Reimagining Cancer Care: the Promise of Theranostics
Theranostics or theragnostics, derived from the words therapy and diagnostics, is an emerging modality of cancer management that attempts to target cancer cells in the body while potentially sparing normal cells from the effects of anti-cancer treatment. There is no gainsaying that the treatment of cancer has proven to be a difficult challenge in medicine and has seen increasingly innovative approaches to achieve more effective results. Theranostics is one of such strategies that makes use of radiopharmaceutical substances for increased precision in the diagnosis and treatment of cancer.
MOLECULAR BASIS OF CANCER AND THE ROLE OF THERANOSTICS
Cancer could potentially develop in any part of the body due to uncontrolled growth and division arising from a single cell. Every cell carries within it deoxyribonucleic acid (DNA), which encodes all information determining its structure and function. The underlying mechanism that initiates cancer involves mutations or aberrations in DNA. Over time, repeated uncontrolled cell divisions starting from the single ‘rogue’ cell forms a collection of cells that carry that genetic aberration. Further mutations may accumulate as this uncontrolled process of cell division continues.
This fundamental knowledge of how cancer arises has driven the development of conventional methods of cancer treatment like chemotherapeutic drugs, which target cells with high rates of cell division. Hence, both cancer cells and other normally rapidly dividing cells such as in hair follicles or bone marrow are affected by these methods. The attack on normal cells is responsible for the common side effects of chemotherapy such as hair loss, anaemia, and immunosuppression.
Theranostics delivers anticancer treatment akin to how a letter bomb is delivered to its target. Firstly, molecular markers unique to cancer cells, like a postcode, are identified. Molecules that bind to these markers on the cancer cells are injected into the body. These injected molecules function like the mailman and can be visualised with special scans when they are bound to their target. Anti-cancer drugs, in this analogy representing the letter bomb, are then attached to these diagnostic molecules and injected. Hence, the treatment is delivered only to cells with specific molecular signatures. Because normal cells do not have these markers like cancer cells do, only cancer cells are attacked.
Image sourced from:
The use of theranostics has been associated with promising results in its application to prostate cancer and neuroendocrine tumours, which are difficult to treat. For instance, using Gallium-68, which emits a glow with a PET-scan, researchers carrying out a trial at the Memorial Sloan Kettering Cancer Center targeted the prostate-specific membrane antigen (PSMA) which is present in very large amounts on prostate cancer cells (Sartor et al., 2021). This was followed by combining Gallium-68 with Lutetium-177, which gives off radiation lethal to cancer cells, a procedure termed Lutetium-177-PSMA-617 therapy.
In this trial, on average, terminally ill men with advanced prostate cancer had a 35% longer survival time than men who received standard treatment. In a more dramatic result, a 64-year-old man with advanced prostate cancer with more than 100 bone metastases, in whom hormonal and chemotherapy treatments had failed, was successfully treated with Lutetium-177-labeled PSMA-617 theranostics, as described above (Basheda., 2021)
Along with the global clinical trials for theranostics in prostate cancer being conducted, further research is ongoing to investigate other molecular markers to be used for different cancer types that would otherwise be unresponsive to conventional treatment. In addition, there are also efforts to investigate optimal dosing for treatments which have already been developed. While this strategy of cancer treatment is not a cure for cancer, it does hold great potential in bringing humanity a step ahead in the war against it.
Basheda, L. 2021. New hope in the fight against prostate cancer: ‘We can win this war’. The Vacaville Reporter, 24 July 2021, viewed 14 November 2021, <https://www.thereporter.com/2021/07/24/new-hope-in-the-fight-against-prostate-cancer-we-can-win-this-war/amp/ >.
Sartor, O., de Bono, J., Chi, K. N., Fizazi, K., Herrmann, K., Rahbar, K., Tagawa, S. T., Nordquist, L. T., Vaishampayan, N., El-Haddad, G., Park, C. H., Beer, T. M., Armour, A., Perez-Contreras, W. J., DeSilvio, M., Kpamegan, E., Gericke, G., Messmann, R. A., Morris, M. J. & Krause, B. J. 2021. Lutetium-177–PSMA-617 for Metastatic Castration-Resistant Prostate Cancer. New England Journal of Medicine, 385, pp.1091-1103.