A physicochemical model of X-ray induced photodynamic therapy (X-PDT) with an emphasis on tissue oxygen concentration and oxygenation

X-PDT is one of the novel cancer treatment approaches that uses high penetration X-ray radiation to activate photosensitizers (PSs) placed in deep seated tumors. After PS activation, some reactive oxygen species (ROS) like singlet oxygen (1O2) are produced that are very toxic for adjacent cells. Efficiency of X-PDT depends on 1O2 quantum yield as well as X-ray mortality rate. Despite many studies have been modeled X-PDT, little is known about the investigation of tissue oxygen content in treatment outcome. In the present study, we predicted X-PDT efficiency through a feedback of physiological parameters of tumor microenvironment includes tissue oxygen and oxygenation properties. The introduced physicochemical model of X-PDT estimates 1O2 production in a vascularized and non-vascularized tumor under different tissue oxygen levels to predict cell death probability in tumor and adjacent normal tissue. The results emphasized the importance of molecular oxygen and the presence of a vascular network in predicting X-PDT efficiency.

A Clinical Trial Using Attrition Combined with 5-Aminolevulinic Acids Based Photodynamic Therapy in Treating Squamous Cell Carcinoma

Background

Squamous cell carcinoma (SCC) is the second most common type of skin cancer, for which non- or mini-invasive treatment is of critical importance. 5-aminolevulinic acids based photodynamic therapy (ALA-PDT) is a mini-invasive approach that causes focal tumor cell injury, apoptosis, and necrosis through light sensitivity. The efficacy of combining ALA-PDT and surgery in treating SCC, however, has not been demonstrated.

Material/Methods

A total of 60 SCC patients were randomly assigned into attrition plus ALA-PDT group (experimental group) and single ALA-PDT treatment group (control group). Clinical efficacy, recurrence rate, and adverse effects were analyzed in conjunction with H&E staining and immunohistochemistry (IHC) staining for p53 expression.

Results

The overall effective rate of the experimental group was 73.3%, which was significantly higher than that of the control group (46.7%). The experimental group also had a lower recurrence rate (16.6% versus 30.0%, p<0.05). Similar rates of adverse effects existed between the two groups. After treatment, abnormal cells disappeared, while the p53 positive rate after treatment was elevated in the two groups (p<0.05 comparison of before and after treatment). The experimental group had a higher p53 positive rate compared to the control group (p<0.05).

Conclusions

Combined therapy of attrition with ALA-PDT significantly elevated the effective treatment rate and can decrease the recurrence rate with reliable safety in treating SCC, thus ALA-PDT can be used as an optimal plan for SCC treatment.

Monitoring oxygen concentration during photodynamic therapy using prompt photosensitizer fluorescence

A novel technique is described that uses either time-resolved or steady state prompt photosensitizer fluorescence to measure local oxygen concentration. Solution experiments conducted with Al(III) phthalocyanine chloride tetrasulfonic acid confirmed that the steady state fluorescence signal is dependent on the oxygen concentration and fluence rate. A relationship between prompt sensitizer fluorescence and sensitizer triplet quenching efficiency is derived which does not require knowledge of the Stern-Volmer constant. Similar relationships are also derived for sensitizer delayed fluorescence and phosphorescence. An explicit photodynamic therapy (PDT) dose metric that incorporates light dosimetry, sensitizer dosimetry, and triplet quenching efficiency is introduced. All components of this metric can be determined by optical measurements.