The Science Behind TKa

Cancer Cell Proliferation

Cancer is defined by uncontrolled cell growth

In a proliferating cancer cell, Thymidine Kinase is continuously expressed and released into the bloodstream.

While Ki67 is a well known proliferation biomarker, it has certain limitations (requires tissue acquired by biopsy, heterogenous expression, etc.). It is typically used only at baseline to characterize a tumor before treatment and is not used for monitoring.

The blood-based DiviTum® TKa test (the name evokes “Dividing Tumor”) does not require a tissue biopsy, can be tested repeatedly during therapy, and can be used as a monitoring tool. DiviTum can quantify the level of thymidine kinase released into the circulation from proliferating cells. This generates a DiviTum activity score which can offer important insights about the proliferative status of a patient’s disease.

DiviTum® TKa test is FDA 510(k) cleared in the US and CE marked in the EU

The DiviTum TKa test can detect an increase or decrease of Thymidine Kinase activity (TKa) levels in the blood. This information can be used as an aid in monitoring disease progression.

In postmenopausal female patients with metastatic HR+ breast cancer, a TKa value of <250 DuA* is associated with the decreased likelihood of disease progression within 30 days or 60 days post testing.1

*DuA (DiviTum® Unit of Activity) = score for the semi-quantitative measurement of thymidine kinase activity (TKa)

1 SWOG S0226 Trial^ – Bergqvist M, et al., Biomarkers 2023 Jan 29;28:3 313–322 and FDA clearance (July 2022).
^Cut-off is based on a healthy population

Ki-67 is a well-known proliferation (but not monitoring) biomarker, which has certain limitations (requires a biopsy, heterogenous expression).

Conventional biomarkers—such as cancer antigen 15-3 (CA 15-3)—are not expressed in all women with mBC1

Low sensitivity of current imaging techniques: up to 40% of mBC patients have non-measurable disease2

TKa testing is a fundamental tool that can help guide more personalized treatment strategies for post-menopausal women diagnosed with HR+ metastatic breast cancer. 

1Gaughran G, Aggarwal N, Shadbolt B, Stuart- Harris R. The utility of the tumor markers CA15.3, CEA, CA-125 and CA19.9 in metastatic breast cancer. Future Medicine website. Published September 18, 2020. Accessed March 7, 2023.
2Larsson AM, Bendahl PO, Aaltonen K, et al. Serial evaluation of serum thymidine kinase activity is prognostic in women with newly diagnosed metastatic breast cancer. Sci Rep. 2020;10(1):4484.


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