Intricacies of Human-AI Interaction in Dynamic Decision-Making for Precision Oncology: A Case Study in Response-Adaptive Radiotherapy

Background

Adaptive treatment strategies that can dynamically react to individual cancer progression can provide effective personalized care. Longitudinal multi-omics information, paired with an artificially intelligent clinical decision support system (AI-CDSS) can assist clinicians in determining optimal therapeutic options and treatment adaptations. However, AI-CDSS is not perfectly accurate, as such, clinicians' over/under reliance on AI may lead to unintended consequences, ultimately failing to develop optimal strategies. To investigate such collaborative decision-making process, we conducted a Human-AI interaction case study on response-adaptive radiotherapy (RT).

Methods

We designed and conducted a two-phase study for two disease sites and two treatment modalities-adaptive RT for non-small cell lung cancer (NSCLC) and adaptive stereotactic body RT for hepatocellular carcinoma (HCC)-in which clinicians were asked to consider mid-treatment modification of the dose per fraction for a number of retrospective cancer patients without AI-support (Unassisted Phase) and with AI-assistance (AI-assisted Phase). The AI-CDSS graphically presented trade-offs in tumor control and the likelihood of toxicity to organs at risk, provided an optimal recommendation, and associated model uncertainties. In addition, we asked for clinicians' decision confidence level and trust level in individual AI recommendations and encouraged them to provide written remarks. We enrolled 13 evaluators (radiation oncology physicians and residents) from two medical institutions located in two different states, out of which, 4 evaluators volunteered in both NSCLC and HCC studies, resulting in a total of 17 completed evaluations (9 NSCLC, and 8 HCC). To limit the evaluation time to under an hour, we selected 8 treated patients for NSCLC and 9 for HCC, resulting in a total of 144 sets of evaluations (72 from NSCLC and 72 from HCC). Evaluation for each patient consisted of 8 required inputs and 2 optional remarks, resulting in up to a total of 1440 data points.

Results

AI-assistance did not homogeneously influence all experts and clinical decisions. From NSCLC cohort, 41 (57%) decisions and from HCC cohort, 34 (47%) decisions were adjusted after AI assistance. Two evaluations (12%) from the NSCLC cohort had zero decision adjustments, while the remaining 15 (88%) evaluations resulted in at least two decision adjustments. Decision adjustment level positively correlated with dissimilarity in decision-making with AI [NSCLC: ρ = 0.53 ( p < 0.001); HCC: ρ = 0.60 ( p < 0.001)] indicating that evaluators adjusted their decision closer towards AI recommendation. Agreement with AI-recommendation positively correlated with AI Trust Level [NSCLC: ρ = 0.59 ( p < 0.001); HCC: ρ = 0.7 ( p < 0.001)] indicating that evaluators followed AI's recommendation if they agreed with that recommendation. The correlation between decision confidence changes and decision adjustment level showed an opposite trend [NSCLC: ρ = -0.24 ( p = 0.045), HCC: ρ = 0.28 ( p = 0.017)] reflecting the difference in behavior due to underlying differences in disease type and treatment modality. Decision confidence positively correlated with the closeness of decisions to the standard of care (NSCLC: 2 Gy/fx; HCC: 10 Gy/fx) indicating that evaluators were generally more confident in prescribing dose fractionations more similar to those used in standard clinical practice. Inter-evaluator agreement increased with AI-assistance indicating that AI-assistance can decrease inter-physician variability. The majority of decisions were adjusted to achieve higher tumor control in NSCLC and lower normal tissue complications in HCC. Analysis of evaluators' remarks indicated concerns for organs at risk and RT outcome estimates as important decision-making factors.

Conclusions

Human-AI interaction depends on the complex interrelationship between expert's prior knowledge and preferences, patient's state, disease site, treatment modality, model transparency, and AI's learned behavior and biases. The collaborative decision-making process can be summarized as follows: (i) some clinicians may not believe in an AI system, completely disregarding its recommendation, (ii) some clinicians may believe in the AI system but will critically analyze its recommendations on a case-by-case basis; (iii) when a clinician finds that the AI recommendation indicates the possibility for better outcomes they will adjust their decisions accordingly; and (iv) When a clinician finds that the AI recommendation indicate a worse possible outcome they will disregard it and seek their own alternative approach.

Novel Definitive Hypofractionated Accelerated Radiation Dose-painting (HARD) for Unresected Soft Tissue Sarcomas

Purpose

Soft tissue sarcomas (STS) are historically radioresistant, with surgery being an integral component of their treatment. With their low α/β, STS may be more responsive to hypofractionated radiation therapy (RT), which is often limited by long-term toxicity risk to surrounding normal tissue. An isotoxic approach using a hypofractionated accelerated radiation dose-painting (HARD) regimen allows for dosing based on clinical risk while sparing adjacent organs at risk.

Methods and Materials

We retrospectively identified patients from 2019 to 2022 with unresected STS who received HARD with dose-painting to high, intermediate, and low-risk regions of 3.0 Gy, 2.5 Gy, and 2.0 to 2.3 Gy, respectively, in 20 to 22 fractions. Clinical endpoints included local control, locoregional control, progression free survival, overall survival, and toxicity outcomes.

Results

Twenty-seven consecutive patients were identified and had a median age of 68 years and tumor size of 7.0 cm (range, 1.2-21.0 cm). Tumors were most often high-grade (70%), stage IV (70%), located in the extremities (59%), and locally recurrent (52%). With a median follow-up of 33.4 months, there was a 3-year locoregional control rate of 100%. The 3-year overall and progression-free survival were 44.9% and 23.3%, respectively. There were 5 (19%) acute and 2 (7%) late grade 3 toxicities, and there were no grade 4 or 5 toxicities at any point.

Conclusions

The HARD regimen is a safe method of dose-escalating STS, with durable 3-year locoregional control. This approach is a promising alternative for unresected STS, though further follow-up is required to determine long-term control and toxicity.

Clinical outcomes of melanoma brain metastases treated with nivolumab and ipilimumab alone versus nivolumab and ipilimumab with stereotactic radiosurgery

PURPOSE

Upfront dual checkpoint blockade with immune checkpoint inhibitors (ICI) has demonstrated efficacy for treating melanoma brain metastases (MBM) in asymptomatic patients. Whether the combination of stereotactic radiosurgery (SRS) with dual checkpoint blockade improves outcomes over dual-checkpoint blockade alone is unknown. We evaluated clinical outcomes of patients with MBM receiving ICI with nivolumab and ipilimumab, with and without SRS.

METHODS

49 patients with 158 MBM receiving nivolumab and ipilimumab for untreated MBM between 2015 and 2022 were identified at our institution. Patient and tumor characteristics including age, Karnofsky Performance Status (KPS), presence of symptoms, cancer history, MBM burden, and therapy course were recorded. Outcomes measured from initiation of MBM-directed therapy included overall survival (OS), local control (LC), and distant intracranial control (DIC). Time-to-event analysis was conducted with the Kaplan-Meier method.

RESULTS

25 patients with 74 MBM received ICI alone, and 24 patients with 84 MBM received concurrent SRS. Median follow-up was 24 months. No differences in age (p = 0.96), KPS (p = 0.85), presence of symptoms (p = 0.79), prior MBM (p = 0.68), prior MBM-directed surgery (p = 0.96) or SRS (p = 0.68), MBM size (p = 0.67), or MBM number (p = 0.94) were seen. There was a higher rate of nivolumab and ipilimumab course completion in the SRS group (54% vs. 24%; p = 0.029). The SRS group received prior immunotherapy more often than the ICI alone group (54% vs. 8.0%; p < 0.001). There was no significant difference in 1-year OS (72% vs. 71%, p = 0.20) and DIC (63% v 51%, p = 0.26) between groups. The SRS group had higher 1-year LC (92% vs. 64%; p = 0.002). On multivariate analysis, LC was improved with combination therapy (AHR 0.38, p = 0.01).

CONCLUSION

In our analysis, patients who received SRS with nivolumab and ipilimumab had superior LC without increased risk of toxicity or compromised immunotherapy treatment completion despite the SRS cohort having higher rates of prior immunotherapy. Further prospective study of combination nivolumab and ipilimumab with SRS is warranted.

Association between Tumor Volume Change on MRI with Surgical Margin Status, Pathological Response, and Local Control Following Pre-Operative Radiation Therapy for Soft Tissue Sarcoma

PURPOSE/OBJECTIVE(S)

The clinical significance of radiographic progression during pre-operative radiation therapy (RT) for soft tissue sarcoma (STS) remains unclear. We sought to evaluate associations between radiographic change on T1 post-contrast (T1c) and T2 weighted magnetic resonance imaging (MRI) with percent pathological response (PR%), positive surgical margins (+SM), and local control (LC).

MATERIALS/METHODS

We retrospectively identified patients with STS undergoing neoadjuvant RT who had both pre- and post-RT MRI prior to surgical resection. Gross tumor volumes were contoured on pre- and post-RT T1c and T2 MRI sequences and relative change in volume from baseline was calculated. Radiographic classification was defined as response (>30% reduction), progression (>30% increase), or stable (≤30% reduction or ≤30% increase). Chi squared, Fishers Exact, and Kruskal Wallis (KW) tests were used to assess differences between groups. Linear and binary logistic regression models used to assess associations between MRI response and PR% and +SM, respectively. LC was modeled with Kaplan Meier methods and log rank tests.

RESULTS

A total of 68 STS patients were identified, with a median follow up of 49 months (range 7-229). With a median age of 60.5 years (25-88) and tumor size of 10.8cm (2.7-25.7), the most common histologies were undifferentiated pleomorphic sarcoma (UPS; 32.4%) and myxoid liposarcoma (ML; 16.2%), and were primarily grade 2-3 disease (89.7%). With a median RT dose of 50 Gy in 25 fractions (44-60Gy), the median radiographic volume change was 2% (-86.4 to 953.6%) and -2.1% (-89.6 to 962.5%) for T1c and T2, respectively. Radiographic classification of response/stable/progression was 25.4%/49.2%/25.4% and 27.9%/52.5%/19.7% for T1c and T2, respectively. Histology (ML vs. UPS) and grade (1 vs. 3) were predictors for radiographic response on both T1c (72.7% vs 18.8%, p = 0.03 and 71.4% vs. 10.4%, p = 0.03) and T2 (71.5% vs. 18.2%, p = 0.02 and 71.4% vs. 14.6%, p = 0.002), respectively. With 6 +SM (8.8%), the rate of +SM for response/stable/progression was 20%/10.3%/0% in T1c (p = 0.2) and 5.9%/12.5%/0% in T2 (p = 0.5). As a continuous variable, neither relative change on T1c (p = 0.2) or T2 (p = 0.4) were associated with +SM. With an overall median PR% of 64% (0-100%), the median PR% was significantly different for response/stable/progression for both T1c (95%/42%/73%, p = 0.02) and T2 (95%/50%/87.5%, p = 0.04). Radiographic change on neither T1c (p = 0.4) or T2 (p = 0.5) were associated with PR% on a continuous basis. With a total of 4 local recurrences, there was no significant difference in LC by radiographic classification on either T1c (p = 0.65) or T2 (p = 0.85).

CONCLUSION

While radiographic response may be correlated with pathological response, radiographic progression on either T1c or T2 following neoadjuvant RT was not associated with a detriment in surgical margins or local control. These findings suggest that STS radiographic "pseudoprogression" is not associated with worse outcome.

Teaching Trainees to be Effective Mentors: A Needs-Based Assessment in Radiation Oncology

PURPOSE/OBJECTIVE(S)

Mentorship plays a critical role in the training and career development of medical trainees. Teaching-the-teacher workshops for residents translate to higher long-term job satisfaction and improved patient communication skills. Further, near-peer mentorship has been associated with increased job satisfaction and patient care experience. Resident-as-mentors can add benefit to the mentorship networks of students, particularly in resource-limited environments, while benefiting residents' own mentorship relations and career satisfaction. We hypothesized that residents would desire to be a mentor, but would lack specific skills needed for effective mentoring of students in radiation oncology.

MATERIALS/METHODS

A multi-institution, cross-sectional study was conducted among residents in the Radiation Oncology Education Collaborative Study Group (ROECSG) Graduate Medical Education working group from 06/2022-10/2022. Participants completed the Mentorship Competency Assessment (MCA), a validated 26-item questionnaire, scored on a Likert scale from 0-7 (0: most unprepared with mentorship skill, 7: most prepared with mentorship skill). The primary endpoint was the average score in individual mentorship skills among participants. Kruskal-Wallis test assessed associations between total MCA score (range 0-182) and demographics.

RESULTS

A total of 36 of 39 participants (92% response rate) responded. A majority were male (58%), from a residency size >10 (75%), and P Gy-2/3 (52%). Most had no formal training in teaching (86%) or mentorship (89%). Many believed they would be a good mentor to students on a rotation (89%), but most felt they would benefit from a formal mentorship program (92%). From the MCA, the mentorship skills residents felt most unprepared for were: coordinating effectively with other mentors (3.4/7), helping mentees acquire resources (3.6/7), negotiating a path to professional independence with mentees (3.6/7), helping mentees network effectively (3.7/7), and working with mentees to set clear expectations of the mentoring relationship (3.9/7). The mentorship skills residents felt most prepared for were: acknowledging mentees' professional contributions (5.6/7), establishing a relationship based on trust (5.6/7), active listening (5.5/7), building mentees' confidence (4.9/7), and working effectively with mentees with personal backgrounds differing from one's own (4.8/7). Higher MCA scores were associated with former training in mentorship (p = 0.0143), and a trend for former training in teaching (p = 0.0525), but was not associated with sex (p = 0.5986), residency size (p = 0.1415), or P Gy-year (p = 0.9747).

CONCLUSION

Residents are interested in mentorship training and report unpreparedness in several important skills. Future work should focus on formal training and assessment of mentoring skills for residents.

Hypofractionated Accelerated Radiation Dose-Painting (HARD) vs. Standard Radiotherapy for Unresected Soft-Tissue Sarcoma

PURPOSE/OBJECTIVE(S)

Conventionally fractionated radiotherapy (CFRT) offers modest local control (LC) for unresected soft tissue sarcoma (STS). Although STS has a low α/β (∼2 - 6) that may benefit from a hypofractionated radiotherapy regimen, it is often limited due to the toxicity risk to surrounding organs. A simultaneous integrated boost to gross disease (2.5 - 3 Gy/fraction), with lower doses to the intermediate and low risk target volume, may offer a safe isotoxic dose escalation approach. We hypothesize that this hypofractionated accelerated radiotherapy dose-painting (HARD) will improve local control compared to CFRT.

MATERIALS/METHODS

We performed a single institution retrospective analysis of patients who received external beam radiotherapy with definitive intent (≥50 Gy) for unresected STS. CFRT was defined as 1.8 - 2 Gy/fraction (Gy/fx). HARD regimens consisted of 60 - 66 Gy at 3 Gy/fx or 70 Gy at 2.5 Gy/fx to gross disease, with 1.8 - 2.4 Gy/fx to intermediate and low risk regions. All anatomical sites and histologies were included. Local control (LC) was defined from date of current diagnosis, estimated by Kaplan-Meier methods via log-rank tests or Cox regression for univariate analysis (UVA), when appropriate. Cox regression multivariate analysis (MVA) included regimen, biological effective dose (α/β 6; BED6), lesion size, age, and grade.

RESULTS

We identified 77 patients with primary and metastatic STS treated with HARD (n = 40) or CFRT (n = 37) between 1990 and 2022, with a median follow up of 24 months in surviving patients. The mean dose for CFRT and HARD are 56.8 Gy (50 - 77.4 Gy) and 64.9 Gy (60 - 70 Gy), respectively. HARD was comprised of 65% for 3 Gy/fx and 35% for 2.5 Gy/fx regimens. At the time of RT, grade 3 (69%) and extremity (39%) tumors were the most common. Tumor histology was very heterogenous across both cohorts, with undifferentiated pleomorphic sarcoma being the most common for HARD (33%) and CFRT (19%). HARD was more often utilized in stage IV patients (55% vs. 19%, p = 0.001) and had a higher mean BED6 (96 vs. 74.2 Gy, p < 0.001) than CFRT, but without differences in age (67 vs. 59 years), tumor size (8 vs. 10 cm), concurrent chemotherapy (35% vs. 30%), Karnofsky performance status (86 vs. 85), follow-up (19 vs. 28 months), and grade (all p > 0.1). On UVA, there was a LC benefit associated with higher BED6 (HR 0.94, 95% CI 0.9 - 0.98, p = 0.002) and the HARD regimen (2-year LC 95% vs. 62%, p < 0.001). On MVA, only HARD (HR 0.07, 95% CI 0.006 - 0.729, p = 0.027) was independently associated with LC.

CONCLUSION

Although the HARD regimen and higher BED6 were both associated with significant improvement in LC, only the HARD regimen independently associated with a local control benefit for unresected STS. These results suggest biologic dose-intensification exploiting the low α/β of STS with an isotoxic hypofractionated regimen may be a favorable strategy for unresectable STS. Future prospective studies are necessary to validate these findings.

TEAMRO: TEAching Mentorship in Radiation Oncology, a Multicenter Prospective Phase 2 Intervention Study on Teaching Mentorship Skills to Residents Working with Medical Students

PURPOSE/OBJECTIVE(S)

While formal curriculum on resident teaching have been associated with improved career growth and sustained positive impact on patient care, mentorship skills are rarely taught in academic medicine. We hypothesized that a formalized resident mentorship curriculum coupled with a near-peer resident-medical student mentoring program would improve resident career growth.

MATERIALS/METHODS

A multi-institutional, prospective, phase 2 intervention study, approved by each participating center's institutional review board, was conducted from 4/2022-10/2022 among interested residents in the Radiation Oncology Education Collaborative Study Group Graduate Medical Education. Intervention included: 1) a 4-week mentorship curriculum (utilizing a Six Steps approach) composed of self-guided readings, didactic lecture, and 30-minute faculty check-in, and 2) a formalized 1:1 resident-medical student mentorship program during an existing radiation oncology sub-internship with weekly meetings. Resident participants completed the Mentorship Competency Assessment (MCA), a 26-item validated survey on mentorship skills in medicine scored from 0 (most unprepared) to 7 (most prepared) before and after the intervention. The primary endpoint was average change in MCA skill from pre- to post-intervention survey, with score ranges from -7 (a decrease in 7 points) to +7 (an increase of 7 points).

RESULTS

A total of 8 residents participated and all completed pre- and post-intervention surveys. Most residents were PGY-4/5 (75%), from programs with >10 residents (68%), and did not have prior training in teaching (88%) or mentorship (88%). Residents met students on average twice weekly (range 1-3) for an average of 2 hours a week (range 1-5). After the program, most residents felt confident in being a future mentor to students (100%), their overall well-being was positively impacted (63%), and their mentorship relationships were positively impacted (50%). All 26 mentorship skills increased on MCA after intervention (average +1.3/7 per skill). Skills that showed greatest improvement were helping mentees network effectively (+2.6/7), acquire resources (+2.1/7), negotiate a path to professional independence (+2.0/7), set career goals (+1.8/7), and balance work and personal life (+1.7/7). Skills that showed least improvement were establishing a relationship based on trust (+0.4/7), identifying and accommodating different communication styles (+0.6/7), providing constructive feedback (+0.7/7), and aligning mentor-mentee expectations (+0.8/7).

CONCLUSION

The formalized mentorship program improved mentorship skills among residents, translating to increased satisfaction in residents' own mentorship relations and overall well-being. Further studies are needed to assess the sustainability of these skills, as well as impact on career growth and satisfaction.

Neoadjuvant Simultaneous Integrated Boost Radiation Therapy Improves Clinical Outcomes for Retroperitoneal Sarcoma

PURPOSE

Neoadjuvant radiation therapy (RT) with standard techniques (ST) offers a modest benefit in retroperitoneal sarcoma (RPS). As the high-risk region (HRR) at risk for a positive surgical margin and recurrence is posterior and away from radiosensitive organs at risk, using a simultaneous integrated boost (SIB) allows targeted dose escalation to the HRR while sparing these organs. We hypothesized that neoadjuvant SIB RT can improve disease control compared with ST, without increasing toxicity.

METHODS AND MATERIALS

We retrospectively identified patients with resectable nonmetastatic RPS from 2000 to 2021 who received neoadjuvant RT of 180 to 200 cGy/fraction to standard volumes. SIB patients received 205 to 230 cGy/fraction to the appropriate HRR. Clinical endpoints included abdominopelvic control (APC), recurrence-free survival (RFS), overall survival (OS), and acute toxicity.

RESULTS

With a median follow-up of 57 months (95% confidence interval [CI], 50-64), there were 103 patients with RPS who received either ST (n = 69) or SIB (n = 34) RT. Median standard volume dose was 5000 cGy (ST) and 4500 cGy (SIB), with a median HRR SIB dose of 5750 cGy. Liposarcomas (79% vs 53%; P = .004) and cT4 tumors (59% vs 19%; P < .001) were more common in the SIB cohort, without a significant difference in the rate of resection (82% vs 81%; P = .88) or R1 margin (53.5% vs 50%; P = .36); there were no R2 resections. SIB was associated with a significant improvement in 5-year APC (96% vs 70%; P = .046) and RFS (60.2% vs 36.3%; P = .036), with a nonsignificant OS difference (90.1% vs 67.5%; P = .164). On multivariable analysis, SIB remained a predictor for APC (hazard ratio, 0.07; 95% CI, 0.01-0.74; P = .027) and RFS (hazard ratio, 0.036; 95% CI, 0.13-0.98; P = .045). SIB showed no significant detriment in toxicity, albeit with a lower rate of overall grade 3 acute toxicity (3% vs 22%; P = .023) compared with ST.

CONCLUSIONS

In RPS, dose escalation with neoadjuvant SIB RT may be independently associated with improved APC and RFS, without a detriment in toxicity, compared with ST. With the addition of standard RT having only a modest benefit compared with surgery alone, our study suggests that future prospective studies evaluating for the benefit of SIB RT should be considered.

Tucatinib and stereotactic radiosurgery in the management of HER2 positive breast cancer brain metastases

PURPOSE

HER2-positive breast cancer has a high risk of brain metastasis. Stereotactic radiosurgery (SRS) is standard of care for limited brain metastases. Tucatinib, a HER2-targeted tyrosine kinase inhibitor, has demonstrated intracranial efficacy in the HER2-CLIMB Trial. However, it is unknown whether tucatinib with SRS is safe or effective.

METHODS

A retrospective analysis of HER2-positive breast cancer treated with SRS and tucatinib for brain metastases management was performed. All patients received tucatinib and SRS for the management of active brain metastases. The primary endpoint was local and distant brain tumor control. Secondary endpoints were intracranial progression free survival (CNS-PFS), systemic PFS, overall survival (OS), and neurotoxicity.

RESULTS

A total of 135 lesions treated with SRS over 39 treatment sessions in 22 patients were identified. Median follow-up from tucatinib initiation was 20.8 months. Local brain control was 94% at 12-months and 81% at 24-months. Distant brain control was 39% at 12-months and 26% at 24-months. Median survival was 21.2 months, with 12- and 24-month OS rates of 84% and 50%, respectively. Median CNS-PFS was 11.3 months, with 12- and 24-month CNS-PFS rates of 44.9% at both time points. Median systemic PFS was not reached, with 12- and 24-month systemic PFS rates of 86% and 57%, respectively. Symptomatic radiation necrosis occurred in 6 (4%) lesions. No additional unexpected toxicities were noted.

CONCLUSIONS

SRS in combination with tucatinib, capecitabine, and trastuzumab appears to be a safe and feasible treatment for HER2 + brain metastases. Further prospective evaluation of potential synergistic effects is warranted.

Clinical outcomes of non-small cell lung cancer brain metastases treated with stereotactic radiosurgery and immune checkpoint inhibitors, EGFR tyrosine kinase inhibitors, chemotherapy and immune checkpoint inhibitors, or chemotherapy alone

OBJECTIVE

Immune checkpoint inhibitors (ICIs) and epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are commonly used in the systemic management of non-small cell lung cancer (NSCLC) brain metastases (BMs). However, optimizing control of NSCLC BM with stereotactic radiosurgery (SRS) and various systemic therapies remains an area of investigation.

METHODS

Between 2016 and 2019, the authors identified 171 NSCLC BM patients with 646 BMs treated with single-fraction SRS within 3 months of receiving treatment with ICIs (n = 56; 33%), EGFR-TKI (n = 30; 18%), chemotherapy and ICIs (n = 23; 14%), or standard chemotherapy alone (n = 62; 36%). Time-to-event analysis was conducted, and outcomes included distant intracranial control (DIC), local control (LC), and overall survival from SRS.

RESULTS

The median follow-up from BM diagnosis was 8.9 months (range 0.3-127 months). The 12-month Kaplan-Meier DIC rates were 37%, 53%, 41%, and 21% (p = 0.047) for the ICI, EGFR-TKI, ICI and chemotherapy, and chemotherapy-alone groups, respectively. On multivariate analysis, DIC was improved with EGFR-TKI (HR 0.4, 95% CI 0.3-0.8, p = 0.005) compared with conventional chemotherapy and treatment with SRS before systemic therapy (HR 0.5, 95% CI 0.3-0.9, p = 0.03) compared with after; and LC was improved with SRS before (HR 0.4, 95% CI 0.2-0.9, p = 0.03) or concurrently (HR 0.3, 95% CI 0.1-0.6, p = 0.003) compared with after. No differences in radionecrosis were noted by timing or type of systemic therapy.

CONCLUSIONS

The authors' analysis showed significant differences in DIC based on receipt of systemic therapy and treatment with SRS before systemic therapy improved DIC. Prospective evaluation of the potential synergism between systemic therapy and SRS in NSCLC BM management is warranted.

Abstract PD7-06: Characteristics of Long-Term Survival in Breast Cancer Brain Metastasis after Stereotactic Radiation

Background: Advances in imaging and systemic therapy have improved the survival for patients with breast cancer brain metastases (BCBM). However, an improved understanding of patients with long-term survival after stereotactic radiation (SRT) for BCBM is warranted and could allow for better prognostication and personalized treatment. Methods: This is a single institution retrospective review of 188 patients who underwent SRT sessions to 685 BCBM from August 2004 to June 2020. Patients who were lost to follow up within 2 years after SRT were excluded. Patients were stratified into 2 groups: those with overall survival (OS) from SRT less than 2 years (short-term survival, STS) and those with OS from SRT of at least 2 years (long-term survival, LTS). Patient, tumor, and treatment characteristics were compared between the 2 groups via the student t-test and Chi-square testing as appropriate. The Kaplan-Meier (KM) method was used to calculate OS, local control (LC), and distant intracranial control (DIC) from the date of SRT. The reverse KM method was used to estimate follow-up from SRT. Results: The median follow up from BCBM diagnosis was 52.8 months (95% CI: 40.5-75.2 months). Of the 685 treated BCBMs, 552 (81%) received stereotactic radiosurgery (SRS) to a median dose of 21 Gy (12-24 Gy) and 133 received fractionated stereotactic radiation therapy (FSRT) to a median dose of 25 Gy (20-35 Gy) in 3-5 fractions. The 2-year LC, DIC, and OS was 78.4%, 26.5%, and 38.3%, respectively. The 5-year OS was 19%. There were 72 patients (38%) in the LTS group and 116 patients (62%) in the STS group. The LTS group had lower rates of invasive lobular carcinoma (0% vs 6%, p=0.001) and higher rate of HER2+ disease (61% vs 30%, p&lt; 0.001). The LTS group had lower rates of concurrent extracranial metastasis (74% vs 89%, p=0.008) and lung metastasis (33% vs 53%, p=0.009), though there were no differences in the rates of bone or liver metastasis. The LTS group had less BCBM at the time of SRT (mean 1.9 vs 2.5, p=0.013) and more often received SRT to a single BCBM (65% vs 42%, p=0.002). There were no significant differences in age or performance status between the groups. Conclusion: Prognosis for patients with BCBM is heterogeneous, as a minority of patients have prolonged OS after SRT. These patients more often have limited BCBM, HER2+ disease, and a lower extracranial disease burden.

Citation Format: Joseph D. Tang, Matthew N. Mills, Chetna Thawani, Daniel E. Oliver, Aixa Soyano, Arnold Etame, Hsiang-Hsuan Michael Yu, Nam Tran, Michael A. Vogelbaum, Peter A. Forsyth, Brian J. Czerniecki, Hatem H. Soliman, Hyo S. Han, Kamran A. Ahmed. Characteristics of Long-Term Survival in Breast Cancer Brain Metastasis after Stereotactic Radiation [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD7-06.

Effects of exogenous amylolytic or fibrolytic enzymes inclusion on in vitro fermentation of lactating dairy cow diets in a dual-flow continuous-culture system

The objective of this study was to determine the effects of including exogenous amylolytic or fibrolytic enzymes in a diet for high-producing dairy cows on in vitro ruminal fermentation. Eight dual-flow continuous-culture fermentors were used in a replicated 4 × 4 Latin square. The treatments were control (CON), a xylanase and glucanase mixture (T1), an α-amylase mixture (T2), or a xylanase, glucanase, and α-amylase mixture (T3). Treatments were included at a rate of 0.008% of diet dry matter (DM) for T1 and T2 and at 0.02% for T3. All treatments replaced the equivalent amount of soybean meal in the diet compared with CON. All diets were balanced to have the same nutrient composition [30.2% neutral detergent fiber (NDF), 16.1% crude protein (CP), and 30% starch; DM basis], and fermentors were fed 106 g/d divided into 2 feedings. At each feeding, T2 was pipetted into the respective fermentor and an equivalent amount of deionized water was added to each fermentor to eliminate potential variation. Experimental periods were 10 d (7 d for adaptation and 3 d for sample collection). Composite samples of daily effluent were collected and analyzed for volatile fatty acids (VFA), NH₃-N, and lactate concentrations, degradability of DM, organic matter, NDF, CP, and starch, and flow and metabolism of N. Samples of fermentor contents were collected from each fermentor at 0, 1, 2, 4, 6, and 8 h after feeding to determine kinetics of pH, NH₃-N, lactate, and VFA concentrations over time. All data were analyzed using PROC GLIMMIX of SAS (SAS Institute Inc.), and the repeated variable of time was included for kinetics measurements. Treatment did not affect mean pH, degradability, N flow and metabolism, or the concentrations of VFA, NH₃-N, or lactate in the effluent samples. Treatment did not affect pH, acetate:propionate ratio, or the concentrations of lactate, NH₃-N, total VFA, acetate, propionate, butyrate, isobutyrate, valerate, or caproate. However, the concentration of total VFA tended to change at each time point depending upon the treatment, and T2 tended to have a greater proportion of 2-methylbutyrate and isovalerate than CON, T1, or T3. As 2-methylbutyrate and isovalerate are branched-chain VFA that are synthesized from branched-chain amino acids, T2 may have an increased fermentation of branched-chain amino acids or decreased uptake by fibrolytic microorganisms. Although we did not observe changes in N metabolism due to the enzymes, there could be changes in microbial populations that utilize branched-chain VFA. Overall, the tested enzymes did not improve in vitro ruminal fermentation in the diet of high-producing dairy cows.

Rectal tumor fragmentation as a response pattern following chemoradiation

Background

Tumor response to neoadjuvant therapy is heterogenous and prognostically important for locally advanced rectal adenocarcinoma (LARC) patients. Commonly applied response classification approaches including tumor regression grading (TRG) and TN downstaging can be discordant. The aim of this study is to compare the prognostic value of discordant tumor response measurement categorized according to the AJCC/CAP TRG schema and ypTN stage.

Methods

This is a single-center retrospective review of 90 consecutive patients with stage II-III rectal cancer receiving neoadjuvant chemoradiation (nCRT), total mesorectal excision (TME) and adjuvant chemotherapy (ACT) between 2007 and 2018. Two pathologists re-examined each case to assign a consensus AJCC TRG. A Cox proportional hazards ratio model assessed the effect of patient, tumor, and treatment factors on disease-free survival (DFS).

Results

Median follow-up after surgery was 46 months (95% CI: 41-50 months). Median age at diagnosis was 55 years (range: 27-80). Most patients were male (58%) and Caucasian (92%) with clinical stage III disease (68%). Seventy-three patients (81%) underwent low anterior resection (LAR), 17 (19%) underwent abdominoperineal resection (APR). The median interval from completion of nCRT to surgery was 62 days (IQR: 56-70 days). The 4-year OS, DFS, and LC was 92.4%, 74.4%, and 90.2%, respectively. In the multivariate analysis, ypTN downstaging was not prognostically significant; however, AJCC TRG score 3 (minimal tumor response to treatment) was strongly predictive for inferior DFS (3-year DFS 79% vs. 25%, P<0.001). Patients with TRG 3 had a significantly higher risk of both local (75% vs. 5%) and distant failure (75% vs. 19%).

Conclusions

Minimal tumor response to neoadjuvant therapy, AJCC TRG 3, irrespective of ypTN downstaging, is a pattern of residual disease that is at highest risk for recurrence. Response categorization discrepancies may be partly explained by alternative patterns of residual disease, including tumor fragmentation, and may be best reflected by TRG. The optimal tumor response categorization method requires further study to best stratify patient risk and management.

The presentation of brain metastases in melanoma, non-small cell lung cancer, and breast cancer and potential implications for screening brain MRIs

PURPOSE

This study assessed the presentation and institutional outcomes treating brain metastases (BM) of breast cancer (BC), non-small cell lung cancer (NSCLC), and melanoma origin.

METHODS

Patients with brain metastases treated between 2014 and 2019 with primary melanoma, NSCLC, and BC were identified. Overall survival (OS) was calculated from dates of initial BM diagnosis using the Kaplan-Meier method.

RESULTS

A total of 959 patients were identified including melanoma (31%), NSCLC (51%), and BC (18%). Patients with BC were younger at BM diagnosis (median age: 57) than NSCLC (65) and melanoma patients (62, p < 0.0001). Breast cancer patients were more likely to present with at least 5 BM (27%) than NSCLC (14%) and melanoma (13%), leptomeningeal disease (23%, 6%, and 6%, p = 0.0004) and receive whole brain radiation therapy (WBRT) (58%, 37%, and 22%, p < 0.0001). There were no differences in surgical resection (24%, 24%, and 29%, p = 0.166). Median OS was shorter for BC patients (9.9, 10.3, and 13.7 months, p = 0.0006).

CONCLUSION

Breast cancer patients were more likely to be younger, present with advanced disease, require WBRT, and have poorer OS than NSCLC and melanoma patients. Further investigation is needed to determine which BC patients are at sufficient risk for brain MRI screening.

Increased Risk for Ipsilateral Breast Tumor Recurrence in Invasive Lobular Carcinoma after Accelerated Partial Breast Irradiation Brachytherapy

BACKGROUND

The suitability criteria for accelerated partial breast irradiation (APBI) from the American Brachytherapy Society (ABS), American Society for Radiation Oncology (ASTRO), and The Groupe Européende Curiethérapie European SocieTy for Radiotherapy & Oncology (GEC-ESTRO) have significant differences.

MATERIALS AND METHODS

This is a single institution retrospective review of 946 consecutive patients with invasive breast cancer who underwent lumpectomy and APBI intracavitary brachytherapy from 2003 to 2018. Overall survival (OS), breast cancer-specific survival (BCSS), relapse-free survival (RFS), and ipsilateral breast tumor recurrence (IBTR) were estimated with Kaplan-Meier method.

RESULTS

Median follow-up time was 60.2 months. Median age was 68 years (46-94 years). The majority of patients had estrogen receptor (ER)-positive disease (94%). There were 821 (87%) cases of invasive ductal carcinoma and 68 cases (7%) of invasive lobular carcinoma (ILC). The 5-year OS, BCSS, RFS, and IBTR were 93%, 99%, 90%, and 1.5%, respectively. Upon univariate analysis, ILC (hazard ratio [HR], 4.6; p = .008) and lack of nodal evaluation (HR, 6.9; p = .01) were risk factors for IBTR. The 10-year IBTR was 2.5% for IDC and 14% for ILC. While the ABS and ASTRO criteria could not predict IBTR, the GEC-ESTRO intermediate risk group was associated with inferior IBTR (p = .04) when compared to both low risk and high risk groups. None of the suitability criteria was able to predict RFS.

CONCLUSION

These results show that APBI is an effective treatment for patients with invasive breast cancer. Expansion of the current eligibility criteria should be considered, although prospective validation is needed. Caution is required when considering APBI for patients with ILC.

IMPLICATIONS FOR PRACTICE

In a large retrospective review of 946 patients with early breast cancer treated with partial mastectomy and accelerated partial breast irradiation (APBI) intracavitary brachytherapy, this study demonstrates durable local control. Patients deemed unsuitable or high risk by the American Brachytherapy Society, American Society for Radiation Oncology, and European Society for Radiotherapy and Oncology guidelines were not at increased risk for ipsilateral breast tumor recurrence (IBTR), suggesting that expansion of the current criteria should be considered. Importantly, however, these results demonstrate that caution should be taken when considering APBI for patients with invasive lobular carcinoma, as these patients had relatively high risk for IBTR (10-year IBTR, 14%).

Capecitabine and stereotactic radiation in the management of breast cancer brain metastases

Background

Little is known about the safety and efficacy of concurrent capecitabine and stereotactic radiotherapy in the setting of breast cancer brain metastases (BCBM).

Methods

Twenty-three patients with BCBM underwent 31 stereotactic sessions to 90 lesions from 2005 to 2019 with receipt of capecitabine. The Kaplan-Meier method was used to calculate overall survival (OS), local control (LC), and distant intracranial control (DIC) from the date of stereotactic radiation. Imaging was independently reviewed by a neuro-radiologist.

Results

Median follow-up from stereotactic radiation was 9.2 months. Receptor types of patients treated included triple negative (n = 7), hormone receptor (HR)+/HER2- (n = 7), HR+/HER2+ (n = 6), and HR−/HER2+ (n = 3). Fourteen patients had stage IV disease prior to BCBM diagnosis. The median number of brain metastases treated per patient was 3 (1 to 12). The median dose of stereotactic radiosurgery (SRS) was 21 Gy (range: 15–24 Gy) treated in a single fraction and for lesions treated with fractionated stereotactic radiation therapy (FSRT) 25 Gy (24–30 Gy) in a median of 5 fractions (range: 3–5). Of the 31 stereotactic sessions, 71% occurred within 1 month of capecitabine. No increased toxicity was noted in our series with no cases of radionecrosis. The 1-year OS, LC, and DIC were 46, 88, and 30%, respectively.

Conclusions

In our single institution experience, we demonstrate stereotactic radiation and capecitabine to be a safe treatment for patients with BCBM with adequate LC. Further study is needed to determine the potential synergy between stereotactic radiation and capecitabine in the management of BCBM.

Trastuzumab Emtansine (T-DM1) and stereotactic radiation in the management of HER2+ breast cancer brain metastases

Background

Due to recent concerns about the toxicity of trastuzumab emtansine (T-DM1) with stereotactic radiation, we assessed our institutional outcomes treating HER2-positive breast cancer brain metastases (BCBM) with T-DM1 and stereotactic radiation.

Methods

This is a single institution series of 16 patients with HER2-positive breast cancer who underwent 18 stereotactic sessions to 40 BCBM from 2013 to 2019 with T-DM1 delivered within 6 months. The Kaplan-Meier method was used to calculate overall survival (OS), local control (LC), distant intracranial control (DIC), and systemic progression-free survival (sPFS) from the date of SRS. A neuro-radiologist independently reviewed follow-up imaging.

Results

One patient had invasive lobular carcinoma, and 15 patients had invasive ductal carcinoma. All cases were HER2-positive, while 10 were hormone receptor (HR) positive. Twenty-four lesions were treated with stereotactic radiosurgery (SRS) to a median dose of 21 Gy (14–24 Gy). Sixteen lesions were treated with fractionated stereotactic radiation (FSRT) with a median dose of 25 Gy (20-30Gy) delivered in 3 to 5 fractions. Stereotactic radiation was delivered concurrently with T-DM1 in 19 lesions (48%). Median follow up time was 13.2 months from stereotactic radiation. The 1-year LC, DIC, sPFS, and OS were 75, 50, 30, and 67%, respectively. There was 1 case of leptomeningeal progression and 1 case (3%) of symptomatic radionecrosis.

Conclusions

We demonstrate that stereotactic radiation and T-DM1 is well-tolerated and effective for patients with HER2-positive BCBM. An increased risk for symptomatic radiation necrosis was not noted in our series.

Abstract PS15-18: Clinical utility of genomic testing for early stage breast cancer patients treated with APBI brachytherapy

Background: Adjuvant radiation after breast conserving surgery (BCS) remains the standard of care for management of patients with early-stage breast cancer (ESBC). Whole breast irradiation (WBI) after lumpectomy for ESBC has demonstrated a 50% reduction in the 10-year rate of recurrence (ROR). NSABP B-39 determined that accelerated partial-breast irradiation (APBI) was effective at reducing the ROR by treating ESBC directly at the tumor bed and that a rigorous course of WBI may not be necessary in select patients. In this study, we determined the impact of genomics and tumor biology on the decision to escalate or de-escalate therapies and on subsequent outcomes beyond anatomic staging for APBI patients. Methods: This analysis included 91 patients with biopsy confirmed invasive ESBC treated with BCS followed by APBI intracavitary brachytherapy at a dose of 34.0 Gy in 10 fractions from 2007 to 2018 who received either MammaPrint (MP) or Oncotype DX (ODx) testing. Clinicopathological risk assessment was performed using MINDACT criteria for clinical guidelines to classify patients as either clinical low risk (CLR) or clinical high risk (CHR). MP stratified patients into either MP Low Risk (MLR) or MP High Risk (MHR). ODx was used with TAILORx-defined cutoffs to stratify patients into either ODx Low Risk (OLR), which is women &gt;50 years of age with HR+, HER2-negative, node-negative breast cancer, Recurrence Score (RS) of 0 to 25 or ODx High Risk (OHR), RS 26-100. If both methods were concordant, the genomic test could not be determined to have impacted the treatment decision. Clinical utility was established in discordant cases when the genomic test guided treatment. Differences in overall survival (OS) were assessed by Kaplan Meier analysis and log-rank test. Relevant clinical data was abstracted from the electronic medical record. Results: Patients (n=91) were 60% CLR and 40% CHR. Of the CLR patients with MP testing, 36% reclassified as MHR; 25% of these (3/12) omitted chemotherapy (CT) despite the discordant result, one of whom (33%) had a local recurrence within 0.25 years of follow-up (FU). Of CHR patients, 54% were MHR, 62% of whom received CT in line with the CHR/MHR result. Of the CHR patients who reclassified as MLR (46%), 91% omitted CT from treatment plans, in alignment with MP results. There were no distant or local recurrences or deaths to date in these groups. About 96% of CLR patients were OLR with 2 events (BC related death). One patient that reclassified as OHR omitted CT despite a discordant CLR/OHR result and has not had a recurrence within 3.9 years of FU. Of the CHR patients who reclassified as OLR (83%), 90% omitted CT in alignment with ODx results; 22% of whom had distant metastases and subsequent death within 1.1 years of FU. Conclusion: 9/11 (82%) of Oncotype discordant patients followed the genomic test recommendation, of whom 22% could not safely do so without impairing outcome. 19/23 (83%) of MammaPrint discordant patients all safely followed this genomic test recommendation. These data suggest that the addition of a genomic signature may allow de-escalation of radiotherapy to APBI even in select high risk patients, provided they follow the systemic therapy recommended by the genomic test result.

CLR/MLR (n=21)CHR/MLR (n=11)CLR/MHR (n=12)CHR/MHR (n=13)Followed MP YES21 (100%)10 (91%)9 (75%)8 (62%)Followed MP NO01 (9%)3 (25%)5 (38%)EVENT001 LRR03-year OS (95% CI)100%100%100%100%CLR/OLR (n=23)CHR/OLR (n=10)CLR/OHR (n=1)CHR/OHR (n=2)Followed ODx YES19 (83%)9 (90%)02 (100%)Followed Odx NO4 (17%)1 (10%)1 (100%)0EVENT2 Deaths at 6.3 and 7.9 years2 Deaths at 0.5 and 1.7 years01 Death at 6.5 years(RS 21 & 25)(RS 17 & 23)(RS 32)3-year OS (95% CI)100%77.8% (36.5-93.9)100%100%

Citation Format: Roberto Diaz, Matthew N Mills, Ronica H Nanda, Lisa L Stout, Scott Dube, Taghrid A Altoos, Jason P Wilson, Kathleen G Allen, Jolanta L Baginski, Peter W Blumencranz. Clinical utility of genomic testing for early stage breast cancer patients treated with APBI brachytherapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS15-18.

Abstract PS14-19: Characteristics of breast cancer brain metastases presentation by subtype and validation of the modified breast graded prognostic assessment

Purpose: Breast cancer brain metastases (BCBM) diagnosis is increasing in frequency due to improved systemic control and imaging techniques. Differences have been noted in rates of central nervous system (CNS) relapse and biologic subtype. The modified breast graded prognostic assessment (breast-GPA) was initially validated in patients treated between 1996-2013 and considers biologic subtype. In this study, we characterize patients diagnosed with BCBM by subtype and validate the breast-GPA in a modern cohort of patients.

Methods: All patients with BCBM treated at our institution with radiotherapy between 2016 and 2019 were identified. Characteristics of patients’ initial brain metastasis diagnosis were retrieved from the clinical chart and radiologic examinations. To test differences between cohorts, the Kruskal-Wallis and Pearson’s chi-square tests were used when appropriate. Overall survival (OS) was calculated from the date of brain metastasis diagnosis to the date of death using the Kaplan-Meier (KM) method, with the log-rank test used to examine differences between groups.

Results: A total of 122 BCBM patients were identified. Breast cancer subtypes included hormone receptor (HR)+/HER2- (45%), triple negative (TN) (25%), HR-/HER2+ (16%), and HR+/HER2+ (14%). The first treatment for BCBM patients following diagnosis was whole brain radiation (51%), surgery followed by stereotactic radiation (28%), and stereotactic radiation (21%). The interval between breast cancer diagnosis and diagnosis of BCBM was longest for HR+/HER2- 4.5 years, followed by TN 2.8 years, HR+/HER2+ 2.3 years, HR-/HER2+ 1.9 years, p=0.003. The interval from systemic metastases to BCBM diagnosis trended towards the shortest for TN patients 6.6 months, p=0.15. A total of 34 patients (28%) were diagnosed with leptomeningeal disease (LMD) at initial brain metastases presentation. LMD was diagnosed most commonly at presentation in HR+/HER2- (36%) followed by , TN (26%), HR-/HER2+ (26%), and HR+/HER2+ (6%), p=0.06. No differences were noted based on receptor typessubtype and age, symptomatic intracranial disease, number of brain metastases, type of first intracranial treatment or concurrent systemic metastases at initial BCBM presentation, all p &gt; 0.05. Twenty-four month KM OS rates following diagnosis of brain metastasis for breast-GPA 0-1, 1.5-2, 2.5-3, and 3.5-4 groups were 14%, 27%, 33%, and 86% (p=0.0005), respectively.

Conclusions: In our institutional analysis, similarities were noted in the initial presentation of BCBM based on receptor typesubtype. Significant differences were noted in OS based on the modified breast-GPA. Further investigation is needed to determine which subtypes of asymptomatic breast cancer patients are at sufficient risk to warrant brain MRI screening.

Citation Format: Yuki Kawahara, Matthew Fahey, Thrisha K Potluri, Matthew N Mills, Nicholas B Figura, Iman R Washington, Roberto Diaz, Timothy J Robinson, Hsiang-Hsuan M Yu, Arnold B Etame, James Liu, Michael A Vogelbaum, Brian J Czerniecki, Peter A Forsyth, Hatem H Soliman, Hyo S Han, Kamran A Ahmed. Characteristics of breast cancer brain metastases presentation by subtype and validation of the modified breast graded prognostic assessment [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS14-19.

Management of ductal carcinoma in situ with accelerated partial breast irradiation brachytherapy: Implications for guideline expansion

PURPOSE

Accelerated partial breast irradiation (APBI) for patients with ductal carcinoma in situ (DCIS) is controversial, and the suitability criteria from the American Brachytherapy Society (ABS), American Society of Therapeutic Radiology and Oncology (ASTRO), and the European Society for Radiotherapy and Oncology (GEC-ESTRO) have important differences.

METHODS AND MATERIALS

This is a single-institution retrospective review of 169 consecutive patients with DCIS who underwent lumpectomy followed by APBI intracavitary brachytherapy from 2003 to 2018. Outcomes, including overall survival, recurrence-free survival (RFS), ipsilateral breast tumor recurrence, and distant metastasis, were estimated with the Kaplan-Meier method.

RESULTS

The median followup time was 62.5 months. Median age was 66 years (47-89 years). The majority of patients had estrogen receptor-positive disease (89%). Fifty patients (30%) had Grade 3 disease. Of the 142 patients with adequate pathology interpretation, 91 and 108 cases had margins ≥ 3 mm and ≥2 mm, respectively. Most patients (72%) were prescribed and started endocrine therapy. Of the patients evaluable for ABS criteria (N = 130), 97 met the suitability criteria. Of the patients evaluable for ASTRO criteria (N = 129), 42 were deemed cautionary and 33 were deemed unsuitable. Of the patients evaluable for GEC-ESTRO criteria (N = 143), 141 cases were at intermediate risk and two were at high risk. Five-year ipsilateral breast tumor recurrence, RFS, and overall survival were 0.6%, 97.7%, and 97.2%, respectively. The ABS, ASTRO, and GEC-ESTRO criteria failed to significantly predict for RFS.

CONCLUSIONS

These results, although limited by short-term followup, indicate that expansion of the eligibility criteria of APBI for patients with DCIS should be considered.

Stereotactic Body Radiation Therapy in Oligometastatic Uterine Cancer: Clinical Outcomes and Toxicity

We report on clinical outcomes in patients with oligometastatic uterine cancer treated with stereotactic body radiation therapy (SBRT). Twenty-seven patients with 61 lesions were treated with SBRT. Median follow-up was 16.9 months. Local control was achieved in 49/61 (80.3%) lesions. One-year local-progression-free survival and overall survival were 75.9% and 65.4%. Lesions with favorable response were smaller than lesions with unfavorable response (p = .007). Liver lesions were less likely to achieve favorable response (p = .0128). There were no grade 3 or 4 events. Treatment with SBRT can provide excellent local control in oligometastatic uterine cancer with minimal toxicity.

Management of brain metastases in breast cancer: a review of current practices and emerging treatments

PURPOSE

Breast cancer brain metastases (BCBM) are becoming an increasingly common diagnosis due to improved systemic control and more routine surveillance imaging. Treatment continues to require a multidisciplinary approach managing systemic and intracranial disease burden. Although, improvements have been made in the diagnosis and management of BCBM, brain metastasis patients continue to pose a challenge for practitioners.

METHODS

In this review, a group of medical oncologists, radiation oncologists, radiologists, breast surgeons, and neurosurgeons specializing in the treatment of breast cancer reviewed the available published literature and compiled a comprehensive review on the current state of BCBM.

RESULTS

We discuss the pathogenesis, epidemiology, diagnosis, treatment options (including systemic, surgical, and radiotherapy treatment modalities), and treatment response evaluation for BCBM. Furthermore, we discuss the ongoing prospective trials enrolling BCBM patients and their biologic rationale.

CONCLUSIONS

BCBM management is an increasing clinical concern. Multidisciplinary management combining the strengths of surgical, systemic, and radiation treatment modalities with prospective trials incorporating knowledge from the basic and translational sciences will ultimately lead to improved clinical outcomes for BCBM patients.

Long term control and preservation of renal function after multiple courses of stereotactic body radiation therapy for renal cell carcinoma

Renal cell carcinoma (RCC) is usually treated with surgery, with or without systemic therapy. For select patients, stereotactic body radiation therapy (SBRT) may be a suitable alternative. Although many reports exist on the successful use of SBRT, very few have described long term outcomes with regard to disease progression and renal function. We report a rare case of a single patient with primary, metastatic, and locally recurrent renal cell carcinoma who was successfully treated with SBRT. The patient has been disease-free for 8 years since treatment, with stable renal function even after two courses of SBRT to her solitary functioning kidney.

Abstract P4-08-15: Locoregional recurrence in invasive breast cancer and association with tumor infiltrating leukocyte (TIL) presence

Background:

The presence of TILs has been correlated with clinical outcomes and response to therapy in breast cancer. However, evaluation of TILs in breast cancer has largely been based on pathologic examination of tumor samples. Here, we report the relationship between invasive breast cancer locoregional recurrence (LRR) and the presence of TILs estimated by transcriptomic analysis with the deconvolution algorithm CIBERSORT.

Methods:

Patients were identified from an IRB-approved prospective tissue collection protocol at one academic institution and two community hospitals. 526 primary breast tumor samples were identified and gene expression profiling was assessed with high density Affymetrix microarray chips. Proportions of 22 different TIL types in samples were inferred based on the CIBERSORT algorithm, which uses gene expression data to estimate TIL presence. TIL presence was determined by dichotomization at the level of the first quartile among all samples (&gt;Q1=TIL presence). Patient characteristics and clinical outcomes were obtained by chart review. Time to event analysis was performed using Kaplan Meier (KM) estimates and the log-rank test. Associations between patient factors, tumor factors, TIL presence, and LRR were explored with univariable (UVA) and multivariable (MVA) analyses. Factors significant on UVA (p&lt;0.10) were included on MVA. P&lt;0.05 was considered statistically significant on MVA.

Results:

526 women with invasive breast cancer and available genomic profiling were retrospectively identified for analysis. Median age at diagnosis was 58 years. 70% of tumors were Stage I-II. 69% were luminal subtypes and 17% were triple negative. 37% received mastectomy, 25% received mastectomy + radiation, and 32% received breast conserving therapy. 64% received chemotherapy, and 62% received hormonal therapy. Median follow-up was 74.4 months. There were 61 LRRs. We found significant differences in time to LRR when comparing presence vs. no presence of resting memory CD4+ T-cells (RMCD4+) (p=0.01), activated natural killer cells (ANK) (p=0.003), and neutrophils (PMNs) (p=0.03). On UVA, factors associated with LRR were patient age at diagnosis (p=0.009), pathologic T stage (p=0.045), Estrogen receptor status (p=0.03), biologic subtype (p=0.01), lymphovascular invasion (LVI) (p=0.018), positive margins (p&lt;0.0001), receipt of hormonal therapy (0.014), and presence of tumor infiltrating RMCD4+ (p=0.012), ANK (p=0.0004), and PMNs (p=0.033). On MVA, factors remaining significant were LVI (HR 2.16 CI 1.13-4.13, p=0.011), positive margins (HR 4.36 CI 1.57-12.11, p=0.018), receipt of hormonal therapy (HR 0.31 CI 0.12-0.77, p=0.042), and presence of RMCD4+ (HR 0.48 CI 0.26-0.88, p=0.017), ANK (HR 0.43 CI 0.23-0.83, p=0.012), and PMNs (HR 2.15 CI 1.02-4.53, p=0.043).

Conclusion:

In this study of 526 women with invasive breast cancer, we identified that enrichment of certain TILs is associated with LRR. These results suggest genomic-based assays of TIL presence may be useful to predict LRR in invasive breast cancer.

Citation Format: Liveringhouse CL, Grass GD, Figura NB, Mills MN, Purcell JD, Rosensweig SR, Blumencranz PW, Allen KG, Ahmed KA, Harrison LB, Torres-Roca JF, Robinson TJ, Diaz R. Locoregional recurrence in invasive breast cancer and association with tumor infiltrating leukocyte (TIL) presence [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-08-15.

Radiotherapy for early stage diffuse large B-cell lymphoma with or without double or triple hit genetic alterations

We investigated whether adding radiation (RT) to systemic therapy improved outcomes in early stage diffuse large B-cell lymphoma (DLBCL) patients with or without double- or triple-hit lymphoma (DHL/THL) biology. This analysis included 183 patients profiled with fluorescent in situ hybridization (FISH) for alterations in MYC, BLC2, and/or BCL6. A total of 146 (80%) were non-DHL/THL, 27 (15%) were DHL, and 10 (6%) were THL. Systemic therapy without RT resulted in inferior freedom from relapse (FFR) (HR: 2.28; 95% CI, 1.10-4.77; p = .02). The median FFR for non-DHL/THL was not reached and was 33 and 22.3 months for DHL and THL, respectively; p < .001. Low-risk (R-IPI <2) DHL/THL patients treated with rituximab-based therapy had 3-year FFR rates of 11% and 71% for systemic therapy without and with RT, respectively; p = .04. No differences in overall survival were observed between the treatment groups. Treatment intensification with RT may improve early stage DHL/THL outcomes.

Histologic heterogeneity of triple negative breast cancer: A National Cancer Centre Database analysis

BACKGROUND

Triple negative breast cancer (TNBC) is an aggressive disease, but recent studies have identified heterogeneity in patient outcomes. However, the utility of histologic subtyping in TNBC has not yet been well-characterised. This study utilises data from the National Cancer Center Database (NCDB) to complete the largest series to date investigating the prognostic importance of histology within TNBC.

METHODS

A total of 729,920 patients (pts) with invasive ductal carcinoma (IDC), metaplastic breast carcinoma (MBC), medullary breast carcinoma (MedBC), adenoid cystic carcinoma (ACC), invasive lobular carcinoma (ILC) or apocrine breast carcinoma (ABC) treated between 2004 and 2012 were identified in the NCDB. Of these, 89,222 pts with TNBC that received surgery were analysed. Kaplan-Meier analysis, log-rank testing and multivariate Cox proportional hazards regression were utilised with overall survival (OS) as the primary outcome.

RESULTS

MBC (74.1%), MedBC (60.6%), ACC (75.7%), ABC (50.1%) and ILC (1.8%) had significantly different proportions of triple negativity when compared to IDC (14.0%, p < 0.001). TNBC predicted an inferior OS in IDC (p < 0.001) and ILC (p < 0.001). Lumpectomy and radiation (RT) were more common in MedBC (51.7%) and ACC (51.5%) and less common in MBC (33.1%) and ILC (25.4%), when compared to IDC (42.5%, p < 0.001). TNBC patients with MBC (HR 1.39, p < 0.001), MedBC (HR 0.42, p < 0.001) and ACC (HR 0.32, p = 0.003) differed significantly in OS when compared to IDC.

CONCLUSION(S)

Our results indicate that histologic heterogeneity in TNBC significantly informs patient outcomes and thus, has the potential to aid in the development of optimum personalised treatments.