In Germany, the use of photodynamic therapy (PDT) avoids many of the drawbacks you highlight in managing brain cancers (Nature 561, S59–S61; 2018). For example, we are able to reach deep-seated tumours, as well as those for which surgery is impossible or impractical.
We use the same PDT agent and delivery that you describe. The difference is in the timing of light application, which replaces, rather than follows, surgery. The light is delivered to the entire tumour through stereotactically placed fibres (see, for example, H. Stepp and W. Stummer Lasers Surg. Med. 50, 399–419; 2018). Because the PDT agent targets tumour cells, the treatment spares healthy brain tissue.
In addition, PDT stimulates the patient’s immune system to kill residual cancer cells (see, for example, A. D. Garg and P. Agostinis Photochem. Photobiol. Sci.13, 474-487; 2014). These immune-stimulatory effects are maximized because our method leaves the entire PDT-treated tumour mass inside the brain.
This approach is showing a promising increase in patients’ long-term survival in feasibility trials. Combining PDT with immune-checkpoint inhibition might further improve outcomes.
Nature 565, 161 (2019)
Competing Financial Interests
Herbert Stepp’s institution gets salary for a postdoc from Medac. Walter Stummer receives consultant fees from NXDC and Photonamic.