Intraarterial iododeoxyuridine infusion combined with irradiation. A pilot study

Radiotherapy for liver metastases: a review of evidence

Over the past decade, there has been an increasing use of radiotherapy (RT) for the treatment of liver metastases. Most often, ablative doses are delivered to focal liver metastases with the goal of local control and ultimately improving survival. In contrast, low-dose whole-liver RT may be used for the palliation of symptomatic diffuse metastases. This review examines the available clinical data for both approaches. The review found that RT is effective both for local ablation of focal liver metastases and for palliation of patients with symptomatic liver metastases. However, there is a lack of a high level of evidence from randomized clinical trials.

Clinical significance of atomic inner shell ionization (ISI) and Auger cascade for radiosensitization using IUdR, BUdR, platinum salts, or gadolinium porphyrin compounds

PURPOSE

Halogenated pyrimidines (iododeoxyuridine [IUdR] and bromodeoxyuridine [BUdR]), platinum salts, and gadolinium porphyrins are heavy atom compounds used as radiosensitizers. For IUdR, it has been hypothesized that iodine inner shell ionizations (ISI) and Auger cascades could be one of the primary radiosensitization mechanisms. The purpose of this paper is to estimate the number of ISI produced per tumor cell and per 2 Gy irradiation in clinically relevant modelings.

MATERIALS AND METHODS

ISI were evaluated using a two-step method. Photon-induced ISI were calculated using the MCNP-4C Monte Carlo code, heavy atom concentrations from clinical data published in the literature, and at various depths in a water phantom irradiated with 6-MV, (60)Co, (137)Cs, or (192)Ir sources. Electron knock-on induced ISI on K, L, and M atomic shells were evaluated with an hybrid method, using simulated electron spectra and cross-sections derived from the Møller formalism. Using a biological dose equivalence of 0.05 Gy per cell ISI, relative biological effectiveness (RBE) values were calculated for each situation.

RESULTS

For platinum and gadolinium, ISI occurs in far less than 0.1% of the cell, whichever is the configuration. For IUdR and BUdR, ISI occurs in between 45% to 483% of the cell. Due to spectrum degradation, about 3 times more photoelectric ISI are generated at greater than shallower depths, and 10 times more for (192)Ir compared with (60)Co or 6-MV X-rays. Photoelectric ISI are about 3 times more frequent for iodine than bromine, but electron knock-on ISI are more frequent on bromine, and at the end about the same number of ISI are generated for both elements. RBEs were found to be between 1.01 and 1.12 for clinically relevant irradiation settings.

CONCLUSIONS

The mechanisms of radiosensitization for platinum and gadolinium are clearly not related to an Auger cascade. For halogenated pyrimidines, however, clinically relevant numbers of ISI are generated within each cell. For IUdR, ISI appears to be strongly tied to the photon spectra. Halogenated pyrimidines should be evaluated again clinically, but using lower energy photons like a (192)Ir implant.

IUdR polymers for combined continuous low-dose rate and high-dose rate sensitization of experimental human malignant gliomas

Local polymeric delivery enhances IUdR radiosensitization of human malignant gliomas (MG). The combined low-dose rate (LDR) (0.03 Gy/h) and fractionated high-dose rate (HDR) treatments result in cures of experimental MGs. To enhance efficacy, we combined polymeric IUdR delivery, LDR, and HDR for treatments of both subcutaneous and intracranial MGs. In vitro: Cells (U251 MG) were trypsinized and replated in triplicate 1 day prior to LDR irradiation in media either without (control) or with 10 microM IUdR. After 72 hr, LDR irradiation cells were acutely irradiated (1.1 Gy/min) with increasing (0, 1.25, 2.5, 5.0, or 10 Gy) single doses. Implantable IUdR polymers [(poly(bis(p-carboxyphenoxy)-propane) (PCPP): sebaic acid (PCPP:SA), 20:80] (50% loading; 10 mg) were synthesized. In vivo: For flank vs. intracranial tumors, mice had 6 x 10(6) subcutaneous vs. 2 x 10(5) intracranial cells. For intracranial or subcutaneous MGs, mice had intratumoral blank (empty) vs. IUdR polymer treatments. One day after implantation, mice had immediate external LDR (3 cGy/h x 3 days total body irradiation) or HDR (2 Gy BID x 4 days to tumor site) or concurrent treatments. For the in vitro IUdR treatments, LDR resulted in a striking increase in cell-killing when combined with HDR. For the in vivo LDR treatments of flank tumors, the growth delay was greater for the IUdR vs. blank polymer treatments. For the combined LDR and HDR, the IUdR treatments resulted in a dramatic decrease in tumor volumes. On day 60 the log V/V0 were -1.7 +/- 0.22 for combined LDR + HDR + IUdR polymer (P < 0.05 vs. combined LDR + HDR + blank polymer). Survival for the intracranial controls was 22.9 +/- 1.2 days. For the blank polymer + LDR vs. blank polymer + LDR + HDR treatments, survival was 25.3 +/- 1.7 (P = NS) vs. 48.1 +/- 3.5 days (P < 0.05). For IUdR polymer + LDR treatment survival was 27.3 +/- 2.3 days (P = NS). The most striking improvement in survival followed the IUdR polymer + LDR + HDR treatment: 66.0 + 6.4 days (P < 0.05 vs. blank polymer + LDR + HDR). The polymeric IUdR delivery plus combined continuous LDR and HDR treatments results in growth delay and improved survival in animals bearing the MG xenografts. This treatment may hold promise for the treatment of human MGs.

Synthetic, implantable polymers for IUdR radiosensitization of experimental human malignant glioma

BACKGROUND

Recently, polymeric controlled delivery of chemotherapy has been shown to improve survival of patients with malignant glioma. We tested the delivery of IUdR via polymers for radiosensitization of experimental intracranial human malignant glioma. To assess efficacy, we measured the in vitro release, the in vivo delivery of IUdR and the resultant radiosensitization of experimental human U251 glioblastoma xenografts.

METHODS

In vitro: To measure release, increasing (10%, 30%, 50%) proportions of IUdR in synthetic [(poly(bis(p-carboxyphenoxy)-propane) (PCPP):sebacic acid (SA) polymer discs were serially incubated in buffered saline and the supernatant fractions were assayed. In vivo: To compare local vs. systemic delivery, mice bearing flank xenografts had intratumoral or contralateral flank IUdR polymer (50% loading) treatments. Mice bearing intracranial (i.c.) xenografts had i.c. vs. flank IUdR polymer treatments. Four or 8 days after implantation of polymers, mice were sacrificed and the percentage tumor cells that were labeled with IUdR was measured using quantitative microscopic immunohistochemistry. For comparisons of radiosensitization, mice bearing i.c. xenografts had i.c. vs. flank IUdR polymers and cranial fractionated external beam irradiation (2 Gy BID x 4 days).

RESULTS

In vitro: Increasing percentage loadings of IUdR resulted in higher percentages of release: 43.7 +/- 0.1, 70.0 +/- 0.2, and 90.2 +/- 0.2 (p < 0.001 ANOVA) for the 10, 30, and 50% loadings, respectively. In vivo: For the flank tumors, both the ipsilateral and contralateral IUdR polymers resulted in similarly high percentages labeling of the tumors vs. time. For the ipsilateral IUdR polymers, the percentages of tumor cellular labeling after 4 vs. 8 days were 45.8 +/- 7.0 vs. 40.6 +/- 3.9 (p = NS. For the contralateral polymer implants, the percentages tumor cellular labeling were 43.9 +/- 10.1 vs. 35.9 +/- 5.2 (p = NS) measured 4 vs. 8 days after implantation. For the i.c. tumors treated with extracranial IUdR polymers, the percentages of tumor cellular labeling were low: 13.9 +/- 8.8 and 11.2 +/- 5.7 measured 4 and 8 days after implantation. For the i.c. tumors having the i.c. IUdR polymers, however, the percentages labeling were comparatively much higher: 34.3 +/- 4.9 and 35.3 +/- 4.0 on days 4 and 8, respectively. For the i.c. tumors, examination of the percentage cellular labeling vs. distance from the implanted IUdR polymer showed labeling was highest closest to the polymer disc. Radiosensitization: For mice bearing i.c. tumors and receiving flank vs. intracranial IUdR polymer treatments, the survival after external beam irradiation was significantly higher for the intracranial treatments: 49 + 8.9 vs. 80 + 4.1 (p = 0.03) days, respectively.

CONCLUSIONS

Implantable biodegradable polymers provide the local, controlled release of IUdR and result in the high, local delivery of IUdR to experimental intracranial human malignant glioma. The local delivery and labeling result in improved survival following radiotherapy. This technique holds promise for the local delivery of IUdR for radiosensitization of human brain tumors.

Synthetic, implantable polymers for local delivery of IUdR to experimental human malignant glioma

PURPOSE

Recently, polymeric controlled delivery of chemotherapy has been shown to improve survival of patients with malignant glioma. We evaluated whether we could similarly deliver halogenated pyrimidines to experimental intracranial human malignant glioma. To address this issue we studied the in vitro release from polymers and the in vivo drug delivery of IUdR to experimental human U251 glioblastoma xenografts.

METHODS AND MATERIALS

In vitro: To measure release, increasing (10%, 30%, 50%) proportions of IUdR in synthetic [(poly(bis(p-carboxyphenoxy)-propane) (PCPP):sebacic acid (SA) polymer discs were serially incubated in buffered saline and the supernatant fractions were assayed. In vivo: To compare local versus systemic delivery, mice bearing flank xenografts had intratumoral or contralateral flank IUdR polymer (50% loading) treatments. Mice bearing intracranial (i.c.) xenografts had i.c. versus flank IUdR polymer treatments. Four or 8 days after implantation of polymers, mice were sacrificed and the percentage tumor cells that were labeled with IUdR was measured using quantitative microscopic immunohistochemistry.

RESULTS

In vitro: Increasing percentage loadings of IUdR resulted in higher percentages of release: 43.7 + 0.1, 70.0 + 0.2, and 90.2 + 0.2 (p < 0.001 ANOVA) for the 10%, 30%, and 50% loadings, respectively. In vivo: For the flank tumors, both the ipsilateral and contralateral IUdR polymers resulted in similarly high percentages labeling of the tumors versus time. For the ipsilateral IUdR polymers, the percentage of tumor cellular labeling after 4 days versus 8 days was 45.8 +/- 7.0 versus 40.6 +/- 3.9 (p = NS). For the contralateral polymer implants, the percentage of tumor cellular labeling were 43.9 +/- 10.1 versus 35.9 +/- 5.2 (p = NS) measured 4 days versus 8 days after implantation. For the i.c. tumors treated with extracranial IUdR polymers, the percentage of tumor cellular labeling was low: 13.9 +/- 8.8 and 11.2 +/- 5.7 measured 4 and 8 days after implantation. For the i.c. tumors having the i.c. IUdR polymers, however, the percentage labeling was comparatively much higher: 34.3 +/- 4.9 and 35.3 +/- 4.0 on days 4 and 8, respectively. For the i.c. tumors, examination of the percentage cellular labeling versus distance from the implanted IUdR polymer showed that labeling was highest closest to the polymer disc.

CONCLUSION

Synthetic, implantable biodegradable polymers provide the local, controlled release of IUdR and result in the high, local delivery of IUdR to experimental intracranial human malignant glioma. This technique holds promise for the local delivery of IUdR for radiosensitization of human brain tumors.

Implantable biodegradable polymers for IUdR radiosensitization of experimental human malignant glioma

PURPOSE

The potential of halogenated pyrimidines for the radiosensitization of human malignant gliomas remains unrealized. To assess the role of local delivery for radiosensitization, we tested a synthetic, implantable biodegradable polymer for the controlled release of 5-iodo-2'-deoxyuridine (IUdR) both in vitro and in vivo and the resultant radiosensitization of human malignant glioma xenografts in vivo.

MATERIALS AND METHODS

In vitro: To measure release, increasing (10%, 30%, 50%) proportions (weight/weight) of IUdR in the polyanhydride [(poly(bis(p-carboxyphenoxy)-propane) (PCPP): sebacic acid (SA) (PCPP : SA ratio 20:80)] polymer discs were incubated (1 ml phosphate-buffered saline, 37 degrees C). The supernatant fractions were serially assayed using high performance liquid chromatography. To measure modulation of release, polymer discs were co-loaded with 20 microCi 5-125-iodo-2'-deoxyuridine (125-IUdR) and increasing (10%, 30%, or 50%) proportions of D-glucose. To test radiosensitization, cells (U251 human malignant glioma) were sequentially exposed to increasing (0 or 10 microM) concentrations of IUdR and increasing (0, 2.5, 5.0, or 10 Gy) doses of acute radiation. In vivo. To measure release, PCPP : SA polymer discs having 200 microCi 125-IUdR were surgically placed in U251 xenografts (0.1-0.2 cc) growing in the flanks of nude mice. The flanks were reproducibly positioned over a collimated scintillation detector and counted. To measure radiosensitization, PCPP : SA polymer discs having 0% (empty) or 50% IUdR were placed in the tumor or contralateral flank. After five days, the tumors were acutely irradiated (500 cGy x 2 daily fractions).

RESULTS

In vitro: Intact IUdR was released from the PCPP : SA polymer discs in proportion to the percentage loading. After 4 days the cumulative percentages of loaded IUdR that were released were 43.7 +/- 0.1, 70.0 +/- 0.2, and 90.2 +/- 0.2 (p < 0.001 ANOVA) for the 10, 30, and 50% loadings. With 0, 10, 30, or 50% D-glucose co-loading, the cumulative release of 125-IUdR from PCPP : SA polymers was 21, 70, 92, or 97% (p < 0.001), respectively, measured 26 days after incubation. IUdR radiosensitized U251 cells in vitro. Cell survival (log10) was -2.02 +/- 0.02 and -3.68 +/- 0.11 (p < 0.001) after the 10 Gy treatment and no (control) or 10 microM IUdR exposures, respectively. In vivo: 125-IUdR Release: The average counts (log10 cpm +/- SEM) (hours after implant) were 5.2 +/- 0.05 (0.5), 4.3 +/- 0.07 (17), 3.9 +/- 0.08 (64), and 2.8 +/- 0.06 (284). Radiosensitization: After intratumoral implantation of empty polymer or intratumoral 50% IUdR polymer, or implantation of 50% IUdR polymers contralateral to tumors the average growth delays of tumors to 4 times the initial volumes were 15.4 +/- 1.8, 20.1 + 0.1, and 20.3 + 3.6 (mean + SEM) days, respectively (p = 0.488 one-way ANOVA). After empty polymer and radiation treatments, no tumors regressed and the growth delay was 31.1 + 2.1 (p = 0.046 vs. empty polymer alone) days. After implantation of 50% IUdR polymers either contralateral to the tumors or inside the tumors, followed by radiation, tumors regressed; growth delays to return to the initial average volumes of 14.0 + 3.6 or 24.2 + 0.2 (p < 0.01) days, respectively.

CONCLUSIONS

Synthetic, implantable biodegradable polymers hold promise for the controlled release and local delivery of IUdR for radiosensitization of gliomas.

Cell line specific radiosensitizing effect of zalcitabine (2',3'-dideoxycytidine)

The potential of zalcitabine (ddC) to act as an ionizing radiation response modifier was tested on exponentially growing human cancer cells in vitro. Two human cell lines, WiDr (colon) and MCF-7 (breast) were exposed to ddC at 10 microM concentration for various lengths of time (18, 24, 48 and 72 h). On the WiDr cell line the dual effect of concentration and duration of exposure prior to irradiation was investigated. Experimental endpoints were clonogenicity and viability, as measured by colony formation assay (CFA) and MTT assay respectively. The impact on cell-cycle distribution prior to irradiation was assessed by flow cytometry using a double labeling technique (propidium iodide and bromodeoxyuridine pulse label). A significant reduction in surviving fraction and viability was observed for WiDr-cells irradiated after pre-exposure to 10 microM for 18, 48 and 72 h as compared to corresponding irradiated controls. At lower concentrations (1 and 5 microM), the radiosensitizing effect was only significant after a 72-h exposure (assessed by CFA). For MCF-7, ddC induced a significant modification of the dose response only with 24 and 48 h preincubation. However, the overall effect was less pronounced as compared to WiDr. Cell-cycle analysis showed accumulation in S-phase, 48 and 72 h after treatment with 10 microM ddC in the WiDr cells, with a progressive shift to late S-phase as shown by the biparametric analysis. The degree of radiosensitization is cell-line dependent with the most important sensitization observed on the most "radioresistant cell line", i.e., the cell line with the lowest alpha value and highest SF 2 (WiDr). For WiDr, radiosensitization by ddC depends on the duration of exposure and the concentration of the drug.

Azidothymidine (AZT) as a potential modifier of radiation response in vitro

The potential effect of AZT as a thymidine analogue on radiation response in vitro was investigated. Two human cell lines (WiDr and HeLa) were used. The effect of 10 microM AZT on exponentially growing cells was studied after different exposure times (24, 48 and 72 h). The surviving fraction (clonogenic assay) or metabolic activity (MTT assay) after irradiation of AZT-exposed cells, was compared to unexposed irradiated controls. Flow cytometry was used to assess the cell-cycle effect of pre-exposure of exponentially growing cells to AZT. AZT had a radioprotective effect for all experimental time points as far as WiDr was concerned. For HeLa the effect was significant at 24 h. Cell-cycle analysis showed a significant accumulation in S-phase at 72 h for WiDr. For HeLa there was a significant accumulation in S-phase at 48 h. We conclude that under the reported experimental conditions, AZT as a thymidine analogue seems to reduce the cytotoxic effect of irradiation.