Tumor treatment by sustained intratumoral release of cisplatin: effects of drug alone and combined with radiation

Dual enhancement in the radiosensitivity of prostate cancer through nanoparticles and chemotherapeutics

Background

Radiotherapy (RT) is an essential component in the treatment regimens for many cancer patients. However, the dose escalation required to improve curative results is hindered due to the normal tissue toxicity that is induced. The introduction of radiosensitizers to RT treatment is an avenue that is currently being explored to overcome this issue. By introducing radiosensitizers into tumor sites, it is possible to preferentially enhance the local dose deposited. Gold nanoparticles (GNPs) are a potential candidate that have shown great promise in increasing the radiosensitivity of cancer cells through an enhancement in DNA damage. Furthermore, docetaxel (DTX) is a chemotherapeutic agent that arrests cells in the G2/M phase of the cell cycle, the phase most sensitive to radiation damage. We hypothesized that by incorporating DTX to GNP-enhanced radiotherapy treatment, we could further improve the radiosensitization experienced by cancer cells. To assess this strategy, we analyzed the radiotherapeutic effects on monolayer cell cultures in vitro, as well as on a mice prostate xenograft model in vivo while using clinically feasible concentrations for both GNPs and DTX.

Results

The introduction of DTX to GNP-enhanced radiotherapy further increased the radiotherapeutic effects experienced by cancer cells. A 38% increase in DNA double-strand breaks was observed with the combination of GNP/DTX vs GNP alone after a dose of 2 Gy was administered. In vivo results displayed significant reduction in tumor growth over a 30-day observation period with the treatment of GNP/DTX/RT when compared to GNP/RT after a single 5 Gy dose was given to mice. The treatment strategy also resulted in 100% mice survival, which was not observed for other treatment conditions.

Conclusions

Incorporating DTX to work in unison with GNPs and RT can increase the efficacy of RT treatment. Our study suggests that the treatment strategy could improve tumor control through local dose enhancement. As the concentrations used in this study are clinically feasible, there is potential for this strategy to be translated into clinical settings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12645-023-00228-0.

Nanotechnology Driven Cancer Chemoradiation: Exploiting the Full Potential of Radiotherapy with a Unique Combination of Gold Nanoparticles and Bleomycin

One of the major issues in current radiotherapy (RT) is the associated normal tissue toxicity. Enhancement of the RT effect with novel radiosensitizers can address this need. In this study, gold nanoparticles (GNPs) and bleomycin (BLM) were used as a unique combination of radiosensitizers. GNPs offer a two-fold promise as a delivery vehicle for BLM and as a radiosensitizing agent. In this study, GNPs were functionalized and complexed with BLM using a gold-thiol bond (denoted GNP-BLM). Our results show that there was a 40% and 10% decrease in cell growth with GNP-BLM vs. free BLM for the MIA PaCa-2 and PC-3 cell lines, respectively. Testing the GNP-BLM platform with RT showed an 84% and 13% reduction in cell growth in MIA PaCa-2 cells treated with GNP-BLM and GNPs, respectively. Similar results were seen with PC-3 cells. The efficacy of this approach was verified by mapping DNA double-strand breaks (DSBs) as well. Therefore, this proposed incorporation of nanomedicine with RT is promising in achieving a significantly higher therapeutic ratio which is necessary to make a paradigm change to the current clinical approach.

Targeting of radio-enhancing drugs

OBJECTIVE

Toxicity to normal tissue is frequently the dose-limiting factor in the chemotherapy and mixed modality treatments of cancer. If the radio-enhancing drug could be localized at the disease site and released slowly over time, then systemic drug toxicities could be decreased while simultaneously maintaining high drug concentrations in the tumor. These considerations support a role for a sustained release intra-tumoral delivery systems for the delivery of radio-enhancing drugs.

METHODS

Two approaches aimed at achieving the end of localizing the radio-enhancing drug to the tumor are described. First, nanoparticles, which have a prolonged circulation time and facility for enhanced tumor targeting. Structural defects in the walls of the tumor vasculature allow the passage of particles too large to pass through the walls of normal blood vessels. This characteristic of tumor blood vessels, referred to as the enhanced permeability and retention (EPR) effect, allows relatively large entities (typically liposomes, nanoparticles, and macromolecular drugs) to pass from the blood vessels to tumor tissue and as a result nanoparticles accumulate in the tumor while being excluded from normal tissue. Second, biodegradable implanted polymers. In these devices, the radio-enhancing drug is physically trapped within the polymer matrix which is implanted in the tumor. The drug is released as the polymer degrades in response to its local environment. The degradation rate of the polymer device can be adjusted to control the rate of drug release. By this means, the level of radio-enhancing drug can be maintained at the tumor site for the duration of radiation treatment.

RESULTS AND CONCLUSIONS

Results of experiments indicate that for both methods tumor control could be optimized by maintaining the radio-enhancing drug at a useful concentration in the tumor over a period of time compatible with the duration of fractionated radiation treatment. These studies have provided proof of principle support for the further development of this approach. To date, while some of the methods and devices for drug delivery described in this paper have been involved in clinical trials, none have so far been developed for routine clinical application.

A ceramic-based anticancer drug delivery system to treat breast cancer

Drug delivery systems offer the advantage of sustained targeted release with minimal side effect. In the present study, the therapeutic efficacy of a porous silica-calcium phosphate nanocomposite (SCPC) as a new delivery system for 5-Fluorouracil (5-FU) was evaluated in vitro and in vivo. In vitro studies showed that two formulations; SCPC50/5-FU and SCPC75/5-FU hybrids were very cytotoxic for 4T1 mammary tumor cells. In contrast, control SCPCs without drug did not show any measurable toxic effect. Release kinetics studies showed that SCPC75/5-FU hybrid provided a burst release of 5-FU in the first 24 h followed by a sustained release of a therapeutic dose (30.7 microg/day) of the drug for up to 32 days. Moreover, subcutaneous implantation of SCPC75/5-FU hybrid disk in an immunocompetent murine model of breast cancer stopped 4T1 tumor growth. Blood analyses showed comparable concentrations of Ca, P and Si in animals implanted with or without SCPC75 disks. These results strongly suggest that SCPC/5-FU hybrids can provide an effective treatment for solid tumors with minimal side effects.

Enhancement of carboplatin toxicity by Pluronic block copolymers

The objective of this study was to examine the effects of three Pluronic triblock copolymers (F127, P85, or L61) on the cytotoxicity of carboplatin to the DHB/K12/TRb rat colorectal carcinoma cell line. Studies to determine the dependence of the sensitization effect on Pluronic dose were carried out for polymer concentrations ranging from 0.0001-10% (w/w). To establish the carboplatin toxicity and its potential enhancement by Pluronic, the drug was delivered to cells in doses ranging from 0-0.5% (w/w) in the presence of Pluronic at a constant concentration. These treatment groups were compared to control groups receiving carboplatin alone. Cell cytotoxicity resulting from the treatments was determined with a mitochondrial enzyme activity assay (WST-1), while cell morphology was examined with May-Grünwald and Giemsa staining. Results indicate that the greatest enhancement of carboplatin toxicity was induced by P85, where the inhibitory concentration (IC(50)) was reduced by 50% (from 0.096 mg/mL for carboplatin alone to 0.048 mg/mL in presence of P85). L61 was toxic to the cells with or without drug (viability<3.5%), while F127 exhibited no sensitizing effect and in some cases increased the cell viability to 130% over the untreated control. The WST-1 results were confirmed by trypan blue exclusion cell counts at 0 and 24 h post treatment. Data conclusively demonstrate that Pluronic P85 is the optimal agent for increased cytotoxicity of carboplatin in this cell line and can potentially be used not only as a drug delivery scheme but also as a chemosensitizing agent in future cancer therapy.

Sensitization to Radiation from an Implanted125I Source by Sustained Intratumoral Release of Chemotherapeutic Drugs

We have investigated tumor response to low-dose-rate irradiation from an implanted 125I source alone or in conjunction with intratumoral drug administration. The drug (cis-DDP or 5-FU) was incorporated homogeneously into the co-polymer CPP-SA, 20:80, and the polymer/drug rods were implanted in the RIF-1 fibrosarcomas growing subcutaneously in C3H mice. Twenty-four hours later, the tumor was implanted with an 125I seed. Tumor growth time was the end point in these experiments. For implanted 125I sources of different dose rates and implant times giving a range of total doses, a consistent dose-response relationship was shown between tumor growth time and total dose. In other experiments, 125I sources of different specific activities were implanted for periods of time adjusted so that the total dose to the tumor was always the same. When the 125I implant was combined with 5-FU, greater than additive responses were seen for both short (30 h) and long (96 h) 125I treatment times. In contrast, a short-duration (30 h) 125I implant combined with cis-DDP was the least effective treatment, giving a combined response that was no better than additive, whereas 96 h exposure to 125I combined with cis-DDP was the most effective combined treatment. It is conjectured that this inverse dose-rate effect seen when cis-DDP is combined with low-dose rate radiation is related to a cell cycle effect and/or to inhibition of repair of radiation damage by cis-DDP.

Treatment of intracranial rat glioma model with implant of radiosensitizer and biomodulator drug combined with external beam radiotherapy

PURPOSE

To evaluate an intracranial polymer implant containing bromodeoxyuridine (BrdUrd) and N-(phosphonacetyl)-L-aspartic acid (PALA) in combination with external beam radiotherapy (EBRT) in the treatment of a rat glioma.

METHODS AND MATERIALS

Combinations of the biomodulators 5-fluorouracil, methotrexate, or PALA with BrdUrd were evaluated as radiosensitizers in vitro by clonogenic assay. In in vivo experiments, BrdUrd and PALA were incorporated into a polyanhydride-based polymer, bis(p-carboxyphenoxy)propane sebacic acid, and implanted in the C6 rat glioma growing intracranially. The effectiveness of treatment was evaluated on the basis of survival. EBRT was given as 10-MV X-rays.

RESULTS

In tissue culture experiments, C6 cells were refractory to radiosensitization by BrdUrd even when the thymidine analog was combined with a biomodulator intended to reduce de novo thymidine synthesis. The most effective compound in vitro was PALA. When PALA and BrdUrd in a polymer formulation were implanted intracranially and combined with 10-Gy EBRT, the treatment was highly effective, with 83% of treated rats surviving 180 days.

CONCLUSION

Although the in vitro results were not encouraging, the combination of intratumoral BrdUrd and PAL with 10-Gy EBRT was highly effective in treating a rat glioma. These results indicate the clinical potential of combined and mixed modality treatments involving intratumoral sustained-release drug delivery.

Etanidazole-loaded microspheres fabricated by spray-drying different poly(lactide/glycolide) polymers: effects on microsphere properties

In this work, a spraying technique was used to encapsulate etanidazole (a hypoxic radiosensitizer) into different poly(lactide/glycolide) polymers. The properties of the obtained microspheres, especially the particle size and distribution, morphology and release rate were investigated. Unexpectedly, poly(L-lactide) (PLLA) shows a fast release rate, comparable to PLGA 50: 50, due to the dissociation of the microspheres although the release rate of the spray-dried microspheres of other polymers decreases with increasing lactide ratio. It is also interesting to note that, contrary to the viscosity sequence of the polymer solutions, the particle size of the microspheres decreases in the order PLGA 50: 50, PLGA 65: 35, PLGA 85: 15 and PDLA. The morphology of microspheres can be affected by polymer properties (e.g. lactide/glycolide ratio, molecular weight, crystallinity and Tg) and fabrication conditions (e.g. solvent and polymer concentration to be sprayed). Although most of the microspheres fabricated by EA have a donghnut-like shape with smooth surface, it is possible to obtain spherical particles by choosing proper polymer type and polymer concentration. A further examination of the mechanisms of the atomization process and the solvent evaporation process reveals their respective effect on droplet formation and particle formation, both of which are essential for the spray-drying technique. It is found that polymer phase transition (affected by the polymer solubility) and its subsequent solvent evaporation processes can finally determine the morphology and the particle size of the spray-dried particles made from different polymers. In essence, the lactide/glycolide ratio of the polymers plays a more important role in affecting the properties of the spray-dried microspheres.

Transscleral permeability and intraocular concentrations of cisplatin from a collagen matrix

This study determined the in vitro permeability of cisplatin through isolated human sclera as delivered by a collagen matrix vehicle. Short-term and long-term intraocular levels of cisplatin were also measured in the rabbit eye after a subconjunctival injection. Cisplatin in either a collagen matrix vehicle or a control balanced salt solution (BSS) vehicle was applied to human sclera mounted in a specially designed in vitro perfusion chamber. The amount of cisplatin that diffused across the sclera was measured in hourly samples for 24 h using atomic absorption spectrometry. In vivo studies were also performed in Dutch Belted rabbits given subconjunctival injections of cisplatin in collagen matrix or in BSS. Eyes were enucleated at 1.5 h and 2 weeks after injection, frozen, and dissected to determine the intraocular cisplatin concentrations. Cisplatin had a peak in vitro scleral permeability constant of 8.3+/-1.2 x 10(-6) and 20.1+/-1.8 x 10(-6) cm/s, delivered in collagen matrix and in BSS, respectively (mean+/-S.D.). At the end of the in vitro experiments, 35.9+/-4.6% of the cisplatin remained in the collagen matrix, while 0.8+/-0.2% remained in the BSS vehicle. Subconjunctival injection of cisplatin in the collagen matrix vehicle achieved 3.3+/-0.1 microg/ml in the vitreous humor at 1.5 h and 0.1+/-0.1 microg/ml at 2 weeks. This vehicle also achieved a cisplatin concentration of 73.5+/-23.9 microg/mg in the choroid and retina at 1.5 h and 3.2+/-1.3 microg/mg at 2 weeks. Compared to BSS, the collagen matrix vehicle provided a more controlled release of cisplatin, and after subconjunctival injection into rabbits, attained higher drug levels in several ocular tissues.

Formation of DNA adducts and tumor growth delay following intratumoral administration of DTI-015

Intratumoral (IT) administration of DTI-015 (BCNU in 100% ethanol) utilizes solvent facilitated perfusion for the treatment of tumors. RIF-1 tumors were treated by IT injection of either ethanol alone or 0.05-1.0 mg of DTI-015 or by i.v. injection of 0.5 mg of BCNU. Treatment with ethanol alone or i.v. injection of 0.5 mg of BCNU did not produce a significant growth delay. In contrast, IT administration of DTI-015 produced a significant growth delay at each of the treatment doses (p < 0.05 to p < 0.001). We have quantified the levels of N7-(2-hydroxyethyl) guanine (N7-HOEtG) in RIF-1 tumors 24h following either IT treatment with 0.5 mg DTI-015 or i.p. administration of 0.5 mg BCNU. Levels of N7-HOEtG (micromol/mol DNA) were < or = 0.08 for both untreated controls and following i.p. treatment with BCNU and 13.1 +/- 5.6 following IT administration of DTI-015. The levels of N7-HOEtG detected in RIF-1 tumors following IT administration of DTI-015 were 164-fold higher than the level(s) of N7-HOEtG in the i.p. BCNU treated tumor samples. These studies demonstrate that IT administration of DTI-015 produces high levels of DNA adducts in the tumor which correspond to a significant increase in tumor growth delay compared to the same dose of BCNU administered systemically.

Ceramic drug delivery: a perspective

Different ceramic substances are offered in the market as bone substitute materials. These include monophasic calcium phosphate ceramics of tricalciumphosphate (TCP) or hydroxyapatite (HA), biphasic calcium phosphate ceramics and multiphasic bio-glasses synthetic calcium phosphate cements. Ceramics with appropriate three-dimensional geometry are able to bind and concentrate bone morphogenetic proteins in circulation and may become osteoinductive (capable of osteogenesis) and can be effective carriers of bioactive peptide or bone cell seeds and are therefore potentially useful in tissue engineering and drug delivery. An attempt has been made to review various drug delivery applications of ceramics.

Tumor treatment by sustained intratumoral release of 5-fluorouracil: effects of drug alone and in combined treatments

PURPOSE

To evaluate an intratumoral polymer implant for sustained delivery of 5-fluorouracil (5-FU) in a mouse tumor model.

METHODS AND MATERIALS

5-FU was incorporated into a polyanhydride-based polymer, bis(p-carboxyphenoxy)propane sebacic acid (CPP:SA) and implanted in RIF-1 mouse fibrosarcoma growing s.c. The effectiveness of treatment was evaluated by tumor growth delay. External beam radiation was 60Co gamma rays, and the source of interstitial radiation was implanted 125I seeds. A second drug, cis-diamminedichloroplatinum (cis-DDP), was administered by intraperitoneal injection or by osmotic pump.

RESULTS

For drug/polymer implant alone, the tumor growth delay was proportional to the amount of drug in the implant. The 5-FU polymer implant was most effective when combined with cis-DDP or with acute or fractionated radiation, and in some cases, the effects of combined treatments were greater than additive. The most effective combination was intratumoral 5-FU and low-dose-rate radiation delivered from an interstitial radiation source.

CONCLUSION

Results indicate that 5-FU can be effectively delivered by polymer implant and that this mode of delivery is particularly appropriate for combined treatments.

Controlled release of rhodium (II) carboxylates and their association complexes with cyclodextrins from hydroxyapatite matrix

Preparation and characterization of a controlled release system of rhodium (II) citrate, acetate. propionate, butyrate and their inclusion or association compounds with cyclodextrin (CD) are described. The porous hydroxyapatite (HA) was characterized by X-ray powder pattern diffraction, FTIR and solid state 31P NMR. Scanning electron microscopy and gas adsorption analysis (BET) were also performed. Release profiles of rhodium (II) carboxylates and their inclusion or association compounds from HA matrix were obtained at different drug loadings (5% and 10%). These were reasonably consistent with a diffusion model. This analysis, mainly using rhodium (II) citrate and butyrate, showed that the strategy of using CDs with a HA matrix may offer a useful new method for the controlled release of these compounds, and hence an alternative strategy for the controlled release of chemotherapeutic agents containing toxic metals. This may be a valuable new technique for localized anti-tumour chemotherapy that minimizes the side effects of such agents.

Intratumoral cancer chemotherapy and immunotherapy: opportunities for nonsystemic preoperative drug delivery

The recent literature documents the growing interest in local intratumoral chemotherapy as well as systemic preoperative chemotherapy with evidence for improved outcomes using these therapeutic modalities. Nevertheless, with few exceptions, the conventional wisdom and standard of care for clinical and surgical oncology remains surgery followed by radiation and/or systemic chemotherapy, as deemed appropriate based on clinical findings. This, in spite of the fact that the toxicity of conventional systemic chemotherapy and immunotherapy affords limited effectiveness and frequently compromises the quality of life for patients. Indeed, with systemic chemotherapy, the oncologist (and the patient) often walks a fine line between attempting tumour remission with prolonged survival and damaging the patient's vital functions to the point of death. In this context, it has probably been obvious for more than 100 years, due in part to the pioneering work of Ehrlich (1878), that targeted or localized drug delivery should be a major goal of chemotherapy. However, there is still only limited clinical use of nonsystemic intratumoral chemotherapy for even those high mortality cancers which are characterized by well defined primary lesions i.e. breast, colorectal, lung, prostate, and skin. There has been a proliferation of intratumoral chemotherapy and immunotherapy research during the past two to three years. It is therefore the objective of this review to focus much more attention upon intratumoral therapeutic concepts which could limit adverse systemic events and which might combine clinically feasible methods for localized preoperative chemotherapy and/or immunotherapy with surgery. Since our review of intratumoral chemoimmunotherapy almost 20 years ago (McLaughlin & Goldberg 1983), there have been few comprehensive reviews of this field; only one of broad scope (Brincker 1993), three devoted specifically to gliomas (Tomita 1991; Walter et al. 1995; Haroun & Brem 2000), one on hepatomas (Venook 2000), one concerning veterinary applications (Theon 1998), and one older review of dermatological applications (Goette 1981). However, none have shed light on practical opportunities for combining intratumoral therapy with subsequent surgical resection. Given the state-of-the-art in clinical and surgical oncology, and the advances that have been made in intratumoral drug delivery, minimally invasive tumour access i.e. fine needle biopsy, new drugs and drug delivery systems, and preoperative chemotherapy, it is timely to present a review of studies which may suggest future opportunities for safer, more effective, and clinically practical non-systemic therapy.

Improvement of combined modality therapy with cisplatin and radiation using electroporation of tumors

PURPOSE

To evaluate whether a local drug delivery method, i.e., electroporation of tumors, increases the radiosensitizing effect of cisplatin.

METHODS AND MATERIALS

Subcutaneous Ehrlich-Lettre ascites (EAT) tumors in CBA mice were treated either by cisplatin, electric pulses, or ionizing radiation. In electrochemotherapy protocol, electric pulses were given to the tumor 3 min after intravenous injection of cisplatin. The interval between electrochemotherapy and irradiation was 20 min. Treatment effectiveness was evaluated by tumor growth delay and local tumor curability.

RESULTS

Electrochemotherapy of EAT tumors proved to be effective treatment, resulting in 12% tumor cures, whereas treatment with cisplatin or electric pulses alone did not yield any tumor cures. As expected, injection of cisplatin 20 min prior to irradiation, increased radioresponse of tumors from 27% to 73% tumor cures. Electroporation of tumors also increased radiation response of tumors to 54% tumor cures. Electrochemotherapy given prior to irradiation increased radioresponsiveness of tumors, resulting in 92% tumor cures.

CONCLUSIONS

This study shows that delivery of cisplatin into the cells by electroporation of tumors increases the radiosensitizing effect of cisplatin. However, some effect may also be ascribed to application of electric pulses to the tumors that in our study also predisposed tumor cells to radiation damage.

Radiosensitization of a mouse tumor model by sustained intra-tumoral release of etanidazole and tirapazamine using a biodegradable polymer implant device

BACKGROUND AND PURPOSE

Drug toxicities are often a limiting factor in long term treatment regimes used in conjunction with radiotherapy. If the drug could be localized to the tumor site and released slowly, then optimal, intra-tumoral drug concentrations could be achieved without the cumulative toxicity associated with repeated systemic drug dosage. In this paper we describe the use of a biodegradable polymer implant for sustained intra-tumoral release of high concentrations of drugs targeting hypoxic cells.

MATERIALS AND METHODS

The RIF-1 tumor was implanted subcutaneously or intramuscularly in C3H mice and irradiated with 60Co gamma rays. The drug delivery device was the co-polymer CPP-SA;20:80 into which the drug was homogeneously incorporated. The hypoxic radiosensitizer Etanidazole or the bioreductive drug Tirapazamine were delivered intra-tumorally by means of implanted polymer rods containing the drugs. Tumor growth delay (TGD) was used as the end point in these experiments.

RESULTS

Both Etanidazole and Tirapazamine potentiated the effects of acute and fractionated radiation in the intra-muscular tumors but neither drug was effective in sub-cutaneous tumors. Since both drugs target hypoxic cells we hypothesized that the lack of effect in the subcutaneous tumor was attributable to the smaller size of the hypoxic fraction in this tumor model. This was confirmed using the hypoxia marker EF5.

CONCLUSIONS

These results indicate that the biodegradable polymer implant is an effective vehicle for the intra-tumoral delivery of Etanidazole and Tirapazamine and that, in conjunction with radiation, this approach could improve treatment outcome in tumors which contain a sub-population of hypoxic, radioresistant cells.

The potentiation of the effect of radiation treatment by intratumoral delivery of cisplatin

PURPOSE

To compare potentiation of the effects of acute or fractionated radiation by cisplatin when the drug was delivered intratumorally by implanted biodegradable polymer, by intraperitoneal injection, or by intraperitoneal osmotic pump.

METHODS AND MATERIALS

Radiation was delivered to a mouse tumor (RIF-1) either in a single dose or in a fractionated regime in conjunction with cisplatin delivered either as a bolus injection, with an osmotic pump, or with a biodegradable polymer rod containing cisplatin. The osmotic pump was implanted in the intraperitoneal cavity of the mouse while the polymer implants were placed directly in the tumor. As the polymer degrades, the drug is released at the treatment site leading to high local concentrations. The osmotic pump, in contrast, leads to prolonged systemic exposure to the drug at low concentrations. Tumor growth delay (TGD) was used as an endpoint in these experiments.

RESULTS

The most effective treatment protocol, in terms of potentiating the effects of radiation was cisplatin delivered by polymer implanted 2 days before an acute dose of radiation (growth modification factor [DMF] = 2.2). Comparison of single and multifraction regimes where polymer implant was on the same day as the commencement of treatment showed greater potentiation of the effect of fractionated than of acute radiation treatment with the DMF for fractionated treatment remaining relatively constant (1.5-1.9) for 5, 8, and 12 fraction treatments. Cisplatin delivered via the osmotic pump did not deliver a high enough dose of cisplatin to produce therapeutic effect in this mouse tumor model and had little impact on response to treatment.

CONCLUSIONS

Our results indicated that cisplatin delivered intratumorally by biodegradable polymer implant was effective in potentiating the effect of both acute and fractionated radiation. For the fractionated treatments the effect was maintained with increasing fraction numbers and treatment time.