late toxicities were no different. There was a significantly higher rate of treatment interruptions in the CF-PMRT compared to the HF-PMRT arm. The results of this interim analysis prove to be promising and patients will continue to be accrued. The final results of this study might have tremendous implications in local practice.

Disparities in Breast-Conserving Therapy vs. Mastectomy among Asian American and Pacific Islander Women

Multiple randomized trials support the use of breast-conserving therapy (BCT), defined as lumpectomy followed by adjuvant radiotherapy, as an alternative to mastectomy for definitive treatment of early-stage (T1-2N0) breast cancer. However, data suggest that Asian American, Native Hawaiian, and Pacific Islander (AANHPI) may undergo mastectomy at higher rates than BCT and may experience barriers to receipt of BCT. The purpose of this study was to examine BCT utilization by disaggregated AANHPI groups to identify differences in receipt of mastectomy versus BCT. The 2004-2017 National Cancer Database was queried to identify women age ≥18 years old diagnosed with cT1-2N0M0 breast cancer treated with either BCT or mastectomy without post-mastectomy radiation therapy. Women were classified based on self-reported race. Multivariable logistic regression defined adjusted odds ratios (OR) assessing the association between race and receipt of BCT versus mastectomy for all patients and separately by cT1-2 stage. All models were adjusted for relevant sociodemographic and clinical factors. Of 794,403 women with cT1-2N0M0 breast cancer, 239,801 (30%) received mastectomy and 554,602 (70%) received BCT. After adjusting for clinical and sociodemographic factors, AANHPI women had greater odds of receiving mastectomy over BCT, compared to White women (OR [95% CI], 1.35 [1.30-1.39]; p<0.001). In contrast, Black women were less likely than White women to receive mastectomy (0.86 [0.84-0.87]; p<0.001). Upon disaggregation, Chinese, Japanese, Filipino, Korean, Vietnamese, and Asian Indian & Pakistani women were more likely to receive mastectomy over BCT compared to White women (p<0.001 for all). Treatment at academic (1.30 [1.27-1.32]), integrated (1.24 [1.21-1.27]), and comprehensive community cancer centers (1.15 [1.13-1.17]) were all associated with greater odds of mastectomy compared to treatment at community cancer programs (all p<0.001). Greater distance from treatment facility (≥50 mi. vs. 0 to <10 mi. [reference], OR 1.50 [1.47-1.53]) and cT2 disease (1.85 [1.82-1.87]) were also associated with greater odds of receiving mastectomy (all p<0.001). In this evaluation of women with early-stage breast cancer, women from several AANHPI groups were more likely to receive mastectomy (as opposed to BCT) compared to White women. While sociocultural preferences, differences in access to and interest in reconstruction, as well as prevalent tumor-to-breast ratios may partially explain the disparities, collectively our data suggest an ongoing need for greater patient involvement in shared-decision making, particularly in vulnerable and understudied Asian populations.