Mechanisms of Intrinsic Radioresistance in Breast Cancer Identify Potential Therapeutic Vulnerabilities

PURPOSE/OBJECTIVE(S)

Clinical management of breast cancer (BC) includes radiation therapy (RT) for most women, though the molecular mechanisms that underly RT response and intrinsic radioresistance are poorly understood. Both in vitro and in vivo models aid in our understanding of radiobiology, and we hypothesized that transcriptional changes caused by radiation in vitro in BC cell lines would be recapitulated in an in vivo mouse xenograft model and uncover targetable mechanisms of radioresistance in BC.

MATERIALS/METHODS

Radiosensitivity was measured with clonogenic survival assays in 16 cell lines. RNA-seq experiments in vitro and in vivo were performed in an RT resistant (SUM-159) and RT sensitive (ZR-75) cell line 24 hrs after 4 Gy or after 2 Gy x 6 fractions, respectively. Differentially expressed genes (DEGs) were identified from RNA-seq data with DeSeq2 followed by pathway analysis with iPathwayGuide.

RESULTS

RT sensitivity was subtype independent in 16 BC cell lines, with SUM-159 radioresistant (SF 0.88) and ZR-75-1 radiosensitive (SF 0.29). There were 75 unique pathways that were significantly altered after RT in SUM-159 cells (53 pathways in vivo only, 36 pathways in vitro only, 14 both conditions; adjusted p-value < 0.05) and 85 unique pathways that were significantly altered after RT in ZR-75-1 cells (16 pathways in vivo only, 72 in vivo only, 3 both conditions; adjusted p-value < 0.05). Pathways that were significantly affected in both cell lines exclusively in the in vitro condition include canonical RT response pathways such as cell cycle, cellular senescence, and DNA replication, though the direction of DEGs were opposite in the two cell lines for each of these pathways. The IL-17 signaling pathway was significantly altered for both cell lines in vivo. Of the pathways that were significantly altered in both conditions for SUM-159 cells, inflammation, including chemokine signaling pathway and cytokine-cytokine receptor interaction, were among the most significant. Significantly more cytokines were upregulated following RT in vivo than in vitro. Cytokines were not upregulated in ZR-75-1 cells in vitro or in vivo.

CONCLUSION

Taken together, the significant changes in the IL-17 pathway and the upregulation of cytokines only in vivo indicate a potential of the tumor microenvironment in the in vivo condition that the in vitro condition lacks. Increased heterogeneity in vivo relative to in vitro may also explain the absence of several canonical RT response pathways in the in vivo conditions for each cell line. Notably, the opposite direction of DEG changes in the canonical RT response pathways between the 2 cell lines with disparate radiosensitivity levels may point to important biologic vulnerabilities that may be targeted in the resistant SUM-159 cells. Future studies are underway using additional BC cell lines and single-cell analysis to better understand RT response heterogeneity.

Transcriptomic Analysis to Uncover the Mechanism of Radiosensitization of AR-Positive Triple Negative Breast Cancers with AR Inhibition

PURPOSE/OBJECTIVE(S)

The androgen receptor (AR) has been shown to drive tumor growth in triple negative breast cancers (TNBC), and previous work demonstrated AR inhibition as a strategy for radiosensitization in AR-positive (AR+) TNBC. Despite its role in radioresistance, the mechanistic role of AR in response to radiation therapy (RT) remains unknown, as does the benefit of 2nd generation anti-androgens in this context. We hypothesized that all 2nd generation anti-AR therapy would radiosensitize similarly and that canonical AR transcriptional function was responsible for radioresistance in these models.

MATERIALS/METHODS

Radiosensitization was assessed using 2nd generation AR antagonists (apalutamide, enzalutamide, and darolutamide) using clonogenic survival assays in MDA-MB-453, SUM185, MFM-223, and MDA-MB-231 cells at 2-6Gy. Cellular fractionation experiments were performed and quantitated to determine the location of the AR protein in cells treated with AR agonists +/- RT. RNA Seq was performed and transcriptomic approaches were used (Advaita iPathway analysis) to investigate AR-mediated effects in response to RT.

RESULTS

Inhibition with the 2nd generation anti-androgens enzalutamide and apalutamide is sufficient to radiosensitize AR+ TNBC models (rER: 1.34-1.41); while darolutamide had no effect on radiosensitivity (rER: 0.96-1.11). Additionally, TNBC cells with low AR expression were not radiosensitized by AR inhibition with any drug (rER: 0.96-1.03). While stimulation with the synthetic androgen methyltrienolone R1881 is sufficient to induce nuclear translocation of AR in AR+ TNBC cells, AR inhibition with enzalutamide, apalutamide, or darolutamide blocked AR nuclear translocation under growth conditions with charcoal stripped serum or fetal bovine serum. When cells are treated with R1881+RT, nuclear translocation of AR was induced at similar or greater levels compared to R1881 alone in AR+ TNBC cells. Combination treatment of RT with enzalutamide in the presence of hormones reduced nuclear localization of AR (32-39% reduction) compared to RT alone. RNA-sequencing after RT identified transcriptional changes potentially regulated by AR+RT, including changes in the NHEJ pathway genes. Additionally, pathway analyses in these models demonstrated changes in the MAPK/ERK signaling pathway, among others, that may regulate RT resistance in AR+ TNBC models.

CONCLUSION

Most 2nd generation anti-androgens confer radiosensitization in AR+ TNBC models with cellular localization changes of AR noted after RT. The known structural differences amongst 2nd generation anti-androgens may account for differences in radiosensitization noted. Furthermore, AR-mediated radioresistance may be due, at least in part, to downstream MAPK/ERK signaling. This work builds on the mechanistic understanding of AR-mediated radioresistance in AR+ TNBC and may expose vulnerabilities to overcome resistance to combination treatment with AR inhibition and RT.

Disparities in Acute Radiation-Related Pain and Dermatitis between Black and White Patients with Early-Stage Breast Cancer Receiving Adjuvant Radiation Following Breast Conserving Surgery

PURPOSE/OBJECTIVE(S)

Historically, black patients with cancer experience poor clinical outcomes and low quality of life due to inadequate screening and management of cancer-related treatment toxicities. There are limited data documenting racial disparities in acute radiation-related toxicities (ARRTs) for patients with early-stage breast cancer. Therefore, we compared ARRTs between Black (B) and White (W) patients receiving adjuvant radiation following breast conserving surgery (BCS).

MATERIALS/METHODS

This retrospective analysis included 317 patients with stage 0/1 breast cancer treated with adjuvant radiation between October 2019 and February 2022. 29% (N = 81) were B and 71% (N = 236) were W, with an average age of 65 (range: 32-88) for both. We abstracted weekly on-treatment-visit clinical notes (OTVs) completed by a nurse and radiation oncologist who utilized the Common Terminology Criteria for Adverse (CTCAE) v4.0 to evaluate each patient's pain score (scaled 0-10, 0 = no pain and 10 = worst), radiation dermatitis (RD; Grade 0-4), as well as non-CTCAE descriptors of pain and presence of hyperpigmentation or pruritus. We compared onset and severity of pain and rates of RD and pruritus between B and W patients.

RESULTS

The proportion reporting pain was significantly lower among B vs. W patients (43.8% vs. 63.6%; P = 0.002). Of patients qualitatively reporting pain, B patients were significantly more likely to have their pain scored as 0 than W patients (24.3% vs. 11.7%; P = 0.024). B patients had significantly lower median pain scores than W patients (P = 0.010), with a median score of 3 (interquartile range [IQR]: 0-5.5) vs. 5 (IQR: 4-8). B patients had a significantly longer time to pain identification than W patients (P = 0.027), with median time to pain of 10th fraction (IQR: 4-13.5) vs. 8th fraction (IQR: 4-11). Radiation dermatitis was graded as 0 (50.6% vs 8.5%; P<0.001), 1 (44.4% vs 82.6%; P<0.001), 2 (14.8% vs 15.3%, P = NS), and 3 (3.7% vs 0.4%; P = 0.023), with no grade 4 RD, amongst B and W patients, respectively. Of note, B patients experiencing mild hyperpigmentation were graded as 0. We found no statistically significant differences in incidence of pruritus.

CONCLUSION

Qualitative and quantitative analyses of ARRTs based on CTCAE v4.0 show discordance in pain scores and radiation dermatitis. The underscoring of pain amongst B patients suggests possible cultural hesitancy to report pain or implicit biases in evaluating pain suggesting the need for alternative ways to discuss and score pain in B patients. Our data suggests that CTCAE does not effectively assess radiation dermatitis in B patients. There are no descriptors of hyperpigmentation in grading of radiation dermatitis in CTCAE, which may lead to underreporting in dark-skinned individuals. Better assessment tools are needed to document ARRTs to ensure appropriate evaluation and treatment across all racial groups.

Does age affect outcome with breast cancer?

Prior data about the influence of age at diagnosis of breast cancer on patient outcomes and survival has been conflicting. Using the Breast Cancer Outcomes Unit database at BC Cancer, this retrospective population-based study identified a cohort of 24,469 patients diagnosed with invasive breast cancer between 2005 and 2014. Median follow-up was 11.5 years. We analyzed clinical and pathological features at diagnosis and treatment specific variables compared across the following age cohorts: <35, 35-39, 40-49, 50-59, 60-69, 70-79, and 80 years of age and older. We assessed the impact of age on breast cancer specific survival (BCSS) and overall survival (OS) by age and subtype. There were distinct clinical-pathological and treatment pattern differences at both extremes of age at diagnosis. Patients <35 and 35-39 years old were more likely to present with higher risk features, HER2 positive or triple-negative biomarkers, and more advanced TNM stage at diagnosis. They were more likely to undergo treatment with mastectomy, axillary lymph node dissection, radiotherapy and chemotherapy. Conversely, patients ≥80 years old were generally more likely to have hormone-sensitive HER2-negative disease, and lower TNM stage at diagnosis. They were less likely to undergo surgery or be treated with radiotherapy and chemotherapy. Both younger and elderly age at breast cancer diagnosis were independent risk factors for poorer prognosis after controlling for subtype, LVI, stage, and treatment factors. This work will help clinicians to more accurately estimate patient outcomes, patterns of relapse, and provide evidence-based treatment recommendations.

Treatment Patterns and Outcomes of Pre-operative Neoadjuvant Radiotherapy in Patients with Early-onset Rectal Cancer

Pre-operative radiotherapy for early-stage rectal cancer has risks and benefits that may impact treatment choice in young patients. We reviewed radiotherapy use and outcomes for rectal cancer by age. Patients with early-stage rectal cancer in the Canadian province of British Columbia from 2002-2016 were identified (n=6232). Baseline characteristics, treatment response, overall survival (OS), disease-free survival (DFS), disease-specific survival (DSS), and locoregional recurrence rate (LRR) were compared between patients &lt;50 (early-onset) (n=532) and ≥50 years old (average-onset) (n=5700). Early-onset patients were more likely to receive pre-operative chemoradiotherapy than short-course radiotherapy (OR: 2.20, 95% CI: 1.67-2.89, P&lt;0.0001), but also had higher nodal (P=0.00096) and overall clinical staging (P=0.033). Cancer downstaging and pCR rates were similar in those receiving neoadjuvant chemoradiotherapy by age. Early-onset and average-onset patients had similar DSS (P=0.91) and DFS (P=0.27) in multivariate analysis unless non-colorectal deaths, which were higher in older patients, were censored in the DFS model (HR: 1.30, 95% CI: 1.01-1.68, P=0.042). LRR also did not differ between age groups (P=0.88). Outcomes did not differ based on radiotherapy type. Young patients with rectal cancer are more likely to present with higher staging and receive long-course chemoradiotherapy. DSS did not differ by age group, however young patients had worse DFS when we censored competing risks of death in older patients.

Characterizing the KRAS G12C mutation in metastatic colorectal cancer: a population-based cohort and assessment of expression differences in The Cancer Genome Atlas

Introduction

In metastatic colorectal cancer (mCRC), RAS mutations impart inferior survival and resistance to anti-epidermal growth factor receptor (EGFR) antibodies. KRAS G12C inhibitors have been developed and we evaluated how KRAS G12C differs from other RAS mutations.

Patients and Methods

This retrospective review evaluated patients in British Columbia, Canada with mCRC and RAS testing performed between 1 January 2016 and 31 December 2018. Sequencing information from The Cancer Genome Analysis (TCGA) was also obtained and analysed.

Results

Age at diagnosis, sex, anatomic location and stage at diagnosis did not differ by RAS mutation type. Progression free survival on first chemotherapy for patients with metastatic KRAS G12C tumours was 11 months. Median overall survival did not differ by RAS mutation type but was worse for both KRAS G12C (27 months) and non-G12C alterations (29 months) than wildtype (43 months) (p = 0.01). Within the TCGA, there was no differential gene expression between KRAS G12C and other RAS mutations. However, eight genes with copy number differences between the G12C and non-G12C RAS mutant groups were identified after adjusting for multiple comparisons (FITM2, PDRG1, POFUT1, ERGIC3, EDEM2, PIGU, MANBAL and PXMP4). We also noted that other RAS mutant mCRCs had a higher tumour mutation burden than those with KRAS G12C mutations (median 3.05 vs 2.06 muts/Mb, p = 4.2e-3) and that KRAS G12C/other RAS had differing consensus molecular subtype distribution from wildtype colorectal cancer (CRC) (p < 0.0001) but not each other (p = 0.14).

Conclusion

KRAS G12C tumours have similar clinical presentation to other RAS mutant tumours, however, are associated with differential copy number alterations.

Abstract P4-07-04: Bc cancer ipsilateral breast tumor recurrence (BCC IBTR) nomogram

INTRODUCTION:. Local and systemic treatments for breast cancer have evolved in the past decades. This study reports the development of a modern population-based nomogram to individualize local recurrence (LR) risk estimates for patients treated with breast conservation surgery (BCS). The magnitude of benefit of adjuvant breast radiotherapy (BRT) depends on individual patient, tumor, and treatment characteristics (1). Nomograms can provide accurate predictions of LR and the absolute LR benefit of BRT that can assist patients in making informed decisions regarding BRT. This nomogram is based on a large cohort of women with prospectively captured biomarker data and modern systemic therapies including anti-human epidermal growth factor receptor 2 (HER2) therapy. METHOD:. Study Population:. The study cohort included women treated curatively for newly diagnosed breast cancer between 1st January 2005 and 31st December 2014. Inclusion criteria were: age &gt;16 years, invasive ductal or lobular carcinoma, stage I-III, and BCS. Patients with metastatic disease, prior or synchronous contralateral breast cancer, unknown tumor or treatment characteristics, or treated with neoadjuvant therapy or mastectomy were excluded. Nomogram Development and Validation:. Age, tumor size, number of positive lymph nodes, grade, margin status, lymphovascular invasion (LVI), extensive intraductal component (EIC), estrogen receptor (ER), progesterone receptor (PR), HER2 status, use of chemotherapy, hormonal therapy, and radiotherapy with or without boost were recorded for each patient. The endpoint was LR as the first event. Fine and Gray’s competing risk model, with distant recurrence and death as competing risks, was used for the multivariable analysis, adjusting for demographics, tumor, and treatment factors. Hazard ratio (HR) and 95% confidence interval (CI) for each variable were calculated. The multivariable model forms the basis for the nomogram, which is being internally validated using the bootstrap and cross-validation. RESULTS:Of 11,310 patients, there were 429 LR (crude risk = 3.8%). The HR and 95% CIs from the Fine and Gray model for each of the variables in the nomogram are presented in the table. Age, number of positive nodes, grade, ER, LVI, margins, hormone therapy, chemotherapy, and radiotherapy were independent prognostic factors for LR. For patients treated with RT, the predicted 10-year cumulative incidence of LR ranged from 2.4% in patients with low-risk disease to 12.5% in patients with high-risk disease. CONCLUSION:A new nomogram for local recurrence, based on patients who had ER/PR/HER2 testing and who received modern systemic therapies is being developed. It will assist clinicians and patients individualize estimates of local recurrence risk and improve shared decision-making regarding the use of BRT in contemporary practice. REFERENCES:. (1)Sanghani, M., et al J Clin Oncol.,2010; 28(5), 718-722.

Cox regression hazard ratios and confidence intervals for variablesCharacteristicHR95%CIp-valueAge0.980.970.99&lt;0.01T-size1.011.001.010.14No. nodes1.041.011.070.005GradeGrade1---Grade21.751.322.33&lt;0.001Grade32.541.813.56&lt;0.001ERNeg---Pos1.441.012.060.046PRNeg---Pos0.790.611.030.084Her2Neg---Pos0.960.731.250.8LVINeg---Pos1.961.552.47&lt;0.001Unk1.360.722.580.3Margin StatusNeg---Close1.411.081.840.011Pos1.681.082.590.200Extensive DCISNo---Yes1.140.841.550.4HTNo---Yes0.520.410.65&lt;0.001ChemoNo---Yes0.540.420.71&lt;0.001RTNo---Yes0.330.260.42&lt;0.001BoostNo---Yes0.800.621.040.094

Citation Format: Dylan Narinesingh, Alan Nichol, Pauline Truong, Lovedeep Gondara, Caroline Speers, Laveniya Kugathasan, Caroline Lohrisch, Dave Voduc, Nafisha Lalani. Bc cancer ipsilateral breast tumor recurrence (BCC IBTR) nomogram [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-07-04.

Impact of TAILORx on chemotherapy prescribing and 21-gene recurrence score-guided treatment costs in a population-based cohort of patients with breast cancer

BACKGROUND

The trial assigning individualized options for treatment (Rx) (TAILORx) confirmed the predictive value of the 21-gene recurrence score (RS) assay in hormone receptor (HR)-positive, HER2-negative, node-negative breast cancer and established thresholds for chemotherapy benefit in younger and older patients. Real-world chemotherapy use and RS-guided treatment costs in British Columbia post-TAILORx were examined.

METHODS

The authors assembled 3 cohorts of HR-positive, HER2-negative, node-negative patients with breast cancer defined by diagnosis: before RS funding (cohort 1 [C1]: January 2013-December 2013), after introduction of public RS funding (cohort 2 [C2]: July 2015-June 2016), and after TAILORx results (cohort 3 [C3]: July 2018-June 2019). Chemotherapy use was compared between cohorts by age and RS. Budgetary impacts of RS testing on chemotherapy costs were evaluated pre- and post-TAILORx.

RESULTS

Among the 2066 patients included, chemotherapy use declined by 19% after RS funding was introduced and by an additional 23% after TAILORx publication (P = .001). Reduction in chemotherapy use was significant for RS 11-20 tumors (C3 vs C2, P = .004). There was no significant change in chemotherapy use in patients >50 years old (C2:12% vs C3:10%, P = .22). RS testing was associated with higher cost savings post-TAILORx, except in patients 70 to 80 years old, where testing led to excess costs when adjusting for the low rate of RS-concordant chemotherapy prescribed.

CONCLUSIONS

TAILORx has had population-based impacts on chemotherapy prescribing in intermediate RS tumors and patients ≤50 years old. The lower clinical use of RS and increased spending in patients 70-80 years old highlights the importance of careful selection of older candidates for high-cost genomic testing.

LAY SUMMARY

The 21-gene recurrence score (RS) test helps predict whether patients with hormone-positive, HER2-negative, lymph node-negative breast cancer are likely to benefit from chemotherapy. The recent trial assigning individualized options for treatment (Rx) (TAILORx) found that patients with intermediate RS tumors did not benefit from chemotherapy. The authors assessed whether TAILORx results translated to real-world changes in chemotherapy prescribing patterns. In this study, chemotherapy use decreased by 23% after TAILORx, with the greatest reductions seen among intermediate RS tumors and younger patients. In contrast, RS testing had lower clinical value and increased treatment costs in elderly patients, which requires further study to ensure optimal care for this age group.

Impact of Tumor Location on Patient Outcomes in Small Bowel Cancers

BACKGROUND

Small bowel cancers are rare gastrointestinal malignancies and tumor location impact on outcomes is unclear.

MATERIAL AND METHODS

A retrospective review was performed on stage I to IV small bowel cancer cases from 2000 to 2017 in British Columbia, Canada. Baseline patient characteristics, disease-free survival (DFS) and overall survival (OS) were evaluated by tumor location and systemic therapy use patterns were summarized.

RESULTS

Of 340 patients included, primary tumor distribution was: duodenum (51.2%), ileum (19.1%), jejunum (18.5%), and unspecified (11.2%). Median DFS for stage I to III disease was 37.7, 49.1, and 26.7 months for duodenal, jejunal, and ileal tumors (P = .018). Median OS was 9.6, 35.2, and 20.1 months for duodenal, jejunal, and ileal tumors (P < .0001). Compared to duodenal primaries, both jejunal and ileal tumors were associated with significantly improved OS (HR 0.43, P < .001 for jejunal; HR 0.71, P = .035 for ileal). Adjuvant therapy was given to 21.6% of stage II and 50.6% of stage III cancers. Among patients with metastatic disease, median OS was 4.2, 11.4, and 6.9 months for duodenal, jejunal, and ileal tumors (P = .0019). Jejunal tumors had the best prognosis (HR 0.48, P = .001 vs. duodenum).

CONCLUSION

Survival differences exist when small bowel cancers were assessed by tumor location, and jejunal tumors portended better prognosis overall.

Association between regional nodal irradiation and breast cancer recurrence-free interval for patients with low-risk, node-positive breast cancer

PURPOSE/OBJECTIVE(S)

Randomized clinical trials have shown that regional nodal irradiation (RNI) in patients with unselected N1 breast cancer improves breast cancer-specific survival. However, the benefit of RNI in women with biologically low risk, N1 breast cancer is uncertain. We conduct a population-based study to determine if RNI is associated with improved breast cancer recurrence-free interval (BCRFI) in this population.

MATERIALS/METHODS

Patients aged 40-79 with pT1-2pN1 (node-positive) breast cancers diagnosed from 2005 to 2014 were identified. Inclusion criteria were modeled off the TAILOR RT study, which is a randomized non-inferiority clinical trial designed to assess the value of RNI in low-risk N1 patients. Eligible patients had BCS (breast-conserving surgery) or mastectomy & axillary lymph node dissection (ALND) with 1-3 positive nodes, BCS and sentinel lymph node biopsy (SLNB) with 1-2 positive nodes, or mastectomy and SLNB with 1 positive node. Additionally, patients had Luminal A breast cancers, as approximated by: estrogen receptor positive (Allred 6-8/8), progesterone receptor positive (Allred 6-8/8), human epidermal growth factor receptor 2 (HER2)-negative, and grade 1-2 immunohistochemical testing. All patients were prescribed hormonal treatment. The primary endpoint of BCRFI, which was the time to any breast cancer recurrence or breast cancer-related death, was analyzed using multivariate competing risks analysis.

RESULTS

The cohort included 1,169 women with a median follow-up of 9.2 years. Radiation treatments were: none (151 treated with mastectomy alone), breast-only (133) and locoregional (885). Patients undergoing RNI were younger (median 58 versus 62 years), more likely to have 2-3 macroscopic lymph nodes involved and more often received chemotherapy (all p<0.05). The 10-year estimate of BCRFI was 90% without RNI versus 90% with RNI (p=0.5). On multivariable analysis, RNI was not a significant predictor of BCRFI (HR=1.0, p=0.9).

CONCLUSION

In this retrospective analysis, RNI was not associated with improved BCRFI for women with biologically low risk, N1 breast cancer. We advocate accrual to the ongoing TAILOR RT study.

Breast Tangent Beam Energy, Surgical Bed-to-Skin Distance and Local Recurrence after Breast-Conserving Treatment

PURPOSE

Higher energy (>6 MV) photons reduce dose inhomogeneity with breast tangent beams, thereby reducing late breast toxicity, but skin and superficial tissue sparing by higher energy beams raises concerns about local recurrence (LR) risk. This study aimed to determine whether beam energy and surgical bed-to-skin distance affect LR.

METHODS AND MATERIALS

This population-based study included newly diagnosed invasive breast cancers without skin involvement (pT1-4a, any-N, M0) treated with breast-conserving surgery and adjuvant whole breast radiotherapy without bolus or beam spoilers. The primary endpoint was the cumulative incidence of LR (CILR). A multivariable analysis (MVA) included mean beam energy, age, T-stage, nodal status, overall stage, lymphovascular invasion (LVI), grade, margin status, extensive intraductal component (EIC), breast cancer subtype, hormone therapy and chemotherapy. In a subgroup with contoured surgical beds, another MVA included surgical bed-to-skin distance.

RESULTS

The cohort consisted of 10,083 women treated from 2002 to 2011, 327 with 4MV, 6,006 with 6 MV, 2,083 with >6-10 MV and 1,667 with >10 MV tangents. The median follow-up time was 11.1 years. The 10-year CILR was 3.1% [95% confidence interval 1.6,5.4] with 4 MV, 2.8% [2.4,3.3] with 6 MV, 4.2% [3.4,5.3] with >6-10 MV and 2.6% [1.9,3.5] with >10 MV. On MVA of the entire cohort, LR risk was increased with positive margins, LVI, EIC, and lack of hormone therapy, but was not associated with beam energy (HR = 1.01 [0.96,1.05], p = 0.8). On MVA of 3,359 patients with contoured surgical beds, LR risk was not associated with surgical bed-to-skin distance (HR = 1.00 [0.99,1.02], p = 0.8).

CONCLUSIONS

Use of higher breast tangent beam energies is not associated with increased risk of local recurrence, including in cases with surgical beds that are close to the skin.

Real-world outcomes of neoadjuvant treatment for HER2 positive early-stage breast cancer

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Background: Patients with HER2 positive early-stage breast cancer (ESBC) with residual disease (RD) following neoadjuvant therapy derive benefit from treatment escalation. However, treatment modifications for patients who achieve a complete pathologic response (pCR) remains controversial. The Neo-Bioscore is a validated prognostic tool used for patients with ESBC treated neoadjuvantly. To understand the impact of pCR on outcomes in a real-world setting, and better refine patient selection for treatment escalation or de-escalation, we investigated the use of the Neo-Bioscore and/or other prognostic variables. Methods: Patients diagnosed from 2005 to 2014 with stage I-III HER2 positive breast cancer and treated with neoadjuvant systemic therapy were identified from the BC Cancer Breast Cancer Outcomes Unit database. Outcomes of interest included breast cancer specific survival (BCSS), overall survival (OS), distant disease- free survival (DRFS), and locoregional recurrence free survival (LRFS), and were assessed using the Kaplan-Meier method, comparing the pCR and RD groups. Multivariate analysis was used to assess clinical and pathologic prognostic factors beyond pCR. Results: Of the 417 patients meeting inclusion criteria, median age was 50, including 38.1% with clinical stage 2 and 58.3% with clinical stage 3 disease and 59.5% with hormone receptor (HR) positive tumors. 98.1% received chemotherapy and 92.6% received trastuzumab. Median follow-up was 9.6 years (9.2, 10.0). Overall, 193 patients (46.3%) achieved a pCR. Those with RD had higher clinical T stage (p < 0.01) and more HR positive disease (p < 0.01). Patients who achieved a pCR had significantly better 5-year BCSS (91.2% vs. 74.8%, p< 0.0001), OS (90.7% vs. 69.9%, p< 0.0001), DRFS (87.9% vs. 66.3%, p< 0.0001) and LRFS (98.9% vs. 92.5%, p= 0.007) in univariate analyses. In multivariate analyses, the neo-bioscore (1 vs 5: HR 0.05, 95% CI 0.003,0.666, p = 0.02), higher pathological T stage (ypT3 vs ypT0: HR 7.2, 95% CI 1.3, 40.9, p = 0.03) and pathological N stage (ypN1 vs ypN0: HR 2.2, 95% CI 1.1, 4.5, p = 0.03) were associated with BCSS, whereas patients’ age, ER status and baseline clinical T and N stage were not. Conclusions: In a real-world population, ESBC patients with HER2 positive tumors treated with neoadjuvant systemic therapy who achieved pCR derived significant improvements across all survival parameters compared to those with RD. However, distant relapses still occurred in 12% of patients who achieved pCR. Further analyses to identify patients with pCR who relapsed are underway to determine who may benefit from treatment escalation. The final pathological stage and neo-bioscore for patients with RD were prognostic in a real-world cohort and should be considered for adjuvant treatment decisions. Validation of these results in an independent cohort are also ongoing to better understand predictive and prognostic variables.

Survival following locoregional recurrence in breast cancer by clinical subtype

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Background: We sought to explore the impact of locoregional recurrence (LRR) on survival in breast cancer (BC) patients in British Columbia treated in the modern era. Methods: A retrospective cohort study design identified patients diagnosed with stage I-III BC from 04/2005-12/2013 treated with surgery and who had a subsequent LRR. Exclusions were death or distant metastasis within 120 days of LRR, bilateral previous/synchronous BC, and other invasive cancers. After LRR, overall survival (OS) and factors associated with OS, including clinical subtype and adjuvant therapy (AdTx), were examined. We defined clinical subtypes as: Luminal (Lum) A-estrogen receptor (ER) and progesterone receptor (PR) positive, HER2 negative, and grade 1 or 2; Lum B-as Lum A but grade 3, or as Lum A but only one of ER or PR positive; triple negative (TNBC)-ER and PR and HER2 negative; and HER2 positive (with any ER, PR). In the absence of earlier LRR, we defined adequate AdTx as: (a) TNBC: >=50% of planned chemotherapy (Chx), (b) HER2 positive: >=50% of planned Chx and >=8 cycles of anti-HER2 therapy, (c) Lum A, B: >=4 years of endocrine therapy and (d) after partial mastectomy or positive final margins: >=50% of radiation therapy dosage. Results: The final cohort had 492 patients with a median follow-up of 7.2 years from LRR and 11.8 years from diagnosis. LRR was local in 69.3% (n=341) and regional +/- local in 30.7% (n=151). Compared with local only, regional recurrences were associated with higher T and N stage, grade, and Lum status (p<=0.01). Biomarkers were re-evaluated at LRR in 82% and changed from initial diagnosis in 32% of those tested: ER expression 3.8% gain, 6.1% loss; PR expression 9.1% gain, 15.1% loss; HER2 overexpression 3.7% gain and 4.8% loss. Over half of patients (n=255, 52%) did not receive adequate AdTx, either by choice or recommendation. A similar proportion with local vs. regional recurrence had inadequate AdTx. Time to death from 1st LRR did not vary significantly between local vs. regional recurrences (median 2.7 years). OS after LRR was lowest in TNBC (median 3.1 years, 24.2% 10-year OS) and longest in Lum A (median not reached, 64.7% 10-year OS) (Table). Conclusions: Our data provide rates of OS after LRR in the era of modern adjuvant therapy. OS after LRR varied by clinical subtype, with TNBC faring the worst, and Lum A the best. Over half had not received adequate AdTx. Despite similar treatment options, OS after LRR was significantly longer for Lum A than B subtypes, underscoring the need for therapy tailored to biology. OS was low in all other subtypes, emphasizing the importance of avoiding LRR.[Table: see text]

Real-World Outcomes of Oxaliplatin-Based Chemotherapy on R0 Resected Colonic Liver Metastasis

INTRODUCTION

In resected colonic liver metastasis (CLM), randomized studies of oxaliplatin-based chemotherapy have demonstrated improvements in disease-free survival (DFS), but not overall survival (OS). Additionally, oxaliplatin regimens have not been compared to non-oxaliplatin chemotherapy. Despite limited evidence, perioperative chemotherapy is often used in the management of CLM. The primary aim of this study was to assess the impact of oxaliplatin chemotherapy regimens on OS in patients who have undergone resection of CLM in a real-world setting.

PATIENTS AND METHODS

Patients who underwent resection of CLM in the provinces of Alberta and British Columbia, Canada, were identified from 1996 to 2016. Perioperative (pre- and/or post-) systemic therapy was categorized as oxaliplatin or non-oxaliplatin-based chemotherapy or no chemotherapy. The primary and secondary outcomes were OS and DFS, respectively.

RESULTS

We identified 511 patients who underwent R0 resection of CLM. A significant difference in median OS was identified among the oxaliplatin, non-oxaliplatin, and no-chemotherapy groups of 100, 60, and 59 months, respectively (P = .009). In multivariate analysis, patients who received oxaliplatin regimens had a lower risk of death (hazard ratio, 0.68; 95% confidence interval, 0.51-0.92; P = .012), whereas the non-oxaliplatin chemotherapy group did not (hazard ratio, 0.88; 95% confidence interval, 0.65-1.20; P = .422) compared with no chemotherapy.

CONCLUSIONS

In this multicenter, retrospective, population-based study, perioperative oxaliplatin-based chemotherapy was associated with improved OS in conjunction with R0 resection of CLM. Further studies should evaluate the optimal duration and sequencing of perioperative chemotherapy in relation to curative-intent surgical resection of CLM.

Abstract PS4-26: Impact of TAILORx data on chemotherapy prescribing in British Columbia

Background: Developed with retrospective data, the 21-gene recurrence score assay (RS) reduces adjuvant chemotherapy (CTx) use in hormone-positive (HR+), HER2-negative, node-negative breast cancer, justifying the assay’s cost. The TAILORx trial prospectively confirmed the predictive value of RS and established thresholds for CTx benefit in younger and older patients. We examined CTx use in British Columbia (BC) following TAILORx publication, as a prelude to exploring age-adjusted cost effectiveness of the assay.

Methods: We assembled 3 cohorts of patients with HR+, HER2-negative, node-negative breast cancer: diagnosed before RS funding (cohort 1: January 1, 2013-December 31, 2013), after introduction of public funding (cohort 2: July 1, 2015-June 30, 2016), and after TAILORx results (cohort 3: July 1, 2018-June 30, 2019). Patients aged 18-80 years with tumors that were grade 3, grade 2 T1b or larger, or any T size and grade if ≤ 40 years of age were included, matching BC funding criteria. Previous in situ or invasive breast cancer cases were excluded. CTx use by age and RS was compared between cohorts using univariate analyses.

Results: 2,066 patients met inclusion criteria (Table 1). CTx use in cohorts 1, 2, and 3 was 21%, 17%, and 13%, respectively. In cohorts 2 plus 3, CTx use was 30% for patients up to 50 years of age and 11% for patients over 50 years of age. Baseline characteristics were balanced, except grade 3 histology (24%, 25%, 17% in cohorts 1, 2, 3, respectively; p=0.01). RS was ≥ 26 in 33% of grade 3 and 34% of PR negative tumors. CTx use declined by 19% after RS funding was introduced and by another 23% after TAILORx publication (p=0.001). Reduction in CTx use was significant for RS 11-20 tumors (cohort 3 vs. 2, p=0.004). A 7.5% nonsignificant increase in CTx was seen for RS 26-30 tumors (cohort 2 vs. 3, p=0.55). There was no significant change in CTx use in patients aged &gt; 50 years (12% in cohort 2 vs. 10% in cohort 3, p=0.22). Among patients aged 70-80 years in cohort 3 with RS, 5% had RS ≥ 26, and of these, 40% had CTx (9% of patients in this age group), compared with 92% CTx use for patients aged ≤ 50 years with RS ≥ 26 (15% of patients in this age group).

Conclusions: CTx use decreased after TAILORx publication, particularly for RS 11-20 tumors. CTx use changed less in patients over 50 years old, suggesting that trial results confirmed pre-existing prescribing practices. CTx use increased in patients with RS 26-30 tumors, reflecting acceptance of the new threshold for CTx benefit established by TAILORx. CTx use was low overall in patients aged &gt; 50 years, especially in those aged 70-80 years, in part due to the very low frequency of high RS tumors. Given these findings, we conclude that cost effectiveness modelling for publicly funded RS should take age into consideration.

Table 1: Receipt of adjuvant chemotherapy (CTx) by 21-gene recurrence score (RS) result before assay availability (cohort 1), after assay availability (cohort 2), and after TAILORx publication (cohort 3) in patients (pts) aged ≤ 50 (a) and 51-80 years (b).a)Age≤ 50, n = 423Cohort123No. of pts who received CTx / No. of pts in group (%)RS not done51/105 (48.6)28/56 (50)1/6 (16.7)RS ≤ 101/5 (20.0)0/17 (0)1/25 (4.0)RS 11-201/8 (12.5)4/52 (7.7)2/67 (3.0)RS 21-251/3 (33.3)8/17 (47.1)10/20 (50.0)RS 26-300/0 (0)5/5 (100)5/5 (100)RS ≥ 312/2 (100)10/11 (90.9)17/19 (89.5)Entire cohort56/123 (45.5)55/158 (34.8)36/142 (25.4)b)Age51-80, n = 1643Cohort123No. of pts who received CTx / No. of pts in group (%)RS not done72/494 (14.6)25/279 (9.0)2/86 (2.3)RS ≤ 100/6 (0)0/60 (0)0/110 (0)RS 11-202/11 (18.2)5/126 (4.0)0/198 (0)RS 21-252/5 (40.0)6/56 (10.7)2/64 (3.1)RS 26-302/3 (66.7)5/20 (25.0)14/35 (40.0)RS ≥ 312/2 (100)31/40 (77.5)37/48 (77.1)Entire cohort80/521 (15.4)72/581 (12.4)55/541 (10.2)

Citation Format: Megan Tesch, Caroline Speers, Rekha Manhas Diocee, Alan Nichol, Caroline Lohrisch. Impact of TAILORx data on chemotherapy prescribing in British Columbia [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 PS4-26.

Breast Cancer Molecular Subtype as a Predictor of Radiation Therapy Fractionation Sensitivity

PURPOSE

The predictive benefit of breast cancer molecular subtypes for systemic therapy approaches has been well established; yet, there is a paucity of data regarding their use as a predictor of radiation therapy fractionation sensitivity. The purpose of this study was to determine whether rates of local recurrence (LR) for patients treated with hypofractionated (HF) radiation therapy, in comparison to conventional fractionation, differ across breast cancer molecular subtypes in a large, prospectively collected cohort treated with modern systemic therapy.

METHODS AND MATERIALS

Patients who received a diagnosis of stage I-III breast cancer between 2005 and 2009 were identified. Molecular subtype was determined using the American Joint Committee on Cancer classification system (luminal-A, luminal-B, HER2+, triple negative [TN]). Multivariable Cox regression modeling was used to identify predictors of LR. LR-free-survival (LRFS) was determined using the Kaplan-Meier method and compared using the log-rank test.

RESULTS

A total of 5868 cases were identified with a median follow-up of 10.8 years. Patients with luminal-A subtype composed 45% of the cohort (n = 2628), compared with 30% luminal-B (n = 1734), 15% HER2+ (n = 903), and 10% TN (n = 603). A total of 76% (n = 4429) of patients were treated with HF. The 10-year LRFS was 97.1% (95% confidence interval [CI], 96.6-97.6) for the whole cohort. The 10-year LRFS based on molecular subtypes was 98.3% (95% CI, 97.6-98.7) luminal-A, 96.6% (95% CI, 95.5-97.4) luminal-B, 97.0% (95% CI, 95.5-98.0) HER2+, and 93.5% (95% CI, 91.1-95.3) TN (P < .001). There was no difference in the 10-year LRFS between patients treated with HF versus conventional fractionation among those with luminal-A (98.2% vs 98.4%; P = .42), luminal-B (96.6% vs 96.8%; P = .90), HER2+ (97.5% vs 95.8%; P = .12), or TN (93.9% vs 92.2%; P = .47). There was no significant interaction between subtype and fractionation regimen.

CONCLUSIONS

These data support the routine use of hypofractionated radiation therapy regimens across all breast cancer subtypes.

Sequence of therapy and survival in patients with advanced pancreatic neuroendocrine tumours

Background

Pancreatic neuroendocrine tumours (pnets) often present as advanced disease. The optimal sequence of therapy is unknown.

Methods

Sequential patients with advanced pnets referred to BC Cancer between 2000 and 2013 who received 1 or more treatment modalities were reviewed, and treatment patterns, progression-free survival (pfs), and overall survival (os) were characterized. Systemic treatments included chemotherapy, small-molecule therapy, and peptide receptor radionuclide therapy.

Results

In 66 cases of advanced pnets, median patient age was 61.2 years (25%-75% interquartile range: 50.8-66.2 years), and men constituted 47% of the group. First-line therapies were surgery (36%), chemotherapy (33%), and somatostatin analogues (32%). Compared with first-line systemic therapy, surgery in the first line was associated with increased pfs and os (20.6 months vs. 6.3 months and 100.3 months vs. 30.5 months respectively, p < 0.05). In 42 patients (64%) who received more than 1 line of therapy, no difference in os or pfs between second-line therapies was observed.

Conclusions

Our results confirm the primary role of surgery for advanced pnets. New systemic treatments will further increase options.

Hypofractionated Adjuvant Radiation Therapy Is Effective for Patients With Lymph Node-Positive Breast Cancer: A Population-Based Analysis

PURPOSE

This study evaluated long-term, population-based, breast cancer-specific outcomes in patients treated with radiation therapy (RT) to the breast/chest wall plus regional nodes using hypofractionated (HF) (40-42.5 Gy/16 fractions) versus conventionally fractionated (CF) regimens (50-50.4 Gy/25-28 fractions).

METHODS AND MATERIALS

A prospective provincial database was used to identify patients with lymph node-positive breast cancer treated with curative-intent breast/chest wall + regional nodal RT from 1998 to 2010. The effect of RT fractionation on locoregional recurrence-free survival (LRRFS), distant recurrence-free survival (DRFS), and breast cancer-specific survival (BCSS) was assessed for the entire cohort and for high-risk subgroups: grade 3, ER-/HER2-, HER2+, and ≥4 positive nodes. Multivariable analysis and 2:1 case-match comparison of HF versus CF were also performed.

RESULTS

A total of 5487 patients met the inclusion criteria (4006 HF and 1481 CF). Median age was 55 years, and median follow-up was 12.7 years. On multivariable analysis, no statistically significant differences were identified in 10-year LRRFS (hazard ratio [HR] 0.87; 95% confidence interval [CI], 0.59-1.27; P = .46), DRFS (HR 0.90; 95% CI, 0.76-1.06; P = .19), or BCSS (HR 0.92; 95% CI, 0.76-1.10; P = .36) between the HF and CF cohorts. There was no statistical difference in breast cancer-specific outcomes in the high-risk subgroups. On analysis of 2962 HF cases matched to 1481 CF controls, no statistical difference was observed in LRRFS (HR 0.98; 95% CI, 0.71-1.33; P = .87), DRFS (HR 0.97; 95% CI, 0.85-1.11; P = .68), or BCSS (HR 1.00; 95% CI, 0.87-1.16; P = .92).

CONCLUSIONS

This large, population-based analysis with long-term follow-up after locoregional RT demonstrated that modest HF provides similar breast cancer-specific outcomes compared with CF. HF is an effective option for patients with stage I to III breast cancer receiving nodal RT.

PET/CT of breast cancer regional nodal recurrences: an evaluation of contouring atlases

BACKGROUND

To validate the Radiation Therapy Oncology Group (RTOG) and European Society for Radiotherapy and Oncology (ESTRO) breast cancer nodal clinical target volumes (CTVs) and to investigate the Radiotherapy Comparative Effectiveness Consortium (RADCOMP) Posterior Neck volume in relation to regional nodal recurrences (RNR).

METHODS

From a population-based database, 69 patients were identified who developed RNR after curative treatment for breast cancer. RNRs were detected with 18-fluorodeoxyglucose-positron emission tomography-computed tomography (PET/CT). All patients were treatment-naïve for RNR when imaged. The RTOG and ESTRO nodal CTVs and RADCOMP Posterior Neck volumes were contoured onto a template patient's CT. RNRs were contoured on each PET/CT and deformed onto the template patient's CT. Each RNR was represented by a 5 mm diameter epicentre, and categorized as 'inside', 'marginal' or 'outside' the CTV boundaries.

RESULTS

Sixty-nine patients with 226 nodes (median 2, range 1-11) were eligible for inclusion. Thirty patients had received adjuvant tangent and regional nodal radiotherapy, 16 tangent-only radiotherapy and 23 no adjuvant radiotherapy. For the RTOG CTVs, the RNR epicentres were 70% (158/226) inside, 4% (8/226) marginal and 27% (60/226) outside. They included the full extent of the RNR epicentres in 38% (26/69) of patients. Addition of the RADCOMP Posterior Neck volume increased complete RNR coverage to 48% (33/69) of patients. For the ESTRO CTVs, the RNR epicentres were 73% (165/226) inside, 2% (4/226) marginal and 25% (57/226) outside. They included the full extent of the RNR epicentres in 57% (39/69) of patients. Addition of the RADCOMP Posterior Neck volume increased complete RNR coverage to 70% (48/69) of patients.

CONCLUSIONS

The RTOG and ESTRO breast cancer nodal CTVs do not fully cover all potential areas of RNR, but the ESTRO nodal CTVs provided full coverage of all RNR epicentres in 19% more patients than the RTOG nodal CTVs. With addition of the RADCOMP Posterior Neck volume to the ESTRO CTVs, 70% of patients had full coverage of all RNR epicentres.

The impact of new systemic therapies on survival and time on hormonal treatment in hormone receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer: A population-based study in British Columbia from 2003 to 2013

BACKGROUND

The purpose of this study was to determine whether new systemic therapy regimens have resulted in improved survival and increased time on first- and second-line hormonal treatment for patients with hormone receptor (HR)-positive metastatic breast cancer (MBC) over time.

METHODS

Patients diagnosed with HR-positive, human epidermal growth factor receptor 2 (HER2)-negative MBC were identified across 3 time cohorts (2003-2005, 2007-2009, and 2011-2013). Data were prospectively collected. Cases with previous, synchronous, or subsequent contralateral breast cancer were excluded. The types of first- and second-line therapies, the times on first- and second-line hormonal treatment, and the median survival times were compared across the cohorts.

RESULTS

Within the time period analyzed, 9 new adjuvant systemic therapies (with or without neoadjuvant therapy) and 2 metastatic systemic therapies were approved at BC Cancer for the treatment of HR-positive, HER2-negative MBC. In the 3 time cohorts, 3953 patients diagnosed with MBC were identified. Among the 2432 patients (62%) who had HR-positive/HER2-negative disease, 2197 (90%) received at least 1 line of systemic therapy after the diagnosis of MBC, and 80% of these patients (1752 of 2197) received first- and/or second-line hormonal treatment. The median duration on hormonal treatment was 9.0 months for the first line and 6.1 months for the second line. The durations were similar across the time cohorts (range for the first line, 8.9-9.0 months; range for the second line, 6.0-6.1 months). The median survival for the entire study population was 2.0 years (95% confidence interval, 1.8-2.1 years), and there was no significant difference between the cohorts (range, 1.9-2.0 years).

CONCLUSIONS

Even though more adjuvant and metastatic systemic therapies have been approved since 2003, population-level gains in survival and the time on hormonal treatment for patients with HR-positive, HER2-negative MBC have not been made over the course of a decade.

Do surgeons convey all the details? A provincial assessment of operative reporting for breast cancer

INTRODUCTION

A breast cancer synoptic operative report was developed using a modified Delphi process METHODS: Data from the British Columbia Cancer Breast Cancer Outcomes Unit (BCOU) was used to analyze the association between the completion of a synoptic operative report and reporting of operative details and The American Society of Breast Surgeons quality indicators.

RESULTS

3662 patients had surgery for breast cancer by 185 surgeons. 2281 reports were narrative and 1007 synoptic. Requested surgical details were more commonly reported with synoptic reports for both posterior (96 vs 58%, p < 0.0001) and anterior margins (96 vs 5%, p < 0.0001). This was true for high and low volume surgeons. Quality Indicators were higher in those cases with an associated synoptic report for high and low volume surgeons.

CONCLUSION

Communication of operative details is improved with synoptic reporting. Investment in platforms to facilitate synoptic reporting could improve patient care through improved multidisciplinary communication.

Abstract ES2-2: Evolving opportunities to personalize radiation decisions - Guiding decisions to omit radiation after breast conserving surgery for invasive breast cancer

Much as the development of molecularly based signatures (OncotypeDx®, MammaPrint®, ProSigna™, etc.) has revolutionized the decision-making process surrounding the need for adjuvant chemotherapy in women with early stage breast cancer, the development of prognostic and predictive signatures to determine the need and efficacy of radiation for women with breast cancer holds similar promise. While preliminary efforts to develop these signatures has been encouraging, much work remains in order to successfully translate these signatures into the clinic. In this educational session, we will review the current status of genomic-based signatures for radiation decision making. We will also review the barriers to clinical adoption and the molecularly stratified trials testing these signatures for treatment omission. Ultimately, for any of these tests to be translated into the clinic it will require demonstration of their accuracy and reproducibility as a test and perhaps more importantly, demonstration of clinical utility and an ability to improve outcomes for women with breast cancer. While not yet realized, the ongoing development of these signatures holds much promise as the field seeks to finally realize “personalized medicine” as it relates to radiation treatment for women with breast cancer.

Citation Format: C Speers. Evolving opportunities to personalize radiation decisions - Guiding decisions to omit radiation after breast conserving surgery for invasive breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr ES2-2.

In the Era After the European Organisation for Research and Treatment of Cancer 'Boost' Study, is the Additional Radiotherapy to the Breast Tumour Bed Still Beneficial for Young Women?

AIMS

The European Organisation for Research and Treatment of Cancer (EORTC) 22,881-10,882 trial showed significant benefit of a radiotherapy boost (RTB) in women ≤40 years in a pre-hormone therapy (HT) era. We determined how the use of HT and RTB changed in response to clinical guidelines and whether the benefit of routine RTB was still observed in the HT era.

MATERIALS AND METHODS

Between 1996 and 2004, a provincial database identified all women ≤40 years with breast cancer who met the inclusion criteria of the EORTC trial. In total, 411 patients were classified into three eras defined by the guidelines: era 1 (discretionary HT, discretionary RTB); era 2 (routine HT, discretionary RTB); era 3 (routine HT, routine RTB). HT use, RTB use and cumulative incidence of local recurrence were calculated and compared across eras.

RESULTS

HT use increased after the first policy change from 13% to 75% for oestrogen receptor-positive patients (P < 0.01). RTB use also increased from 33% to 76% following the second policy change (P < 0.01). At 10 years, the cumulative incidence of local recurrence was 12% in era 1, 6% in era 2 and 6% in era 3 (era 2 versus era 3, P = 0.92). For patients in the routine HT era (eras 2 and 3 combined) there was no significant difference in local recurrence between RTB and 'no RTB' patients (6% versus 7%, P = 0.81).

CONCLUSIONS

The routine use of HT and RTB increased significantly after new practice guidelines. Introduction of the HT guideline was associated with a 6% improvement in local recurrence at 10 years. No improvement in local recurrence was associated with the introduction of the RTB guideline in the HT era. The routine use of a boost in unselected young women with negative margins should be re-evaluated in the current HT era.

Clinical and pathologic characteristics of early-onset colorectal cancer (EoCRC)

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Background: Although CRC incidence continues to fall in patients over 50 due to adoption of screening programs, there has been an increasing incidence in patients < 50 where screening does not occur. We investigated the clinical and pathologic characteristics of EoCRC in BC. Methods: We retrospectively analyzed 27612 patients diagnosed with CRC and referred to BC Cancer between 1990-2016. Patients < 50 were classified as early onset CRC and analyzed for baseline and disease characteristics. Results: In the 2540/27612 (9.2%) of patients < 50, patients were more likely to be female (OR 1.33, 95% CI 0.61-1.44, P < 0.0001), have left sided tumors (OR 1.50, 95% CI 1.35-2.01, P < 0.0001), have poorly differentiated tumors (OR 1.24, 95% CI 1.10-1.34, P = 0.0003), and more patients presented with metastatic disease (OR 1.26, 95% CI 1.15-1.38, P < 0.0001) compared to patients ≥50. At diagnosis, patients < 50 were more likely to have a significant complication related to the primary tumor (OR 1.18, 95% CI 1.06-1.32, P = 0.0041), specifically, greater rates of perforation (OR 1.84, 95% CI 1.47-2.31, P < 0.0001). Although high risk features used to guide adjuvant therapy decisions in patients < 50 with stage II CRC were not higher, with similar T4 prevalence, poor differentiation, lymphovascular and perineural invasion, and less inadequate lymph node harvesting (≤12) (all p > 0.05), rates of adjuvant therapy were higher (OR 2.39, 95% CI 1.91-3.00, P < 0.0001). This was also noted in stage III CRC (OR 4.11 95% CI 3.07-5.48, P < 0.0001). Age impacted overall survival, with younger patients of all stages living longer (HR 0.72, 95% CI 0.68-0.76, P < 0.0001). Similar findings were noted for stage I-III CRC (HR 0.54 0.50-0.58, P < 0.0001) and for patients once they became metastatic (HR 0.84 95% CI 0.75-0.93, P = 0.0025). To control for competing causes of death, we looked at disease specific survival, which continued to show improved outcomes for patients age < 50 in stage I-III (HR 0.88 95% CI 0.81-0.97, P = 0.0016) and stage IV (HR 0.77 95% CI 0.72-0.84, P < 0.0001) CRC. Conclusions: EoCRC patients present with unique clinical and pathologic characteristics which may impact outcome. While the population < 50 has comparable outcomes, they may undergo increased rates of treatment.

Cardiac death after breast radiotherapy and the QUANTEC cardiac guidelines

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Cardiovascular risk factors predict for cardiac death after breast radiotherapy.

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Cardiovascular risk factors should be modified in breast cancer patients.

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Radiation induced cardiac death at 10-years is low if mean heart dose is <3.3 Gy.

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Radiation induced cardiac death at 10-years is low if maximum LAD dose is <45.4 Gy.

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Studies are needed to evaluate heart and LAD constraints in the CT-planning era.

Background

Breast/chest wall irradiation (RT) increases risk of cardiovascular death. International Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) guidelines state for partial heart irradiation a “V25Gy <10% will be associated with a <1% probability of cardiac mortality” in long-term follow-up after RT. We assessed whether women treated with breast/chest wall RT 10-years ago who died of cardiovascular disease (CVD) violated QUANTEC guidelines.

Materials/methods

A population-based database identified all cardiovascular deaths in women with early-stage breast cancer <80 years, treated with adjuvant breast/chest wall RT from 2002 to 2006. Ten-year rate of cardiovascular death was calculated using a Kaplan-Meier method. Patients were matched on a 2:1 basis with controls that did not die of CVD. For left-sided cases, the heart and left anterior descending (LAD) artery were retrospectively delineated. Dose-volume histograms were calculated, and heart V25Gy compared to QUANTEC guidelines.

Results

5249 eligible patients received breast/chest wall RT from 2002 to 2006: 76 (1.4% at 10-years) died of CVD by June 2015. Forty-two patients received left-sided RT (1.7% CVD death at 10-years), 34 right-sided RT (1.3% at 10-years). Heart V25Gy did not exceed 10% in any left-sided cases. No cardiac dosimetry parameter distinguished left-sided cases from controls.

Conclusions

QUANTEC guidelines were not violated in any patient that died of CVD after left-sided RT. The risk of radiation induced cardiac death at 10-years appears to be very low if MHD is <3.3 Gy and maximum LAD dose (EQD2₃ Gy) is <45.4 Gy. Further studies are needed to evaluate heart and LAD constraints in the CT-planning era.

Comparative efficacy of neoadjuvant to adjuvant chemotherapy for the treatment of early-stage HER2 negative breast cancer: A population-based analysis

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Background: The use of neoadjuvant treatment has increased over the past decade due to its ability to assess tumour sensitivity to systemic treatment in vivo, and to downstage women for increased breast conserving surgery. Recent studies have stratified patients with residual disease to receive additional treatment, which has resulted in meaningful improvements in survival. However, meta-analysis data suggest similar long-term outcomes for patients treated with neoadjuvant chemotherapy (NACT) compared to adjuvant chemotherapy (ACT) in historical randomized trials. The comparative efficacy in a real-world setting utilizing modern chemotherapy regimens is unknown. Methods: A retrospective review of the BC Cancer Breast Cancer Outcomes Unit (BCOU) was performed to identify patients with stage I-III HER-2 negative breast cancer treated with chemotherapy at the BC Cancer Agency from 2005-2010. Patients were then divided into 2 groups: those who received neoadjuvant chemotherapy (NACT) and those who received adjuvant chemotherapy (ACT). A matched analysis (age, stage, subtype) for patients treated with NACT vs ACT (matched 1:3) was then performed using a propensity scoring method to compare distant disease-free survival (DDFS), breast cancer specific survival (BCSS) and overall survival (OS). No patients received adjuvant chemotherapy for residual disease after NACT. Results: A total of 656 patients met the inclusion criteria, consisting of 164 NACT and 492 ACT cases. Median age was 49 years (37-68) in the NACT group vs 49 (37-65) in the ACT group (p = 0.71). The majority had stage 3 disease, 64% in both groups (p = 1.0). Most were hormone receptor positive (HR+), 67.1% vs 70.7% in the NACT vs ACT groups, respectively (p = 0.41). 5-year DDFS was 75% with NACT (95%CI 67, 82) and 77% with ACT (95%CI 72, 81), p = 0.87. 5-year OS for patients treated with NACT was 77% (95%CI 71, 84) and 80% (95%CI 75, 85) for patients treated with ACT, p = 0.33. 5-year BCSS was 80% with NACT (95% CI 70, 86) and 82% (95%CI 77, 86) with ACT, p = 0.75. Multivariate analysis for tumour size, nodal involvement and subtype are ongoing. Conclusions: The use of NACT compared to ACT in a population-based setting did not result in significant differences in DDFS, OS or BCSS. Acknowledging the comparative efficacy of these approaches will be informative to determine if the addition of subsequent adjuvant treatment for patients with residual disease after NACT will lead to differential benefits in a population-based setting.

Abstract P4-08-27: The 21-gene Recurrence® (RS) Score assay in estrogen receptor positive node negative breast cancer: Real-world chemotherapy usage and patient characteristics within the intermediate and high-risk RS category

Background:

The Oncotype Dx, a 21-gene recurrence score (RS) assay, has been validated as a prognostic tool in early-stage, hormone receptor-positive, HER2-negative breast cancer. A RS of ≥ 31 is predictive for chemotherapy benefit. However, it has not been clearly established whether more intensive chemotherapy regimens for these patients provide further benefit and whether higher RS stratifications (≥41) influence treatment decisions.

Methods:

From the prospective British Columbia (BC) Breast Cancer Outcomes Unit database, we identified patients with N0 disease who received Oncotype Dx testing from May 2010 to December 2016. Patients with previous or synchronous breast cancer, and patients treated with neoadjuvant chemotherapy were excluded. Groups were defined that had an Oncotype Dx RS of 31-40 and ≥ 41. Demographic characteristics and type of chemotherapy received were collected. Additional subgroups were defined for patients who had a RS of 21-25 and who were ≤ 50 years old and &gt; 50 years old.

Results:

We identified 1,202 patients who received Oncotype Dx testing over the time period studied, with 14.8% (n=178) having a RS of ≥ 31. Among these high-risk patients, the median age was 58 (range 34-79), 90% received hormonal therapy and 85% received chemotherapy. In this cohort, 46% received docetaxel and cyclophosphamide for 4 cycles and 28% received 3rd generation chemotherapy. The use of 3rd generation chemotherapy in patients with a RS of ≥ 41 was significantly higher than in patients with RS between 31-40 (39% vs 22%, p = 0.006). Among patients who had a RS of 21-25 and who were ≤ 50 years old (n = 49), 53% received chemotherapy. Of patients who had a RS of 21-25 and who were &gt; 50 years old (n = 127), 16% received chemotherapy.

Conclusions:

Among patients with a RS ≥ 31, decisions regarding chemotherapy usage were heterogeneous with docetaxel and cyclophosphamide for 4 cycles being the most commonly used regimen. However, in those with a RS ≥ 41, 3rd generation chemotherapy was preferred. Patients with a RS between 21-25 and who were ≤ 50 years old received more chemotherapy than patients who were &gt; 50 years old.

 RS 31-40 (n=116)RS ≥ 41 (n=62)RS ≥ 31 (n=178)Median age58.0 (range, 36-79)57.5 (range 34-78)58.0 (range 34-79)Pre-menopausal28.4%29.0%28.7%Hormonal therapy93.1%83.9%89.9%Chemotherapy86.2%82.3%84.8%DCx4 (1)54.3% (n=63/116) Median age 59.0 (range, 36 – 78)30.6% (n=19/62) Median age 64.0 (range, 42 – 78)46.1% (n=82/178) Median age 59.5 (range, 36 – 78)3rd generation chemo (2)21.6% (n=25/116) Median age 56.0 (range, 39 – 79)38.7% (n=24/62) Median age 52.0 (range, 34 – 76)27.5% (n=49/178) Median age 54.0 (range, 34 – 79)Other chemo10.3% (n=12/116) Median age 57.5 (range, 52 – 78)12.9% (n=8/62) Median age 64.0 (range, 42 – 72)11.2% (n=20/178) Median age 58.5 (range, 42 – 78)(1) Docetaxel and cyclophosphamide, 4 cycles (2) Anthracycline and Taxane containing regimens, 6 cycles or 8 cycles

Citation Format: Le D, Chia S, Simmons C, Speers C, Gondara L, Nichol A, Lohrisch C, Gelmon KA. The 21-gene Recurrence® (RS) Score assay in estrogen receptor positive node negative breast cancer: Real-world chemotherapy usage and patient characteristics within the intermediate and high-risk RS category [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 P4-08-27.

Abstract P4-08-03: Looking forward to the TNM 9th edition: Is it time to stage the different breast cancer subtypes as distinct diseases?

Background: For clinical purposes, four subtypes of breast cancer: Luminal A (LumA), Luminal B (LumB), Her2-positive (H2P) and Triple-Negative (TN) are commonly recognized. This study investigated staging them independently as different diseases. The hypothesis was that the anatomic staging system of the 8th TNM edition would have good prognostic performance within each breast cancer subtype, as defined by estrogen receptor (ER), progesterone receptor (PR), Her2 amplification (H2) and grade.

Methods: Using the Breast Cancer Outcomes Unit database, we identified patients treated without neoadjuvant therapy between 2005 and 2009, when use of anti-Her2 therapy (AH2T) was routine for H2+ disease. We approximated the four subtypes of breast cancer described in Table 48.2 of the revised January 25, 2018 version of the TNM 8th edition (https://cancerstaging.org/references-tools/deskreferences/Pages/Breast-Cancer-Staging.aspx) as follows: LumA ER3+ AND PR3+ AND H2- AND (G1-2); LumB All Non-LumA (ER+ OR PR+) AND H2-; H2P All H2+; and TN ER- AND PR- AND H2-. Breast cancer-specific survival (BCSS) was determined for anatomic stages I-IV within each subtype by the Kaplan-Meier method. The predominant usage of hormone therapy (HT), chemotherapy (ChT) and AH2T was compared by subtype for patients &lt; 70 years, who were generally eligible for ChT.

Results: The median follow-up for the 8,640 patients was 10.0 years. The numbers of patients within each subtype were: LumA = 2,288, LumB = 4,097, H2P = 1,374, and TN = 881. The predominant systemic therapies used by subtype were: LumA: HT = 60.2% and HT+ChT = 29.8%; LumB: HT = 45.9% and HT+ChT = 42.1%; H2P: HT+ChT+AH2 = 40.1% and ChT+AH2 = 35.0%; and TN: ChT = 79.1%. The confidence intervals for BCSS in stages I, II, III, and IV were distinct for the four subtypes, as shown in Table 1.

BCSS by Stage for Clinical Breast Cancer Subtypes1-year BCSSLumA (%) (CI)LumB (%) (CI)H2P (%) (CI)TN (%) (CI)Stage I98.1 (97.0, 98.8)96.5 (95.5, 97.2)95.4 (92.9, 97.0)90.4 (86.5, 93.2)Stage II93.4 (91.1, 95.1)86.5 (84.6, 88.3)87.2 (84.1, 89.7)81.4 (77.3, 84.9)Stage III79.9 (71.8, 85.9)66.1 (61.5, 70.3)74.0 (68.1, 78.9)58.0 (48.3, 66.5)Stage IV42.9 (17.7, 66.0)16.9 (8.1, 28.6)33.1 (18.6, 48.3)0.0 (0.0, 0.0)

Conclusions: The anatomic staging system provided reliable BCSS prognostication within breast cancer subtypes. Individualizing treatment using anatomic staging within breast cancer subtypes, would permit decisions about the volume of radiotherapy and the need for intensification of systemic therapy to be made using the familiar and time-tested risk metric of disease extent. In the future, as breast cancer subtyping becomes more sophisticated, prognostication using anatomic staging within these distinct diseases should become increasingly accurate.

Citation Format: Nichol AM, Lohrisch CA, Gondara L, Speers C, Gelmon KA. Looking forward to the TNM 9th edition: Is it time to stage the different breast cancer subtypes as distinct diseases? [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 P4-08-03.