NCCN Clinical Practice Guidelines Research Articles

Ovarian Cancer, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology.

Epithelial ovarian cancer is the leading cause of death from gynecologic cancer in the United States and is the country's fifth most common cause of cancer mortality in women. A major challenge in treating ovarian cancer is that most patients have advanced disease at initial diagnosis. These NCCN Guidelines discuss cancers originating in the ovary, fallopian tube, or peritoneum, as these are all managed in a similar manner. Most of the recommendations are based on data from patients with the most common subtypes─high-grade serous and grade 2/3 endometrioid. The NCCN Guidelines also include recommendations specifically for patients with less common ovarian cancers, which in the guidelines include the following: carcinosarcoma, clear cell carcinoma, mucinous carcinoma, low-grade serous, grade 1 endometrioid, borderline epithelial, malignant sex cord-stromal, and malignant germ cell tumors. This manuscript focuses on certain aspects of primary treatment, including primary surgery, adjuvant therapy, and maintenance therapy options (including PARP inhibitors) after completion of first-line chemotherapy.

Prevalence of Anemia and Compliance With NCCN Guidelines for Evaluation and Treatment of Anemia in Patients With Gynecologic Cancer.

NCCN recommends evaluation and treatment of all patients with cancer who have anemia. Few studies have evaluated the prevalence of anemia among patients with gynecologic cancer and compliance with the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Hematopoietic Growth Factors. We performed a single-institution retrospective cohort study of patients diagnosed with primary gynecologic cancer between 2008 and 2018. We identified tumor registry-confirmed patients using ICD-O codes from the Synthetic Derivative database, a deidentified copy of Vanderbilt's electronic medical records. Patients were included if they were between ages 18 and 89 years, received initial care at Vanderbilt University Medical Center, and had a hemoglobin measurement within the first 6 months of diagnosis. Anemia was defined as a hemoglobin level ≤11 g/dL and was graded using CTCAE version 5.0. A total of 939 patients met inclusion criteria, with a median age of 60 years. The most common malignancy was uterine cancer. At the time of cancer diagnosis, 186 patients (20%) were noted to have anemia. Within 6 months of diagnosis, 625 patients (67%) had anemia, of whom 200 (32%) had grade 3 anemia and 209 (33%) underwent any evaluation of anemia, including 80 (38%) with iron studies performed. Of the patients with iron studies performed, 7 (9%) had absolute iron deficiency and 7 (9%) had possible functional iron deficiency. Among those with anemia within 6 months of diagnosis, 260 (42%) received treatment for anemia, including blood transfusion (n=205; 79%), oral iron (n=57; 22%), intravenous iron (n=8; 3%), vitamin B12 (n=37; 14%), and folate supplementation (n=7; 3%). Patients with ovarian cancer were significantly more likely to have anemia and undergo evaluation and treatment of anemia. Anemia is pervasive among patients with gynecologic cancer, but compliance with the NCCN Guidelines is low. Our data suggest that there are opportunities for improvement in the evaluation and management of anemia.

Operating on Jehovah's Witnesses: A Challenging Surgical Issue.

Blood transfusion is often utilized in surgery. Greece is the second-highest consumer of blood components in Europe. It has been shown that at least half of all transfusions are unnecessary and could be avoided. Jehovah's Witnesses (JWs) are a Christian religion that do not accept transfusion of whole blood or the four primary components of blood-namely, red blood cells, white blood cells, platelets, and plasma. This a retrospective study from September of 2015 to January of 2018, analyzing all JWs who underwent an elective operation at the Second Department of Propaedeutic Surgery in Laiko University Hospital. Twenty-nine (Rogers et al. in NCCN Guidelines Version 2.2014 Cancer- and Chemotherapy-Induced Anemia. NCCN Clinical Practice Guidelines in Oncology. National Comprehensive Cancer Network, Fort Washington, 2013) JW patients, 23 females (74.1%) and eight males, were operated on during the aforementioned period. The median ASA score was 1 (range 1-3), and only two of the patients needed postoperative monitoring in the ICU. Almost half of the patients (45.1%) needed iron infusion and EPO injection preoperatively. Two patients presented with postoperative complications, with no postoperative deaths. In conclusion, we found that surgery, in our small group of JW patients, was safe and successful despite the lack of blood transfusion. Techniques developed to treat JW patients should be more widely used to improve clinical outcomes and reduce costs to the healthcare system.

Interpretation of updated pathological contents for cervical cancer in NCCN clinical practice guidelines, version 1, 2020

针对《2020年宫颈癌临床实践指南》涉及的病理更新内容进行解读，内容包括基于人乳头状瘤病毒（human papillomavirus，HPV）病因学的宫颈腺癌组织学新分类，HPV相关性宫颈腺癌浸润方式分类（Silva分类），对复发、进展或转移性宫颈癌患者进行NTRK基因融合检测推荐以及对宫颈癌肿瘤分期的病理评估等，旨在帮助国内病理同行加深对该指南病理更新内容的认识和理解。.

Genetic/Familial High-Risk Assessment: Breast, Ovarian, and Pancreatic, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

The NCCN Guidelines for Genetic/Familial High-Risk Assessment: Breast, Ovarian, and Pancreatic focus primarily on assessment of pathogenic or likely pathogenic variants associated with increased risk of breast, ovarian, and pancreatic cancer and recommended approaches to genetic testing/counseling and management strategies in individuals with these pathogenic or likely pathogenic variants. This manuscript focuses on cancer risk and risk management for BRCA-related breast/ovarian cancer syndrome and Li-Fraumeni syndrome. Carriers of a BRCA1/2 pathogenic or likely pathogenic variant have an excessive risk for both breast and ovarian cancer that warrants consideration of more intensive screening and preventive strategies. There is also evidence that risks of prostate cancer and pancreatic cancer are elevated in these carriers. Li-Fraumeni syndrome is a highly penetrant cancer syndrome associated with a high lifetime risk for cancer, including soft tissue sarcomas, osteosarcomas, premenopausal breast cancer, colon cancer, gastric cancer, adrenocortical carcinoma, and brain tumors.

CheckMate 743: A Glimmer of Hope for Malignant Pleural Mesothelioma

CheckMate 743: A Glimmer of Hope for Malignant Pleural Mesothelioma

Multiple Myeloma, Version 3.2021, NCCN Clinical Practice Guidelines in Oncology.

Multiple myeloma is a malignant neoplasm of plasma cells that accumulate in bone marrow, leading to bone destruction and marrow failure. This manuscript discusses the management of patients with solitary plasmacytoma, smoldering multiple myeloma, and newly diagnosed multiple myeloma.

50 Years Ago in TheJournalofPediatrics: From Toxicity to Specificity, an Overview on Acute Lymphocytic Leukemia Treatment

Pinkel D. Treatment of childhood acute lymphocytic leukemia. J Pediatr 1970;77:1089-91. Acute lymphoblastic leukemia (ALL) is the most common malignancy in childhood and the most curable disease in pediatric oncology. In the 1960s, ALL was an almost uniformly fatal disease, but due to new therapies and breakthroughs in the last 50 years, the current 5-year survival rate has improved to 89% in children and 61% in young adults.1Brown P. Inaba H. Annesley C. Beck J. Colace S. Dallas M. et al.Pediatric Acute Lymphoblastic Leukemia, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology.J Natl Compr Canc Netw. 2020; 18: 81-112Crossref PubMed Scopus (19) Google Scholar The essence of ALL treatment remains the same and continues to be grouped in the following phases: induction, consolidation, and a prolonged maintenance. One of the most significant changes is the individualization of each patient, classifying them according to risk stratification, predictive biomarkers, molecular prognosis, and monitoring of minimal residual disease, aiming to reduce complications and mortality of chemotherapy itself. Another major shift includes central nervous system prophylaxis, an essential part of ALL management and a prerequisite for successful treatment.2Rafei H. Kantarjian H.M. Jabbour E.J. Recent advances in the treatment of acute lymphoblastic leukemia.Leuk Lymphoma. 2019; 60: 2606-2621Crossref Scopus (15) Google Scholar Fifty years ago, “complete remission” was based on Bisel morphologic criteria, which Pinkel considered insufficient, as it excluded central nervous system involvement. Today, analytic minimal residual disease testing using flow cytometry is a strong prognostic indicator in all leukemia subtypes.3Kaplan J.A. Leukemia in children.Pediatr Rev. 2019; 40: 319-331Crossref Scopus (11) Google Scholar The last decade has seen significant advances in treatment; thanks to molecular biology, Paul Ehrlich's “magic bullet” concept is reaching its full realization. Today, we are in the era of monoclonal antibody therapy with new drugs such as blinatumomab, inotuzumab, and chimeric antigen receptor T cells, which target specific abnormal molecules and pathways of cancer cells.2Rafei H. Kantarjian H.M. Jabbour E.J. Recent advances in the treatment of acute lymphoblastic leukemia.Leuk Lymphoma. 2019; 60: 2606-2621Crossref Scopus (15) Google Scholar These new therapies came with new complications and adverse effects, so the imperative to improve supportive care, comfort, and quality of life remains. However, they pave the way to a future in which treatment toxicity for patients is minimized. The challenges of 50 years ago are being today addressed with the goal to completely phase out conventional chemotherapy.

Serum Lipid Profile and Steroid Hormone Levels in Patients With Colorectal Cancer

Background: Lipids are usually crucial to develop tumors, and dyslipidemia is correlated with the high chance of colon and colorectal cancer (CRC). Steroid hormones such as estrogen and progesterone can decrease the risk of CRC development. Objectives: The present study aimed to compare the serum levels of lipid profile and steroid hormones in patients with CRC and healthy controls. Methods: The present study included 40 consecutive adult patients with CRC in the Mazandaran Cancer Center, Sari, Iran, between 2017 and 2020. The diagnosis of CRC was evaluated based on colonoscopy with biopsy and CT scan. Also, the diagnosis of CRC was based on NCCN clinical practice guidelines in oncology. Blood samples were taken before treatment during routine testing. A 5 mL of peripheral blood was collected from each patient. All patients signed the written consent for the study. Also, a total of 40 healthy subjects were selected as healthy controls from the same area during a routine physical examination, which was also confirmed by screening colonoscopy and pathology. Serum total cholesterol (TCH) and triglyceride (TG) levels were quantitatively determined by the colorimetric method. Low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were determined by the turbidimetric immunoassay. Steroid hormones were quantitatively determined by the enzyme-linked immunosorbent assay (ELISA) according to the reagent manufacturer’s instruction. To analyze data, the SPSS software package (version 21) was applied. Results: Among all the indicators studied, the mean ± SD of testosterone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels was higher (1.85 ± 1.63 ng/mL, 15.35±0.13 mIU/L, 12.42±0.12.16 mIU/mL) in patients with CRC than healthy controls (0.40±.0.21 ng/mL, 6.27±0.50 mIU/mL, 2.89±0.20 mIU/mL, P<0.05 respectively). The results in subgroups showed that the mean testosterone (0.91±1.2 ng/L), FSH (19.11±16 mIU/mL) , LH (14.49±14 mIU/mL) levels in the female patients with CRC was higher than healthy female controls and had more statistical significance(P=0.02, 0.00, 0.00), respectively. The area under the AUC cure of the testosterone, FSH, and LH indicates positive test (0.670, 0.726 and 0.775). Conclusion: Changes in the levels of steroid hormones and lipids could correlate with the elevated chance of CRC. Therefore, assessment of multiple markers might overcome and provide better judgment in patients with CRC.

Central Nervous System Cancers, Version 3.2020, NCCN Clinical Practice Guidelines in Oncology.

The NCCN Guidelines for Central Nervous System (CNS) Cancers focus on management of adult CNS cancers ranging from noninvasive and surgically curable pilocytic astrocytomas to metastatic brain disease. The involvement of an interdisciplinary team, including neurosurgeons, radiation therapists, oncologists, neurologists, and neuroradiologists, is a key factor in the appropriate management of CNS cancers. Integrated histopathologic and molecular characterization of brain tumors such as gliomas should be standard practice. This article describes NCCN Guidelines recommendations for WHO grade I, II, III, and IV gliomas. Treatment of brain metastases, the most common intracranial tumors in adults, is also described.

315P High-penetrance breast and/or ovarian cancer susceptibility genes in Filipinos

Breast cancer is the most common cancer seen in women worldwide. In the Philippines, 24,798 cases of breast cancer were diagnosed in 2018, making up 17.6% of 141,021 newly diagnosed cases of cancer in the country. Genetic counseling and testing for hereditary cancers is a relatively new undertaking for medical oncologists in the Philippines. Previous studies show that prevalence of BRCA mutations in Filipinos is 5.1% to 6.8%, which is consistent with data found in the Asian population. However, no studies have yet been done looking at multigene panel testing for Filipino patients who meet the testing criteria for high-penetrance breast and/or ovarian cancer susceptibility genes. From September 2019 to May 2020, we did multigene panel testing (Invitae Multi-Cancer Panel) for patients who met the testing criteria for high-penetrance breast and/or ovarian cancer susceptibility genes (NCCN Clinical Practice Guidelines in Oncology: Genetic/Familial High-Risk Assessment: Breast, Ovarian, and Pancreatic, Version 1.2020 – December 4, 2019). We tested 24 patients (23 females, 1 male; 29-81 years old), including 14 with breast cancer, 4 with ovarian cancer, 1 with both breast and ovarian cancer, 2 with pancreatic cancer, and 3 with no cancer but strong family history. Among the 24 patients tested, none had pathogenic BRCA1/2 mutations. However, one (4%) had a pathogenic PALB2 mutation (c.757_758del (p.Leu253Ilefs*3)), fourteen (58%) had one or more variants of uncertain significance (ALK, ATM, BARD1, BRCA2, CDKN1B, EGFR, KIT, MSH2, MSH6, MUTYH, NF1, NTHL1, POLE, RAD51D, RECQL4, SDHA, SDHB, SMARCA4, SMARCB1, TSC1), and nine (38%) had negative results. As cancer genetics becomes more mainstream, use of multigene panels has been increasing, and cost of testing has been decreasing, making this more accessible to the average Filipino cancer patient. This is the first study to document the presence of other high-penetrance breast and/or ovarian cancer susceptibility genes in Filipinos. However, more research has to be done as we still do not know all the genes that may cause hereditary breast cancer and use of multigene panels increases the rates of detecting variants of uncertain significance and other incidental findings.

Small Renal Masses With Tumor Size 0 to 2 cm: A SEER-Based Study and Validation of NCCN Guidelines.

The NCCN Clinical Practice Guidelines in Oncology for Kidney Cancer recommend active surveillance as an option for initial management of T1a 0- to 2-cm renal lesions, in addition to partial nephrectomy, radical nephrectomy, and focal ablation. However, contemporary data regarding the distribution of patient and renal cell carcinoma characteristics within this special patient group are scarce. Within the SEER database (2002-2016), 13,364 patients with T1aNanyMany 0- to 2-cm renal lesions treated with nephrectomy were identified. Data were tabulated according to histologic subtype, Fuhrman grade (FG1-2 vs FG3-4), age category, and sex. In addition, rates of synchronous metastases were quantified. Overall, clear-cell (69.3%), papillary (21.4%), chromophobe (6.9%), multilocular cystic (2.0%), sarcomatoid dedifferentiation (0.2%), and collecting-duct histologic subtypes (0.2%) were identified. Advanced age was associated with a lower rate of FG1-2 clear cell histologic subtype (70.8%-50.3%) but higher rates of FG1-2 papillary (11.1%-23.9%) and chromophobe histologic subtypes (6.2%-8.5%). Overall, 14.5% individuals harbored FG3-4 clear cell (9.8%) or FG3-4 papillary histologic subtypes (4.8%), and both were more prevalent in men. FG3-4 clear-cell and FG3-4 papillary histologic subtypes increased with age, more so in women than in men. The overall rate of synchronous metastases was 0.4% and ranged from 0 in the multilocular cystic subtype to 0.9% in the FG3-4 papillary histologic subtype, respectively, except for 13.8% in the sarcomatoid dedifferentiation histologic subtype. Most T1a 0- to 2-cm renal cell carcinoma represents the low-grade clear-cell or low-grade papillary histologic subtype, with an FG3-4 minority. Even in patients with the FG3-4 histologic subtype, rates of synchronous metastases are virtually zero.

Cost-Effectiveness of Initial Versus Delayed Lanreotide for Treatment of Metastatic Enteropancreatic Neuroendocrine Tumors.

The Controlled Study of Lanreotide Antiproliferative Response in Neuroendocrine Tumors (CLARINET) trial showed prolonged progression-free survival in patients initially treated with lanreotide versus placebo. We evaluated the cost-effectiveness of upfront lanreotide versus active surveillance with lanreotide administered after progression in patients with metastatic enteropancreatic neuroendocrine tumors (NETs), both of which are treatment options recommended in NCCN Clinical Practice Guidelines in Oncology for Neuroendocrine and Adrenal Tumors. We developed a Markov model calibrated to the CLARINET trial and its extension. We based the active surveillance strategy on the CLARINET placebo arm. We calculated incremental cost-effectiveness ratios (ICERs) in dollars per quality-adjusted life-year (QALY). We modeled lanreotide's cost at $7,638 per 120 mg (average sales price plus 6%), used published utilities (stable disease, 0.77; progressed disease, 0.61), adopted a healthcare sector perspective and lifetime time horizon, and discounted costs and benefits at 3% annually. We examined sensitivity to survival extrapolation and modeled octreotide long-acting release (LAR) ($6,183 per 30 mg). We conducted one-way, multiway, and probabilistic sensitivity analyses. Upfront lanreotide led to 5.21 QALYs and a cost of $804,600. Active surveillance followed by lanreotide after progression led to 4.84 QALYs and a cost of $590,200, giving an ICER of $578,500/QALY gained. Reducing lanreotide's price by 95% (to $370) or 85% (to $1,128) per 120 mg would allow upfront lanreotide to reach ICERs of $100,000/QALY or $150,000/QALY. Across a range of survival curve extrapolation scenarios, pricing lanreotide at $370 to $4,000 or $1,130 to $5,600 per 120 mg would reach ICERs of $100,000/QALY or $150,000/QALY, respectively. Our findings were robust to extensive sensitivity analyses. The ICER modeling octreotide LAR is $482,700/QALY gained. At its current price, lanreotide is not cost-effective as initial therapy for patients with metastatic enteropancreatic NETs and should be reserved for postprogression treatment. To be cost-effective as initial therapy, the price of lanreotide would need to be lowered by 48% to 95% or 27% to 86% to reach ICERs of $100,000/QALY or $150,00/QALY, respectively.

Myeloid/Lymphoid Neoplasms with Eosinophilia and TK Fusion Genes, Version 3.2021, NCCN Clinical Practice Guidelines in Oncology.

Eosinophilic disorders and related syndromes represent a heterogeneous group of neoplastic and nonneoplastic conditions, characterized by more eosinophils in the peripheral blood, and may involve eosinophil-induced organ damage. In the WHO classification of myeloid and lymphoid neoplasms, eosinophilic disorders characterized by dysregulated tyrosine kinase (TK) fusion genes are recognized as a new category termed, myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB or FGFR1 or with PCM1-JAK2. In addition to these aforementioned TK fusion genes, rearrangements involving FLT3 and ABL1 genes have also been described. These new NCCN Guidelines include recommendations for the diagnosis, staging, and treatment of any one of the myeloid/lymphoid neoplasms with eosinophilia (MLN-Eo) and a TK fusion gene included in the 2017 WHO Classification, as well as MLN-Eo and a FLT3 or ABL1 rearrangement.

Clinical Utility of 18F-FDG PET/CT in Staging Localized Breast Cancer Before Initiating Preoperative Systemic Therapy.

18F-fluorodeoxyglucose PET/CT is recommended as an optional study in the current NCCN Clinical Practice Guidelines in Oncology for Breast Cancer after CT of the chest, abdomen, and pelvis with contrast and bone scan (CTBS) in stage IIA-IIIC breast cancer. We evaluated our experience with the use of PET/CT in this setting before beginning primary systemic therapy (PST) prior to planned surgery. We performed medical record abstractions of all adult female patients with clinical stage IIA-IIIC breast cancer diagnosed at Montefiore Medical Center from January 1, 2014, through January 1, 2019, who underwent PET/CT before PST. We calculated the proportion of patients upstaged after PET/CT and examined the cost and radiation exposure associated with PET/CT compared with CTBS. A total of 195 patients with 196 breast cancers (bilateral disease in 1 patient) met the study inclusion criteria and had PET/CT as the first imaging study before PST. The overall upstaging rate for regional nodal metastasis and/or distant metastasis was 37% (73/196), including 24% for stage IIA (9/38), 39% for stage IIB (31/79), 54% for stage IIIA (22/41), 27% for stage IIIB (8/30), and 37% for stage IIIC (3/8). The overall upstaging rate for distant metastasis was 14% (27/196), including 0% for stage IIA, 13% for stage IIB (10/79), 22% for stage IIIA (9/41), 17% for stage IIIB (5/30), and 37% for stage IIIC (3/8). Medicare reimbursement rates were $1,604.37 for PET/CT and $1,679.94 for CTBS. The radiation dose for PET/CT was 14 mSv versus 21 mSv for CTBS. Approximately 37% of patients with clinical stage IIA-IIIC breast cancer who underwent PET/CT before PST showed more extensive disease, including 23% with more extensive nodal metastasis and 14% with distant metastasis. Given its high detection rate, comparable cost, lower radiation dose, and greater convenience, PET/CT should be considered as an alternative to CTBS rather than "optional" after CTBS, especially in patients who require an efficient and expeditious workup before initiating PST.

Sites of distant metastasis in Merkel cell carcinoma differ by primary tumor site and are of prognostic significance: A population-based study in the Surveillance, Epidemiology, and End Results database from 2010 to 2016

Sites of distant metastasis in Merkel cell carcinoma differ by primary tumor site and are of prognostic significance: A population-based study in the Surveillance, Epidemiology, and End Results database from 2010 to 2016

Head and Neck Cancers, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology.

Treatment is complex for patients with head and neck (H&N) cancers with specific site of disease, stage, and pathologic findings guiding treatment decision-making. Treatment planning for H&N cancers involves a multidisciplinary team of experts. This article describes supportive care recommendations in the NCCN Guidelines for Head and Neck Cancers, as well as the rationale supporting a new section on imaging recommendations for patients with H&N cancers. This article also describes updates to treatment recommendations for patients with very advanced H&N cancers and salivary gland tumors, specifically systemic therapy recommendations.

Hodgkin Lymphoma, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology.

The NCCN Clinical Practice Guidelines in Oncology for Hodgkin Lymphoma (HL) provide recommendations for the management of adult patients with HL. The NCCN panel meets at least annually to review comments from reviewers within their institutions, examine relevant data, and reevaluate and update their recommendations. Current management of classic HL involves initial treatment with chemotherapy alone or combined modality therapy followed by restaging with PET/CT to assess treatment response. Overall, the introduction of less toxic and more effective regimens has significantly advanced HL cure rates. This portion of the NCCN Guidelines focuses on the management of classic HL.

Hematopoietic Cell Transplantation, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology

Hematopoietic cell transplantation (HCT) involves the infusion of hematopoietic progenitor cells into patients with hematologic disorders with the goal of re-establishing normal hematopoietic and immune function. HCT is classified as autologous or allogeneic based on the origin of hematopoietic cells. Autologous HCT uses the patient's own cells while allogeneic HCT uses hematopoietic cells from a human leukocyte antigen-compatible donor. Allogeneic HCT is a potentially curative treatment option for patients with certain types of hematologic malignancies, and autologous HCT is primarily used to support patients undergoing high-dose chemotherapy. Advances in HCT methods and supportive care in recent decades have led to improved survival after HCT; however, disease relapse and posttransplant complications still commonly occur in both autologous and allogeneic HCT recipients. Allogeneic HCT recipients may also develop acute and/or chronic graft-versus-host disease (GVHD), which results in immune-mediated cellular injury of several organs. The NCCN Guidelines for Hematopoietic Cell Transplantation focus on recommendations for pretransplant recipient evaluation and the management of GVHD in adult patients with malignant disease.

Guideline-Concordant Treatment Among Elderly Women With HER2-Positive Metastatic Breast Cancer in the United States.

It is crucial to identify whether women with HER2-positive (HER2+) metastatic breast cancer (MBC) are treated according to treatment guidelines and whether treatment disparities exist. This study examined guideline-concordant treatment among women with HER2+ MBC and determined the magnitude of differences in treatment between those with positive and negative hormone receptor (HR) status using a nonlinear decomposition technique. A retrospective observational cohort study was conducted using the SEER-Medicare linked database. The study cohort consisted of women aged ≥66 years diagnosed with HER2+ MBC in 2010 through 2013 (n=241). Guideline-concordant initial treatment after cancer diagnosis was defined based on the NCCN Clinical Practice Guidelines in Oncology for Breast Cancer. A multivariable logistic regression was performed to identify significant predictors of guideline-concordant treatment. A postregression decomposition was conducted to identify the magnitude of disparities in treatment by HR status. Of 241 women included in the study, a total of 76.8% received guideline-concordant treatment. These women were significantly more likely to have positive HR status (P=.0298), have good performance status (P=.0009), and more oncology visits (P<.0001). With 1-year increments in age at cancer diagnosis, the likelihood of receiving guideline-concordant treatment reduced by 5% (P=.0356). The decomposition analysis revealed that 19.0% of the disparity in guideline-concordant treatment between women with positive and negative HR status was explained by differences in their characteristics. Enabling characteristics (marital status, income, and education) explained the highest (22.8%) proportion of the disparity. Nearly one-quarter of the study cohort did not receive guideline-concordant treatment. Our findings suggest opportunities to improve cancer care for elderly women with negative HR status who are unpartnered or have lower socioeconomic status. The high unexplained portion of the disparity by HR status can be due to patient treatment preferences, propensity to seek care, and organizational and physician-level characteristics that were not included in the study.