Plasma thymidine kinase 1 activity and outcome of ER+ HER2- metastatic breast cancer patients treated with palbociclib and endocrine therapy

Palbociclib in Older Patients with Advanced/Metastatic Breast Cancer: A Systematic Review

BACKGROUND

Palbociclib in combination with endocrine therapy is approved for treatment of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer. In addition to clinical trials, several real-world studies have evaluated the effectiveness of palbociclib. With increased life expectancy in the general population, breast cancer in older women is also expected to increase.

OBJECTIVE

The aim was to systematically review evidence from both clinical trials and real-world studies for palbociclib treatment outcomes in older patients with HR+/HER2- advanced/metastatic breast cancer (a/mBC). Older patients are often underrepresented in clinical trials, and real-world evidence (RWE) will enrich the analysis of palbociclib outcomes in this subgroup of patients.

DESIGN

A systematic literature search in PubMed, EMBASE, and Cochrane Library through May 4, 2023, yielded 2355 unique articles. A total of 52 articles (13 and 39 articles reporting results from seven randomized controlled trials [RCTs] and 37 RWE studies, respectively) were included based on study eligibility criteria.

RESULTS

All RCTs used age cutoffs of ≥ 65 years to define older population (n = 722; 437 received palbociclib); all RWE studies, except one with an age cutoff of > 60 years, had age cutoffs of ≥ 65 years or higher to define older population (n = 9840; 7408 received palbociclib). Overall, in studies that compared efficacy (progression-free survival [seven RCTs, 20 RWE studies], overall survival [four RCTs, 11 RWE studies], tumor response [three RWE studies], and clinical benefit rate [one RCT, two RWE studies]) and safety outcomes (three RCTs, three RWE studies) between older and younger patients, palbociclib showed similar benefits, regardless of age. Results from two RCTs and two RWE studies showed that global quality of life (QoL) was maintained in older patients receiving palbociclib. Overall, palbociclib dose modifications (two RWE studies), dose reductions (one RCT, seven RWE studies), and treatment discontinuation rates (three RCTs, three RWE studies) were higher in older patients compared with younger patients; however, these differences did not appear to adversely impact efficacy outcomes.

CONCLUSIONS

In this systematic review, data from RCTs showed that palbociclib was effective, well tolerated, and maintained QoL in older patients with HR+/HER2- a/mBC. Palbociclib treatment in older patients in real-world settings was associated with similar clinical benefit as in RCTs.

PROSPERO REGISTRATION

CRD42023444195.

Thymidine kinase activity levels in serum can identify HR+ metastatic breast cancer patients with a low risk of early progression (SWOG S0226)

BACKGROUND

Some patients with metastatic breast cancer (MBC) stay on endocrine therapy (ET) for years and others progress quickly. Serum thymidine kinase activity (TKa), an indicator of cell-proliferation, is a potential biomarker for monitoring ET and predicting MBC outcome. We have previously reported TKa as being prognostic in MBC in SWOG S0226. Here, new data on progression within 30/60 days post sampling, with a new, FDA approved version of DiviTum®TKa highlighting differences vs. a Research Use Only version is reported.

METHODS

1,546 serum samples from 454 patients were assessed, collected at baseline and at 4 subsequent timepoints during treatment. A new predefined cut-off tested the ability to predict disease progression. A new measuring unit, DuA (DiviTum® unit of Activity) is adopted.

RESULTS

A DiviTum®TKa score <250 DuA provides a much lower risk of progression within 30/60 days after blood draw, the negative predictive value (NPV) was 96.7% and 93.5%, respectively. Patients <250 DuA experienced significantly longer progression-free survival and overall survival, demonstrated at baseline and for all time intervals.

CONCLUSIONS

DiviTum®TKa provides clinically meaningful information for patients with HR+ MBC. Low TKa levels provide such a high NPV for rapid progression that such patients might forego additional therapy added to single agent ET.Trial registration: NCT00075764.

Serum thymidine kinase activity in patients with HR-positive/HER2-negative advanced breast cancer treated with ribociclib plus letrozole: results from the prospective BioItaLEE trial

BACKGROUND

Thymidine kinase 1 (TK1) is an enzyme downstream of the CDK4/6 pathway, with a critical role in DNA synthesis; serum TK1 activity (sTKa) is a novel liquid biopsy biomarker of tumour cell proliferation.

METHODS

The phase IIIb, BioItaLEE trial (NCT03439046) collected sera from postmenopausal patients with hormone receptor-positive (HR+), HER2-negative (HER2-) advanced breast cancer (ABC) treated with first-line ribociclib plus letrozole at baseline, day 15 of cycle 1 (C1D15), day 1 of cycle 2 (C2D1), and at first imaging. Associations between sTKa assessed at different time points or sTKa dynamic patterns, and progression-free survival (PFS) were evaluated using multivariate Cox models.

RESULTS

Overall, 287 patients were enroled. Median follow-up was 26.9 months. High sTKa (>median) at baseline was associated with higher risk of progression (hazard ratio [HR], 2.21; 95% confidence interval [95% CI], 1.45, 3.37; P = 0.0002); similar results were observed for patients with high sTKa levels at C1D15 and C2D1. Early sTKa dynamic patterns were strongly predictive of PFS. The pattern with high sTKa levels at C2D1 following initial decrease at C1D15 was associated with higher risk of progression versus the pattern with low sTKa levels at both time points (HR, 2.89; 95% CI, 1.57, 5.31; P = 0.0006), while the pattern with high sTKa levels at C1D15 was associated with the shortest PFS (HR, 5.65; CI: 2.84, 11.2; P < 0.0001). Baseline and dynamic sTKa changes provided independent information.

CONCLUSIONS

sTKa appears to be a new promising prognostic and pharmacodynamic biomarker in patients with HR+/HER2- ABC treated with ribociclib plus letrozole as first-line therapy.

Multi-Omics Integration Analysis of TK1 in Glioma: A Potential Biomarker for Predictive, Preventive, and Personalized Medical Approaches

Multi-omics expression datasets obtained from multiple public databases were used to elucidate the biological function of TK1 and its effects on clinical outcomes. The Kaplan-Meier curve, a predictive nomogram mode, and the time-dependent receiver operating characteristic (ROC) curve were established to assess the role of TK1 expression in glioma prognosis. TK1 was overexpressed in glioma compared with normal samples, and patients with elevated expression of TK1 had poor overall survival. The ROC curves indicated a high diagnostic value of TK1 expression in patients of glioma; the areas under the ROC curve (AUC) were 0.682, 0.735, and 0.758 for 1 year, 3 years, and 5 years of glioma survival, respectively. For a model based on TK1 expression and other clinical characteristics, the values of AUC were 0.864, 0.896, and 0.898 for 1 year, 3 years, and 5 years, respectively. Additionally, the calibration curve indicated that the predicted and observed areas at 1 year, 3 years, and 5 years of survival were in excellent agreement. Three types of TK1 alterations-missense mutations, splice mutations, and amplifications-were identified in 25 of 2706 glioma samples. The TK1-altered group had better overall survival than the unaltered group. Single-cell function analysis showed that TK1 was positively associated with proliferation, the cell cycle, DNA repair, DNA damage, and epithelial-mesenchymal transition in glioma. Immunoinfiltration analysis indicated that TK1 expression might play different roles in low-grade glioma and glioblastoma multiforme tumor microenvironments, but TK1 expression was positively associated with activated CD4 and Th2, regardless of tumor grade. In summary, our findings identified TK1 as a novel marker for predicting clinical outcomes and a potential target for glioma.

Prognostic Parameters of Palbociclib in HR+/HER2- Advanced Breast Cancer: A Narrative Review

Recent studies have demonstrated that the combination of Cyclin-Dependent Kinase 4/6 Inhibitor (CDK4/6i) and endocrine therapy (ET) is more effective than ET alone and significantly improves progression-free survival (PFS) and overall survival (OS) in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor-2 negative (HER2-) breast cancer (BC). Palbociclib is the first CDK4/6i approved for use, and its clinical advantages have been shown. However, 30% of patients will continue to develop secondary drug resistance. Therefore, exploring the parameters that can predict the efficacy of Palbociclib and developing a clinical prediction model is essential for evaluating the prognosis of patients.

Clinical Value on Combined Detection of Serum CA724, DKK1, and TK1 in Diagnosis of Gastric Cancer

Objective

To explore the clinical value on combined detection of serum carbohydrate antigen 724 (CA724), secreted protein dickkopf-1 (DKK1), and thymidine kinase 1 (TK1) in the diagnosis of gastric cancer (GC).

Methods

The clinical data of 63 GC patients (GC group) and 54 patients with benign gastric lesions (control group) admitted to Zhu Xianyi Memorial Hospital of Tianjin Medical University from June 2020 to June 2021 were retrospectively analyzed. The levels of serum CA724, DKK1, and TK1 in the two groups were detected by electrochemiluminescence instrument, enzyme-linked immunosorbent assay, and enhanced chemiluminescence. The diagnostic efficacy of single detection and combined detection was analyzed by drawing the receiver operating characteristic (ROC) curve.

Results

Compared with the control group, the serological indexes of patients in GC group were markedly higher (P < 0.001). ROC curve analysis showed that the areas under the curve of serum CA724, DKK1, TK1, and combined detection in the diagnosis of GC were 0.849, 0.754, 0.685, and 0.923, respectively; and the sensitivity and specificity of their combined detection were higher than those of separate detection.

Conclusion

The levels of serum CA724, DKK1, and TK1 were highly expressed in GC patients, with a higher diagnostic value for GC in their combined detection, which can effectively screen and assist the diagnosis of GC.

Biomarkers for Cyclin-Dependent Kinase 4/6 Inhibitors in the Treatment of Hormone Receptor-Positive/Human Epidermal Growth Factor Receptor 2-Negative Advanced/Metastatic Breast Cancer: Translation to Clinical Practice

PURPOSE

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors have emerged as effective treatments for patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced/metastatic breast cancer (mBC). Dedicated research efforts have been undertaken to find predictive biomarkers of response or resistance to these therapies although no molecular biomarkers for mBC have reached the clinic so far. This review aims to summarize and evaluate the performance of biomarkers in predicting progression-free survival in phase II and III clinical trials of CDK4/6 inhibitors in HR+/HER2- mBC.

METHODS

For this narrative review, a structured literature search of PubMed, Embase, and the Cochrane library (CENTRAL) was performed. Phase II or III clinical trials of a CDK4/6 inhibitor in patients with HR+/HER2- mBC reporting on at least one molecular biomarker analysis of progression-free survival were included. Publications and selected conference abstracts were included up until November 2021.

RESULTS

Twenty-two articles reporting biomarker results of 12 clinical trials were included. Retinoblastoma protein status and cyclin E1 mRNA expression were promising baseline biomarkers, whereas PIK3CA circulating tumor DNA ratio on treatment relative to baseline, change in plasma thymidine kinase activity, and circulating tumor cell count were potential dynamic biomarkers of response. A number of biomarkers were unsuccessful, despite a strong mechanistic rationale, and others are still being explored.

CONCLUSION

Our review of clinical trials showed that there are a number of promising biomarkers at baseline and several dynamic biomarkers that might predict response to CDK4/6 inhibitors. Validation of these findings and assessment of clinical utility are crucial to make the final translation to clinical practice. Better understanding of disease heterogeneity and further elucidation of resistance mechanisms could inform future studies of rationally selected biomarkers.

A phase II trial of an alternative schedule of palbociclib and embedded serum TK1 analysis

Palbociclib 3-weeks-on/1-week-off, combined with hormonal therapy, is approved for hormone receptor positive (HR+)/HER2-negative (HER2−) advanced/metastatic breast cancer (MBC). Neutropenia is the most frequent adverse event (AE). We aim to determine whether an alternative 5-days-on/2-days-off weekly schedule reduces grade 3 and above neutropenia (G3 + ANC) incidence. In this single-arm phase II trial, patients with HR+/HER2− MBC received palbociclib 125 mg, 5-days-on/2-days-off, plus letrozole or fulvestrant per physician, on a 28-day cycle (C), as their first- or second-line treatment. The primary endpoint was G3 + ANC in the first 29 days (C1). Secondary endpoints included AEs, efficacy, and serum thymidine kinase 1 (sTK1) activity. At data-cutoff, fifty-four patients received a median of 13 cycles (range 2.6–43.5). The rate of G3 + ANC was 21.3% (95% CI: 11.2–36.1%) without G4 in C1, and 40.7% (95% CI: 27.9–54.9%), including 38.9% G3 and 1.8% G4, in all cycles. The clinical benefit rate was 80.4% (95% CI: 66.5–89.7%). The median progression-free survival (mPFS) (95% CI) was 19.75 (12.11–34.89), 33.5 (17.25–not reached [NR]), and 11.96 (10.43–NR) months, in the overall, endocrine sensitive or resistant population, respectively. High sTK1 at baseline, C1 day 15 (C1D15), and C2D1 were independently prognostic for shorter PFS (p = 9.91 × 10⁻⁴, 0.001, 0.007, respectively). sTK1 decreased on C1D15 (p = 4.03 × 10⁻⁷), indicating target inhibition. Rise in sTK1 predicted progression, with the median lead time of 59.5 (inter-quartile range: −206.25–0) days. Palbociclib, 5-days-on/2-days-off weekly, met its primary endpoint with reduced G3 + ANC, without compromising efficacy. sTK1 is prognostic and shows promise in monitoring the palbociclib response. ClinicalTrials.gov#: NCT3007979.

Serum thymidine kinase activity in patients with hormone receptor-positive and HER2-negative metastatic breast cancer treated with palbociclib and fulvestrant

BACKGROUND

Biomarkers for cyclin-dependent kinase 4/6 inhibitors, such as palbociclib, for patients with hormone receptor-positive/HER2-negative metastatic breast cancer are lacking. Thymidine kinase is a proliferation marker downstream of the cyclin-dependent kinase 4/6 pathway. We prospectively investigated the prognostic role of serum thymidine kinase activity (sTKa), in patients treated with Palbociclib + fulvestrant.

PATIENTS AND METHODS

PYTHIA was a phase II, single-arm, multicentre, trial that enrolled 124 post-menopausal women with endocrine-resistant hormone receptor-positive/HER2-negative metastatic breast cancer. Serum samples were collected pre-treatment (pre-trt; n = 122), at day 15 of cycle 1 (D15; n = 108), during the one week-off palbociclib before initiating cycle 2 (D28; n = 108) and at end of treatment (n = 76). sTKa was determined centrally using Divitum®, a refined ELISA-based assay with a limit of detection of 20 Divitum Units (Du)/L. The primary study endpoint was progression-free survival, assessed for its association with pre- and on-treatment sTKa.

RESULTS

Data from 122 women were analysed. Pre-treatment sTKa was not associated with clinical characteristics and moderately correlated with tissue Ki-67. Palbociclib + fulvestrant markedly suppressed sTKa levels at D15, with 83% of patients recording levels below limit of detection. At D28, sTKa showed a rebound in 60% of patients. At each timepoint, higher sTKa was associated with shorter progression-free survival (each p < 0.001), with the strongest effect at D15.

CONCLUSIONS

STKa is an independent prognostic biomarker in patients treated with palbociclib. High pre-treatment sTKa and its incomplete suppression during treatment may identify patients with poorer prognosis and primary resistance. This warrants validation in prospective comparative trials. CLINICALTRIALS.

GOV IDENTIFIER

NCT02536742; EudraCT 2014-005387-15.

Plasma Thymidine Kinase Activity as a Novel Biomarker in Metastatic Melanoma Patients Treated with Immune Checkpoint Inhibitors

Simple Summary

Immune checkpoint inhibitors (ICI) are effective in fractions of patients with disseminated melanoma. Significant toxicity can also occur from the treatments, that, in addition, are expensive. It is therefore important to increase the knowledge of predictive factors and their efficacy in different patient groups. This study is the first to analyze the plasma activity of thymidine kinase (TK), an enzyme involved in DNA synthesis and repair, as a biomarker in melanoma patients. In this study, high TK activity (TKa) levels in melanoma patients were associated with poor baseline factors, such as poor performance status, high plasma lactate dehydrogenase levels, and advanced tumor stage. High TKa levels were also associated with a poor efficacy of immune checkpoint inhibitors. TKa is hence a novel and interesting plasma biomarker in melanoma and should be further studied to define its role as a prognostic and predictive marker in this disease.

Abstract

Background. Immune checkpoint inhibitors (ICI) are effective in fractions of patients with disseminated melanoma. This study is the first to analyze the plasma activity of thymidine kinase (TK), an enzyme involved in DNA synthesis and repair, as a biomarker in melanoma patients. Methods. Plasma samples were collected prior to treatment start in patients with unresectable metastatic cutaneous melanoma, treated with ICI (anti-CTLA-4 and/or anti-PD-1). Plasma TK activity (TKa) levels were determined using the DiviTum TKa ELISA assay. TKa levels were correlated with patients’ baseline characteristics, response rate (RR), progression-free survival (PFS), and overall survival (OS). Results. In the 90 study patients, the median TKa level was 42 Du/L (range <20–1787 Du/L). A significantly higher plasma TKa was found in patients with ECOG performance status ≥1 (p = 0.003), M1c-d disease (p = 0.015), and elevated lactate dehydrogenase levels (p < 0.001). The RR was 63.2% and 30.3% in those with low or high TKa, respectively (p = 0.022). The median PFS was 19.9 and 12.6 months in patients with low or high TKa, respectively (hazard ratio (HR) 1.83 (95% CI, 1.08–3.08), p = 0.024). The median OS was >60 months and 18.5 months in patients with low or high TKa, respectively (HR: 2.25 (95% CI, 1.25–4.05), p = 0.011. Conclusions. High pretreatment plasma TKa levels were significantly associated with worse baseline characteristics and poor response and survival in ICI-treated melanoma patients. TKa is hence a novel and interesting plasma biomarker in melanoma and should be further studied to define its role as a prognostic and predictive marker in this disease.

Evaluating Serum Thymidine Kinase 1 in Patients with Hormone Receptor-Positive Metastatic Breast Cancer Receiving First-line Endocrine Therapy in the SWOG S0226 Trial

PURPOSE

Serum thymidine kinase 1 (sTK1) activity is associated with poor prognosis in metastatic breast cancer (MBC). We assessed the prognostic effect of sTK1 in patients with hormone receptor-positive MBC treated on a prospective randomized trial of anastrozole (A) versus A plus fulvestrant (A + F).

PATIENTS AND METHODS

sTK1 was assessed in 1,726 serums [baseline (BL), cycles 2, 3, 4, and 7] using the DiviTum assay. A prespecified cutoff of ≥200 Du/L was considered high. Progression-free survival (PFS) and overall survival (OS) were analyzed by Kaplan-Meier, log-rank tests, and Cox regression.

RESULTS

BL sTK1 was elevated in 171 (40%) of 432 patients. Patients with high versus low BL sTK1 had significantly worse PFS [median 11.2 vs. 17.3 months, HR = 1.76; 95% confidence interval (CI; 1.43-2.16); P < 0.0001] and OS [median 30 vs. 58 months, HR = 2.38; 95% CI (1.91-2.98); P < 0.0001]. OS was significantly better for patients with high sTK1 who did not have prior adjuvant tamoxifen and who received A + F versus A alone [median 46 vs. 21 months, HR = 0.58; 95% CI (0.38-0.87); P = 0.0087]. Patients with low sTK1 had no difference in outcomes by therapy (P = 0.44). At serial timepoints, high versus low sTK1 had significantly worse subsequent PFS and OS [at cycle 2: PFS HR = 1.70, 95% CI (1.34-2.17); P < 0.0001, OS HR = 2.51, 95% CI (1.93-3.26); P < 0.0001].

CONCLUSIONS

High sTK1 at BL and subsequent timepoints is associated with worse prognosis in patients with MBC starting first-line endocrine therapy (ET). Patients with low sTK1 at BL have comparable outcomes on single-agent or combination ET.

Circulating Biomarkers of CDK4/6 Inhibitors Response in Hormone Receptor Positive and HER2 Negative Breast Cancer

CDK4/6 inhibitors (CDK4/6i) and endocrine therapy are the standard treatment for patients with hormone receptor-positive and HER2 negative (HR+/HER2-) metastatic breast cancer. Patients might show intrinsic and acquired resistance, which leads to treatment failure and progression. Circulating biomarkers have the potential advantages of recognizing patients who might not respond to treatment, monitoring treatment effects and identifying markers of acquired resistance during tumor progression with a simple withdrawal of peripheral blood. Genomic alterations on circulating tumor DNA and serum thymidine kinase activity, but also circulating tumor cells, epigenetic or exosome markers are currently being tested as markers of CDK4/6i treatment response, even though none of these have been integrated into clinical practice. In this review, we discuss the recent advancements in the development of circulating biomarkers of CDK4/6i response in patients with HR+/HER2-breast cancer.

Prognostic role of serum thymidine kinase 1 kinetics during neoadjuvant chemotherapy for early breast cancer

Background

Emerging data support the use of thymidine kinase 1 (TK1) activity as a prognostic marker and for monitoring of response in breast cancer (BC). The long-term prognostic value of TK1 kinetics during neoadjuvant chemotherapy is unclear, which this study aimed to elucidate.

Methods

Material from patients enrolled to the single-arm prospective PROMIX trial of neoadjuvant epirubicin, docetaxel and bevacizumab for early BC was used. Ki67 in baseline biopsies was assessed both centrally and by automated digital imaging analysis. TK1 activity was measured from blood samples obtained at baseline and following two cycles of chemotherapy. The associations of TK1 and its kinetics as well as Ki67 with event-free survival and overall survival (OS) were evaluated using multivariable Cox regression models.

Results

Central Ki67 counting had excellent correlation with the results of digital image analysis (r = 0.814), but not with the diagnostic samples (r = 0.234), while it was independently prognostic for worse OS [adjusted hazard ratio (HR_adj) = 2.72, 95% confidence interval (CI) 1.19-6.21, P = 0.02]. Greater increase in TK1 activity after two cycles of chemotherapy resulted in improved event-free survival (HR_adj = 0.50, 95% CI 0.26-0.97, P = 0.04) and OS (HR_adj = 0.46, 95% CI 0.95, P = 0.04). There was significant interaction between the prognostic value of TK1 kinetics and Ki67 (p_interaction 0.04).

Conclusion

Serial measurement of serum TK1 activity during neoadjuvant chemotherapy provides long-term prognostic information in BC patients. The ease of obtaining serial samples for TK1 assessment motivates further evaluation in larger studies.

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This is a correlative analysis of a prospective phase II study on neoadjuvant chemotherapy for breast cancer.

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Serial measurement of serum TK1 activity during treatment provides independent long-term prognostic information.

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We demonstrate the validity and clinical utility of both central and automated image analysis-based Ki67 assessment.

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Finally, we explore the biologic correlations between TK1 and Ki67.

CDK4/6 inhibitors: A focus on biomarkers of response and post-treatment therapeutic strategies in hormone receptor-positive HER2-negative breast cancer

CDK4/6 inhibitors (CDK4/6i) in combination with endocrine therapy are the mainstay of treatment for patients with hormone receptor-positive, HER2 negative (HR+/HER2neg) metastatic breast cancer. However, resistance - either de novo or acquired - invariably occurs, leading to treatment failure and cancer progression. Genomic alterations, gene expression data and circulating biomarkers have been correlated to response to treatment, but to date no biomarker has been approved to stratify patients. Treatment strategies after progression on CDK4/6i are yet to be standardized. Current approaches include endocrine therapy alone or in combination with target therapy, or chemotherapy. New agents are in clinical development based on potential mechanisms of acquired resistance. Here we will review recent advancements in biomarkers of response to CDK4/6i, and in post- treatment therapeutic strategies.