Marjan Ruevekamp

Outcome of mTHPC Mediated Photodynamic Therapy is Primarily Determined by the Vascular Response

Abstract We have previously shown that the efficacy of photodynamic therapy (PDT) using the photosensitizer meso-tetra-hydroxyphenyl-chlorin (mTHPC) correlated with plasma drug levels at the time of illumination rather than drug levels in human tumor xenografts or mouse skin. These results suggested that vascular-mediated effects could be important determinants of PDT response in vivo. In the present study we further investigated the relationship between PDT response, mTHPC pharmacokinetics and the localization and extent of vascular damage induced in human squamous cell carcinoma xenografts (HNXOE). Plasma levels of mTHPC decreased exponentially with time after injection, whereas tumor drug levels remained maximal for at least 48 h. At 3 h after administration mTHPC was localized in the blood vessels, whereas at later times it was distributed throughout the whole tumor. Illumination at 3 h after mTHPC, which resulted in 100% long-term tumor cure, led to a marked reduction of vascular perfusion and increased tumor hypoxia at 1 h after treatment. Illumination at 48 h resulted in rapid regrowth of most tumors and only 10% cure. This protocol did not affect a significant decrease in vascular perfusion or increase in tumor hypoxia. These data show that optimal responses to mTHPC-mediated PDT were primarily dependent on the early vascular response, and that plasma drug levels at the time of illumination could predict this relationship.

Photodynamic therapy in the treatment of multiple primary tumours in the head and neck, located to the oral cavity and oropharynx

Objectives:  Multiple primary tumours are a common problem in the head and neck cancer patients. Curative surgery or radiotherapy of these tumours can be very mutilating or even impossible. This study aims at evaluating meta‐tetrahydroxy‐phenyl chlorin‐mediated photodynamic therapy for second or multiple primary tumours in the head and neck.

The importance of In situ light dosimetry for photodynamic therapy of oral cavity tumors

Photodynamic therapy (PDT) is being evaluated for treatment of localized head and neck cancer. “Light dose” is usually prescribed as incident fluence, which takes no account of reflected and scattered light. This study investigates variations in total tissue fluence for a given incident fluence in the oral cavity.

Does tumour uptake of Foscan determine PDT efficacy

Preferential retention of photosensitizers in tumours has always been one of the major goals in the search for new photosensitizers and has determined the design of clinical trials with respect to the interval between drug administration and illumination. The purpose of this study was to investigate the importance of tumour and plasma concentrations of Foscan (mTHPC, meta‐tetrahydroxyphenylchlorin) in relation to PDT effect. Both pharmacokinetic and tumour‐response studies were carried out in mice bearing s.c. RIF1 tumours. mTHPC was injected in 1 or 2 doses of 0.3 mg.kg\‐1. For distribution studies, 14C‐labelled mTHPC was given 5 min to 48 hr before determination of plasma and tumour drug levels. Non‐labelled sensitizer was used to determine the PDT efficacy for illumination at 5 min to 48 hr after drug administration. PDT efficacy was greatest for illumination at 1 to 3 hr, and for an interval of 48 hr there was no significant tumour‐growth delay. In contrast, mTHPC tumour drug levels reached a maximum 6 hr after injection and remained high for 48 hr. A comparison of pharmacokinetics and response studies revealed no significant correlation between tumour mTHPC levels and tumour response. There was, however, a significant correlation between plasma drug levels and tumour response for time intervals of 1 to 48 hr. This association may imply that PDT protocols should use shorter drug‐light intervals in combination with lower drug doses. This would increase safety and decrease the extent and duration of normal tissue photosensitization. Int. J. Cancer 73:236–239, 1997.

CELLULAR PHARMACOKINETICS OF CARBOPLATIN AND CISPLATIN IN RELATION TO THEIR CYTOTOXIC ACTION

We have studied the cellular pharmacokinetics of carboplatin (CBDCA), as part of the evaluation of the antitumor activity of CBDCA in cancers limited to the peritoneal cavity in comparison with cisplatin (cDDP). The uptake of CBDCA into L1210 (lymphosarcoma), CC531 (colonic carcinoma), COV413.B (human ovarian carcinoma) and NB1 (human neuroblastoma) cells was 1.5 to 13 times lower than the uptake of cDDP. The uptake of CBDCA into human ovarian carcinoma cells, taken directly from patients, was also 8-20 times lower than cDDP. Platinum concentrations, expressed as a percentage of the total intracellular Pt concentration, were similar for CBDCA and cDDP in cytosol and nucleus/membrane fractions. A second major difference between the drugs was their binding to DNA. Less CBDCA-DNA than cDDP-DNA adducts were formed after incubation at equimolar amounts of drug with isolated salmon sperm DNA (5-25 times less). A 16-69 times higher concentration of CBDCA than cDDP was needed to induce similar changes in cell growth activity (50% [3H]thymidine inhibition) in CC531 and COV413.B cells, indicating that equitoxicity can only be achieved when tumor cells are exposed to higher concentrations of CBDCA than cDDP. Similar toxicity was achieved in CC531 cells after incubation with a 16-fold higher CBDCA dose than cDDP. Comparable intracellular platinum concentrations, however, were obtained with a 10-fold higher CBDCA dose, suggesting that cellular pharmacokinetics of the drugs are different. Regarding drug uptake and pharmacokinetics the mechanism of action of CBDCA differed from cDDP at a cellular level.

Photodynamic therapy for malignant mesothelioma: preclinical studies for optimization of treatment protocols.

Abstract Effective photodynamic therapy (PDT) depends on the optimization of factors such as drug dose, drug–light interval, fluence rate and total light dose (or fluence). In addition sufficient oxygen has to be present for the photochemical reaction to occur. Oxygen deficits may arise during PDT if the photochemical reaction consumes oxygen more rapidly than it can be replenished, and this could limit the efficacy of PDT. In this study we investigated the influence of the drug–light interval, illumination-fluence rate and total fluence on PDT efficacy for the photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC). The effect of increasing the oxygenation status of tumors during PDT was also investigated. PDT response was assessed from tumor-growth delay and from cures for human malignant mesothelioma xenografts grown in nude mice. Tumor-bearing mice were injected intravenously with 0.15 or 0.3 mg·kg−1 mTHPC, and after intervals of 24–120 h, the subcutaneous tumors were illuminated with laser light (652 nm) at fluence rates of 20, 100 or 200 mW·cm−2. Tumor response was strongly dependent on the drug–light interval. Illumination at 24 h after photosensitization was always significantly more effective than illumination at 72 or 120 h. For a drug–light interval of 24 h the tumor response increased with total fluence, but for longer drug–light intervals even high total fluences failed to produce a significant delay in tumor regrowth. No fluence-rate dependence of PDT response was demonstrated in these studies. Nicotinamide injection and carbogen breathing significantly increased tumor oxygenation and increased the tumor response for PDT schedules with illumination at 24 h after photosensitizer injection.

Optimizing meso-tetra-hydroxyphenyl-chlorin-mediated photodynamic therapy for basal cell carcinoma.

Abstract Meso-tetra-hydroxyphenyl-chlorin (mTHPC)-mediated photodynamic therapy (PDT) has shown to be effective in the treatment of patients with multiple basal cell carcinoma (BCC). In the present study we further optimized the drug-light interval and examined the correlation between plasma drug levels and treatment efficacy. Thirteen patients with multiple BCC (a total of 366 lesions) were included in the study. Following intravenous administration of 0.1 mg kg−1 mTHPC, lesions were illuminated with 10 J cm−2 light (652 nm, 100 mW cm−2) at 12, 24, 48, 72 or 96 h. Plasma samples were taken prior to each illumination for determination of mTHPC levels, and tumor response was evaluated at 6 months and 1 year. Both univariable and multivariable analyses showed that optimal treatment outcome was obtained for a drug-light interval of 24 h when plasma drug levels were high. Overall, good cosmetic results with little or no scarring were obtained in 87% of the treated lesions and no serious side effects were observed. We optimized mTHPC-mediated PDT for patients suffering from multiple BCC by determining the most effective drug-light interval and showed that this treatment offers significant advantages over surgical resection.

Foscan-mediated photodynamic therapy for a peritoneal-cancer model: Drug distribution and efficacy studies

Distribution of the photosensitizer Foscan® (meta‐tetrahydroxyphenylchlorin, mTHPC), after i.v. or i.p. injection, was investigated in Wag/Rij rats bearing i.p. tumours. These results were compared with the efficacy of mTHPC‐mediated photodynamic therapy for illumination intervals of 4 hr to 3 days. For the distribution experiments a single tumour (CC531 colon carcinoma) was implanted intra‐abdominally in a fat pad, or a cell suspension (1 × 106 CC531 cells) was injected into the peritoneal cavity, which results in a dissemination of tumour nodules on the peritoneum. 14C‐mTHPC was not selectively taken up in the single‐tumour model after i.v. or i.p. injection, but higher concentrations were achieved for i.p. administration. For this tumour model the concentration ratios between tumour and normal tissue never exceeded a value of 3. In the disseminated‐tumour model, an uptake of up to 40% of the injected dose was found per gram tumour at 4 hr after an i.p. injection and this resulted in very high (>14) concentration ratios of tumour to normal tissues. Low uptake was found after the i.v. injection route (1% of the injected dose per gram tumour) with lower tumour/normal tissue ratios (<8). The efficacy of i.p. photodynamic therapy (IPPDT) was evaluated using the single‐tumour model only. The lower abdomen was illuminated at 4 hr to 3 days after mTHPC, and tumour size was repeatedly measured via a small laparoscopy. Significant delay in tumour regrowth was achieved for 6 J · cm−2 at 1 day after i.v., or at 4 hr after i.p. mTHPC (p values 0.019 and 0.045 respectively). Response to PDT, of tumours implanted in the fat pad, was not greater for i.p. administration of the photosensitizer and there was a poor correlation between times of maximum drug uptake in tumours and optimal illumination times for PDT efficacy. Int. J. Cancer 73:230–235, 1997.

Doppler optical coherence tomography to monitor the effect of photodynamic therapy on tissue morphology and perfusion

We investigated the feasibility of using optical coherence tomography (OCT) for noninvasive real-time visualization of the vascular effects of photodynamic therapy (PDT) in normal and tumor tissue in mice. Perfusion control measurements were initially performed after administrating vaso-active drugs or clamping of the subcutaneous tumors. Subsequent measurements were made on tumor-bearing mice before and after PDT using the photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC). Tumors were illuminated using either a short drug light interval (D-L, 3 h), when mTHPC is primarily located in the tumor vasculature or a long D-L interval (48 h), when the drug is distributed throughout the whole tumor. OCT enabled visualization of the different layers of tumor, and overlying skin with a maximal penetration of < or =0.5-1 mm. PDT with a short D-L interval resulted in a significant decrease of perfusion in the tumor periphery, to 20% of pre-treatment values at 160 min, whereas perfusion in the skin initially increased by 10% (at 25 min) and subsequently decreased to 60% of pre-treatment values (at 200 min). PDT with a long D-L interval did not induce significant changes in perfusion. The concept of using noninvasive OCT measurements for monitoring early, treatment-related changes in morphology and perfusion may have applications in evaluating effects of anti-angiogenic or antivascular (cancer) therapy.

Oxygen depletion during and after mTHPC-mediated photodynamic therapy in RIF1 and H-MESO1 tumors.

Abstract Schouwink, J. H., Oppelaar, H., Ruevekamp, M., Van der Valk, M., Hart, G., Baas, P. and Stewart, F. A. Oxygen Depletion during and after mTHPC-Mediated Photodynamic Therapy in RIF1 and H-MESO1 Tumors. Radiat. Res. 159, 190–198 (2003). During photodynamic therapy (PDT), low oxygenation levels, induced both by oxygen consumption and by vascular occlusion, can lead to an inefficient photochemical reaction that may compromise the efficacy of PDT. In the present studies, tumor oxygenation was measured before, during and after meta-tetrahydroxyphenylchlorin (mTHPC)-mediated PDT of murine RIF1 tumors and human mesothelioma xenografts (H-MESO1). Tumor pO2 was measured in real time with Eppendorf polarography, and the extent of relative hypoxia at specific times was measured by immunohistochemical staining. Significant decreases in median pO2 values, as well as an increase in the number of values below 2.5 mmHg, were seen during and after PDT in RIF1 tumors, although there was a large intertumoral variation. Tumor pO2 values did not change significantly in H-MESO1 tumors. Staining with antibodies against the hypoxia marker EF3 showed significant increases in relative hypoxia after PDT in both tumor types compared with separate groups of untreated controls. Our results are consistent with PDT-induced oxygen depletion (reduced pO2) leading to an increase in relative hypoxia in RIF1 tumors. Extensive necrosis in the H-MESO1 tumors may have prevented the detection of PDT-induced hypoxia using the Eppendorf polarographic needle, whereas immunohistochemistry did reveal increases in relative hypoxia.