Racial Difference in Outcomes in Breast Cancer Patients with Residual Nodal Disease after Neoadjuvant Chemotherapy

PURPOSE/OBJECTIVE(S)

African Americans (AA) requiring neoadjuvant chemotherapy (NAC) have been associated with worse outcomes. Residual nodal disease (ypN+) after NAC represents a highly unfavorable risk factor. We hypothesized that even within this unfavorable subgroup, that racial differences in outcome would persist.

MATERIALS/METHODS

An IRB-approved retrospective review of breast cancer (BC) patients in a multi-institutional study was performed between 2005-2018 to identify ypN+ patients (excluding metastatic or inflammatory BC). Clinico-pathologic parameters stratified by race were collected and analyzed. For molecular subtype analyses, patients were stratified into triple negative (TN), hormone receptor (HR)+/HER2-, and HR+/HER2+, and HR-/HER2+ subtypes. Overall survival (OS), disease free survival (DFS) and recurrence outcomes were obtained, and univariate and multivariate (MVA) logistic regression models were constructed and analyzed.

RESULTS

Among 404 ypN+ patients, 107 (26%) were AA, and 297 (74%) were non-AA. Median follow-up for the non-AA group was 3.8 years (y) (IQR 2.4-6.3) and 3.5y (IQR 2.0-6.2) for the AA group. Clinical and pathologic patient characteristics (age, molecular subtypes, BRCA status, histology, grade, smoking status, primary surgery type, axillary/reconstruction surgery rates, margin status, stage) were without significant statistical differences between the non-AA and AA group, except the non-AA group had proportionally more cN3 disease (10.5% vs. 5.1%; p = .01). Despite this, AA demonstrated worse OS and DFS outcomes (Table). AA also had significantly worse local (15% vs. 6.7%, p = .02), regional (11.2% vs. 5.1%, p = .05) and distant recurrences (32.7% vs. 22.6%, p = .05) compared to non-AA. On MVA for OS and DFS, HR+ status, clinical stage, and AA race (HR 2.1 (CI 1.3-3.4), p = .004 and HR 1.7 (CI 1.1-2.6), p = .01 respectively) remained significant. Molecular subtype analysis demonstrated that AA with HR+/HER2- but not the TN subtypes demonstrated significantly worse outcomes (Table). Utilization of endocrine therapy was not different between AA and non-AA patients (94% vs. 97%, p = 0.3) to explain this discrepancy. Worse outcomes in HER2 subtype for AA group was suggested but could not be statistically verified due to insufficient sample size. There was no discernible difference in chemotherapy and radiation therapy regimen or compliance between the AA and non-AA groups.

CONCLUSION

AA patients who fail to achieve nodal clearance with NAC had higher local, regional and distant recurrence, and worse survival compared to non-AA, particularly those with non-TN status. These differences could not be readily explained by therapeutic disparity, or compliance. These hypothesis generating findings suggest need to explore biological implications, and alternative therapeutic strategies for this unfavorable subgroup.

Multi-Institutional Phase II Trial Using Dose Escalated Five Fraction Stereotactic Partial Breast Irradiation (S-PBI) with GammaPodTM for Early-Stage Breast Cancer

PURPOSE/OBJECTIVE(S)

We report on our early experience of a multi-institutional phase II study of dose escalated five fraction stereotactic partial breast irradiation (S-PBI) for early-stage breast cancer after partial mastectomy using the GammaPodTM stereotactic radiation system.

MATERIALS/METHODS

Patient eligibility included DCIS or invasive epithelial histologies, AJCC clinical stage 0, I, or II with tumor size < 3 cm, and negative margins. Prior safety of Phase I dose escalation has been reported. Dose was 40 Gy delivered in 5 fractions to the CTV, and minimum dose 30 Gy in 5 fractions to the PTV. CTV margin was 1 cm and PTV margin 3 mm. For PTV cavities larger than 100cc, dose was reduced to 35Gy in 5 fractions to the CTV and 30 Gy in 5 fractions to the PTV. Primary endpoint of the study is to determine the 3-year patient global cosmesis score (4-point scale excellent, good, fair, or poor) and adverse cosmesis using a dose escalated approach with smaller PTV margins than conventional methods. Both patients and physicians completed baseline and subsequent cosmesis outcome questionnaires. Treatment related toxicity was graded using the NCI version 4.0 and RTOG/EORTC late radiation scale.

RESULTS

From 3/2019-10/2021, 74 patients were treated respectively. Of these, 38 were treated to 40Gy and 36 were treated to 35 Gy. Median follow up (f/u) was 24 months (mo), range (r) 3-39mo. Median age was 63 years (r 43-77). Histology included 28 DCIS, and 46 invasive carcinomas. 45/46 invasive tumors were ER+. 60/74 (81%) patients received endocrine therapy, and 7/74 patient received chemotherapy. There were 221 acute grade 1 toxicities, and 28 Grade 2 toxicities. No grade 3 or higher acute toxicities were reported (< 90 days). The most common Grade 2 toxicities were radiation dermatitis (10), breast pain (8), blister (4), skin infection (2), nipple discharge (2), and fatigue (2). In the late period, there were 54 Grade 1 late toxicities, 4 Grade 2 late toxicities, and no Grade 3 or higher late toxicities. Grade 2 toxicities included fibrosis (2), and pain (2). Two patients developed grade 1 asymptomatic nonpalpable fat necrosis both diagnosed at 12 months after radiation treatments. The most common grade 1 late toxicities were breast pain (14), hyperpigmentation (8), fibrosis (10), and fatigue (5). Physicians scored cosmesis excellent or good 70/73 (95.8%), 58/60 (96.7%), 36/36 (100%),17/17(100%) respectively at baseline, 12 months, 24 months, and 36months post SBRT, while patients scored the same periods 62/71 (83.7%), 53/59 (89.8%), 33/36 (91.6%), 17/18 (94.4%). There have been no reports of disease recurrences.

CONCLUSION

Results at 24-month median follow-up, of our dose escalated stereotactic partial breast 5 fraction regimen, has low acute and late toxicity, while maintaining high proportion of excellent/good cosmetic outcomes. Continued analysis of all cohorts is in progress.

CLINICAL TRIALS

gov identifier is NCT03581136.

A Comprehensive Deep Learning Framework for Automatic Target Volumes Segmentation in Post-Operative Stereotactic Partial Breast Irradiation (S-PBI)

PURPOSE/OBJECTIVE(S)

In S-PBI, accurate delineation of post-surgical tumor bed volume (TBV) and clinical target volume (CTV) are crucial tasks to achieve effective radiotherapy outcomes. However, manual contouring is labor intensive, time consuming, and largely relies on the experience of clinicians. We aimed to propose a deep learning (DL) approach which mimics physicians' contouring practice to accurately segment target volumes in post-operative breast CT images.

MATERIALS/METHODS

Our approach incorporated domain knowledge into a 3D U-Net based DL model for breast target volumes (TBV and CTV) delineation. Our TBV segmentation approach was inspired by the marker-guidance procedure in manual delineation, where the visual clues provided by the markers assist physicians in defining TBV. For this purpose, a distance-transformation coupled with a Gaussian filter was adopted to convert markers' locations on the CT images to saliency maps. Subsequently, the CT images and the corresponding saliency maps formed a two-channel input for the segmentation model. For CTV segmentation, TBV was incorporated as an input in addition to the CT images, guiding the model to encode the location-related image features. The architecture allowed the network to emulate the oncologist's manual delineation where CTV is derived from TBV via a margin expansion, followed by correcting the extensions for anatomical barriers of tumor invasion (e.g., skin, chest wall). We retrospectively collected 175 prone CT images from 35 post-operative breast cancer patients who received 5-fraction partial breast irradiation (PBI) regimen on a Co-60 prone based S-PBI unit. The 35 patients were randomly split into 25, 5, and 5 for model training, validation, and testing respectively.

RESULTS

We evaluated the performance of the developed DL model on the testing dataset by comparing the predicted volumes with the manually delineated contours (ground truth) using Dice similarity coefficient (DSC), 95th percentile Hausdorff distance (HD95), and average symmetric surface distance (ASD). For TBV segmentation, our model achieved mean (standard deviation) of 0.76 (±2.7), 6.76 (±1.83) mm, and 1.9 (±0.66) mm for DSC, HD95, and ASD respectively. For CTV segmentation, our model achieved 0.94 (±0.02), 2.46 (±0.5) mm, and 0.53 (±0.14) mm for DSC, HD95, and ASD respectively. The proposed auto-segmentation approach generated TBV and CTV masks in ∼11 seconds per CT volume, implying significantly improved efficiency compared to manual contouring.

CONCLUSION

We developed a comprehensive DL framework mimicking clinical contouring practice for auto-segmentation of target volumes in S-PBI. The results demonstrated high levels of agreement between the predicted contours and physicians' manual contours. The approach is promising for improving the efficiency and accuracy of the on-line treatment planning workflow, such as adaptive based S-PBI.

Prognostic Impact of Mismatch Repair Deficiency on Stage I-II Endometrioid Endometrial Cancer Treated with Adjuvant Radiation Therapy: A Multi-Institutional Analysis

PURPOSE/OBJECTIVE(S)

To report the impact of mismatch repair (MMR) status on outcomes in patients with stage I-II endometrioid endometrial cancer (EEC).

MATERIALS/METHODS

This is a multi-institutional retrospective cohort study across 11 institutions. Preliminary data from 7 centers is available for analysis. Patients with known MMR status and stage I-II EEC status post-surgical staging treated with adjuvant radiation therapy were included. Overall survival (OS) and recurrence-free survival (RFS) rates were estimated by the Kaplan-Meier method. Univariate and multivariate analyses were performed by Cox proportional hazard models for OS/RFS. Statistical analyses were conducted using statistical software.

RESULTS

A total of 573 patients with median age at diagnosis of 65 years (Interquartile Range (IQR) 58-71) were eligible. Most patients were White (79%), had FIGO 2009 Stage I (89.7%) and FIGO grade 1-2 (74.7%). MMR deficiency (dMMR) was reported in 191 patients (33%) while 382 patients (67%) had preserved MMR (pMMR). External beam radiation therapy (EBRT) +/- vaginal brachytherapy (VBT) was delivered to 124 patients (21.6%) while 449 patients (78.4%) received VBT alone. After a median follow-up of 41 months ((IQR) 28-60 months), the estimated OS and RFS rates for the entire cohort were 95.1% and 85%, respectively. On univariate analysis, age >65 (p < 0.001), grade 3 (p < 0.001), presence of lymphovascular space invasion (LVSI) (p = 0.039) and deep myometrial invasion (p = 0.03) were associated with worse OS. The OS was inferior in the dMMR group, however, it did not reach significance (92% vs 96.1%, p = 0.06). On multivariate analysis, older age (p < 0.001) and grade 3 (p = 0.002) were the only predictors for worse OS. On univariate analysis for RFS, age >65 (p = 0.02), grade 3 (p = 0.018) and dMMR (72.9% vs 91%, p < 0.001) were associated with worse RFS. On multivariate analysis, age >65 (p = 0.015) and dMMR (p < 0.001) were significant predictors of worse RFS.

CONCLUSION

Preliminary data from 7 out of 11 participating institutions showed that dMMR status leads to significantly decreased RFS in patients with early-stage EEC. While awaiting the results of NRG GYN020 and RAINBO prospective trials, this large study suggests that treatment intensification could be warranted in patients with dMMR early-stage EEC.

Enough and Some to Spare: Improved OAR Sparing with Daily Online Cone Beam Adaptive Radiation Therapy (OnC-ART) of the Cervix

PURPOSE/OBJECTIVE(S)

The standard of care treatment for locally advanced cervical cancer involves pelvic chemoradiation. During treatment planning, the cervix and uterus contours are expanded by 1.5 to 2 cm margins to account for inter- and intrafractional motion per the consensus guidelines. Daily online cone-beam adaptive radiation therapy (OnC-ART) accounts for interfractional motion, thus significantly reducing CTV to PTV margins. In this study, we compared the dosimetry of standard larger margin plans (IGRT) to 0.5 cm margins for patients treated with daily OnC-ART and hypothesized that daily OnC-ART with reduced margins will have improved dosimetry.

MATERIALS/METHODS

A retrospective cohort of 10 patients with cervical cancer (stage IIB - IIIC2) treated with 260 definitive daily fractions of OnC-ART chemoradiation between April 2021 and December 2022 was included. Initial plans were generated with OnC-ART and IGRT CTV to PTV margins as follows: combined cervix, uterus, and GTV (0.5 cm vs. 1.5 cm), combined parametria and vagina (0.5 cm vs. 1 cm), nodal chains (0.5 cm vs. 0.5 cm), and gross nodes (0.5 cm vs. 0.5 cm). The initial IGRT plan was copied to synthetic CTs generated for each fraction in the adaptive workflow containing the daily contours of all targets and OARs. The dosimetry of each IGRT fraction was compared to the dose delivered from each daily OnC-ART fraction. Statistical significance was defined as p < 0.05.

RESULTS

When compared with dosimetry from daily IGRT, the daily OnC-ART plans had significantly improved CTV coverage and less hotspots with improvements in D95% (+1.6%), D99% (+2.9%), and Dmax (-0.9%). Bowel bag and bowel loops showed significant improvements in Dmax (-1.4% and - 2.6%), V40 (-6.2% and -5.3%), and V45 (-6.1% and 5.5%). The daily OnC-ART plans had a mean bowel bag V40 of 177.4 cm3. Contrastingly, the mean bowel bag V40 for the large margin IGRT plans was 268.7 cm3. The bladder and rectum also showed significant improvements in Dmax (-1.7% and -1.6%), V40 (-25.2% and -36.0%), and V30 (-9.7% and -17.1%). The daily OnC-ART plans had a mean bladder and rectum V40 of 41.6 cm3 and 18.4 cm3, and the large margin IGRT plans had a mean bladder and rectum V40 of 65.1 cm3 and 40.8 cm3. Bone marrow had a significantly reduced dose with improvements in Dmean (-3.2%), V10 (-2.7%), and V20 (-3.3%).

CONCLUSION

Reduced CTV to PTV margins achievable with daily OnC-ART is shown to not only improve sparing of critical OARs, especially the bladder and rectum, but also improves target coverage compared to larger margins from daily IGRT. The clinical impact of these dosimetric improvements is currently undergoing investigation.

The Changing Profile of Academic Radiation Oncology Leaders: Updates over the Past Decade

PURPOSE/OBJECTIVE(S)

To report objective characteristics of program directors (PDs) and chairpersons and examine contemporary trends of their demographic and academic profiles from 2013 to 2023. We hypothesize that there are significant changes in the profiles of our radiation oncology leaders over the past decade.

MATERIALS/METHODS

A total of 89 PDs and 85 chairpersons in the Accreditation Council for Graduate Medical Education (ACGME)-approved residency programs in the U.S were queried for analysis. Demographic data on race, ethnicity, post graduate training, years in practice were obtained from publicly available online resources (e.g., institutional websites and online networking services for physicians). Variables on academic productivity and professional accolades included Hirsh-index, National Institute of Health (NIH) research grant (R), the ASTRO fellowship designation, and leadership positions in professional society meetings. Descriptive analyses, including Fisher's exact tests, were performed to compare findings from the published article in 2013 on this topic (Wilson LD et al. IJROBP 2013).

RESULTS

A total of 36 out of 89 PDs (40.4%) and 11 out of 85 chairpersons (12.8%) were females, revealing higher proportion of females from the initial analysis: 40.4 vs. 24.1% for PDs (p = 0.025) and 12.8 vs. 9.2% for chairpersons (p = 0.618). 29 out of 89 (32.6%) PDs and 30 out of 85 (35.3%) chairpersons were non-White. The median length of practice for PDs and chairpersons were 11 and 29 years, respectively. 38 out of 89 PDs (42.7%) and 11 out of 85 (12.9%) chairpersons were employed at the institution of their training. 7 out of 89 (7.9%) for PDs and 51 out of 85 (60.0%) for chairpersons were awarded FASTRO designation. Median H-index showed increasing trends for PDs (14.5 vs 9) and chairpersons (40 vs 29) from the initial analysis.

CONCLUSION

While most PDs and chairpersons are males, female representation has increased in radiation oncology leadership in the last 10 years, most notably among PDs. Academic productivity among our leaders has also increased. These trends highlight the changes in the landscape of our leadership characteristics.