Antitumor Effect and Induced Immune Response Following Exposure of Hexaminolevulinate and Blue Light in Combination with Checkpoint Inhibitor in an Orthotopic Model of Rat Bladder Cancer

Photodynamic Therapy in the Treatment of Cancer-The Selection of Synthetic Photosensitizers

Photodynamic therapy (PDT) is a promising cancer treatment method that uses photosensitizing (PS) compounds to selectively destroy tumor cells using laser light. This review discusses the main advantages of PDT, such as its low invasiveness, minimal systemic toxicity and low risk of complications. Special attention is paid to photosensitizers obtained by chemical synthesis. Three generations of photosensitizers are presented, starting with the first, based on porphyrins, through the second generation, including modified porphyrins, chlorins, 5-aminolevulinic acid (ALA) and its derivative hexyl aminolevulinate (HAL), to the third generation, which is based on the use of nanotechnology to increase the selectivity of therapy. In addition, current research trends are highlighted, including the search for new photosensitizers that can overcome the limitations of existing therapies, such as heavy-atom-free nonporphyrinoid photosensitizers, antibody-drug conjugates (ADCs) or photosensitizers with a near-infrared (NIR) absorption peak. Finally, the prospects for the development of PDTs are presented, taking into account advances in nanotechnology and biomedical engineering. The references include both older and newer works. In many cases, when writing about a given group of first- or second-generation photosensitizers, older publications are used because the properties of the compounds described therein have not changed over the years. Moreover, older articles provide information that serves as an introduction to a given group of drugs.

Post-Operational Photodynamic Therapy of the Tumor Bed: Comparative Analysis for Cold Knife and Laser Scalpel Resection

In this paper, we report on a study regarding the efficiency of the post-operational phototherapy of the tumor bed after resection with both a cold knife and a laser scalpel in laboratory mice with CT-26 tumors. Post-operational processing included photodynamic therapy (PDT) with a topically applied chlorin-based photosensitizer (PS), performed at wavelengths of 405 or 660 nm, with a total dose of 150 J/cm2. The selected design of the tumor model yielded zero recurrence in the laser scalpel group and 92% recurrence in the cold knife group without post-processing, confirming the efficiency of the laser scalpel in oncology against the cold knife. The application of PDT after the cold knife resection decreased the recurrence rate to 70% and 42% for the 405 nm and 660 nm procedures, respectively. On the other hand, the application of PDT after the laser scalpel resection induced recurrence rates of 18% and 30%, respectively, for the considered PDT performance wavelengths. The control of the penetration of PS into the tumor bed by fluorescence confocal microscopy indicated the deeper penetration of PS in the case of the cold knife, which presumably provided deeper PDT action, while the low-dose light exposure of deeper tissues without PS, presumably, stimulated tumor recurrence, which was also confirmed by the differences in the recurrence rate in the 405 and 660 nm groups. Irradiation-only light exposures, in all cases, demonstrated higher recurrence rates compared to the corresponding PDT cases. Thus, the PDT processing of the tumor bed after resection could only be recommended for the cold knife treatment and not for the laser scalpel resection, where it could induce tumor recurrence.

Immune Contexture Changes Following Blue Light Cystoscopy with Hexaminolevulinate in Bladder Cancer

Background

Transurethral resection of bladder tumor (TURBT) is a central component in the diagnosis of non-muscle-invasive bladder cancer (NMIBC) and can be guided by several optical imaging techniques for better visualization of lesions.

Objective

To investigate if a change in tumor microenvironment (TME) composition could be observed as an effect of hexaminolevulinate (HAL)-assisted blue light cystoscopy (BLC) in TURBT samples from patients with bladder cancer.

Design setting and participants

This was a retrospective study of 40 patients with bladder cancer who underwent either BLC-guided TURBT (n = 20) or white light cystoscopy (WLC)-guided TURBT (n = 20) before radical cystectomy (RC). Tissue samples (n = 80) were collected from paired TURBT and RC specimens for all 40 patients. Tumor tissue was stained using multiplex immunofluorescence and immunohistochemistry.

Outcome measurements and statistical analysis

Immune cell infiltration was assessed according to the proportions of each immune cell or immune evasion marker and the relative change from TURBT as baseline was calculated. Statistical comparisons between groups were performed using the Wilcoxon rank-sum test or the paired-sample Wilcoxon test.

Results and limitations

Comparison of relative changes in the TME revealed a significant decrease in stromal infiltration of cytotoxic T cells (p = 0.024), B cells (p = 0.041), and stromal cells expressing PD-1 (p = 0.011) in patients treated with BLC-guided TURBT compared to WLC-guided TURBT.

Conclusions

Our pilot study showed that HAL-BLC during TURBT in bladder cancer may influence the immune cell composition and TME.

Patient summary

We investigated the potential therapeutic effect of blue light versus white light for guidance in removing bladder tumors via the urethra in patients with bladder cancer. For blue light guidance, a compound called hexaminolevulinate is used to visualize tumor tissue. We found changes in immune cell composition that may have been influenced by the blue light guidance.

Efficacy and safety of photodynamic therapy for non-muscle-invasive bladder cancer: a systematic review and meta-analysis

Background

Photodynamic therapy (PDT) is a promising treatment for non-muscle-invasive bladder cancer (NMIBC), we conducted this systematic review to comprehensively assess its efficacy and safety.

Methods

A comprehensive literature research was conducted using PubMed, Web of Science, and Scopus, and studies reporting the safety and efficacy of PDT in NMIBC were included. Complete response (CR) rates, recurrence-free survival (RFS) at different time points, and complication incidences were extracted and synthesized. Pooled results were presented as rates with a 95% confidence interval (95% CI).

Results

Overall, 28 single arm studies were included in the meta-analysis. For unresectable NMIBC, therapeutic PDT achieved CR in 68% (95% CI: 59%-77%) of patients. Among these CR cases, 71% (95% CI: 56%-85%) and 38% (95% CI: 12%-64%) have a RFS longer than 12 and 24 months, respectively. For Tis patients, the CR rate was 68% (95% CI: 56%-80%), and 84% (95% CI: 48%-100%) and 13% (95% CI: 1%-32%) have a RFS longer than 12 and 24 months. For patients with resectable tumors, post-resection adjuvant PDT could provide a 12 and 24 months RFS in 81% (95% CI:76%-87%) and 56% (95% CI:41%-71%) of them. Especially, for NMIBC patients who failed BCG therapy, adjuvant PDT could still achieve a 1-year and 2-year RFS in 68% (95% CI:51%-86%) and 56% (95% CI:32%-81%) patients. The complications were mostly mild and transient, including lower urinary tract symptoms and photosensitivity.

Conclusion

Both therapeutic and adjuvant PDT present satisfying safety and efficacy for NMIBC, including these cases that are resistant to the standard of care. As a promising option for NMIBC, PDT deserves further exploration by future high-quality research.

Systematic review registration

https://inplasy.com/inplasy-2022-11-0043/, INPLASY2022110043.

Photodynamic Therapy

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