Local physiological changes during photodynamic therapy

Busch, Theresa M.

doi:10.1002/lsm.20355

Cited by 73 publications

(56 citation statements)

References 37 publications

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“…The advantage of computerswitched fractionated light delivery with multiple interstitial fibers is that fractionated light can be constantly delivered to the tumor or target organ in various sequences of on/off durations. This may be important as the blood flow and O 2 delivery changes overtime, with a reported initial increase and then decrease (34). Potentially, this change in blood flow and oxygenation can be monitored by sequential illumination and detection in the multifiber array and the duration of on/off sequences adjusted.…”

Section: Discussionmentioning

confidence: 99%

Fractionated versus Standard Continuous Light Delivery in Interstitial Photodynamic Therapy of Dunning Prostate Carcinomas

Xiao¹,

Halls²,

Dickey

et al. 2007

Clinical Cancer Research

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Purpose: The study aims to compare the standard/continuous light delivery with fractionated light delivery for interstitial photodynamic therapy (PDT) of prostate cancer. Experimental Design: Dunning R3327 prostate tumor models were established in male syngeneic rats. When tumors reached f3,000 mm 3 , animals were randomized to various treatment groups. Three hours after QLT0074 injection, tumors were illuminated by 690-nm light delivered by a computer-controlled switch, which sequentially directed light to one of the seven optical fibers in cycles. For comparison, tumors were treated with continuous illumination.Tumors treated with light-only served as control. Dynamic contrast-enhanced magnetic resonance imaging was used to monitor tumor perfusion changes before and after PDT. Results: Tumor response (animal survival) to PDT with fractionated light delivery was PDT dose dependent in both tumor models. Rats bearing anaplastic tumor treated by fractionated light (PDT dose: 1.5 mg/kg QLT0074, 900 J light) had a median survival of 51days with 25% tumor cures compared with that of 26 days with no tumor cure by continuous illumination (P = 0.015) and 14 days by light-only (P = 0.0001). Rats bearing well-differentiated tumor treated by fractionated light had a median survival of 82 days compared with 65 days by continuous illumination (P = 0.001) and 37 days by light-only. PDT with fractionated light generated a perfusion reduction of 80% compared with 52% for continuous illumination in well-differentiated tumors. Conclusions: Fractionated light delivery is more effective than continuous light delivery in PDT of prostate cancer (solid tumors). These results warrant further investigation in clinical trials.

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Section: Discussionmentioning

confidence: 99%

Fractionated versus Standard Continuous Light Delivery in Interstitial Photodynamic Therapy of Dunning Prostate Carcinomas

Xiao¹,

Halls²,

Dickey

et al. 2007

Clinical Cancer Research

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“…It has been suggested that this is due to poor control of local photosensitizer concentration, 8,9 the local light dose in the tissue, 10,11 and unknown tissue oxygen concentration. [12][13][14] These factors may lead to large variability in the locally deposited dose of singlet oxygen and other reactive oxidative species.…”

Section: Introductionmentioning

confidence: 99%

System for interstitial photodynamic therapy with online dosimetry: first clinical experiences of prostate cancer

et al. 2010

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Abstract. The first results from a clinical study for Temoporfinmediated photodynamic therapy ͑PDT͒ of low-grade ͑T1c͒ primary prostate cancer using online dosimetry are presented. Dosimetric feedback in real time was applied, for the first time to our knowledge, in interstitial photodynamic therapy. The dosimetry software IDOSE provided dose plans, including optical fiber positions and light doses based on 3-D tissue models generated from ultrasound images. Tissue optical property measurements were obtained using the same fibers used for light delivery. Measurements were taken before, during, and after the treatment session. On the basis of these real-time measured optical properties, the light-dose plan was recalculated. The aim of the treatment was to ablate the entire prostate while minimizing exposure to surrounding organs. The results indicate that online dosimetry based on real-time tissue optical property measurements enabled the light dose to be adapted and optimized. However, histopathological analysis of tissue biopsies taken six months post-PDT treatment showed there were still residual viable cancer cells present in the prostate tissue sections. The authors propose that the incomplete treatment of the prostate tissue could be due to a too low light threshold dose, which was set to 5 J/cm 2 .

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“…Some photosensitizers may act as vascular agents at short times after injection and at high fluence rates, where only the vasculature is sufficiently oxygenated, and produce direct cell kill at low fluence rates and long times after injection. 72 An additional level of complexity arises from the fact that the response to PDT is not confined to the cells where the singlet oxygen is deposited but can involve physiological 73 and immunological 74,75 responses as well.…”

Section: Iib5 Pdt Biologymentioning

confidence: 99%

The role of photodynamic therapy (PDT) physics

2008

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Photodynamic therapy ͑PDT͒ is an emerging treatment modality that employs the photochemical interaction of three components: light, photosensitizer, and oxygen. Tremendous progress has been made in the last 2 decades in new technical development of all components as well as understanding of the biophysical mechanism of PDT. The authors will review the current state of art in PDT research, with an emphasis in PDT physics. They foresee a merge of current separate areas of research in light production and delivery, PDT dosimetry, multimodality imaging, new photosensitizer development, and PDT biology into interdisciplinary combination of two to three areas. Ultimately, they strongly believe that all these categories of research will be linked to develop an integrated model for real-time dosimetry and treatment planning based on biological response.

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Local physiological changes during photodynamic therapy

Abstract: Photodynamic therapy creates distinct, measurable changes in tumor oxygen and blood flow during illumination. These physiological changes may ultimately affect treatment efficacy.

Cited by 73 publications

References 37 publications

Fractionated versus Standard Continuous Light Delivery in Interstitial Photodynamic Therapy of Dunning Prostate Carcinomas

Fractionated versus Standard Continuous Light Delivery in Interstitial Photodynamic Therapy of Dunning Prostate Carcinomas

System for interstitial photodynamic therapy with online dosimetry: first clinical experiences of prostate cancer

The role of photodynamic therapy (PDT) physics

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