Invasive breast Cancer treatment in Tanzania: landscape assessment to prepare for implementation of standardized treatment guidelines.

BACKGROUND: Incidence of breast cancer continues to rise in low- and middle-income countries, with data from the East African country of Tanzania predicting an 82% increase in breast cancer from 2017 to 2030. We aimed to characterize treatment pathways, receipt of therapies, and identify high-value interventions to increase concordance with international guidelines and avert unnecessary breast cancer deaths. METHODS: Primary data were extracted from medical charts of patients presenting to Bugando Medical Center, Tanzania, with breast concerns and suspected to have breast cancer. Clinicopathologic features were summarized with descriptive statistics. A Poisson model was utilized to estimate prevalence ratios for variables predicted to affect receipt of life-saving adjuvant therapies and completion of therapies. International and Tanzanian guidelines were compared to current care patterns in the domains of lymph node evaluation, metastases evaluation, histopathological diagnosis, and receptor testing to yield concordance scores and suggest future areas of focus. RESULTS: We identified 164 patients treated for suspected breast cancer from April 2015-January 2019. Women were predominantly post-menopausal (43%) and without documented insurance (70%). Those with a confirmed histopathology diagnosis (69%) were 3 times more likely to receive adjuvant therapy (PrR [95% CI]: 3.0 [1.7-5.4]) and those documented to have insurance were 1.8 times more likely to complete adjuvant therapy (1.8 [1.0-3.2]). Out of 164 patients, 4% (n = 7) received concordant care based on the four evaluated management domains. The first most common reason for non-concordance was lack of hormone receptor testing as 91% (n = 144) of cases did not undergo this testing. The next reason was lack of lymph node evaluation (44% without axillary staging) followed by absence of abdominopelvic imaging in those with symptoms (35%) and lack of histopathological confirmation (31%). CONCLUSIONS: Patient-specific clinical data from Tanzania show limitations of current breast cancer management including axillary staging, receipt of formal diagnosis, lack of predictive biomarker testing, and low rates of adjuvant therapy completion. These findings highlight the need to adapt and adopt interventions to increase concordance with guidelines including improving capacity for pathology, developing complete staging pathways, and ensuring completion of prescribed adjuvant therapies.

Understanding women's perspectives on breast cancer is essential for cancer control: knowledge, risk awareness, and care-seeking in Mwanza, Tanzania.

BACKGROUND: Breast Cancer is the most common cancer in women worldwide. Since 2008, Mwanza, Tanzania, has worked to provide comprehensive cancer services through its Zonal consultant hospital. New national guidelines focused on clinical breast exam requires that women be aware of and seek care for breast concerns. Therefore, this study aims to understand breast cancer awareness in Mwanza and describe women-level barriers, care-seeking behavior, and perspectives on breast cancer. METHODS: A community-based survey was administered to conveniently sampled women aged 30 and older to assess women's perspectives on breast cancer and care-seeking behavior. RESULTS: Among 1129 women with a median age of 37 (IQR: 31-44) years, 73% have heard of cancer and 10% have received breast health education. Women self-evaluated their knowledge of breast cancer (from 1-none to 10-extremely knowledgeable) with a median response of 3 (IQR: 1-4). Only 14% felt they knew any signs or symptoms of breast cancer. Encouragingly, 56% of women were fairly-to-very confident they would notice changes in their breasts, with 24% of women practicing self-breast examination and 21% reporting they had received a past breast exam. Overall, 74% said they would be somewhat-to-very likely to seek care if they noticed breast changes, with 96% noting severity of symptoms as a motivator. However, fear of losing a breast (40%) and fear of a poor diagnosis (38%) were most frequent barriers to care seeking. In assessing knowledge of risk factors, about 50% of women did not know any risk factors for breast cancer whereas 42% of women believed long term contraceptive use a risk factor. However, 37% and 35% of women did not think that family history or being older were risk factors, respectively. CONCLUSIONS: The success of efforts to improve early diagnosis in a setting without population-based screening depends on women being aware of breast cancer signs and symptoms, risks, and ultimately seeking care for breast concerns. Fortunately, most women said they would seek care if they noticed a change in their breasts, but the low levels of cancer knowledge, symptoms, and common risk factors highlight the need for targeted community education and awareness campaigns.

G1T48, an oral selective estrogen receptor degrader, and the CDK4/6 inhibitor lerociclib inhibit tumor growth in animal models of endocrine-resistant breast cancer.

PURPOSE: The combination of targeting the CDK4/6 and estrogen receptor (ER) signaling pathways with palbociclib and fulvestrant is a proven therapeutic strategy for the treatment of ER-positive breast cancer. However, the poor physicochemical properties of fulvestrant require monthly intramuscular injections to patients, which limit the pharmacokinetic and pharmacodynamic activity of the compound. Therefore, an orally available compound that more rapidly reaches steady state may lead to a better clinical response in patients. Here, we report the identification of G1T48, a novel orally bioavailable, non-steroidal small molecule antagonist of ER. METHODS: The pharmacological effects and the antineoplastic mechanism of action of G1T48 on tumors was evaluated using human breast cancer cells (in vitro) and xenograft efficacy models (in vivo). RESULTS: G1T48 is a potent and efficacious inhibitor of estrogen-mediated transcription and proliferation in ER-positive breast cancer cells, similar to the pure antiestrogen fulvestrant. In addition, G1T48 can effectively suppress ER activity in multiple models of endocrine therapy resistance including those harboring ER mutations and growth factor activation. In vivo, G1T48 has robust antitumor activity in a model of estrogen-dependent breast cancer (MCF7) and significantly inhibited the growth of tamoxifen-resistant (TamR), long-term estrogen-deprived (LTED) and patient-derived xenograft tumors with an increased response being observed with the combination of G1T48 and the CDK4/6 inhibitor lerociclib. CONCLUSIONS: These data show that G1T48 has the potential to be an efficacious oral antineoplastic agent in ER-positive breast cancer.

Correction to: Pharmacokinetic and pharmacodynamic analysis of fulvestrant in preclinical models of breast cancer to assess the importance of its estrogen receptor-α degrader activity in antitumor efficacy.

The article Pharmacokinetic and pharmacodynamic analysis of fulvestrant in preclinical models of breast cancer to assess the importance of its estrogen receptor-α degrader activity in antitumor efficacy, written by Suzanne E. Wardell, Alexander P. Yllanes, Christina A. Chao, Yeeun Bae, Kaitlyn J. Andreano, Taylor K. Desautels, Kendall A. Heetderks, Jeremy T. Blitzer, John D. Norris, Donald P. McDonnell, was originally published electronically on the publisher's internet portal on September 27, 2019 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on November 16, 2019 to © The Author(s) 2019 and the article is forthwith distributed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The original article has been corrected.

Pharmacokinetic and pharmacodynamic analysis of fulvestrant in preclinical models of breast cancer to assess the importance of its estrogen receptor-α degrader activity in antitumor efficacy.

PURPOSE: Fulvestrant is a selective estrogen receptor downregulator (SERD) that is approved for first- or second-line use as a single agent or in combination with cyclin dependent kinase or phosphatidylinositol 3-kinase inhibitors for the treatment of metastatic breast cancer. Fulvestrant exhibits exceptionally effective antitumor activity in preclinical models of breast cancer, a success that has been attributed to its robust SERD activity despite modest receptor downregulation in patient tumors. By modeling human exposures in animal models we probe the absolute need for SERD activity. METHODS: Three xenograft models of endocrine therapy-resistant breast cancer were used to evaluate the efficacy of fulvestrant administered in doses historically used in preclinical studies in the field or by using a dose regimen intended to model clinical exposure levels. Pharmacokinetic and pharmacodynamic analyses were conducted to evaluate plasma exposure and intratumoral ER downregulation. RESULTS: A clinically relevant 25 mg/kg dose of fulvestrant exhibited antitumor efficacy comparable to the historically used 200 mg/kg dose, but at this lower dose it did not result in robust ER downregulation. Further, the antitumor efficacy of the lower dose of fulvestrant was comparable to that observed for other oral SERDs currently in development. CONCLUSION: The use of clinically unachievable exposure levels of fulvestrant as a benchmark in preclinical development of SERDs may negatively impact the selection of those molecules that are advanced for clinical development. Further, these studies suggest that antagonist efficacy, as opposed to SERD activity, is likely to be the primary driver of clinical response.

Dysregulation of mitochondrial dynamics proteins are a targetable feature of human tumors.

Altered mitochondrial dynamics can broadly impact tumor cell physiology. Using genetic and pharmacological profiling of cancer cell lines and human tumors, we here establish that perturbations to the mitochondrial dynamics network also result in specific therapeutic vulnerabilities. In particular, through distinct mechanisms, tumors with increased mitochondrial fragmentation or connectivity are hypersensitive to SMAC mimetics, a class of compounds that induce apoptosis through inhibition of IAPs and for which robust sensitivity biomarkers remain to be identified. Further, because driver oncogenes exert dominant control over mitochondrial dynamics, oncogene-targeted therapies can be used to sensitize tumors to SMAC mimetics via their effects on fission/fusion dynamics. Collectively, these data demonstrate that perturbations to the mitochondrial dynamics network induce targetable vulnerabilities across diverse human tumors and, more broadly, suggest that the altered structures, activities, and trafficking of cellular organelles may facilitate additional cancer therapeutic opportunities.

Inhibiting androgen receptor nuclear entry in castration-resistant prostate cancer.

Clinical resistance to the second-generation antiandrogen enzalutamide in castration-resistant prostate cancer (CRPC), despite persistent androgen receptor (AR) activity in tumors, highlights an unmet medical need for next-generation antagonists. We have identified and characterized tetra-aryl cyclobutanes (CBs) as a new class of competitive AR antagonists that exhibit a unique mechanism of action. These CBs are structurally distinct from current antiandrogens (hydroxyflutamide, bicalutamide, and enzalutamide) and inhibit AR-mediated gene expression, cell proliferation, and tumor growth in several models of CRPC. Conformational profiling revealed that CBs stabilize an AR conformation resembling an unliganded receptor. Using a variety of techniques, it was determined that the AR-CB complex was not recruited to AR-regulated promoters and, like apo AR, remains sequestered in the cytoplasm, bound to heat shock proteins. Thus, we have identified third-generation AR antagonists whose unique mechanism of action suggests that they may have therapeutic potential in CRPC.

Evaluation of the pharmacological activities of RAD1901, a selective estrogen receptor degrader.

Endocrine therapy, using tamoxifen or an aromatase inhibitor, remains a first-line treatment for estrogen receptor 1 (ESR1) positive breast cancer. However, tumor resistance limits the duration of response. The clinical efficacy of fulvestrant, a selective ER degrader (SERD) that triggers receptor degradation, has confirmed that ESR1 often remains engaged in endocrine therapy resistant cancers. Recently developed, selective ER modulators (SERMs)/SERD hybrids (SSHs) that facilitate ESR1 degradation in breast cancer cells and reproductive tissues have been advanced as an alternative treatment for advanced breast cancer, particularly in the metastatic setting. RAD1901 is one SSH currently being evaluated clinically that is unique among ESR1 modulators in that it readily enters the brain, a common site of breast cancer metastasis. In this study, RAD1901 inhibited estrogen activation of ESR1 in vitro and in vivo, inhibited estrogen-dependent breast cancer cell proliferation and xenograft tumor growth, and mediated dose-dependent downregulation of ESR1 protein. However, doses of RAD1901 insufficient to induce ESR1 degradation were shown to result in the activation of ESR1 target genes and in the stimulation of xenograft tumor growth. RAD1901 is an SSH that exhibits complex pharmacology in breast cancer models, having dose-dependent agonist/antagonist activity displayed in a tissue-selective manner. It remains unclear how this unique pharmacology will impact the utility of RAD1901 for breast cancer treatment. However, being the only SERD currently known to access the brain, RAD1901 merits evaluation as a targeted therapy for the treatment of breast cancer brain metastases.

Bazedoxifene exhibits antiestrogenic activity in animal models of tamoxifen-resistant breast cancer: implications for treatment of advanced disease.

PURPOSE: There is compelling evidence to suggest that drugs that function as pure estrogen receptor (ER-α) antagonists, or that downregulate the expression of ER-α, would have clinical use in the treatment of advanced tamoxifen- and aromatase-resistant breast cancer. Although such compounds are currently in development, we reasoned, based on our understanding of ER-α pharmacology, that there may already exist among the most recently developed selective estrogen receptor modulators (SERM) compounds that would have usage as breast cancer therapeutics. Thus, our objective was to identify among available SERMs those with unique pharmacologic activities and to evaluate their potential clinical use with predictive models of advanced breast cancer. EXPERIMENTAL DESIGN: A validated molecular profiling technology was used to classify clinically relevant SERMs based on their impact on ER-α conformation. The functional consequences of these observed mechanistic differences on (i) gene expression, (ii) receptor stability, and (iii) activity in cellular and animal models of advanced endocrine-resistant breast cancer were assessed. RESULTS: The high-affinity SERM bazedoxifene was shown to function as a pure ER-α antagonist in cellular models of breast cancer and effectively inhibited the growth of both tamoxifen-sensitive and -resistant breast tumor xenografts. Interestingly, bazedoxifene induced a unique conformational change in ER-α that resulted in its proteasomal degradation, although the latter activity was dispensable for its antagonist efficacy. CONCLUSION: Bazedoxifene was recently approved for use in the European Union for the treatment of osteoporosis and thus may represent a near-term therapeutic option for patients with advanced breast cancer.