College Of American Pathologists Guidelines Research Articles

HER2 quantitative continuous scoring for accurate patient selection in HER2 negative trastuzumab deruxtecan treated breast cancer

Many targeted cancer therapies rely on biomarkers assessed by scoring of immunohistochemically (IHC)-stained tissue, which is subjective, semiquantitative, and does not account for expression heterogeneity. We describe an image analysis-based method for quantitative continuous scoring (QCS) of digital whole-slide images acquired from baseline human epidermal growth factor receptor 2 (HER2) IHC-stained breast cancer tissue. Candidate signatures for patient stratification using QCS of HER2 expression on subcellular compartments were identified, addressing the spatial distribution of tumor cells and tumor-infiltrating lymphocytes. Using data from trastuzumab deruxtecan-treated patients with HER2-positive and HER2-negative breast cancer from a phase 1 study (NCT02564900; DS8201-A-J101; N = 151), QCS-based patient stratification showed longer progression-free survival (14.8 vs 8.6 months) with higher prevalence of patient selection (76.4 vs 56.9%) and a better cross-validated log-rank p value (0.026 vs 0.26) than manual scoring based on the American Society of Clinical Oncology / College of American Pathologists guidelines. QCS-based features enriched the HER2-negative subgroup by correctly predicting 20 of 26 responders.

Locoregional Recurrence Patterns in Patients With Different Molecular Subtypes of Breast Cancer

While numerous studies have consistently reported that the molecular subtypes of breast cancer (BC) are associated with different patterns of distant metastasis, few studies have investigated the association of tumor subtypes with locoregional recurrence. To investigate the patterns of ipsilateral breast tumor recurrence (IBTR), regional recurrence (RR), and contralateral BC (CBC) according to tumor subtypes. This retrospective cohort study used the clinical records of patients who underwent BC surgery at a single institution in South Korea between January 2000 and December 2018. Data were analyzed from May 1, 2019, to February 20, 2023. Ipsilateral breast tumor recurrence, RR, and CBC events. The primary outcome was differences in annual incidence patterns of IBTR, RR, and CBC according to tumor subtypes. Hormone receptor (HR) status was assessed by immunohistochemical staining assay, and ERBB2 status was evaluated according to American Society of Clinical Oncology and College of American Pathologists guidelines. A total of 16 462 female patients were included in the analysis (median age at time of operation, 49.0 years [IQR, 43.0-57.0 years]). The 10-year IBTR-, RR-, and CBC-free survival rates were 95.9%, 96.1%, and 96.5%, respectively. On univariate analysis, HR-/ERBB2+ tumors had the worst IBTR-free survival (vs HR+/ERBB2- subtype: adjusted hazard ratio, 2.95; 95% CI, 2.15-4.06), while the HR-/ERBB2- subtype had the worst RR- and CBC-free survival among all subtypes (vs HR+/ERBB2- subtype, RR: adjusted hazard ratio, 2.95; 95% CI, 2.37-3.67; CBC: adjusted hazard ratio, 2.12; 95% CI, 1.64-2.75). Subtype remained significantly associated with recurrence events in Cox proportional hazards regression analysis. Regarding the annual recurrence pattern, the IBTR patterns of HR-/ERBB2+ and HR-/ERBB2- subtypes showed double peaks, while HR+/ERBB2- tumors showed a steadily increasing pattern without distinguishable peaks. Additionally, the HR+/ERBB2- subtype seemed to have a steady RR pattern, but other subtypes showed the highest RR incidence at 1 year following surgery, which then gradually decreased. The annual recurrence incidence of CBC gradually increased among all subtypes, and patients with the HR-/ERBB2- subtype had a higher incidence than patients with other subtypes over 10 years. Younger patients (age ≤40 years) had greater differences in IBTR, RR, and CBC patterns between subtypes than did older patients. In this study, locoregional recurrence occurred with different patterns according to BC subtypes, with younger patients having greater differences in patterns among subtypes than older patients. The findings suggest that tailoring surveillance should be recommended regarding differences in locoregional recurrence patterns according to tumor subtypes, particularly for younger patients.

CDKN2A/p16 evaluation in cytology specimens.

CDKN2A/p16 evaluation in cytology specimens.

Awareness of Placental Pathologic Examination Criteria and Utilization of Pathology Reports among Obstetricians

Background and Objectives: Several studies have reported a low rate of pathological examination of the placentas and a poor utilization of pathology reports. We assessed Saudi obstetricians' awareness and utilization of the placental pathological examination guidelines of the College of American Pathologists (CAP) and evaluated their understanding of the reports. Materials and Methods: An anonymous survey was distributed to obstetricians registered in the Saudi Commission of Health Specialties database. We examined the association between the participants' level of training or practice as well as their institution type with the surveyed elements. Results: Of 292 respondents, 34.2% were aware of the CAP guidelines. Most of them were practicing in government hospitals. Moreover, 18.2% of them routinely sent the placenta for pathological examination, and approximately 70.5% routinely reviewed the pathology reports and understood the nomenclature used; these percentages were significantly higher among university hospital practitioners. The residents were the least aware of the CAP guidelines and the least likely to review and understand the pathology reports. Regardless of the CAP guidelines awareness, the most common indication for placental pathologic examination was fetal anomalies, followed by medicolegal reasons and infections. Conclusions: Placental pathologic examination appeared uniformly underutilized in Saudi Arabia. Obstetricians are required to generate awareness of the need to comply with the CAP guidelines and to improve the understanding and utilization of pathology reports.

Analysis of D- and L- Isomers of (Meth)amphetamine in Human K2EDTA Plasma

Methamphetamine and its metabolite amphetamine are frequently abused drugs. Whether obtained legally or from clandestine laboratories it is of relevance to determine the chiral makeup of these drugs for investigative purpose. Although urine and oral fluid matrices are commonly offered, less available to independent laboratories are techniques to verify dextro (D-) or levo (L-) (meth)amphetamine from human K2EDTA plasma. This paper outlines the development and validation of a method that includes the addition of internal standard and a two-step liquid-liquid extraction to remove the analytes from human K2EDTA plasma by triple quadrupole mass spectrometry (LC-MS/MS). The assay was validated according to the United States Food and Drug Administration and College of American Pathologists guidelines, including assessment of the following parameters in plasma validation samples: linear range, limit of detection, lower limit of quantitation, matrix effects, inter- and intra-day assay precision and accuracy, carry over, linearity of dilution, matrix effects and stability. The outcome is a validated and reliable method for the determination of D- and L- isomer concentration of meth(amphetamine) human plasma samples that can be easily adopted by independent clinical laboratories.

Analytical Validation of Familial Hypercholesterolemia Biomarkers in Dried Blood Spots.

Heterozygous familial hypercholesterolemia (HeFH) is a common, treatable genetic disorder characterized by premature atherosclerosis and cardiovascular disease, yet the majority of affected individuals remain undiagnosed. Newborn screening could play a role in identification of at-risk individuals and provide an opportunity for early intervention, prior to the onset of symptoms. The objective of this study was to develop and validate assays for quantification of candidate HeFH biomarkers in dried blood spots (DBS). Commercially available enzyme assay kits for quantification of serum total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C) were modified for high-throughput analysis of DBS. Apolipoprotein B (ApoB) concentrations in DBS were measured using an immunoassay with modifications from published studies. All three assays were validated according to the College of American Pathologists guidelines for clinical laboratories. The performance of TC, LDL-C, and ApoB assays was assessed by precision, recovery, limit of quantification (LOQ) and linearity. Precision studies yielded coefficients of variation (CV) of less than 15%, with recovery greater than 75% for all three assays. The determined LOQ and linearity were comparable to serum-based assays. In a direct comparison between serum and DBS concentrations, positive correlations were demonstrated for TC, LDL-C, and ApoB. Additionally, the initial evaluation of the three biomarker concentrations within the unaffected population was similar to values obtained in previous published studies. This study reports on methods for quantification of TC, LDL-C, and ApoB in DBS. Assay validation results were within acceptable limits for newborn screening. This is an important first step toward the identification of newborns with HeFH.

Robot-assisted versus video-assisted thoraco-laparoscopic McKeown's esophagectomy for esophageal cancer: a propensity score-matched analysis of minimally invasive approaches.

Minimally invasive esophagectomy for esophageal cancer decreases overall complication rate and leads to faster postoperative recovery. Robot-assisted minimally invasive esophagectomy is becoming more common. Its three-dimensional view and wristed instruments may provide advantages over traditional thoraco-laparoscopic techniques. There are limited studies comparing robotic and conventional thoraco-laparoscopic esophagectomy. This study aimed to evaluate short-term outcomes of robot-assisted McKeown esophagectomy (RAME) and video-assisted McKeown esophagectomy (VAME). All consecutive patients undergoing minimally invasive McKeown esophagectomy for middle and distal third esophageal cancer between January 2016 and December 2018 at our center were included in this study. Data on baseline characteristics, pathological data and short-term outcomes were collected in a dedicated database. Postoperative complications were defined as per recommendations of Esophagectomy Complications Consensus Group. Histopathologic assessment was performed as per College of American Pathologists guidelines. Propensity score matching was performed for comparison between RAME and VAME groups using age, gender, performance status, American Society of Anesthesiologists grade, body mass index, Charlson Index, tumor location, clinical tumor stage, and neoadjuvant treatment as covariates. A total of 74 patients were included, 25 of whom underwent RAME and 49 underwent VAME. Propensity score matching on 1:1 basis produced 25 pairs of patients, comparable in terms of baseline characteristics. Total operative time and estimated blood loss was similar between the two groups. Length of hospital stay was significantly lower in RAME group. Major postoperative complications (Clavien-Dindo grade ≥ 3A) were more common in VAME group, but not statistically significant. Median number of harvested lymph nodes and R0 resection rate did not differ in between the two groups. In our experience, robot-assisted McKeown esophagectomy was comparable to video-assisted McKeown esophagectomy in terms of safety, feasibility and oncologic adequacy. Use of the robot was associated with reduced hospital stay. Further randomized controlled studies with larger patient samples are needed to compare the two.

Practice of Placenta Submission for Histopathological Examination, Experience of a Teaching/Tertiary Care Hospital in Saudi Arabia.

ObjectivesThe aim of this study is to determine the appropriateness of histopathologic examination of the placenta at King Abdulaziz University Hospital (KAUH), Jeddah, based on the guidelines of the College of American Pathologists (CAP).MethodsIt is a retrospective review of obstetric and pathologic records for all deliveries at KAUH, between January 1, 2017, and April 30, 2019. The placentae were assessed for eligibility to undergo pathologic examination. Furthermore, examined and non-examined placentae meeting the CAP criteria were compared based on their actual indications.ResultsThere were 8,929 deliveries, of which 1,444 (16.2%) placentae met the CAP guidelines. A total of 583/1,444 placentae (40.4%; 95% confidence interval [CI] = 37.8-43) were sent for pathologic examination. Of the 7,485 placentae that did not require submission for pathological examination, as determined by the pathologist, 7,456 (99.6%; 95% CI = 99.4-99.7) were not submitted appropriately. The labor and delivery staff were more likely to submit placentae with fetal/neonatal indications rather than those with maternal indications for examination, which was statistically significant (odds ratio = 6.5; 95% CI = 5.08-8.30).ConclusionWhile most of the examined placentae at KAUH met the CAP guidelines, there was a substantial under-submission of eligible placentae. Further studies are advised to reveal the reasons behind this underestimation so that correctional measures may be adopted, as placenta examination is a valuable tool to understand the risk factors and pathogenesis of deleterious maternal, neonatal, and fetal events.

Adequacy of Surgical Pathology Reports of Colorectal Carcinoma and Its Significance.

IntroductionColorectal cancer is the fifth most common cancer in the world. For loco-regionally confined disease surgery is the definitive treatment. An adequate surgical pathology report is mandatory for the selection of adjuvant therapy. The objective of this study is to analyze whether adequate information is provided or not in the surgical pathology reports of colorectal carcinoma as according to College of American Pathologists (CAP) guidelines.MethodThis is a cross-sectional study carried out in the Department of Clinical Oncology, Jinnah Postgraduate Medical Center (JPMC) Karachi, tertiary care hospital in Pakistan. The duration of the study was from February 2020 to January 2021. A total of 153 surgical pathology reports issued by 11 different hospital-based laboratories after definitive surgery was assessed to look at its concordance rate with the checklist adapted from the CAP guidelines.ResultsOut of 153 surgical pathology reports, clinical information was provided in 72.5% of reports. Details of tumor extension were present in 88.2%, tumor margin in 75%, surgical procedure in 79%, and tumor deposits in 39.2% of reports. Macroscopic details including tumor perforation and evaluation of mesorectum were documented in 51.6% and 53.5% of the reports respectively. Details regarding perineural invasion along with lymphovascular invasion were present in 81.6% and 93% of the reports, respectively. The treatment effect was documented in only 25% of reports and regional lymph node status has been described in 85% of reports. Parameters described in all surgical pathology reports were: tumor site, tumor type, histologic type, and histologic grade. The pathological stage of the disease was documented in 91.5% of the reports.ConclusionThis study concluded that surgical pathology reports of the majority of pathology laboratories were not fully adhered to the checklist provided by the CAP guidelines. This will affect post-operative management along with the prediction of disease prognosis.

A phase I open-label study to investigate safety and tolerability, efficacy, pharmacokinetics, pharmacodynamics, and immunogenicity of MT-5111 in patients with HER2-positive tumors.

TPS258 Background: Engineered toxin bodies (ETBs) are comprised of a proprietarily engineered form of Shiga-like Toxin A subunit genetically fused to antibody-like binding domains. ETBs work through novel mechanisms of action & are capable of forcing internalization, self-routing through intracellular compartments to the cytosol & inducing potent cell-kill via the enzymatic & permanent inactivation of ribosomes. MT-5111 is a de-immunized ETB targeting HER2+ solid tumors. Its novel mechanism of action, via enzymatic ribosome inactivation, may not be subject to resistance mechanisms that exist for tyrosine kinase inhibitors, antibody-drug conjugates, or antibody modalities. MT-5111 binds an epitope on HER2, distinct from trastuzumab or pertuzumab, that may provide for combination potential with other HER2-targeting agents. MT-5111 is a 55 kilodalton protein & may have improved tumor penetration capability. The objective of this trial will be to determine the safety, tolerability, & maximum tolerated dose (MTD) of MT-5111 in patients (pts) with advanced HER2+ solid tumors. Methods: This Phase 1, first-in-human, open-label, dose escalation & expansion study will evaluate MT-5111 monotherapy in pts with HER2-positive solid tumors. The primary objective is to determine the MTD; secondary objectives include pharmacokinetics, tumor response & immunogenicity. Part 1 consists of MT-5111 dose escalation (0.5, 1.0, 2.0, 3.0, 4.5, 6.75, 10µg/kg/dose) based on a modified 3+3 design (n≤42 pts); Part 2 (dose expansion) will evaluate MT-5111 at the MTD in ≤98 pts. All pts will be administered MT-5111 over 30 min via IV infusion on Days 1, 8, & 15 of each 21-day cycle until disease progression, unacceptable toxicity, death, withdrawal of consent, or another reason for withdrawal. Part 1 will include pts with any HER2+ solid cancers. Part 2 will enroll 3 expansion cohorts: HER2+ breast (BC), HER2+ gastric or gastroesophageal junction adenocarcinomas (collectively referred as gastroesophageal adenocarcinomas [GEA]) & other HER2+ solid cancers. Immunohistochemistry (IHC) status must be 2+ or 3+, regardless of in situ hybridization (ISH) results; if no IHC is available for pts with BC or GEA, ISH criteria per the American Society of Clinical Oncology College of American Pathologists guidelines will be used. In metastatic cases, HER2 positivity must be demonstrated on metastatic lesions. Pts with HER2+ BC should have had ≥2 lines of HER2-directed therapy; pts with HER2+ GEA should have received or been intolerant to trastuzumab. Pts with evaluable disease may be included in Part 1; in Part 2, all pts must have ≥1 measurable lesion per Response Evaluation Criteria in Solid Tumors v1.1. Further details can be found on clinicaltrials.gov (NCT04029922). Enrollment, which began in September 2019, is ongoing. Clinical trial information: NCT04029922.

Pathologic examination of placenta: a study on 500 live births to assess conformity to College of American Pathologists (CAP) guidelines and clinicopathologic correlation

Purpose Pathological examination of placenta is vital to understand the pathophysiology of adverse perinatal outcomes, prevention of recurring conditions in subsequent pregnancies and medico-legal risk assessment. The College of American Pathologists (CAP) has published a set of guidelines to help guide the submission of placentas to pathology. However, awareness and conformity to these guidelines are not well established and vary from one institution to the other. We aimed to examine the appropriateness of placental pathologic examination at our institution and their conformity to guidelines in this audit type study to help improve our practices. Materials and methods Detailed retrospective review of obstetrical records was performed including history and delivery reports for a total of 500 consecutive live births noting whether the placenta was sent for pathologic evaluation according to CAP guidelines. Sensitivity and specificity of placental examination were calculated based on the 2 × 2 contingency table. Results The sensitivity and specificity of pathologic examination of placenta in conformity to CAP guidelines were 63.4% and 91.6%, respectively. The most common indications for submission were maternal followed by fetal and placental indications. Concordant clinico-pathologic correlation was found in 87/135 placentas submitted. Conclusions Placenta has long been ignored with limited understanding of the value of its examination. More awareness of CAP guidelines is needed to appropriately submit placentas for pathologic examination. Each institution needs to develop their own set of guidelines taking guidance from CAP guidelines and tailored to its population. Meaningful communication between obstetricians, neonatologists, and pathologists is key to improving the utility of pathologic examination of placenta and the application of results for better patient care.

Variable Expression of MSH6 in Endometrial Carcinomas With Intact Mismatch Repair and With MLH1 Loss Due to MLH1 Methylation.

Immunohistochemistry for mismatch repair proteins MLH1, MSH2, MSH6, and PMS2 is an effective screen to detect individuals at risk for Lynch syndrome. College of American Pathologists guidelines stipulate that protein expression should be reported as present versus absent, as most patients with germline mutations in a mismatch repair gene have complete loss of protein expression in tumor cells. A similar approach is employed to screen for cancer patients eligible for immune checkpoint blockade. This "all or none" interpretive approach ignores substantial evidence that mismatch repair may be more finely regulated by other mechanisms. We have observed clinically that MSH6 expression is variable, even in carcinomas that are overall considered positive for MSH6 expression. A proof-of-principle study was therefore designed to more rigorously quantify the protein expression of MSH6 and its binding partner, MSH2, using image analysis applied to age-matched endometrioid grade 2 subsets that were either mismatch repair intact or MLH1-deficient due to MLH1 gene methylation. In both endometrioid groups, MSH6 expression was significantly lower than MSH2 expression. MSH6 expression increased in higher grade, mismatch repair intact serous carcinomas, but it was still significantly lower than that for MSH2. MSH2 expression was consistently high across the 3 different tumor groups. These results suggest that MSH6 expression is subject to wide fluctuations in expression, even when overall its expression is considered intact. While such fluctuations are likely not relevant for Lynch syndrome screening, they may be more impactful when considering patients eligible for immune checkpoint blockade.

Pathologic Outcomes of Systemic Therapy Followed By Stereotactic Body Radiation Therapy for Pancreatic Cancer in a Novel Lateral Decubitus Treatment Position

Outcomes of multi-fraction stereotactic body radiotherapy (SBRT) for pancreatic cancer (PC) report low rates of toxicity and high local control, improving feasibility for combination with more intensive systemic therapy regimens. However, SBRT in the ablative range poses risk to adjacent normal structures, excluding this option for tumors within 1 cm of a mucosal organ. In this study, we report our initial experience with treatment outcomes in the lateral decubitus position. An IRB retrospective query identified all patients with pancreatic body adenocarcinoma treated with systemic chemotherapy followed by SBRT in the lateral decubitis position. SBRT was delivered to the entire gross disease with 30 Gy in 5 fractions with focal dose escalation up to 40 Gy to the tumor/vessel interface (TVI) as long as constraints were met. Patients were explored for resection if no metastasis or progression was imaged on restaging scans. The primary endpoints were pathologic response and margin status. Descriptive analysis was performed with statistical software. The median age of the cohort was 68.9 (range, 50-83 yrs), with a white (94%) and male (56%) predominance. Initial staging of the 18 patients who met criteria included 10 (56%) patients diagnosed with borderline resectable disease (BRPC) and 8 (44%) with locally advanced disease (LAPC). 7 (44%) patients were treated with FOLFIRINOX, 5 (28%) with gemcitabine/nab-paclitaxel, 4 (22%) with gemcitabine/capecitabine/docetaxel, and 1 (6%) with gemcitabine/paclitaxel preceding SBRT. A median dose of 40 Gy (range, 33-40 Gy) was delivered to the TVI for all patients. 5 BRPC (28%) and 3 LAPC (17%) patients went to surgery, with 7 of these patients undergoing an R0 resection (88%) and 1 BRPC patient with an R1 resection. Pathologic tumor regression grades by the College of American Pathologists guidelines were 12.5% Grade 1, 75% Grade 2, and 12.5% Grade 3. Lateral decubitus treatment expands inclusion of pancreatic body patients for SBRT with focal TVI dose escalation leading to margin negative resection and significant partial tumor response, warranting future studies exploring ablative dosing in this position.

Reassignment of HER2 status for subgroups of breast cancer according to the 2018 updated American Society of Clinical Oncology and College of American Pathologists guidelines: The impact of combined immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) reflex testing in a large national reference laboratory.

3144 Background: Updated ASCO/CAP Guidelines for HER2 testing in breast cancer have been most impactful on the resolution of certain challenging groups of FISH results. We review the change in assignment of HER2 status in a large series of breast cancers referred to a large national reference laboratory for FISH testing since the introduction of the 2018 updated guidelines. Methods: Patient samples submitted to the Mayo Clinic Cytogenetics Laboratory (N = 2208) were analyzed by FISH. Samples with Group 2, Group 3, or Group 4 FISH results were reflexed to immunohistochemistry (IHC) in our central laboratory; FISH slides for those cases with equivocal 2+ IHC results were re-scored in the regions of invasive cancer showing more intense membranous staining. A subset of 202 samples with Group 4 FISH results were also reflexed to the previously employed reflex FISH assay (HER2/D17S122), and these were also re-analyzed according to the new reflex IHC/FISH process. Results: 382 of 2208 breast cancer samples tested (17.3%) had FISH results categorized as Group 2 (N = 17, 0.8%), Group 3 (N = 34, 1.5%), or Group 4 (N = 331, 15%) and required reflex IHC testing, and of those, 75% were 2+ equivocal and required targeted re-analysis of the FISH slide according to the 2018 updated guidelines. Re-analysis of the FISH slide resulted in switching between Groups 1-5 in 19.4% of cases, but HER2 status was changed by FISH re-scoring in only 7.7% of cases re-scored (1.0% of all samples), generally due to only minor shifts in HER2 copy number and HER2/control ratios between the initial and IHC-guided reflex FISH scores. In the subset of 202 cases tested by both reflex methods, the previously employed HER2/D17S122 reflex probe set was positive in 123 cases (60.9%), whereas reflex IHC/FISH was positive in only 10 cases (7.9%). Including positive reflex IHC (0.4%) and positive reflex FISH results (2.1%), the overall assignment of positive HER2 status on our series of 2208 cases was 11.5%. Conclusions: Overall rates of HER2 positive FISH results have declined under the most recent ASCO/CAP guideline update as a consequence of new recommendations for reflex testing for Groups 2-4. This change is largely due to reassignment of Group 2 and Group 4 results as negative in the absence of positive IHC.

Validation of immunohistochemical tests performed on cytology cell block material: Practical application of the College of American Pathologists' guidelines.

The advent of fiberoptic endoscopy with biopsy has revolutionized procurement of specimens from deep sites. This has translated into more cytologic specimens whereby the material is limited and best handled by cytology laboratory staff. While the diagnosis of the pathologic process is of utmost importance, there is increasing expectation that the diagnosis be specific and accurate as not to require additional biopsy for initiation of treatment. This expectation has driven demand in immunohistochemical (IHC) and molecular studies conducted specifically on material processed as cytology specimens. The Clinical Laboratory Improvement Amendments of 1988 requires laboratories in the United States of America to verify the performance of patient tests. Due to varying laboratory practices with respect to validation of IHC assays, the College of American Pathologists introduced guidelines for analytic validation of IHC tests. These guidelines address how to perform validation by recommending the number of cases in the validation set, comparator concordance, and when to revalidate. The main thrust of the guidelines is based on formalin-fixed paraffin-embedded tissue with only one expert consensus opinion referring to validation of IHC tests on cytology specimens which delegates to the medical director, the determination of number of positive and negative cases to be tested. This article will outline how an academic center approaches validation of IHC studies performed on cytology cell block specimens using the College of American Pathologists guidelines. A stepwise approach from selection of antibodies to validate followed by building the validation panel and evaluating the stain results for concordance against the gold standard of histology tissue specimen will be described. A rationale for dealing with discordant results and future innovations will conclude the report.

Utility of Human Epidermal Growth Factor Receptor 2 (HER2) Retesting of Histologic Grade 3 Invasive Breast Carcinomas.

American Society of Clinical Oncology and College of American Pathologists guidelines recommend repeated evaluation of human epidermal growth factor receptor 2 (HER2) status on surgical specimens from patients with a diagnosis by core-needle biopsy of Grade 3, HER2-negative invasive tumors of the breast. However, there are limited data to support reflexive testing. To evaluate the utility of HER2 retesting of histologic Grade 3, HER2-negative invasive breast carcinomas. We evaluated 78 patients from Kaiser Permanente East Bay in whom Grade 3, HER2-negative invasive breast carcinoma was diagnosed between 2015 and 2017 by core biopsy, to compare HER2 status on core biopsy vs excisional biopsy specimen. The HER2 status was determined by immunohistochemistry, fluorescent in situ hybridization, or both. All patients were retested for HER2 status on surgical specimen according to the aforementioned guidelines. Recipients of neoadjuvant chemotherapy were excluded. One of the 78 patients demonstrated negative-to-positive status discordance between core biopsy and surgical specimens and was treated with trastuzumab. One patient was HER2 negative by core biopsy and was HER2 equivocal by immunohistochemical and fluorescent in situ hybridization evaluation of the surgical specimen. Seventy-six patients demonstrated concordant HER2 status between core biopsy and surgical specimens. The rate of clinically significant HER2 status discordance between core biopsy and surgical specimens in patients with Grade 3 breast carcinoma is low. However, given the dramatically improved survival conferred by trastuzumab therapy, our findings support reflex HER2 testing of surgical specimens for patients with core biopsy-diagnosed HER2-negative breast carcinoma.

Pathologic outcomes of systemic therapy followed by stereotactic body radiation therapy (SBRT) for pancreatic cancer (PC) in a novel lateral decubitus treatment position.

415 Background: Outcomes of multi-fraction stereotactic body radiotherapy (SBRT) for PC report low rates of toxicity and high local control, improving feasibility for combination with more aggressive systemic therapy regimens. However, SBRT in the ablative range poses risk to adjacent normal structures, excluding this option for tumors within 1 cm of a mucosal organ. In this study, we report our initial experience with treatment in the lateral decubitus position. Methods: An IRB retrospective query identified patients with pancreatic body adenocarcinoma treated with systemic chemotherapy followed by SBRT in the lateral decubitis position. SBRT was delivered to the entire gross disease with 30 Gy in 5 fractions with focal dose escalation up to 40 Gy to the tumor/vessel interface (TVI) as long as constraints were met. Patients were explored for resection if no metastasis or progression on restaging scans. The primary endpoints were pathologic response and margin status. Descriptive analysis was performed with SPSS 24. Results: The median age of the cohort was 68.6 (range, 50-83 yrs), with a white (94%) and male (59%) predominance. Initial staging of the 17 patients who met criteria included 10 (59%) patients diagnosed with borderline resectable disease (BRPC) and 7 (41%) with locally advanced disease (LAPC). 7 (41%) patients were treated with FOLFIRINOX, 5 (29%) with gemcitabine/nab-paclitaxel, 4 (24%) with gemcitabine/capecitabine/docetaxel, and 1 (6%) with gemcitabine/paclitaxel preceding SBRT. A median dose of 40 Gy (range, 33-40 Gy) was delivered to the TVI for all patients. 5 BRCP (29%) and 2 LAPC (12%) patients went to surgery, with 6 of these patients undergoing an R0 resection (86%) and 1 BRPC patient with an R1 resection. Pathologic tumor regression grades by the College of American Pathologists guidelines were 14% Grade 1, 71% Grade 2, and 14% Grade 3. Conclusions: Lateral decubitus treatment expands inclusion of pancreatic body patients for SBRT with focal TVI dose escalation leading to margin negative resection and significant partial tumor response, warranting future studies exploring ablative dosing in this position.

Evaluation of Biomarkers in Multiple Ipsilateral Synchronous Invasive Breast Carcinomas.

The College of American Pathologists guidelines recommend testing additional tumor foci in multifocal invasive breast carcinomas for the biomarkers estrogen receptor (ER), progesterone receptor, and HER2 only if the carcinomas show different morphologies or grades. To assess clinical significance of testing for biomarkers in additional tumor foci in multifocal invasive breast tumors. Retrospective analysis of 118 patients diagnosed with ipsilateral synchronous multifocal breast carcinomas from January 2015 through March 2016 at Mount Sinai Hospital (New York, New York). Eighty-six cases were tested for at least 1 of the 3 biomarkers in additional tumor foci. Fifteen cases (17%) showed discordant staining between the 2 foci for at least one biomarker. Of the 7 of 67 ER-discordant cases (10%), 4 (57%) showed major variation from negative to positive expression, including 3 cases in which a smaller tumor focus was strongly positive for ER whereas the index tumor was negative. Similarly, within the 7 of 67 progesterone receptor-discordant cases (10%), 4 (57%) showed major variation from negative to positive, and in 3 cases with major discordance, the index tumor was negative for progesterone receptor, whereas a smaller focus was positive. A difference in HER2 expression was noted in 5 of 86 cases (6%). In only 5 of the 15 patients (33%) with discordant results, biomarker testing on additional foci would have been offered per the College of American Pathologists recommendations because of differences in histology or grading. Of the remaining 10 patients, 7 (70%) with positive results on smaller foci would have been deprived of appropriate adjuvant systemic treatment if the smaller focus had not been tested. We propose that negative values expressed in the primary tumor be repeated routinely on additional ipsilateral synchronous tumors.

Abstract PD7-02: Value-based medicine: Are the 2013 guidelines for HER2 testing clinically significant and cost effective?

Abstract Background: In the U.S., around 252,710 new breast cancer cases will be diagnosed in the year 2017. About 15-20% of these patients will be candidates for treatment with Her-2 directed therapy. The College of American Pathologists (CAP) published initial guidelines for immunohistochemistry (IHC) in 2003 with revisions in 2007 and 2013. 2013 guidelines define 3+(positive) as >10% intense complete membrane staining similar to 2003; >30% complete in 2007. Equivocal 2+ category in 2013 includes incomplete staining > 10% for the first time; this was negative in 2003 and 2007.Hypothesis: The 2013 guidelines do not result in more true positives but increased equivocal cases resulting in clinical uncertainty and increased cost. Methods : A retrospective analysis was performed of all IHC and FISH testing done at a single institution with a single pathology reader from 2003-2016. Criteria for IHC and FISH positivity were followed for each time period and compared to one another for positive and negative HER2 expression. The equivocal categories than compared for outcome by FISH. Ultimate numbers for percentage in each category compared for statistical significance. Results: IHC NegativeEquivocalPositiveTotal(1) 2003279, 70.6%71, 17.9%45, 11.3%395(2) 2007187, 71.6%49, 18.7%25, 9.5%261(3) 2013181, 61.7%79, 26.9%33, 11.2%293Total647199103949Chi-SquareDFValueProbOverall410.40.03 Period 1 vs 220.50.75Period 1 vs 328.20.01Period 2 vs 326.40.04 IHC Equivocal Reflex to FISH NegativeEquivocalPositiveTotal(1) 200358, 82.8%1, 1.4%11, 15.7%70(2) 200734, 80.9%0, 0.0%8, 19.0%42(3) 201362, 82.6%6, 8.0%7, 9.3%75Total154726187DF4Chi-Square8.3Asymptotic Pr> ChiSq0.08Exact Pr ≥ ChiSq0.07 When further analysis was carried out, period 1 and 2 were added together and compared to period 3. When all positives and negatives were compared, there was no statistical difference between the periods. However in the equivocal category, Period 1 and 2 were statistically different than period 3. In fact the only change in period 3 was the increase in the equivocal cases (same case-equivocal IHC and FISH). Conclusion: In the 2013 CAP guidelines, 2+ IHC now includes incomplete staining in >10% of cells. This does not result in more positive cases as was the intention but an increase in the equivocal category by 8.19%. This adds to clinical uncertainty as to how to treat this group of patients. A send out for FISH is labor intensive, slow and costs on average of $650/case. With over 250,000 new cases expected this year in the U.S. this cost exceeds $13million. From all our data, the best parameters for IHC testing would be; positive-strong, complete staining in >10% cells and equivocal to eliminate the incomplete staining category. This would yield the highest number of true positives by FISH and almost eliminate ultimate equivocal cases. Citation Format: Sharma A, Vadehra D, Talal K, Hegde P, Wu R, Tannenbaum S. Value-based medicine: Are the 2013 guidelines for HER2 testing clinically significant and cost effective? [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD7-02.

194 Antecedent Conformity of Diagnostic and Molecular Testing Patterns in Clinical Practice for Newly Diagnosed Acute Myeloid Leukemia With American Society of Hematology and College of American Pathologists Guidelines

194 Antecedent Conformity of Diagnostic and Molecular Testing Patterns in Clinical Practice for Newly Diagnosed Acute Myeloid Leukemia With American Society of Hematology and College of American Pathologists Guidelines