Maternal Embryonic Leucine Zipper Kinase (MELK) as a Novel Mediator and Biomarker of Radioresistance in Human Breast Cancer

PURPOSE

While effective targeted therapies exist for estrogen receptor-positive and HER2-positive breast cancer, no such effective therapies exist for triple-negative breast cancer (TNBC); thus, it is clear that additional targets for radiosensitization and treatment are critically needed.

EXPERIMENTAL DESIGN

Expression microarrays, qRT-PCR, and Western blotting were used to assess MELK RNA and protein expression levels. Clonogenic survival assays were used to quantitate the radiosensitivity of cell lines at baseline and after MELK inhibition. The effect of MELK knockdown on DNA damage repair kinetics was determined using γH2AX staining. The in vivo effect of MELK knockdown on radiosensitivity was performed using mouse xenograft models. Kaplan-Meier analysis was used to estimate local control and survival information, and a Cox proportional hazards model was constructed to identify potential factors impacting local recurrence-free survival.

RESULTS

MELK expression is significantly elevated in breast cancer tissues compared with normal tissue as well as in TNBC compared with non-TNBC. MELK RNA and protein expression is significantly correlated with radioresistance in breast cancer cell lines. Inhibition of MELK (genetically and pharmacologically) induces radiation sensitivity in vitro and significantly delayed tumor growth in vivo in multiple models. Kaplan-Meier survival and multivariable analyses identify increasing MELK expression as being the strongest predictor of radioresistance and increased local recurrence in multiple independent datasets.

CONCLUSIONS

Here, we identify MELK as a potential biomarker of radioresistance and target for radiosensitization in TNBC. Our results support the rationale for developing clinical strategies to inhibit MELK as a novel target in TNBC. Clin Cancer Res; 22(23); 5864-75. ©2016 AACR.

Abstract S4-05: Interrogating the landscape of long noncoding RNAs in breast cancer to identify predictors of tamoxifen resistance

Background: We previously performed an informatics-based analysis on RNA sequencing libraries from 7,256 tumor and normal tissue specimens to delineate the landscape of long noncoding RNAs (lncRNAs) in the human transcriptome. This analysis identified 58,648 lncRNAs, including over 45,000 novel transcripts (Iyer MK et al, Nature Genetics, 2015). We now interrogate this lncRNA compendium to identify top candidate estrogen receptor (ER)-associated lncRNAs in breast cancer and characterize their association with disease progression.

Methods: To prioritize differentially expressed lncRNAs in cancer vs normal tissue, and in ER+ vs ER- disease, we performed Sample Set Enrichment Analysis (SSEA) on >1000 RNA Seq libraries, from breast cancer and normal tissue samples from The Cancer Genome Atlas project. The effect of the top prioritized lncRNA on cancer phenotypes was studied via in vitro proliferation, colony formation, invasion and tamoxifen resistance assays in MCF7 and T47D cells, and via in vivo mouse xenograft studies and chick chorioallantoic membrane (CAM) assays. To study the mechanism by which this lncRNA promotes tumor progression, we identified its top protein interactors and subdomains responsible for function, and then studied the effects of disrupting function of this lncRNA on cancer phenotypes. Finally, in a "guilt-by-association" study, we developed a signature of 150 protein coding genes most strongly associated with our lncRNA of interest, and investigated the association of this signature with clinical outcomes using Oncomine analyses.

Results: SSEA analysis on over 1000 TCGA samples nominated Breast Cancer Associated Transcript (BRCAT 431) as the top overexpressed ER-regulated lncRNA in breast cancer. In vitro experiments demonstrate that siRNA-mediated knockdown of BRCAT431 resulted in significantly decreased proliferation, colony formation, and invasion (by >50% in most assays). Tamoxifen resistance was associated with significantly increased BRCAT431 levels in both MCF7 and T47D cells, and knockdown of BRCAT431 reversed tamoxifen resistance. In vivo xenograft and CAM studies demonstrate that knockdown of BRCAT431 also significantly decreased xenograft growth and tumor invasion by >50%. RNA pulldown followed by mass spectrometry identified the RNA binding protein hnRNPL as a key protein interacting with BRCAT431. Deletion studies identified a 27 base region of BRCAT431 necessary for its interaction with hnRNPL, and loss of this region abrogated BRCAT431- induced invasion. Finally, guilt-by-association studies demonstrate a strong association between BRCAT431 overexpression and tumor grade, recurrence, and metastases.

Conclusion: In this study, we develop the largest reported compendia of breast cancer lncRNAs. We prioritize BRCAT431 as the top lncRNA upregulated in ER-positive breast cancers, and demonstrate that it confers aggressive oncogenic phenotypes in vitro and in vivo. We identify a novel mechanism by which this lncRNA functions. Our results suggest that by promoting tamoxifen resistance, BRCAT431 increases the clinical risk of recurrence and metastases in breast cancer. Overall, this study supports the rationale for investigating lncRNAs as novel biomarkers and therapeutic targets in breast cancer.

Citation Format: Feng FY, Niknafs Y, Han S, Ma T, Speers C, Malik R, Evans J, Zhang C, Pierce LJ, Hayes DF, Rae JM, Chinnaiyan AM. Interrogating the landscape of long noncoding RNAs in breast cancer to identify predictors of tamoxifen resistance. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr S4-05.

Breast Cancer Version 2.2015

Breast cancer is the most common malignancy in women in the United States and is second only to lung cancer as a cause of cancer death. The overall management of breast cancer includes the treatment of local disease with surgery, radiation therapy, or both, and the treatment of systemic disease with cytotoxic chemotherapy, endocrine therapy, biologic therapy, or combinations of these. This portion of the NCCN Guidelines discusses recommendations specific to the locoregional management of clinical stage I, II, and IIIA (T3N1M0) tumors.

Development of a new photonumeric scale for acute radiation dermatitis in patients with breast cancer

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Background: The Common Terminology Criteria for Adverse Events (CTCAE) is frequently used to grade the severity of acute radiation dermatitis (ARD), but has not been validated despite decades of clinical use. We sought to develop a photonumeric scale to consistently describe ARD in breast cancer patients undergoing radiation (RT). Methods: Patients enrolled on a prospective study that included photographs and quantitative measurements of erythema and hyperpigmentation using colorimetry. 209 photographs from 35 patients with white skin and 369 photographs from 50 patients with skin of color were used to develop two photonumeric scales. Predominant erythema (in white skin) OR hyperpigmentation (in skin of color) were rated on a 4 point scale, with grading of desquamation on a separate 3 point scale. Four raters used both CTCAE and photonumeric scales to independently score all photographs. Intra- and inter-rater agreements were assessed using weighted kappa scores. Results: Using the CTCAE, 95% of photos were rated as grade 1 or 2. There was a trend toward higher grade in patients with skin of color, with grade 2 toxicity in 43% vs. 24%. Intra-rater agreement for CTCAE ratings was 65—87% (kappa 0.34—0.67), with a wide range of inter-rater agreement (56—81% agreement fraction, kappa 0.04—0.58). Using the photonumeric scale, intra-rater agreement was high for erythema/hyperpigmentation in patients with white skin (74—82%, kappa 0.49—0.70) and skin of color (69—86%, kappa 0.55—0.79), along with desquamation (78—87%, kappa 0.52—0.66). There was moderate inter-rater agreement for erythema/hyperpigmentation (51—82%, kappa 0.15—0.71) and desquamation (63—88%, kappa 0.36—0.58). Colorimetric measurements correlated strongly with photonumeric grade. Conclusions: We report a new photonumeric scale for ARD in breast cancer patients with satisfactory reliability across the spectrum of skin pigmentation. Intra-physician ratings were consistent, with moderate inter-physician agreement. The CTCAE functions as a binary scale, with 95% of ARD rated as grade 1 or 2 toxicity. Future work includes correlation with patient-reported outcomes and physician ratings at the point-of-care. Funded by a Munn Idea Grant (G011480).

Regional Nodal Irradiation in Early-Stage Breast Cancer

BACKGROUND

Most women with breast cancer who undergo breast-conserving surgery receive whole-breast irradiation. We examined whether the addition of regional nodal irradiation to whole-breast irradiation improved outcomes.

METHODS

We randomly assigned women with node-positive or high-risk node-negative breast cancer who were treated with breast-conserving surgery and adjuvant systemic therapy to undergo either whole-breast irradiation plus regional nodal irradiation (including internal mammary, supraclavicular, and axillary lymph nodes) (nodal-irradiation group) or whole-breast irradiation alone (control group). The primary outcome was overall survival. Secondary outcomes were disease-free survival, isolated locoregional disease-free survival, and distant disease-free survival.

RESULTS

Between March 2000 and February 2007, a total of 1832 women were assigned to the nodal-irradiation group or the control group (916 women in each group). The median follow-up was 9.5 years. At the 10-year follow-up, there was no significant between-group difference in survival, with a rate of 82.8% in the nodal-irradiation group and 81.8% in the control group (hazard ratio, 0.91; 95% confidence interval [CI], 0.72 to 1.13; P=0.38). The rates of disease-free survival were 82.0% in the nodal-irradiation group and 77.0% in the control group (hazard ratio, 0.76; 95% CI, 0.61 to 0.94; P=0.01). Patients in the nodal-irradiation group had higher rates of grade 2 or greater acute pneumonitis (1.2% vs. 0.2%, P=0.01) and lymphedema (8.4% vs. 4.5%, P=0.001).

CONCLUSIONS

Among women with node-positive or high-risk node-negative breast cancer, the addition of regional nodal irradiation to whole-breast irradiation did not improve overall survival but reduced the rate of breast-cancer recurrence. (Funded by the Canadian Cancer Society Research Institute and others; MA.20 ClinicalTrials.gov number, NCT00005957.).

Development and validation of a novel platform-independent metastasis signature in human breast cancer

Purpose

The molecular drivers of metastasis in breast cancer are not well understood. Therefore, we sought to identify the biological processes underlying distant progression and define a prognostic signature for metastatic potential in breast cancer.

Experimental design

In vivo screening for metastases was performed using Chick Chorioallantoic Membrane assays in 21 preclinical breast cancer models. Expressed genes associated with metastatic potential were identified using high-throughput analysis. Correlations with biological function were determined using the Database for Annotation, Visualization and Integrated Discovery.

Results

We identified a broad range of metastatic potential that was independent of intrinsic breast cancer subtypes. 146 genes were significantly associated with metastasis progression and were linked to cancer-related biological functions, including cell migration/adhesion, Jak-STAT, TGF-beta, and Wnt signaling. These genes were used to develop a platform-independent gene expression signature (M-Sig), which was trained and subsequently validated on 5 independent cohorts totaling nearly 1800 breast cancer patients with all p-values < 0.005 and hazard ratios ranging from approximately 2.5 to 3. On multivariate analysis accounting for standard clinicopathologic prognostic variables, M-Sig remained the strongest prognostic factor for metastatic progression, with p-values < 0.001 and hazard ratios > 2 in three different cohorts.

Conclusion

M-Sig is strongly prognostic for metastatic progression, and may provide clinical utility in combination with treatment prediction tools to better guide patient care. In addition, the platform-independent nature of the signature makes it an excellent research tool as it can be directly applied onto existing, and future, datasets.

Wide Variation in the Diffusion of a New Technology: Practice-Based Trends in Intensity-Modulated Radiation Therapy (IMRT) Use in the State of Michigan, With Implications for IMRT Use Nationally

IMRT use grew significantly across the state of Michigan over time, with four-fold variability among centers, which was related to facility characteristics.

Abstract P6-03-08: Androgen receptor (AR): A novel target for radiosensitization and treatment in triple-negative breast cancers (TNBC)

Background: Increased rates of locoregional recurrence have been observed in TNBC despite the use of chemotherapy and radiation (RT). Thus, approaches that result in radiosensitizaton of TNBC are critically needed. We have previously characterized the radiation response of 21 breast cancer cell (BCC) lines using clonogenic survival assays. We now pair this data with high-throughput drug screen data available through cancer cell line encyclopedia studies to identify AR as a top target for radiosensitization and assess AR inhibition as a radiosensitization strategy for TNBC.

Methods: Clonogenic survival assays were performed to determine the intrinsic RT sensitivity of 21 BCC lines (0-8 Gy RT). IC50 values were determined for 130 clinically available compounds and correlation coefficients were calculated using IC50 values (for drug sensitivity) and SF-2Gy (for radiation sensitivity). Gene expression was measured using Affymetrix microarrays and protein expression was measured using reverse-phase protein lysate arrays (RPPA) of human tumor samples (n=2,061) and BCC lines (n=51). AR function was assessed using siRNA knockdown or inhibition with MDV3100 (enzalutamide). Kaplan-Meier analysis was performed to determine the clinical impact of AR expression on local control and survival. A Cox proportional hazards model was constructed to identify potential factors of survival, and multivariate analysis was used to determine variables most significantly associated with LRF survival.

Results: Our radiosensitizer screen nominated bicalutamide as one of the most effective drugs in treating radioresistant BCC lines (R2= 0.46, p-value &lt;0.001). Recognizing that a subgroup of TNBC includes AR expressing tumors, we interrogated the expression of AR in &gt;2000 human breast tumor samples and found signifi[not]cant heterogeneity in AR expression with an increase in TNBC (35% of tumors) compared to non-TNBC (28% of tumors). This same heterogeneity was also identified in human BCC lines. There was a strong correlation between AR RNA expression and protein expression (R2= 0.72, p &lt;0.0001). Inhibition of AR using both siRNA and MDV3100 induced radiation sensitivity in vitro with an enhancement ratio (ER) of 1.35-1.42 in AR-positive TNBC lines. No such radiosensitization was seen in AR-negative TNBC or ER-positive, AR-negative BCC lines. Radiosensitization was at least partially dependent on impaired dsDNA break repair mediated by DNAPKcs. In vivo assessment of tumor growth inhibition with RT and anti-AR strategies are currently underway. Clinically, analyses of patients with TNBC showed that patients whose tumors had high expression of AR had markedly higher rates of LR after RT than patients with low expression of AR (HR for LR 2.9-3.2, p-value &lt;0.01, 2 independent datasets). There was no difference in LR in TNBC patients not treated with RT when stratified by AR expression status. In multivariate analysis, AR expression was the variable most significantly associated with worse LRF survival after RT with a HR of 3.58 (p-value &lt; 0.01).

Conclusion: Our results implicate AR as a mediator of radioresistance in breast cancer and support the rationale for developing clinical strategies to inhibit AR as a novel radiosensitizing target in TNBC.

Citation Format: Corey Speers, Shuang G Zhao, Meilan Liu, Joseph Evans, Prasanna Alluri, Daniel F Hayes, Felix Y Feng, Lori J Pierce. Androgen receptor (AR): A novel target for radiosensitization and treatment in triple-negative breast cancers (TNBC) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-03-08.

Abstract P1-15-01: Association between ischemic cardiac events and targeting of the internal mammary nodal region with adjuvant radiation for breast cancer

Background: Cardiac toxicity has been well documented following adjuvant breast cancer radiation therapy (RT) using outdated treatment methods. Limited information exists, however, regarding cardiac outcomes following contemporary RT fields and techniques. Inclusion of the internal mammary nodal (IMN) field for appropriately selected patients with breast cancer coincided with our department’s transition to computed-tomography (CT) based planning. The objectives of this study, therefore, were to assess the risk of ischemic cardiac events following IMN irradiation and to assess the risks following CT-based versus two-dimensional (2D) planning.

Methods: All patients treated with adjuvant RT for breast cancer and without history of additional chest RT from January 1, 1984 – December 31, 2007 in our department were assessed. CT planning for breast cancer began for select patients in 1997 and was used for all patients as of 2001. The inclusion of the IMN region was determined by review of our clinical database. Ischemic cardiac endpoints were defined as myocardial infarction, coronary artery bypass grafting procedure, angioplasty/stent placement, and/or diagnosis of coronary artery disease. A text-based and diagnosis code-based search was used to flag possible endpoints which were then confirmed by manual chart review. Hypertension (HTN), diabetes (DM), hyperlipidemia (HLD), and anthracycline use were identified by a diagnosis code-based search.

Results: We identified 2,126 patients who received adjuvant RT. Median follow-up was 9.6 years. 311 (14.6%) patients had IMNs targeted and 1,813 (85.3%) did not (data not available for 2 patients). RT to the IMNs was not associated with a higher risk of ischemic cardiac events (HR: 0.88, P = 0.731). 1,072 (50.4%) patients had CT planning, 1,003 (47.2%) had 2D planning, and no information was available for 51 (2.4%) patients. Overall, there were 56 (5.6%) ischemic events in the 2D cohort and 27 (2.5%) in the CT cohort. After truncating follow-up to 10 years to account for differential potential follow-up, there were 28 (2.8%) and 23 (2.2%) ischemic cardiac events, respectively. The table lists the association of patient and treatment characteristics and risk of ischemic cardiac events. HTN, HLD, and DM were each associated with a significantly increased risk of ischemic cardiac events.

Conclusions: After reviewing all patients treated in our department for breast cancer from 1984 – 2007, we were unable to find an association between IMN irradiation and ischemic cardiac events. CT-based planning has been shown to allow accurate targeting of the IMNs. These data suggest that even with inclusion of the IMNs, CT-based planning minimizes dose to the heart and coronary arteries thereby decreasing the risk of ischemic cardiac toxicity. These results will be followed with time.

Association between characteristics and ischemic cardiac eventsCharacteristicHazard Ratio95% Confidence IntervalP-valueRT to the IMNs0.880.42-1.830.7312D vs. CT planning1.140.68-1.910.613Left vs. right1.210.79-1.850.372Anthracycline use0.750.44-1.260.270HTN5.612.06-15.300.001HLD1.901.25-2.900.003DM3.111.99-4.86&lt;0.001

Citation Format: Adam L Liss, Kent A Griffith, Reshma Jagsi, Jean M Moran, Robin B Marsh, Todd M Koelling, Lori J Pierce. Association between ischemic cardiac events and targeting of the internal mammary nodal region with adjuvant radiation for breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-15-01.

Abstract P1-15-12: Development of a photonumeric scale for acute radiation dermatitis in breast cancer patients

Purpose

Scales for rating acute radiation dermatitis (ARD) are inconsistent and have not been validated despite decades of clinical use, making ARD difficult to report reliably. We sought to design a photonumeric scale to consistently describe ARD in breast cancer patients undergoing radiation (RT).

Methods

Patients undergoing RT for breast cancer were enrolled on a prospective study that included photographs and reporting of physician-rated erythema, hyperpigmentation, and CTCAE toxicity score at baseline and 2, 4, and 6 weeks after initiating RT. Erythema and hyperpigmentation were also quantified using a hand-held colorimetric device. Photographs were taken using a standardized protocol that included 3 views to fully assess the breast/chest wall, axilla, and inframammary fold. 209 photographs from 35 patients with white skin (Fitzpatrick skin types I-IV) and 369 photographs from 50 patients with skin of color (Fitzpatrick skin types V-VI) were clustered according to the apparent severity of ARD. Due to the prevalence of hyperpigmentation that obscured erythema in patients with skin of color, separate images were used to illustrate ARD in this population. Two photonumeric scales (for white skin and skin of color) were developed via an iterative process until group consensus was achieved. Four raters with experience in the evaluation of ARD in breast cancer patients used the photonumeric scale to independently score the entire collection of photographs, sequenced in random order. Intra- and inter-rater agreements were assessed using weighted kappa scores.

Results

Of the 35 patients with white skin, 20% experienced severe erythema, and 40% experienced dry or moist desquamation. Of the 50 patients with skin of color, 34% experience severe hyperpigmentation, and 48% experienced dry or moist desquamation. Using the photonumeric scales, we observed high intra-rater agreement for independent ratings of erythema or hyperpigmentation (70 to 89% agreement fraction, kappa 0.55 to 0.81) and desquamation (79 to 87% agreement fraction, kappa 0.52 to 0.64). Similarly, we observed moderate to high inter-rater agreement for independent ratings of erythema or hyperpigmentation (61 to 76% agreement fraction, kappa 0.40 to 0.62) and desquamation (69 to 84% agreement fraction, kappa 0.36 to 0.58). Quantitative measurements of erythema in white patients using colorimetry correlated strongly with photonumeric grade (correlation coefficient 0.76, p&lt;0.001), as did physician-rated erythema at the point-of-care (p&lt;0.001). Fitzpatrick score was not significantly associated with maximum photonumeric erythema grade (p = 0.14).

Conclusions

We report a new photonumeric scale with high intra- and inter-rater reliability for acute radiation dermatitis in breast cancer patients. To our knowledge, this is the first rigorously evaluated scale that is applicable to patients across the spectrum of skin pigmentation, including white skin and skin of color. The photonumeric scale will facilitate consistent reporting of acute radiation dermatitis in research and clinical settings using a simple, standardized instrument. Future work will include prospective real-time clinical validation with multiple raters and correlation with patient-reported outcomes.

Funded by a Munn Idea Grant (G011480).

Citation Format: Dean Shumway, Eleanor M Walker, Nirav Kapadia, Thy Thy Do, Kent Griffith, Mary Feng, Bonnie DePalma, Reshma Jagsi, Yolanda Helfrich, Erin Gillespie, Alexandria Miller, Adam Liss, Lori J Pierce. Development of a photonumeric scale for acute radiation dermatitis in breast cancer patients [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-15-12.

Development and Validation of a Novel Radiosensitivity Signature in Human Breast Cancer

PURPOSE

An unmet clinical need in breast cancer management is the accurate identification of patients who will benefit from adjuvant radiotherapy. We hypothesized that integration of postradiation clonogenic survival data with gene expression data across breast cancer cell (BCC) lines would generate a radiation sensitivity signature (RSS) and identify patients with tumors refractive to conventional therapy.

EXPERIMENTAL DESIGN

Using clonogenic survival assays, we identified the surviving fraction (SF-2Gy) after radiation across a range of BCC lines. Intrinsic radiosensitivity was correlated to gene expression using Spearman correlation. Functional analysis was performed in vitro, and enriched biologic concepts were identified. The RSS was generated using a Random Forest model and was refined, cross-validated, and independently validated in additional breast cancer datasets.

RESULTS

Clonogenic survival identifies a range of radiosensitivity in human BCC lines (SF-2Gy 77%-17%) with no significant correlation to the intrinsic breast cancer subtypes. One hundred forty-seven genes were correlated with radiosensitivity. Functional analysis of RSS genes identifies previously unreported radioresistance-associated genes. RSS was trained, cross-validated, and further refined to 51 genes that were enriched for concepts involving cell-cycle arrest and DNA damage response. RSS was validated in an independent dataset and was the most significant factor in predicting local recurrence on multivariate analysis, outperfoming all clinically used clinicopathologic features.

CONCLUSIONS

We derive a human breast cancer-specific RSS with biologic relevance and validate this signature for prediction of locoregional recurrence. By identifying patients with tumors refractory to standard radiation this signature has the potential to allow for personalization of radiotherapy.

Web based pathology assessment in RTOG 98-04

Aims

Radiation Therapy Oncology Group 98-04 sought to identify women with ‘good risk’ ductal carcinoma in situ (DCIS) who receive no significant benefit from radiation. Enrolment criteria excluded close or positive margins and grade 3 disease. To ensure reproducibility in identifying good risk pathology, an optional web based teaching tool was developed and a random sampling of 10% of submitted slides were reviewed by a central pathologist.

Methods

Submitting pathologists were asked to use the web based teaching tool and submit an assessment of the tool along with the pathology specimen form and DCIS H&E stained slide. Per protocol pathology was centrally reviewed for 10% of the cases.

Results

Of the 55 DCIS cases reviewed, three had close or positive margins and three were assessed to include grade 3 DCIS, therefore 95% of DCIS cases reviewed were correctly graded, and 89% reviewed were pathologically appropriate for enrolment. Regarding the teaching tool, 13% of DCIS cases included forms that indicated the website was used. One of these seven who used the website submitted DCIS of grade 3.

Conclusions

Central review demonstrates high pathological concordance with enrolment eligibility, particularly with regard to accurate grading. The teaching tool appeared to be underused.

Targeted radiosensitization with PARP1 inhibition: optimization of therapy and identification of biomarkers of response in breast cancer

Sustained locoregional control of breast cancer is a significant issue for certain patients. Inhibition of PARP1 is a promising strategy for radiosensitization (RS). We sought to optimize therapy with PARP1 inhibition and radiation (RT) by establishing the most effective treatment schedule, degree of PARP1-mediated RS, and identify early biomarkers predictive of efficacy in breast cancer models. Using clonogenic survival assays, we assessed intrinsic radiosensitivity and RS induced by PARP1 inhibition in breast cancer cell lines. Potential biomarkers of response were evaluated using western blotting, flow cytometry, and immunofluorescence with validation in vivo using tumor xenograft experiments. Across a panel of BC and normal breast epithelial cell lines, the PARP1 inhibitor ABT-888 preferentially radiosensitizes breast cancer (vs. normal) cells with enhancement ratios (EnhR) up to 2.3 independent of intrinsic BC subtype or BRCA mutational status. Concurrent and adjuvant therapy resulted in the highest EnhR of all schedules tested. The degree of RS did not correlate with pretreatment markers of PARP1 activity, DNA damage/repair, or cell cycle distribution. Increases in PARP1 activity 24 h after RT were associated with sensitivity after combination treatment. Findings were confirmed in breast cancer xenograft models. Our study demonstrates that PARP1 inhibition improves the therapeutic index of RT independent of BC subtype or BRCA1 mutational status and that PARP1 activity may serve as a clinically relevant biomarker of response. These studies have led to a clinical trial (TBCRC024) incorporating intratreatment biomarker analyses of PARP1 inhibitors and RT in breast cancer patients.

PARP-1 inhibitors and radiotherapy sensitivity: future prospects for therapy?

SUMMARY 

Despite the efficacy of multimodality treatment for women with breast cancer, sustained locoregional control remains a significant issue. Efforts to identify effective targeted therapies for treatment of these patients have intensified in recent years. The PARP family of proteins represents one potential target. PARP-1 is a DNA repair enzyme that plays a critical role in base excision repair, homologous recombination, nonhomologous end joining and transcriptional regulation. In this review, we discuss the rationale for using PARP-1 inhibitors clinically, the role of PARP-1 in DNA damage repair and the potential clinical utility of using PARP-1 inhibitors as a radiosensitization strategy. We will also review the most relevant clinical trials using various PARP-1 inhibitors and the future of biomarker development to predict response to PARP-1 inhibition.

Decline of cosmetic outcomes following accelerated partial breast irradiation using intensity modulated radiation therapy: results of a single-institution prospective clinical trial

PURPOSE

To report the final cosmetic results from a single-arm prospective clinical trial evaluating accelerated partial breast irradiation (APBI) using intensity modulated radiation therapy (IMRT) with active-breathing control (ABC).

METHODS AND MATERIALS

Women older than 40 with breast cancer stages 0-I who received breast-conserving surgery were enrolled in an institutional review board-approved prospective study evaluating APBI using IMRT administered with deep inspiration breath-hold. Patients received 38.5 Gy in 3.85-Gy fractions given twice daily over 5 consecutive days. The planning target volume was defined as the lumpectomy cavity with a 1.5-cm margin. Cosmesis was scored on a 4-category scale by the treating physician. Toxicity was scored according to National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE version 3.0). We report the cosmetic and toxicity results at a median follow-up of 5 years.

RESULTS

A total of 34 patients were enrolled. Two patients were excluded because of fair baseline cosmesis. The trial was terminated early because fair/poor cosmesis developed in 7 of 32 women at a median follow-up of 2.5 years. At a median follow-up of 5 years, further decline in the cosmetic outcome was observed in 5 women. Cosmesis at the time of last assessment was 43.3% excellent, 30% good, 20% fair, and 6.7% poor. Fibrosis according to CTCAE at last assessment was 3.3% grade 2 toxicity and 0% grade 3 toxicity. There was no correlation of CTCAE grade 2 or greater fibrosis with cosmesis. The 5-year rate of local control was 97% for all 34 patients initially enrolled.

CONCLUSIONS

In this prospective trial with 5-year median follow-up, we observed an excellent rate of tumor control using IMRT-planned APBI. Cosmetic outcomes, however, continued to decline, with 26.7% of women having a fair to poor cosmetic result. These results underscore the need for continued cosmetic assessment for patients treated with APBI by technique.

Breast cancer, version 3.2013: featured updates to the NCCN guidelines

These NCCN Guidelines Insights highlight the important updates specific to the management of HER2-positive metastatic breast cancer in the 2013 version of the NCCN Clinical Practice Guidelines in Oncology for Breast Cancer. These include new first-line and subsequent therapy options for patients with HER2-positive metastatic breast cancer.

Radiation-induced increases in PARP1 activity to predict for long-term radiosensitization by PARP1 inhibition in preclinical breast cancer models

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Background: Sustained locoregional (LR) control of breast cancer (BCa) is a significant issue for patients with inflammatory disease or chest wall recurrences. Inhibition of poly(adenosine diphosphate-ribose) (PAR) polymerase 1 (PARP1), a DNA damage response protein, is a promising strategy for radiosensitization (RS). We investigated RS by PARP1 inhibition and aimed to identify early biomarkers (BMs) predictive of long-term treatment efficacy in preclinical BCa models. Methods: Clonogenic survival assays in 12 BCa and normal epithelial cell lines were used to determine the degree of RS conferred by the PARP1 inhibitor ABT-888 and to optimize the sequencing of therapy. Immunoblots, immunofluorescent staining, flow cytometery, and xenograft studies were used to evaluate for pre-/intra-treatment BMs predicting for subsequent response to therapy. Results: ABT-888 preferentially radiosensitized BCa (vs. normal) cells (enhancement ratios (EnhR) up to 2.3 across different subtypes). The highest EnhRs resulted from concurrent and adjuvant ABT-888. The degree of RS did not correlate with pretreatment markers of PARP1 activity (e.g., PAR levels), DNA damage/repair (e.g. gamma-H2AX & RAD51 foci), or cell cycle distribution. However, increases in PARP1 activity from pretreatment to 24 hours after RT, was associated with long-term clonogenic death after treatment with ABT-888 + radiation (RT) (Spearman's coefficient=0.8, p=0.002). The four cell lines significantly radiosensitized by PARP1 inhibition (EnhR>1.5) averaged a 2-fold increase in PAR levels following RT. Findings were also confirmed in SKBR3 and MDA-231 BCa xenograft models. Conclusions: Our study demonstrates that PARP1 inhibition improves the therapeutic index of RT in BCa cell lines. Treatment-induced increase in PARP1 activity 24 hours after RT predicts for long-term radiosensitization by PARP1 inhibition and is a potential biomarker of response. These studies have led to a clinical trial, incorporating intratreatment BM analyses, of PARP inhibitors and RT in BCa patients currently open for accrual through the Translational Breast Cancer Research Consortium.

Variation in the use of intensity-modulated radiation therapy (IMRT) in the state of Michigan: 2005-2010

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Background: Interest is growing in value in health care, defined as better outcomes at lower costs. A primary driver of cost in radiation oncology is the use of IMRT. We examined the patterns and correlates of use of IMRT across Michigan using publicly available data. Methods: As a certificate of need state, Michigan requires every radiation oncology facility to report yearly the number of external beam and IMRT treatments delivered. Data for 2005-2008 were obtained through a Freedom of Information Act request of the Michigan Department of Community Health, while 2009-2010 data were available at its website. Percentage of external beam treatments delivered using IMRT (IMRT%) was examined across centers over time and repeated-measures longitudinal linear regression was used to identify factors associated with use. Results: During 2005-2010, 48 to 65 centers reported data. Median IMRT% (range) rose steadily during the study period: 2005 16% (0-64); 2006 21% (0-57); 2007 27% (0-79); 2008 37% (7-85); 2009 41% (0-87) 2010 45% (7-100). There was also significant between-center variation (see table). Regression modeling demonstrated that IMRT% was associated with year (+6.7% per year, p<0.0001), facility type (+7.1% freestanding versus hospital, p<0.11), facility annual volume (+5.0% high volume: 7,000+ versus low: <7,000, p=0.01) and the interaction between year and volume (low volume +2.4% per year versus high volume p<0.02). The significant interaction between year and volume suggests that the greatest IMRT% growth was in low volume centers (6.7% per year versus 4.3% per year for high volume). Conclusions: IMRT utilization has grown steadily across Michigan between 2005 and 2010. There is significant variation in its use that appears to be related in part to facility characteristics. The newly established Michigan Radiation Oncology Quality Collaborative (MROQC) is beginning to explore the use of IMRT in patients with breast and lung cancer statewide to identify those groups of patients where improved outcomes may justify its higher cost. [Table: see text]

Is there a dose-response relationship for heart disease with low-dose radiation therapy?

PURPOSE

To quantify cardiac radiation therapy (RT) exposure using sensitive measures of cardiac dysfunction; and to correlate dysfunction with heart doses, in the setting of adjuvant RT for left-sided breast cancer.

METHODS AND MATERIALS

On a randomized trial, 32 women with node-positive left-sided breast cancer underwent pre-RT stress single photon emission computed tomography (SPECT-CT) myocardial perfusion scans. Patients received RT to the breast/chest wall and regional lymph nodes to doses of 50 to 52.2 Gy. Repeat SPECT-CT scans were performed 1 year after RT. Perfusion defects (PD), summed stress defects scores (SSS), and ejection fractions (EF) were evaluated. Doses to the heart and coronary arteries were quantified.

RESULTS

The mean difference in pre- and post-RT PD was -0.38% ± 3.20% (P=.68), with no clinically significant defects. To assess for subclinical effects, PD were also examined using a 1.5-SD below the normal mean threshold, with a mean difference of 2.53% ± 12.57% (P=.38). The mean differences in SSS and EF before and after RT were 0.78% ± 2.50% (P=.08) and 1.75% ± 7.29% (P=.39), respectively. The average heart Dmean and D95 were 2.82 Gy (range, 1.11-6.06 Gy) and 0.90 Gy (range, 0.13-2.17 Gy), respectively. The average Dmean and D95 to the left anterior descending artery were 7.22 Gy (range, 2.58-18.05 Gy) and 3.22 Gy (range, 1.23-6.86 Gy), respectively. No correlations were found between cardiac doses and changes in PD, SSS, and EF.

CONCLUSIONS

Using sensitive measures of cardiac function, no clinically significant defects were found after RT, with the average heart Dmean <5 Gy. Although a dose response may exist for measures of cardiac dysfunction at higher doses, no correlation was found in the present study for low doses delivered to cardiac structures and perfusion, SSS, or EF.

Quantifying dose to the reconstructed breast: can we adequately treat?

To evaluate how immediate reconstruction (IR) impacts postmastectomy radiotherapy (PMRT) dose distributions to the reconstructed breast (RB), internal mammary nodes (IMN), heart, and lungs using quantifiable dosimetric end points. 3D conformal plans were developed for 20 IR patients, 10 autologous reconstruction (AR), and 10 expander-implant (EI) reconstruction. For each reconstruction type, 5 right- and 5 left-sided reconstructions were selected. Two plans were created for each patient, 1 with RB coverage alone and 1 with RB + IMN coverage. Left-sided EI plans without IMN coverage had higher heart Dmean than left-sided AR plans (2.97 and 0.84 Gy, p = 0.03). Otherwise, results did not vary by reconstruction type and all remaining metrics were evaluated using a combined AR and EI dataset. RB coverage was adequate regardless of laterality or IMN coverage (Dmean 50.61 Gy, D95 45.76 Gy). When included, IMN Dmean and D95 were 49.57 and 40.96 Gy, respectively. Mean heart doses increased with left-sided treatment plans and IMN inclusion. Right-sided treatment plans and IMN inclusion increased mean lung V(20). Using standard field arrangements and 3D planning, we observed excellent coverage of the RB and IMN, regardless of laterality or reconstruction type. Our results demonstrate that adequate doses can be delivered to the RB with or without IMN coverage.

Metastatic breast cancer, version 1.2012: featured updates to the NCCN guidelines

These NCCN Guidelines Insights highlight the important updates/changes specific to the management of metastatic breast cancer in the 2012 version of the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Breast Cancer. These changes/updates include the issue of retesting of biomarkers (estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2) on recurrent disease, new information regarding first-line combination endocrine therapy for metastatic disease, a new section on monitoring of patients with metastatic disease, and new information on endocrine therapy combined with an mTOR inhibitor as a subsequent therapeutic option.

Radiotherapy in the treatment of hereditary breast cancer

Hereditary breast cancer represents approximately 5% to 10% of breast cancers and a larger portion of patients with early-onset disease. Given the relatively recent identification of the BRCA1 and BRCA2 genes, the available literature with respect to outcomes related to radiation therapy has inherent limitations with relatively small patient numbers and a lack of prospective randomized trials. There is, however, a growing body of literature describing treatment and toxicity outcomes in patients undergoing radiation therapy after breast-conserving surgery and after mastectomy for breast cancer patients who have BRCA1 and BRCA2 mutations. Acknowledging the limitations in the available data, there does not appear to be any evidence of more severe normal tissue reactions or compromised long-term survival rates in women electing breast-conserving surgery and radiation. These studies are reviewed in this article. Outcomes related to radiation therapy in patients with variants in other breast cancer-related genes, such as p53, ATM, CHEK2, PALB2, and PTEN, are even less well documented because of the paucity of data. Available reports on radiation-related outcomes in these and single nucleotide polymorphisms in radiation repair and response genes are discussed.

Abstract P5-13-02: Impact of Adjuvant Trastuzumab on Local Regional Recurrence: Data from the NCCTG N9831 Study

Background: Trastuzumab (H) improves disease-free survival (DFS) in patients (pts) with HER2 positive breast cancer (BR Ca) when used with adjuvant chemotherapy. We herein compare the rates of local regional recurrence (LRR) in pts randomized to adjuvant chemotherapy with or without adjuvant H.

Methods: The phase 3 randomized trial NCCTG N9831 enrolled 3505 pts with high risk HER2 positive Br Ca to evaluate the effect of adjuvant H on DFS. Pts were randomized to either doxorubicin (A) and cyclophosphamide (C) followed by paclitaxel (T); or AC→TH→H. RT was given concurrently with H after ACT chemotherapy. Pts analyzed underwent lumpectomy (L) + radiotherapy (RT), mastectomy (M) alone, or M+RT. All pts underwent sentinel lymph node biopsy alone and/or axillary dissection. 2816 pts were eligible for competing risk analysis of LRR as a first event (competing risks were distant recurrence, contralateral Br Ca, second primary cancer, or death). Median follow-up is 5.3 years.

Results: Primary breast therapy included L+RT 1062 (38%), M 711 (25%), and M+RT 1043 (37%). Axillary dissection was performed in 90% of pts but less frequently with L+RT (83%) compared to M (88%) or M+RT (98%), chi-sq P&lt;0.001. Stage at presentation was I 41%, II 51%, and III 8% with a significant greater proportion of higher stage pts undergoing M+RT, chi-sq P&lt;0.001. Overall the 5-year LRR rate was 4.1% (95% CI 3.5-4.9%) and similar among the treatment groups: L+RT 4.7% (95% CI 3.6-6.1%), M 3.5% (95% CI 2.4-5.1%), and M+RT 2.3% (95% CI 1.6-3.4%). Among pts with a LRR, 66% were local recurrence only, 11% were local-regional, and 23% were regional only. In the L+RT patients with a LRR, the corresponding rates were 74%, 7%, and 19%, respectively. In the M patients with a LRR, the corresponding rates were 40%, 23%, and 37%, respectively. In the M+RT patients with LRR, the rates were 79%, 4%, and 17%, respectively. H is associated with a non-statistically significant reduction in the risk of LRR for pts who receive L+RT or M+RT (Table 1). No such trend was seen in the M alone group but the number of events was low.

Table 1. LRR According to Local and Adjuvant Treatment Groups

Conclusion: The LRR as the first reported site of failure was low with a median 5. 3 year follow-up. Adjuvant H was associated with a trend of lower LRR in the pts treated with L + RT or M+RT. This observation suggests an additive effect of RT and H on LRR that warrants further investigation. The small number of local-regional events in this one randomized trial supports further investigation of LRR across other adjuvant trastuzumab trials.

Evaluation of four techniques using intensity-modulated radiation therapy for comprehensive locoregional irradiation of breast cancer

PURPOSE

To establish optimal intensity-modulated radiation therapy (IMRT) techniques for treating the left breast and regional nodes, using moderate deep-inspiration breath hold.

METHODS AND MATERIALS

We developed four IMRT plans of differing complexity for each of 10 patients following lumpectomy for left breast cancer. A dose of 60 Gy was prescribed to the boost planning target volume (PTV) and 52.2 Gy to the breast and supraclavicular, infraclavicular, and internal mammary nodes. Two plans used inverse-planned beamlet techniques: a 9-field technique, with nine equispaced axial beams, and a tangential beamlet technique, with three to five ipsilateral beams. The third plan (a segmental technique) used a forward-planned multisegment technique, and the fourth plan (a segmental blocked technique) was identical but included a block to limit heart dose. Dose--volume histograms were generated, and metrics chosen for comparison were analyzed using the paired t test.

RESULTS

Mean heart and left anterior descending coronary artery doses were similar with the tangential beamlet and segmental blocked techniques but higher with the segmental and 9-field techniques (mean paired difference of 15.1 Gy between segmental and tangential beamlet techniques, p < 0.001). Substantial volumes of contralateral tissue received dose with the 9-field technique (mean right breast V2, 58.9%; mean right lung V2, 75.3%). Minimum dose to ≥95% of breast PTV was, on average, 45.9 Gy with tangential beamlet, 45.0 Gy with segmental blocked, 51.4 Gy with segmental, and 50.2 Gy with 9-field techniques. Coverage of the internal mammary region was substantially better with the two beamlet techniques than with the segmental blocked technique.

CONCLUSIONS

Compared to the 9-field beamlet and segmental techniques, a tangential beamlet IMRT technique reduced exposure to normal tissues and maintained reasonable target coverage.

Development and validation of a heart atlas to study cardiac exposure to radiation following treatment for breast cancer

PURPOSE

Cardiac toxicity is an important sequela of breast radiotherapy. However, the relationship between dose to cardiac structures and subsequent toxicity has not been well defined, partially due to variations in substructure delineation, which can lead to inconsistent dose reporting and the failure to detect potential correlations. Here we have developed a heart atlas and evaluated its effect on contour accuracy and concordance.

METHODS AND MATERIALS

A detailed cardiac computed tomography scan atlas was developed jointly by cardiology, cardiac radiology, and radiation oncology. Seven radiation oncologists were recruited to delineate the whole heart, left main and left anterior descending interventricular branches, and right coronary arteries on four cases before and after studying the atlas. Contour accuracy was assessed by percent overlap with gold standard atlas volumes. The concordance index was also calculated. Standard radiation fields were applied. Doses to observer-contoured cardiac structures were calculated and compared with gold standard contour doses. Pre- and post-atlas values were analyzed using a paired t test.

RESULTS

The cardiac atlas significantly improved contour accuracy and concordance. Percent overlap and concordance index of observer-contoured cardiac and gold standard volumes were 2.3-fold improved for all structures (p < 0.002). After application of the atlas, reported mean doses to the whole heart, left main artery, left anterior descending interventricular branch, and right coronary artery were within 0.1, 0.9, 2.6, and 0.6 Gy, respectively, of gold standard doses.

CONCLUSIONS

This validated University of Michigan cardiac atlas may serve as a useful tool in future studies assessing cardiac toxicity and in clinical trials which include dose volume constraints to the heart.

Radiation dose-volume effects in the heart

The literature is reviewed to identify the main clinical and dose-volume predictors for acute and late radiation-induced heart disease. A clear quantitative dose and/or volume dependence for most cardiac toxicity has not yet been shown, primarily because of the scarcity of the data. Several clinical factors, such as age, comorbidities and doxorubicin use, appear to increase the risk of injury. The existing dose-volume data is presented, as well as suggestions for future investigations to better define radiation-induced cardiac injury.

Radiation-related heart disease: current knowledge and future prospects

The heart has traditionally been considered a radio-resistant organ that would be unaffected by cardiac doses below about 30 Gray. During the last few years, however, evidence that radiation-related heart disease can occur following lower doses has emerged from several sources. These include studies of breast cancer patients, who received mean cardiac doses of 3–17 Gray when given radiotherapy following surgery, and studies of survivors of the atomic bombings of Japan who received doses of up to 4 Gray.

At doses above 30 Gray, radiation-related heart disease may occur within a year or two of exposure and risk increases with higher radiotherapy dose, younger age at irradiation, and the presence of conventional risk factors. At lower doses the typical latent period is much longer and is often more than a decade. However, the nature and magnitude of the risk following lower doses is not well characterized, and it is not yet clear whether there is a threshold dose below which there is no risk.

The evidence regarding radiation-related heart disease comes from several different disciplines. The present review brings together information from pathology, radiobiology, cardiology, radiation oncology and epidemiology. It summarises current knowledge, identifies gaps in that knowledge, and outlines some potential strategies for filling them. Further knowledge about the nature and magnitude of radiation-related heart disease would have immediate application in radiation oncology. It would also provide a basis for radiation protection policies for use in diagnostic radiology and occupational exposure.

Unacceptable cosmesis in a protocol investigating intensity-modulated radiotherapy with active breathing control for accelerated partial-breast irradiation

PURPOSE

To report interim cosmetic results and toxicity from a prospective study evaluating accelerated partial-breast irradiation (APBI) administered using a highly conformal external beam approach.

METHODS AND MATERIALS

We enrolled breast cancer patients in an institutional review board-approved prospective study of APBI using beamlet intensity-modulated radiotherapy (IMRT) at deep-inspiration breath-hold. Patients received 38.5 Gy in 3.85 Gy fractions twice daily. Dosimetric parameters in patients who maintained acceptable cosmesis were compared with those in patients developing unacceptable cosmesis in follow-up, using t-tests.

RESULTS

Thirty-four patients were enrolled; 2 were excluded from analysis because of fair baseline cosmesis. With a median follow-up of 2.5 years, new unacceptable cosmesis developed in 7 patients, leading to early study closure. We compared patients with new unacceptable cosmesis with those with consistently acceptable cosmesis. Retrospective analysis demonstrated that all but one plan adhered to the dosimetric requirements of the national APBI trial. The mean proportion of a whole-breast reference volume receiving 19.25 Gy (V50) was lower in patients with acceptable cosmesis than in those with unacceptable cosmesis (34.6% vs. 46.1%; p = 0.02). The mean percentage of this reference volume receiving 38.5 Gy (V100) was also lower in patients with acceptable cosmesis (15.5% vs. 23.0%; p = 0.02).

CONCLUSIONS

The hypofractionated schedule and parameters commonly used for external beam APBI and prescribed by the ongoing national trial may be suboptimal, at least when highly conformal techniques such as IMRT with management of breathing motion are used. The V50 and V100 of the breast reference volume seem correlated with cosmetic outcome, and stricter limits may be appropriate in this setting.

NCCN Task Force Report: Estrogen Receptor and Progesterone Receptor Testing in Breast Cancer by Immunohistochemistry

The NCCN Task Force on Estrogen Receptor and Progesterone Receptor Testing in Breast Cancer by Immunohistochemistry was convened to critically evaluate the extent to which the presence of the estrogen receptor (ER) and progesterone receptor (PgR) biomarkers in breast cancer serve as prognostic and predictive factors in the adjuvant and metastatic settings, and the ability of immunohistochemical (IHC) detection of ER and PgR to provide an accurate assessment of the expression of these biomarkers in breast cancer tumor tissue. The task force is a multidisciplinary panel of 13 experts in breast cancer who are affiliated with NCCN member institutions and represent the disciplines of pathology, medical oncology, radiation oncology, surgical oncology, and biostatistics. The main overall conclusions of the task force are ER is a strong predictor of response to endocrine therapy; ER status of all samples of invasive breast cancer or ductal carcinoma in situ (DCIS) should be evaluated by IHC; IHC measurements of PgR, although not as important clinically as ER, can provide useful information and should also be performed on all samples of invasive breast cancer or DCIS; IHC is the main testing strategy for evaluating ER and PgR in breast cancer and priority should be given to improve the quality of IHC testing methodologies; all laboratories performing IHC assays of ER and PgR should undertake formal validation studies to show both technical and clinical validation of the assay in use; and all laboratories performing IHC assays of hormone receptors in breast cancer should follow additional quality control and assurance measures as outlined in the upcoming guidelines from the American Society of Clinical Oncology and College of American Pathologists.

Variability of target and normal structure delineation for breast cancer radiotherapy: an RTOG Multi-Institutional and Multiobserver Study

PURPOSE

To quantify the multi-institutional and multiobserver variability of target and organ-at-risk (OAR) delineation for breast-cancer radiotherapy (RT) and its dosimetric impact as the first step of a Radiation Therapy Oncology Group effort to establish a breast cancer atlas.

METHODS AND MATERIALS

Nine radiation oncologists specializing in breast RT from eight institutions independently delineated targets (e.g., lumpectomy cavity, boost planning target volume, breast, supraclavicular, axillary and internal mammary nodes, chest wall) and OARs (e.g., heart, lung) on the same CT images of three representative breast cancer patients. Interobserver differences in structure delineation were quantified regarding volume, distance between centers of mass, percent overlap, and average surface distance. Mean, median, and standard deviation for these quantities were calculated for all possible combinations. To assess the impact of these variations on treatment planning, representative dosimetric plans based on observer-specific contours were generated.

RESULTS

Variability in contouring the targets and OARs between the institutions and observers was substantial. Structure overlaps were as low as 10%, and volume variations had standard deviations up to 60%. The large variability was related both to differences in opinion regarding target and OAR boundaries and approach to incorporation of setup uncertainty and dosimetric limitations in target delineation. These interobserver differences result in substantial variations in dosimetric planning for breast RT.

CONCLUSIONS

Differences in target and OAR delineation for breast irradiation between institutions/observers appear to be clinically and dosimetrically significant. A systematic consensus is highly desirable, particularly in the era of intensity-modulated and image-guided RT.

Evaluation of multiple breathing states using a multiple instance geometry approximation (MIGA) in inverse-planned optimization for locoregional breast treatment

PURPOSE

Although previous work demonstrated superior dose distributions for left-sided breast cancer patients planned for intensity-modulated radiation therapy (IMRT) at deep inspiration breath hold compared with conventional techniques with free-breathing, such techniques are not always feasible to limit the impact of respiration on treatment delivery. This study assessed whether optimization based on multiple instance geometry approximation (MIGA) could derive an IMRT plan that is less sensitive to known respiratory motions.

METHODS AND MATERIALS

CT scans were acquired with an active breathing control device at multiple breath-hold states. Three inverse optimized plans were generated for eight left-sided breast cancer patients: one static IMRT plan optimized at end exhale, two (MIGA) plans based on a MIGA representation of normal breathing, and a MIGA representation of deep breathing, respectively. Breast and nodal targets were prescribed 52.2 Gy, and a simultaneous tumor bed boost was prescribed 60 Gy.

RESULTS

With normal breathing, doses to the targets, heart, and left anterior descending (LAD) artery were equivalent whether optimizing with MIGA or on a static data set. When simulating motion due to deep breathing, optimization with MIGA appears to yield superior tumor-bed coverage, decreased LAD mean dose, and maximum heart and LAD dose compared with optimization on a static representation.

CONCLUSIONS

For left-sided breast-cancer patients, inverse-based optimization accounting for motion due to normal breathing may be similar to optimization on a static data set. However, some patients may benefit from accounting for deep breathing with MIGA with improvements in tumor-bed coverage and dose to critical structures.

NCCN Task Force Report: Breast Cancer in the Older Woman

Breast cancer is common in older women, and the segment of the U.S. population aged 65 years and older is growing rapidly. Consequently, awareness is increasing of the need to identify breast cancer treatment recommendations to assure optimal, individualized treatment of older women with breast cancer. However, the development of these recommendations is limited by the heterogeneous nature of this population with respect to functional status, social support, life expectancy, and the presence of comorbidities, and by the underrepresentation of older patients with breast cancer in randomized clinical trials. The NCCN Breast Cancer in the Older Woman Task Force was convened to provide a forum for framing relevant questions on topics that impact older women with early-stage, locally advanced, and metastatic breast cancer. The task force is a multidisciplinary panel of 18 experts in breast cancer representing medical oncology, radiation oncology, surgical oncology, geriatric oncology, geriatrics, plastic surgery, and patient advocacy. All task force members were from NCCN institutions and were identified and invited solely by NCCN. Members were charged with identifying evidence relevant to their specific expertise. During a 2-day meeting, individual members provided didactic presentations; these presentations were followed by extensive discussions during which areas of consensus and controversy were identified on topics such as defining the “older” breast cancer patient; geriatric assessment tools in the oncology setting; attitudes of older patients with breast cancer and their physicians; tumor biology in older versus younger women with breast cancer; implementation of specific interventions in older patients with breast cancer, such as curative surgery, surgical axillary staging, radiation therapy, reconstructive surgery, endocrine therapy, chemotherapy, HER2-directed therapy, and supportive therapies; and areas requiring future studies. (JNCCN 2008;6[Suppl 4]:S1–S25)

Statement of the science concerning locoregional treatments after preoperative chemotherapy for breast cancer: a National Cancer Institute conference

PURPOSE

To review the state of the science with respect to diagnostic imaging and locoregional therapy for patients with breast cancer receiving preoperative chemotherapy.

METHODS

Published data relevant to clinical staging, monitoring of tumor response, and locoregional therapy for patients with breast cancer treated with preoperative chemotherapy were reviewed.

RESULTS

High-quality data from prospective randomized trials are limited. Available data suggest that locoregional therapy decisions should be based on both the pretreatment clinical extent of disease and the pathologic extent of the disease after chemotherapy. Accordingly, physical examination and imaging studies that accurately define the initial extent of disease are required before treatment. Sentinel lymph node biopsy can be performed either before or after preoperative chemotherapy for patients with clinical N0 disease. The success of breast conservation after preoperative chemotherapy depends on careful patient selection and achieving negative surgical margins. Adjuvant breast radiation is indicated for all patients treated with breast conservation. For patients treated with mastectomy, chest-wall and regional nodal radiation should be considered for those who present with clinical stage III disease or have histologically positive lymph nodes after preoperative chemotherapy. Additional prospective studies are needed to determine the value of postmastectomy radiation for patients with stage II breast cancer who have negative lymph nodes after chemotherapy.

CONCLUSION

The increased use of preoperative chemotherapy has raised new questions concerning the optimal methods to stage and monitor disease response to treatment and how to optimize locoregional treatment. The available evidence suggests that a multidisciplinary approach improves outcomes.

NCCN Task Force Report: breast cancer in the older woman

Breast cancer is common in older women, and the segment of the U.S. population aged 65 years and older is growing rapidly. Consequently, awareness is increasing of the need to identify breast cancer treatment recommendations to assure optimal, individualized treatment of older women with breast cancer. However, the development of these recommendations is limited by the heterogeneous nature of this population with respect to functional status, social support, life expectancy, and the presence of comorbidities, and by the underrepresentation of older patients with breast cancer in randomized clinical trials. The NCCN Breast Cancer in the Older Woman Task Force was convened to provide a forum for framing relevant questions on topics that impact older women with early-stage, locally advanced, and metastatic breast cancer. The task force is a multidisciplinary panel of 18 experts in breast cancer representing medical oncology, radiation oncology, surgical oncology, geriatric oncology, geriatrics, plastic surgery, and patient advocacy. All task force members were from NCCN institutions and were identified and invited solely by NCCN. Members were charged with identifying evidence relevant to their specific expertise. During a 2-day meeting, individual members provided didactic presentations; these presentations were followed by extensive discussions during which areas of consensus and controversy were identified on topics such as defining the "older" breast cancer patient; geriatric assessment tools in the oncology setting; attitudes of older patients with breast cancer and their physicians; tumor biology in older versus younger women with breast cancer; implementation of specific interventions in older patients with breast cancer, such as curative surgery, surgical axillary staging, radiation therapy, reconstructive surgery, endocrine therapy, chemotherapy, HER2-directed therapy, and supportive therapies; and areas requiring future studies.

Neoadjuvant Docetaxel and Capecitabine and the Use of Thymidine Phosphorylase as a Predictive Biomarker in Breast Cancer

PURPOSE

Thymidine phosphorylase (TP) induction by docetaxel is a proposed mechanism for the observed preclinical synergy of docetaxel and capecitabine (DC). We evaluated whether TP protein expression is increased by docetaxel and correlates with pathologic complete response (pCR) in breast cancer patients.

EXPERIMENTAL DESIGN

Women with stage II to III breast cancer were given four cycles of neoadjuvant docetaxel 36 mg/m(2) i.v. over 30 min on days 1, 8, and 15 and capecitabine 2,000 mg/d, in two divided doses, on days 5 to 21 of a 28-day cycle. Radiology-directed biopsies of the breast tumors were done at baseline and 5 days after the first dose of docetaxel to evaluate TP expression. Following DC therapy, patients had core breast biopsies, and if residual disease was present, received four cycles of standard dose-dense doxorubin and cyclophosphamide (AC).

RESULTS

The pCR rate was 26.9% (95% confidence interval, 11.6-47.8). Up-regulation of TP expression was not observed by either quantitative immunofluorescence (QIF) or immunohistochemistry. Radiology-directed core biopsy after neoadjuvant chemotherapy accurately predicted pathologic response in 88% (95% confidence interval, 69.8-97.6) of the cases. Neither level of TP expression nor TP up-regulation correlated with pCR. Significant toxicity resulted in therapy discontinuation in 3 of 26 patients.

CONCLUSIONS

DC chemotherapy exhibited a similar pCR rate compared with standard taxane regimens, with increased toxicity. TP expression was not up-regulated after docetaxel and did not correlate with therapeutic response. Core breast biopsy after neoadjuvant chemotherapy accurately predicted pathologic response.