Palladium-Induced Temporal Internalization of MHC Class I Contributes to T Cell-Mediated Antigenicity

Palladium (Pd) is a widely used metal and extremely important biomaterial for the reconstruction of occlusions during dental restorations. However, metallic biomaterials can cause serious allergic reactions, such as Pd-related oral mucositis seen in dentistry. Metal allergy is categorized as a type IV allergy and we demonstrated that CD8 T cells play an important role in Pd allergy previously. As TCR of CD8 T cells recognizes MHC class I/peptide complex, the antigen specificity to this complex seems to be generated during Pd allergy. However, it remains unknown if Pd affects the MHC class I/peptide complex. In this study, we investigated the behavior of the MHC class I/peptide complex in response to Pd treatment. We found that PdCl₂ treatment altered peptide presentation on MHC class I and that co-culture with Pd-treated DC2.4 cells induced activation of Pd-responsive TCR-expressing T cell line. Furthermore, PdCl₂ treatment induced temporal MHC class I internalization and inhibition of membrane movement suppressed Pd-induced T cell-mediated antigenicity. These data suggest that Pd-induced MHC class I internalization is critical for generation of antigenicity through a mechanism including differential peptide loading on MHC class I, which results in Pd allergy.

Synthesis and characterization of palladium nanoparticles by chemical and green methods: A comparative study on hepatic toxicity using zebrafish as an animal model

Nanoparticles synthesized by chemical methods are of a matter of concern, whereas, the green methods are said to be eco-friendly and environmentally safe. In this study, the toxicity of palladium nanoparticles (Pd NPs) synthesized through chemical co-precipitation and green route method using Annona squamosa seed kernels (As-Pd NPs) were evaluated using zebrafish as an animal model. The synthesized nanoparticles (NPs) were characterized using UV-Visible spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray (EDX), Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS) and Zeta potential. Zebrafish (Danio rerio) were exposed to 0.4 ng/L of Pd NPs and As-Pd NPs for 96-h, further oxidative stress parameters and histological changes were evaluated. The superoxide dismutase (SOD), catalase (CAT) activity and the lipid peroxidation (LPO) levels were elevated in the Pd NPs groups. But in the As-Pd NPs group, the SOD activity showed a biphasic nature while the CAT activity gradually declined till the 96-h compared to the control and Pd NPs groups. The LPO levels in the As-Pd NPs groups showed a measurable increase till 72-h and sudden decline at the end of 96-h. Anomalies in the histological changes such as ruptured hepatocytes, sinusoidal congestion, vacuolation and accumulation of erythrocytes were observed in both the NPs treated groups but As-Pd NPs exhibited lesser lesions than the control and Pd NPs groups. However, our present study reveals the possible reliability of the nanoparticles and the mechanism of scavenging activity suggesting that the As-Pd NPs synthesized by green route are less toxic comparing to the chemically synthesized Pd NPs.

Analysis of Spatial Dose-Volume Relationships and Decline in Sexual Function Following Permanent Brachytherapy for Prostate Cancer

OBJECTIVE

To explore relationships between dose to periprostatic anatomic structures and erectile dysfunction (ED) outcomes in an institutional cohort treated with prostate brachytherapy.

METHODS

The Sexual Health Inventory for Men (SHIM) instrument was administered for stage cT1-T2 prostate cancer patients treated with Pd-103 brachytherapy over a 10-year interval. Dose volume histograms for regional organs at risk and periprostatic regions were calculated with and without expansions to account for contouring uncertainty. Regression tree analysis clustered patients into ED risk groups.

RESULTS

We identified 115 men treated with definitive prostate brachytherapy who had 2 years of complete follow-up. On univariate analysis, the subapical region (SAR) caudal to prostate was the only defined region with dose volume histograms parameters significant for potency outcomes. Regression tree analysis separated patients into low ED risk (mean 2-year SHIM 20.03), medium ED risk (15.02), and high ED risk (5.54) groups. Among patients with good baseline function (SHIM ≥ 17), a dose ≥72.75 Gy to 20% of the SAR with 1 cm expansion was most predictive for 2-year potency outcome. On multivariate analysis, regression tree risk group remained significant for predicting potency outcomes even after adjustment for baseline SHIM and age.

CONCLUSION

Dose to the SAR immediately caudal to prostate was predictive for potency outcomes in patients with good baseline function. Minimization of dose to this region may improve potency outcomes following prostate brachytherapy.

Intratumoral Injection of Low-Energy Photon-Emitting Gold Nanoparticles: A Microdosimetric Monte Carlo-Based Model

Gold nanoparticles (Au NPs) distributed in the vicinity of low-dose rate (LDR) brachytherapy seeds could multiply their efficacy thanks to the secondary emissions induced by the photoelectric effect. Injections of radioactive LDR gold nanoparticles (LDR Au NPs), instead of conventional millimeter-size radioactive seeds surrounded by Au NPs, could further enhance the dose by distributing the radioactivity more precisely and homogeneously in tumors. However, the potential of LDR Au NPs as an emerging strategy to treat cancer is strongly dependent on the macroscopic diffusion of the NPs in tumors, as well as on their microscopic internalization within the cells. Understanding the relationship between interstitial and intracellular distribution of NPs, and the outcomes of dose deposition in the cancer tissue is essential for considering future applications of radioactive Au NPs in oncology. Here, LDR Au NPs (¹⁰³Pd:Pd@Au-PEG NPs) were injected in prostate cancer tumors. The particles were visualized at time-points by computed tomography imaging ( in vivo), transmission electron microscopy ( ex vivo), and optical microscopy ( ex vivo). These data were used in a Monte Carlo-based dosimetric model to reveal the dose deposition produced by LDR Au NPs both at tumoral and cellular scales. ¹⁰³Pd:Pd@Au-PEG NPs injected in tumors produce a strong dose enhancement at the intracellular level. However, energy deposition is mainly confined around vesicles filled with NPs, and not necessarily close to the nuclei. This suggests that indirect damage caused by the production of reactive oxygen species might be the leading therapeutic mechanism of tumor growth control, over direct damage to the DNA.

Synthesis and Characterization of Novel Cu(II), Pd(II) and Pt(II) Complexes with 8-Ethyl-2-hydroxytricyclo(7.3.1.0(2,7))tridecan-13-one-thiosemicarbazone: Antimicrobial and in Vitro Antiproliferative Activity

New Cu(II), Pd(II) and Pt(II) complexes, (Cu(L)(H₂O)₂(OAc)) (1), (Cu(HL)(H₂O)₂(SO₄)) (2), (Cu(L)(H₂O)₂(NO₃)) (3), (Cu(L)(H₂O)₂(ClO₄)) (4), (Cu(L)₂(H₂O)₂) (5), (Pd(L)(OAc))H₂O (6), and (Pt(L)₂) (7) were synthesized from 8-ethyl-2-hydroxytricyclo(7.3.1.0^2,7)tridecan-13-one thiosemicarbazone (HL). The ligand and its metal complexes were characterized by IR, ¹H-NMR, ¹³C-NMR, UV-Vis, FAB, EPR, mass spectroscopy, elemental and thermal analysis, magnetic susceptibility measurements and molar electric conductivity. The free ligand and the metal complexes have been tested for their antimicrobial activity against E. coli, S. enteritidis, S. aureus, E. faecalis, C. albicans and cytotoxicity against the NCI-H1573 lung adenocarcinoma, SKBR-3 human breast, MCF-7 human breast, A375 human melanoma and HL-60 human promyelocytic leukemia cell lines. Copper complex 2 exhibited the best antiproliferative activities against MCF-7 human breast cancer cells. A significant inhibition of malignant HL-60 cell growth was observed for copper complex 2, palladium complex 6 and platinum complex 7, with IC₅₀ values of 1.6 µM, 6.5 µM and 6.4 µM, respectively.

Epigallocatechin gallate acts synergistically in combination with cisplatin and designed trans-palladiums in ovarian cancer cells

In this study, synergism in activity from the sequenced combinations of three trans-palladiums (denoted as TH5, TH6 and TH7) with green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG), as well as that with cisplatin, was investigated in a number of human ovarian tumour models as a function of sequence of administration. Cellular accumulation of platinum and palladium, and the levels of platinum-DNA and palladium-DNA binding were also determined for the 0/4 h and 0/0 h sequences of administration. The results of the study show that co-administration of cisplatin with EGCG (0/0 h) produces weak synergism in both cisplatin-sensitive (A2780) and cisplatin-resistant (A2780(cisR)) cell lines whereas (0/4 h) administration produces pronounced synergism in both. In contrast, bolus administration of EGCG with TH5, TH6 and TH7 produces marked antagonism except that with TH5, in the A2780(cisR) cell line, where a mild synergism is observed. In the case of TH5, TH6 and TH7, administration of drugs with a time gap (0/4 h or 4/0 h combinations) produces sequence-dependent synergism in both A2780 and A2780(cisR) cell lines, whereas in the case of cisplatin, marked antagonism is observed with the 4/0 h sequence of administration in the A2780 cell line. Whereas the highly synergistic 0/4 h sequence of combination of cisplatin with EGCG is found to be associated with pronounced cellular accumulation of platinum and a high level of platinum-DNA binding, no such clear trend can be seen for any of the combinations of TH5, TH6 and TH7 with EGCG. The results of the present study provide support to the idea that sequenced combinations of platinum drugs and tumour-active palladium compounds with selected phytochemicals such as EGCG may provide a means of overcoming drug resistance.

[Pharmacokinetic and dosimetric characteristics of new radiopharmaceutical based on complexes of 103Pd and albumin microspheres]

Results of the study of absorbed dose formed in organs and tissues of mice after administration of new therapeutic radiopharmaceutical on the base of 103Pd and albumin microspheres (MSA) are presented. Pharmacokinetic parameters of preparation distribution in the body of animals were experimentally determined and then absorbed doses were calculated using MCNP code for the developed mathematical model of mouse. It was shown that absorption of 103Pd-MSA in tumor, physical properties of 103Pd and daughter radionuclide 103mRh provide a targeted irradiation of tumor as compared with the adjusting tissues and critical organs. In administration to tumor muscle tissue of the leg of experimental animals after 15 days following the injection of 103Pd-MSA the accumulated absorbed dose was 15 times less than corresponding one in tumor. In a critical organ (kidneys) the accumulated absorbed dose was 20 times less than in tumor. The work performed as a stage of pre-clinical testing of the radiopharmaceutical.

In vitro and in vivo trypanocidal effects of the cyclopalladated compound 7a, a drug candidate for treatment of Chagas' disease

Chagas' disease, a neglected tropical infection, affects about 18 million people, and 100 million are at risk. The only drug available, benznidazole, is effective in the acute form and in the early chronic form, but its efficacy and tolerance are inversely related to the age of the patients. Side effects are frequent in elderly patients. The search for new drugs is thus warranted. In the present study we evaluated the in vitro and in vivo effect of a cyclopalladated compound (7a) against Trypanosoma cruzi, the agent of Chagas' disease. The 7a compound inhibits trypomastigote cell invasion, decreases intracellular amastigote proliferation, and is very effective as a trypanocidal drug in vivo, even at very low dosages. It was 340-fold more cytotoxic to parasites than to mammalian cells and was more effective than benznidazole in all in vitro and in vivo experiments. The 7a cyclopalladate complex exerts an apoptosis-like death in T. cruzi trypomastigote forms and causes mitochondrion disruption seen by electron microscopy.

Comparison of sensitizers by detecting reactive oxygen species after photodynamic reaction in vitro

The production of reactive oxygen species (ROS) has a crucial effect on the result of photodynamic therapy (PDT). Because of this fact, we examined the ROS formation by means of three porphyrin sensitizers (TPPS(4), ZnTPPS(4) and PdTPPS(4)) and compared their effectivity for induction of cell death in the G361 (human melanoma) cell line. The porphyrins used are very efficient water-soluble aromatic dyes with a potential application in photomedicine and have a high tendency to accumulate in the membranes of intracellular organelles such as lysosomes and mitochondria. Interaction between the triplet excited state of the sensitizer and molecular oxygen leads to the production singlet oxygen and other reactive oxygen species to induce cell death. Production of ROS was investigated by molecular probe CM-H(2)DCFDA. Our results demonstrated that ZnTPPS(4) induces the highest ROS production in the cell line compared to TPPS(4) and PdTPPS(4) at concentrations of 1, 10, and 100 microM and light dose of 1 J cm(-2). We also observed a consequence between ROS production and cell survival. In conclusion, these results demonstrate that photodynamic effect depends on sensitizer type, its concentration and light dose.

Determination of biological vector characteristics and nanoparticle dimensions for radioimmunotherapy with radioactive nanoparticles

Radioimmunotherapy with biological vector labeled with radioactive nanoparticles is investigated from a dosimetric point of view. Beta (32P, 90Y) and low-energy X-ray radionuclides (103Pd) are considered. Dose distributions inside solid tumors have been calculated using MCNPX 2.5.0. Nanoparticle dimensions and biological vector characteristics are also determined in order to reach the 50 Gy prescribed dose inside the entire tumor volume. The worst case of an avascular tumor is considered. Results show that for beta-emitting nanoparticles, a set of data (covering fraction, biological half-life, and nanoparticle radius) can be found within acceptable ranges (those of classical radioimmunotherapy). These sources (with Emax approximately few MeV) can be used for the treatment of tumors with a maximum diameter of about 1 cm. Low-energy X-rays (E<25 keV) can be used to extend the range of tumor diameter to 4-5 cm but require very tight biological vector characteristics.

Dosimetry of an Extracapsular Anulus Following Permanent Prostate Brachytherapy

PURPOSE

Recent studies have suggested that extracapsular brachytherapy treatment margins correlate with biochemical control. It is likely that volumetric geographic dosimetric parameters will be more robust than selected radial measurements. Accordingly, we evaluated extracapsular volumetric dosimetric parameters in low-risk patients.

MATERIALS AND METHODS

A total of 263 low-risk prostate cancer patients randomized to Pd-103 versus I-125 were implanted with a brachytherapy target volume consisting of the prostate with a 5-mm periprostatic margin. The median follow-up was 4.2 years. All patients were implanted at least 3 years prior to analysis. Within 2 hours of implantation, an axial CT was obtained for postimplant dosimetry. A 5-mm three-dimensional periprostatic anulus was constructed around the prostate and evaluated in its entirety and in 90 degrees segments. Prostate and anular dosimetric parameters consisted of V100/V150/V200 and D90. Biochemical progression-free survival (bPFS) was defined as a PSA < or =0.50 ng/mL after nadir.

RESULTS

The Pd-103 and I-125 arms were well-matched in terms of clinical, biochemical, and pathologic presentation. Six-year bPFS was 96.8% versus 99.2% for I-125 versus Pd-103 (P = 0.149). The most recent median posttreatment PSA was <0.04 ng/mL for both isotopes. No significant differences in postoperative anular doses were discerned between bPFS and failed patients.

CONCLUSIONS

A postimplant 5-mm, three-dimensional periprostatic anulus provides substantial information regarding dosimetric coverage. However, with a median follow-up of 4.2 years, such volumetric and geographic parameters have not proven useful in predicting biochemical outcome in low-risk patients.

The current role of imaging for prostate brachytherapy

Prostate brachytherapy is a radiotherapy technique for early stage prostate cancer that uses imaging guidance to place radioactive sources directly into the prostate gland. Transrectal ultrasound is used to facilitate a template-guided transperineal approach to the prostate and permits a highly conformal method of prostate radiotherapy with doses far higher than can be achieved with other radiation techniques. Maturing data has validated this technique as an acceptable treatment option with favourable and durable biochemical outcomes. The radiologist has a major role to play in the process: patient selection, guiding source delivery and follow-up after treatment all require close collaboration with colleagues in Radiation Oncology and Medical Physics. This review emphasises the specific contribution of imaging in the context of currently reported outcomes data.

Is seminal vesicle implantation with permanent sources possible? A dose–volume histogram analysis in patients undergoing combined 103Pd implantation and external beam radiation for T3c prostate cancer

PURPOSE

Combined brachytherapy and external beam radiation therapy (EBRT) of the prostate and seminal vesicles (SVs) is evolving as a successful treatment option for high-risk prostate cancer. Dose-volume histogram (DVH) analysis of the SV was performed in patients with biopsy-positive SV who received implantation of the SV and prostate.

METHODS AND MATERIALS

Fifteen consecutive patients with high-risk features (prostate-specific antigen [PSA] > or =10 ng/mL, Gleason score > or = 7, or clinical stage > or = T2b) and a positive SV biopsy were treated with a 103Pd implant of the prostate and SV followed by 45Gy of EBRT. DVHs were generated for the prostate and total SV volume (SVT). In addition, the SV was divided into 3-mm-thick volumes identified as SV1, SV2, SV3, SV4, SV5, and SV6 starting from the junction of the prostate and SV and extending distally. Delivered dose was defined as the D90 (dose delivered to 90% of the organ on DVH).

RESULTS

The median number of seeds implanted into the prostate and the SVT was 59 (41-94) and 9 (4-21), respectively. The median D90 values for the prostate, SVT, SV1, SV2, SV3, SV4, SV5, and SV6 were 103.2 (87.4-137.1), 46.2 (4.0-69.4), 76.0 (31.2-147), 63.4 (25.1-145.9), 49.7 (15.3-118), 27.4 (9.3-135.1), 14.2 (2.3-100.3), and 3.9 (0-61.5) Gy, respectively.

CONCLUSIONS

Implantation of the SV using a real-time intraoperative approach is technically feasible and results in higher doses to the SV than has been reported with implantation of the prostate alone. Although dose distribution in the SV can be variable and unpredictable, these doses, in combination with 45 Gy of EBRT, may be adequate to control disease spread in these organs.

Bioassay by intratracheal instillation for detection of lung toxicity due to fine particles in F344 male rats

We have established and documented an in vivo bioassay for detection of hazards with intratracheally instilled fine particles, which can be used for risk assessment of toxicity of materials inhaled into deep lung tissue of humans (Yokohira et al. Establishment of a bioassay system for detection of lung toxicity due to fine particle instillation: sequential histopathological changes with acute and subacute lung damage due to intratracheal instillation of quartz in F344 male rats. J Toxicol Pathol 2005;18:13-8). For validation we here examined toxicity of fine particles from quartz, hydrotalcite, potassium octatitanate, palladium oxide and carbon black with this bioassay. A total of 108, 10-week-old F344/DuCrj male rats were randomly divided into 8 groups. Groups 1 to 5 underwent intratracheal instillation of the 5 test particles (4 mg/rat) suspended in 0.2 ml vehicle (saline or 10% propylene glycol and 1% sodium carboxymethyl cellulose in saline: PG-CMC) with a specially designed aerolizer, and subgroups of 7 rats were killed on Days 1 and 28 thereafter. Groups 6 and 7 similarly were exposed to saline and PG-CMC, respectively, as vehicle controls, while group 8 was maintained untreated. Using histopathological changes and immunohistochemically assessed bromodeoxyuridine (BrdU) labeling indices, inducible nitric oxide synthase (iNOS) and matrix metalloproteinase-3 (MMP-3) levels as end points, the quartz treated group exhibited high toxicity, while the values for the other particle-treated groups pointed to only slight effects. Although additional efforts are needed to establish advantages and disadvantages with our bioassay, models featuring intratracheal instillation clearly can be useful for detection of acute or subacute lung toxicity due to inhaled fine particles by using histopathological scoring and markers like BrdU and iNOS for screening purposes in short-term studies.

Role of external beam radiotherapy with low-dose-rate brachytherapy in treatment of prostate cancer

OBJECTIVES

To report a single-institution experience and analysis of the role of supplemental external beam radiotherapy (EBRT) with brachytherapy. EBRT is often used in addition to low-dose-rate brachytherapy in the treatment of prostate cancer, particularly for disease with adverse features.

METHODS

A cohort of 189 consecutive patients, who had undergone low-dose-rate brachytherapy at our institution and who had demographic, disease, and treatment information and a minimum of 2 years of follow-up available, constituted the study group. This cohort was divided into two major groups according to the use of supplemental EBRT. Using two successive prostate-specific antigen rises greater than 1 ng/mL as the definition of failure, biochemical failure-free survival curves were constructed for the EBRT and no-EBRT groups and compared using the log-rank test. Additionally, a multivariate analysis of all major disease and treatment factors was performed using the Cox proportional hazards model.

RESULTS

Despite the greater proportion of adverse disease factors in the EBRT group, the 5-year biochemical failure-free survival rate in the EBRT versus no-EBRT groups was 80% versus 59%, respectively (P < 0.01). On multivariate analysis, the only factor reaching significance in predicting biochemical control was the use of EBRT (P = 0.043).

CONCLUSIONS

In our study, the addition of EBRT conferred a significant biochemical control advantage when added to low-dose-rate brachytherapy. Because our study was not designed to permit detailed subset analyses, more work is needed to determine the precise brachytherapy population that will benefit from this use of supplemental EBRT.

Dose rate dependence of the relative biological effectiveness of 103Pd for continuous low dose rate irradiation of BA1112 rhabdomyosarcoma cells in vitro relative to acute exposures

PURPOSE

To measure the relative biological effectiveness (RBE) of continuous low dose rate irradiation (CLDRI) using 103Pd sources relative to acute high dose rate irradiations (AHDRI) from a 250 kVp x-ray beam and an x-ray beam having an equivalent mono-energetic photon energy equal to the average energy of the 103Pd source for BA1112 rhabdomyosarcoma cells.

MATERIALS AND METHODS

A customized 103Pd irradiator was built to provide CLDRI using 103Pd at different dose rates relevant to clinical interstitial brachytherapy to BA1112 rhabdomyosarcoma cells growing in exponential phase in culture. A special x-ray beam that simulates the photon energies emitted by the 103Pd source was also developed to provide acute high dose rate irradiation at those energies. Cell survival curves from different irradiation conditions were measured. The RBE with respect to AHDRI using standard 250 kVp x-rays was determined from the doses required to achieve a cell surviving faction of 0.01.

RESULTS

For acute irradiation, the RBE of the x-rays simulating (103)Pd was 1.24 relative to 250 kVp x-rays. A profound dose rate effect was observed at low dose rates in the range of 6.8 - 14.4 cGy/h that are typical of permanent interstitial brachytherapy. At cell-surviving fraction of 0.01, the RBE of CLDRI at 6.8 and 14.4 cGy/h using 103Pd sources was reduced by a factor of 3 and 2, respectively, relative to the acute exposure. This observation is in good agreement with recent in vivo tumor cure studies performed on BA1112 tumor.

CONCLUSION

The relative biological effectiveness of the photons emitted by 103Pd depends on both the linear energy transfer (LET) of the low energy photons and the dose rate of the irradiation. The higher LET of 103Pd photons is biologically more effective in killing BA1112 tumor cells compared to conventional 250 kVp x-rays when both are delivered at the same dose rate. But the gain in RBE that results from the higher LET can be quickly negated by the reduced dose rate of the irradiation.

Cross-reactivity between nickel and palladium demonstrated by systemic administration of nickel

Concomitant patch test reactions to nickel and palladium have frequently been reported in patients undergoing investigation because of suspected allergic contact dermatitis. Theoretically, these reactions can be explained by multiple, concomitant, simultaneous sensitization as well as cross-sensitization. We studied whether concomitant reactions to nickel and palladium could represent cross-sensitization in females hypersensitive to combinations of nickel, palladium and cobalt. Females were patch tested with serial dilutions of nickel sulfate, cobalt chloride and palladium chloride on the upper back. 1 month later, when the patch test reactions were gone, the patients were randomized into 2 groups that were challenged orally with either nickel or placebo. 1 day later, the areas of previous positive patch test reactions were read in a blind way looking for flare-up reactions. Nickel provocation but not placebo yielded flare-up reactions on sites previously tested with nickel (P = 0.012) and palladium (P = 0.006), but were also observed on sites previously tested with cobalt, even though this was not statistically significant. Flare-up reactions of previous patch test reactions to nickel and palladium after oral challenge with nickel speak in favour of a cross-reactivity mechanism.

Variability of prostate brachytherapy preimplant dosimetry: A multi-institutional analysis

PURPOSE

To conduct a multi-institutional comparison of prostate brachytherapy pre-implant dosimetry of Pd-103 and I-125.

METHODS AND MATERIALS

Eight experienced brachytherapists submitted Pd-103 and I-125 monotherapeutic and boost pre-implant dosimetry plans for central review. All 32 plans were calculated using the same transrectal ultrasound volumetric study. Seeds of any strength were acceptable, but were restricted to Theraseed Model 200 (Theragenics Inc., Buford, GA) and Oncura Oncoseed Model 6711 (Oncura, Plymouth Meeting, PA). The dosimetric analysis included evaluation of target volume, target to prostate ratio, target length, number of needles, seed activity, number of seeds, total activity, total activity divided by treatment planning volume, the use of extracapsular seeds, and average treatment margins (defined as the perpendicular distance between the prostate capsule and the 100% isodose line). Prostate coverage was defined in terms of V(100)/V(150)/V(200)/V(300) and D(100)/D(90)/D(50), whereas urethral dosimetry consisted of UV(100)/UV(150)/UV(200) and UD(90)/UD(50).

RESULTS

The mean planning target volume to prostate volume ratio varied dramatically (mean 1.29, range 0.99-1.76) with the target length ranging from 3.5 to 4.5 cm. Although the prostate V(100) was >95% in all cases, the V(150) ranged from 29.9% to 92.1% and the V(200) from 6.72% to 52.5%. The urethral V(100) was 100% in all cases with six of the eight brachytherapists limiting the UV(150) to <3%. However, the median urethral dose varied by up to 50%. Treatment margins also varied significantly (average 3.98 mm, range 0.32-7.68 mm). All brachytherapists used extracapsular seeds with five implanting >25% of the seeds in extracapsular locations (range 6.4-58.2%). In addition, significant variability existed in the number of needles, number of seeds, and seed strength.

CONCLUSIONS

This study highlights the substantial variability that exists regarding target volume, seed strength, dose homogeneity, treatment margins, and extracapsular seed placement, although prostate brachytherapy prescription doses are uniform. The standardization of pre-implant dosimetry is essential for meaningful multi-institutional comparisons of biochemical outcomes and morbidity.

A Monte Carlo brachytherapy study for dose distribution prediction in an inhomogeneous medium

The purpose of this study was to present a theoretical analysis of how the presence of bone in interstitial brachytherapy affects dose rate distributions. This study was carried out using a Monte Carlo simulation of the dose distribution in homogeneous medium for 3 commonly used brachytherapy seeds. The 3 seeds investigated in this study are iridium-192 (192Ir) iodine-125 (125I), and palladium-103 (103Pd). The computer code was validated by comparing the specific dose rate (Lambda), the radial dose function g(r), and anisotropy function F(r,theta;) for all 3 seeds with the AAPM TG-43 dosimetry formalism and current literature. The 192Ir seed resulted in a dose rate of 1.115 +/- 0.001 cGy-hr(-1)-U(-1), the 125I seed resulted in a dose rate of 0.965 +/- 0.006 cGy/h(-1)/U(-1), and the 103Pd seed resulted in a dose rate of 0.671 +/- 0.002 cGy/h(-1)/U(-1). The results for all 3 seeds are in good agreement with the AAPM TG-43 and current literature. The validated computer code was then applied to a simple inhomogeneous model to determine the effect bone has on dose distribution from an interstitial implant. The inhomogeneous model showed a decrease in dose rate of 2% for the 192Ir, an increase in dose rate of 84% for 125I, and an increase in dose rate of 83% for the 103Pd at the surface of the bone nearest to the source.

[Expression and significance of caspase-3 gene in apoptotic muscle cells 103Pd radioactive stent bile duct in dogs]

OBJECTIVE

To discuss the expression and significance of caspase-3 gene in the apoptotic muscle cells in gamma-radiation-induced muscle cell lines.

METHODS

The caspase-3 mRNA in the control and gamma-radiation induced apoptotic muscle cells was analysed by RT-PCR.

RESULTS

The expression of caspase-3 gene transcript was higher in 103Pd radioactive stent dog bile duct than in general stent dog bile duct, and apoptotic muscle cells were higher in 103Pd radioactive stent dog bile duct than in general stent dog bile duct.

CONCLUSIONS

The high level expression of caspase-3 gene may help to understand the muscle cells sensitivity to gamma-radiation apoptosis. 103Pd radioactive stent may increase the expression of caspase-3 gene in dog bile duct and prevent the billiary narrow when dog bile duct was injured by balloon.

[Effect of 103palladium radioactive stent on expression of smooth muscle actin in bile duct during healing process and its significance]

OBJECTIVE

To observe the effect of radiation on the expression of smooth muscle actin (SMA) in the bile duct during the healing process and the inhibitory function of (103)palladium (Pd) radioactive stent on the stricture of bile duct after injury.

METHODS

Twelve mongrel dogs were made models of bile duct injury: duodenotomy was performed, a balloon catheter was inserted into the general bile duct and saline with high pressure was perfused thereinto to cause laceration of the mucosa, and then the balloon catheter was withdrawn and ordinary alloy stent or (103)Pd radioactive stent was inserted into the general bile duct. Thirty days after the dogs were killed. Their bile ducts were taken out to undergo HE staining to observe the area of general bile duct, thickness of the tunica intima, area of residual bile duct cavity, stricture degree, and circumference of bile duct. The expression of SMA in the bile duct tissue was detected by immunoistochemistry.

RESULTS

SMA was expressed in 5 of the 6 specimens of bile duct in the (103)Pd radioactive stent group and 2 of the 6 specimens of the ordinary stent group (P < 0.01). The maximum thickness of tunica intima of general bile duct was 0.78 mm +/- 0.12 mm in the (103)Pd radioactive stent group, significantly less than that of the ordinary stent group (1.86 mm +/- 0.14 mm, P < 0.01). The percentage of maximum stricture area of the (103)Pd radioactive stent group was 23% +/- 16%, significantly lower that that of the ordinary stent group (56% +/- 22%, P < 0.01). The circumference of bile duct cavity of the (103)Pd radioactive stent group was 9.7 mm +/- 1.6 mm, significantly longer that of the ordinary stent group (7.0 mm +/- 1.4 mm, P < 0.01).

CONCLUSION

(103)Pd radioactive stent reduces the expression of SMA in the bile duct during the healing process, thus inhibiting the stricture of bile duct caused by scar contracture at the anastomotic stoma.

Iodine 125 Versus Palladium 103 Implants for Prostate Cancer

PURPOSE

The purpose of this study was to evaluate the clinical outcomes and compare complication rates for patients with prostate cancer treated with iodine 125 ((125)I) and palladium 103 ((103)Pd) prostate brachytherapy at a single institution.

PATIENTS AND METHODS

Between 1992 and 2002, 272 patients with prostate cancer were treated with ultrasound-guided transperineal implantation incorporating (125)I (107 patients) or (103)Pd (165 patients). Three months of hormonal therapy was incorporated into the treatment program in 33% of the patients in both groups. Nineteen percent of those treated with (125)I were treated with a combination of implantation plus external-beam radiation therapy. Only 6% of the group receiving (103)Pd implants were treated with such a combination. For those treated with (125)I implantation alone, the minimum tumor dose was 145 Gy. The minimum tumor dose for those treated with (103)Pd alone was 125 Gy. Those treated with a combination of external-beam radiation therapy and (125)I received 45 Gy via 1.8-Gy fractions followed by implantation with a minimum tumor dose of 110 Gy. For those treated with external-beam radiation therapy and (103)Pd, the doses were 45 Gy via 1.8-Gy fractions followed by implantation with minimum tumor dose of 98 Gy. Outcomes were evaluated based on radionuclide used, T stage, Gleason score, prostate-specific antigen, and prognostic group. Complications were also evaluated for each radionuclide. The mean follow-up for the (125)I group was 55 months, and the range was 12-108 months. The mean follow-up for the (103)Pd group was 44 months, and the range was 12-72 months.

RESULTS

The 5-year biochemical disease-free survival rates for those in the favorable group (clinical stage T1c or T2, prostate-specific antigen level <10, Gleason score <7) were 92% for the (125)I group and 92% for the patients treated with (103)Pd. The 5-year disease-free survival rates for those in the intermediate and poor prognostic groups, which were combined, was 72% and 74%, respectively, for (125)I and (103)Pd. There was no statistically significant difference for either modality for any treatment group tested. In those treated with implantation alone, patients treated with (125)I had higher complication rates than those treated with (103)Pd (15% vs 4%). (125)I-treated patients had a grade 2 complication rate of 8% and a grade 3-4 complication rate of 7%, compared with 3% and 1%, respectively, for the (103)Pd-treated patients.

CONCLUSION

Despite the different management recommendations that evolved during the study period, the clinical outcome for patients treated with either radionuclide were similar with respect to biochemical disease-free survival. Although specific dosimetric comparisons are not valid given differences in imaging over the study course, the complication rate appears to be somewhat higher for (125)I, which is consistent with a radiobiologic model.

High Dose Rate Brachytherapy as Prostate Cancer Monotherapy Reduces Toxicity Compared to Low Dose Rate Palladium Seeds

PURPOSE

We evaluated the potential for differing acute and chronic toxicities between 2 monotherapy methods of image guided conformal brachytherapy, high dose rate (HDR) brachytherapy alone and low dose rate (LDR) permanent palladium seeds.

MATERIALS AND METHODS

A total of 149 patients with biopsy proven, early stage prostate cancer were consecutively treated with interstitial brachytherapy as the sole method of treatment at William Beaumont Hospital between 1999 and 2001. Of the 149, 65 patients were treated with HDR using 192 iridium (192Ir), and 84 patients were treated with LDR using 103 palladium (103Pd). The majority of patients had clinical stage II, T1c or T2a disease, pretreatment prostate specific antigen less than 10 ng/ml and Gleason score 6 or less. Neoadjuvant hormones were used in 36% of patients for gland volume optimization. All treatments were performed transperineally with trans-rectal ultrasound guidance and fluoroscopy for verification of needle/seed positions. The HDR dose was 38 Gy delivered in 4 fractions, 2 times daily during 2 days. The LDR dose was 120 Gy. Acute and chronic toxicities were scored according to the Common Toxicity Criteria scale, version 2.0.

RESULTS

Median followup for all patients was 35 months. The 2 treatment groups were well-balanced with respect to age, clinical stage, prostate specific antigen, Gleason score, use of neoadjuvant hormones, pretreatment genitourinary symptoms, implanted gland volume and length of followup. Biochemical control (American Society for Therapeutic Radiology and Oncology definition) was 97% and 98% for LDR and HDR, respectively. HDR brachytherapy alone was associated with decreased acute rates of grade 1 to 3 dysuria (67% versus 36%, p <0.001), urinary frequency/urgency (92% versus 54%, p <0.001) and rectal pain (20% versus 6%, p = 0.017). These differences remained significant when patients who received prior hormonal therapy were excluded from analysis. Selected chronic toxicities were also decreased with HDR, including long-term urinary frequency and urgency, 32% (HDR) vs 56% (103Pd), p = 0.004. There were no differences in the rates of chronic dysuria, urinary incontinence, retention or hematuria. Urethral stricture rates were 8% in the HDR alone group vs 3% for 103 Pd (p = 0.177). The 3-year actuarial impotence rate was 45% for the LDR group and only 16% for HDR. The majority of complications were grade 1. No grade 4 toxicities were encountered in either group. HDR decreased treatment cost by 19%.

CONCLUSIONS

While HDR (192 iridium) and LDR (103Pd) monotherapy maintained the same biochemical control, the use of HDR brachytherapy as monotherapy was associated with decreased rates of acute urinary frequency, urgency, dysuria and rectal pain compared to LDR. Chronic urinary frequency, urgency and grade 2 rectal toxicities were also decreased with HDR. A dramatic decrease (66%) was noted in the rate of sexual impotency with HDR. In addition, patients treated with HDR did not remain radioactive after treatment. There was a decrease in cost from not purchasing seeds per patient. HDR monotherapy as prostate cancer treatment resulted in the same biochemical control with much lower toxicity. It is an accepted, convenient, cost-effective method of prostate brachytherapy for patients with favorable risk prostate cancer.

Epididymitis after prostate brachytherapy

OBJECTIVES

To analyze the incidence, time-course, and potential predisposing factors for what was clinically diagnosed as postimplant epididymitis.

METHODS

Of 517 patients randomized and treated on two treatment protocols, with a planned total accrual of 1200, 5 patients were identified who developed clinically diagnosed epididymitis after iodine-125 or pallidium-103 prostate brachytherapy. Implants were performed by standard techniques, using a modified peripheral loading pattern. Perioperative antibiotics (cefazolin and ciprofloxacin) were given to 258 patients, according to physician preference. Treatment-related morbidity was monitored by mailed questionnaires, using standard American Urological Association (AUA) and Radiation Therapy Oncology Group criteria at 1, 3, 6, 12, and 24 months. Patients who did not respond to the mailed questionnaires were interviewed by telephone. Although the patients were not queried specifically regarding epididymitis, its occurrence was noted when discovered in the course of follow-up examinations.

RESULTS

Postimplant epididymitis occurred in 5 (1%) of 517 consecutive brachytherapy patients. None of the 5 patients had had a prior history of orchitis, epididymitis, vasectomy, or preimplant catheterization. The symptoms of epididymitis first appeared at 4, 7, 10, 150, and 300 days after implantation. Patients with epididymitis had prostate volumes, preimplant AUA scores, and ages typical of other implant patients. No association was apparent between postimplant epididymitis and the degree of implant-related prostate swelling or the number of seeds implanted. Only the preimplant AUA score predicted for epididymitis, but 2 of the 5 patients had low scores. Only 1 (0.4%) of the 258 patients who received perioperative antibiotics developed epididymitis, and 4 (1.5%) of the 259 patients with prophylactic antibiotics developed epididymitis.

CONCLUSIONS

Epididymitis is an uncommon postimplant complication occurring in 1% of a large patient cohort. That epididymitis patients had greater preimplant AUA scores is consistent with a retrograde infection route, at least in some cases.

Intrabiliary radiation inhibits smooth muscle formation and biliary duct remodelling after balloon overstretching injury in dogs

BACKGROUND

Internal metallic stents have been widely used in clinical practice, but a high postoperative restenosis rate limits its application. The purpose of this study was to determine the effect of intrabiliary radiation on muscle formation and biliary duct remodeling after biliary duct balloon injury in dogs.

METHODS

Twenty male dogs (15 - 20 kg) were randomly divided into treatment group (n = 10) and control group (n = 10). Balloon overstretching injury was induced using a balloon catheter placed across the biliary duct. Subsequently, a 103Pd radioactive stent was positioned at the target site in each animal in the treatment group, providing the injured biliary duct with a radiation dose of 12.58 x 10(7) Bq. Dogs in the control group received Ni-Ti stents. All the dogs were killed one month after initial injury. The injured sections were dissected free from the dogs, and were processed for histological and morphological study. Cross-sections were stained with hematoxylin-eosin, Masson's trichrome, and Verhoef-van Giesen. Muscle formation area and lumen area were determined using a computer-assisted image analysis system.

RESULTS

Compared with the control group, 103Pd radioactive stents significantly reduced muscle formation area (78.3%, P < 0.01), and percentage area of stenosis [control stents: (60.0 +/- 21.6)%, 103Pd radioactive stents: (31.6 +/- 9.5)%]. In addition, in the treatment group, the biliary duct lumen area was significantly larger than that in the control group (P < 0.01).

CONCLUSIONS

103Pd radioactive stents providing a radioactive dose of 12.58 x 10(7) Bq are effective in reducing muscle formation and biliary duct remodeling after balloon overstretching injury.

The effects of edema on urethral dose following palladium-103 prostate brachytherapy

The effects of edema on urethral dose after interstitial prostate brachytherapy with palladium-103 (103Pd) were studied. Fifty patients underwent a 90-Gy 103Pd implant followed by dosimetric computed tomography (CT). Twenty-one days later, a Foley catheter was reinserted and a dosimetric CT was repeated. The mean reduction in prostate volume between day 0 and day 21 was 16%. Median prostate D90 on day 0 was 89.7 Gy (range 59.5 to 127) and 99.5 Gy (range 62.5 to 130) on day 21. Median prostate V100 was 90% (range 63 to 98%) on day 0 and 96% (range 66 to 99%) on day 21. Median V150 was 61% (range 31 to 85%) on day 0 and 75% (range 39 to 93%) on day 21. Median urethral D50 was 107 Gy (range 57 to 201) on day 0 and 126 Gy (range 64 to 193) on day 21. Regression analysis demonstrated a significant correlation between the decrease in the prostate volume and the increased urethral D50 (r 0.58, p < 0.05). Acute urinary toxicity was 32% grade 0, 38% grade 1, and 30% grade 2. The median urethral D50 increased by a mean of 18% with a correlation coefficient of 0.58 (p < 0.05). Catheterization of the urethra was well tolerated and was of value in better characterizing urethral dose after 103Pd brachytherapy.

Comparison of intraoperative dosimetric implant representation with postimplant dosimetry in patients receiving prostate brachytherapy

PURPOSE

To compare the results of intraoperative dosimetry with those of CT-based postimplant dosimetry in patients undergoing prostate seed implantation.

METHODS AND MATERIALS

Seventy-seven patients with T1-T3 prostate cancer received an ultrasound-guided permanent seed implant (36 received (125)I, 7 (103)Pd, and 34 a partial (103)Pd implant plus external beam radiation therapy). The implantation was augmented with an intraoperative dosimetric planning system. After the peripheral needles were placed, 5-mm axial images were acquired into the treatment planning system. Soft tissue structures (prostate, urethra, and rectum) were contoured, and exact needle positions were registered. Seeds were placed with an applicator, and their positions were entered into the planning system. The dose distributions for the implant were calculated after interior needle and seed placement. Postimplant dosimetry was performed 1 month later on the basis of CT imaging. Prostate and urethral doses were compared, by using paired t tests, for the real-time dosimetry in the operating room (OR) and the postimplant dosimetry.

RESULTS

The mean preimplant prostate volume was 39.8 cm(3), the postneedle planning volume was 41.5 cm(3) (p<0.001), and the 1-month CT volume was 43.6 cm(3) (p<0.001). The mean difference between the OR dose received by 90% of the prostate (D(90)) and the CT D(90) was 3.4% (95% confidence interval, 2.5-6.6%; p=0.034). The mean dose to 30% of the urethra was 120% of prescription in the OR and 138% on CT. The mean difference was 18% (95% confidence interval, 13-24%; p<0.001).

CONCLUSIONS

Although small differences exist between the OR and CT dosimetry results, these data suggest that this intraoperative implant dosimetric representation system provides a close match to the actual delivered doses. These data support the use of this system to modify the implant during surgery to achieve more consistent dosimetry results.

Monte carlo investigation of the dosimetric properties of the new 103Pd BrachySeedPd-103 Model Pd-1 source

Recently, 103Pd brachytherapy sources have been increasingly used for interstitial implants as an alternative to 125I sources. The BrachySeedPd-103 Model Pd-1 seed is one of the latest in a series of new brachytherapy sources that have become available commercially. The dosimetric properties of the seed were investigated by Monte Carlo simulation, which was performed using the Integrated Tiger Series CYLTRAN code. Following the AAPM Task Group 43 formalism, the dose rate constant, radial dose function, and anisotropy parameters were determined. The dose rate constant, A, was calculated to be 0.613 +/- 3% cGy h(-1) U(-1). This air kerma strength was derived from Monte Carlo simulation using the point extrapolation method. The radial dose function, g(r), was computed at distances from 0.15 to 10 cm. The anisotropy function, F(r,theta), and anisotropy factor, phi(an)(r), were calculated at distances from 0.5 to 7 cm. The anisotropy constant, phi(an), was determined to be 0.978, which is closer to unity than most other 103Pd seeds, indicating a high degree of uniformity in dose distribution. The dose rate constant and the radial dose function were also investigated by analytical modeling, which served as an independent evaluation of the Monte Carlo data, and found to be in good agreement with the Monte Carlo results.

Interstitial thermal therapy in patients with localized prostate cancer: histologic analysis

OBJECTIVES

To examine, by way of histologic examination, the destruction of excised prostate glands treated with thermal ablation. Thermal ablation treatment with permanently implanted temperature self-regulating rods is being used in the treatment of localized prostate cancer.

METHODS

Four patients with biopsy-proven prostate cancer, who had been scheduled for routine radical prostatectomy with a gland size of less than 70 g, Gleason sum of 7 or less, and prostate-specific antigen values less than 10.0 ng/mL, were implanted with 70 degrees C rods under ultrasound and fluoroscopic control. The patients were then given multiple thermal treatments. Glands were removed and histologically analyzed to access the thermal destruction.

RESULTS

Histologic examination revealed confluent thermal destruction within the rod array when the rods were placed end-to-end and no farther than 1 cm apart. Little necrosis was seen outside the array. To ensure the necessary destruction, the rods must be placed at the capsule, including posteriorly near the rectum. The results indicated that energy levels greater than 40 W-min/g of tissue should be used. This can be achieved by implanting 1.5 rods/g of prostate and treating the patient for 60 minutes. In 3 of the 4 patients, no residual cancer was found in the gland after thermal treatment.

CONCLUSIONS

Histologic examination has aided in determining the implant density and treatment time and, therefore, the necessary energy, for adequate necrosis. The technique demonstrates the ability to destroy the prostate adequately, including tissue at the capsule. This new procedure appears promising in the treatment of localized prostate cancer.

Dosimetric parameters for three low-energy brachytherapy sources using the Monte Carlo N-particle code

Monte Carlo calculations have been performed for the purpose of characterizing the dosimetric properties of three brachytherapy sources. The three sources are manufactured by Syncor Pharmaceuticals Inc. and consist of two 125I seeds (BT-125-1 and BT-125-2) and one 103Pd seed (BT-103-3). The BT-125-1 and BT-125-2 seed consists of a solid palladium and silver core, respectively. A thin layer (0.5 microm) of 125I is adsorbed onto the solid core for each seed and encased within a titanium housing. The BT-103-3 seed consists of a central gold marker and four resin balls encased within a titanium housing. A thin layer of 103Pd is bonded onto each resin ball. The dosimetric properties, including the dose rate constant, radial dose function, and anisotropy were calculated in water according to the TG-43 protocol using the Monte Carlo N-Particle code. The dose rate constant was calculated to be 0.955+/-0.005 and 0.967+/-0.005 cGyh(-1) U(-1) for the BT-125-1 and BT- 125-2 seeds, respectively. A dose rate constant of 0.659+/-0.005 cGy h(-1) U(-1) was calculated for the BT-103-3 seed. Radial dose function, g(r), calculated to a distance of 10 cm, and an isotropy function, F(r, theta), calculated for radii from 0.5 to 7.0 cm, were found to be in close agreement with previously published data.

Role of body piercing in the induction of metal allergies

BACKGROUND

Metal allergies have been linked to body piercing in women, but few studies have explored this phenomenon in men. It has been postulated that nickel/cobalt and nickel/palladium exhibit coreactivity in patients allergic to metals.

OBJECTIVES

(1) Determine the incidence rate and the source for the induction of metal allergy in 3 groups of men: unpierced, one site-pierced, and multiple sites-pierced; and (2) evaluate the degree of coreactivity between nickel/cobalt and nickel/palladium.

METHODS

Men aged 18 to 43 years (n = 118) were patch-tested using the North American Contact Dermatitis Group's protocol to nickel sulfate 2.5%, gold sodium thiosulfate 0.5%, cobalt chloride 1%, and palladium chloride 1%.

RESULTS

Eleven (9.3%) subjects had at least 1 positive reaction. When characterized by the number of pierced sites, positive reactions were seen in 2 of 50 (4.0%) unpierced, 3 of 27 (11.1%) one site-pierced, and 6 of 41 (14.6%) multiply pierced men. The number of piercings was a statistically significant predictor of metal allergy (P = .04). Four (66.7%) cobalt and no palladium reactions occurred in nickel-positive subjects. The source for the induction of the allergic response was primarily jewelry, which accounted for 5 of 6 nickel allergies and 2 of 3 gold allergies. Silver jewelry was a significant predictor of an allergic response.

CONCLUSION

This study represents the first report that the number of body piercings has positive bearing on the incidence of metal allergy in men. The data also support the theory of coreactivity for nickel/cobalt, but not for nickel/palladium.

Quantification of the selective retention of palladium octabutoxynaphthalocyanine, a potential photothermal drug, in mouse tissues

Palladium octabutoxynaphthalocyanine (PdNc(OBu)8) is a potential photothermal therapy (PTT) agent, absorbing strongly in the near-infrared region with no ability to induce photodynamic-type sensitisation (unlike many related napthalocyanines). We report here on the application of high pressure liquid chromatography (HPLC) with near-infrared absorption detection for the determination of the tissue accumulation and clearance of PdNc(OBu)8 in a tumour-bearing mouse model (Balb/c mice with EMT6 carcinoma tumour). Due to its insolubility in aqueous-based solvents, the drug was delivered intraperitoneally in a Cremophor-containing vehicle. Good selective accumulation of the drug into the tumour versus muscle or skin is observed, with the best combination of selectivity and tumour concentration occurring at 24-72 h after drug administration. Clearance times are quite long. Comparison with other similar drugs as reported in the literature indicates that the Cremophor-containing vehicle is likely in large part responsible for the observed pharmacokinetic behaviour. This drug shows potential for PTT and will be investigated further for therapy in this animal model.

[Brachytherapy with palladium-103--a new way to deliver radiation therapy for localized prostatic cancer]

The incidence of prostate cancer is increasing and, due to the use of PSA, more and more patients are diagnosed with localized disease. These patients may be offered treatment with the intent to cure. Traditionally, this has been either by radical prostatectomy or some form of radiation therapy. This article describes the minimally invasive method with permanent seed implantation. The procedure, indications, contraindications, side effects and results from the literature 28 patients have been treated so far with acceptable proximate side effects and reductions in serum-PSA as expected.

Improvement of transperineal implant dosimetry by intraoperative cystoscopic confirmation of prostate anatomy

PURPOSE

A simple, inexpensive method to aid in the accurate placement of permanent seeds for prostate brachytherapy is described. The effect of identifying the prostate base and apex cystoscopically relative to registration seeds placed at the beginning of the implant is discussed.

MATERIALS AND METHODS

At the beginning of each implant procedure a pair of marker seeds are first placed in the prostate, including 1 seed at the base and 1 at the apex. Using a cystoscope, the urologist identifies the prostatic base and apex, and a fluoroscopic record is obtained. The positions of the base and apex relative to the marker seeds are monitored throughout the case via fluoroscopy to aid in needle and seed placement for the implant.

RESULTS

Use of this method significantly improved coverage of the prostate apex, reduced overall dose variance in the prostate base and improved overall gland dosimetry by 22% as measured by the D90 quality metric (minimal dose which covers 90% of the prostate volume).

CONCLUSIONS

While the clinical efficacy of improved target coverage on local control and survival awaits further clinical investigation, we encourage others to adopt this easy technique to ensure better, more consistent interstitial implants.

Dosimetric effects of edema in permanent prostate seed implants: a rigorous solution

PURPOSE

To derive a rigorous analytic solution to the dosimetric effects of prostate edema so that its impact on the conventional pre-implant and post-implant dosimetry can be studied for any given radioactive isotope and edema characteristics.

METHODS AND MATERIALS

The edema characteristics observed by Waterman et al (Int. J. Rad. Onc. Biol. Phys, 41:1069-1077; 1998) was used to model the time evolution of the prostate and the seed locations. The total dose to any part of prostate tissue from a seed implant was calculated analytically by parameterizing the dose fall-off from a radioactive seed as a single inverse power function of distance, with proper account of the edema-induced time evolution. The dosimetric impact of prostate edema was determined by comparing the dose calculated with full consideration of prostate edema to that calculated with the conventional dosimetry approach where the seed locations and the target volume are assumed to be stationary.

RESULTS

A rigorous analytic solution on the relative dosimetric effects of prostate edema was obtained. This solution proved explicitly that the relative dosimetric effects of edema, as found in the previous numerical studies by Yue et. al. (Int. J. Radiat. Oncol. Biol. Phys. 43, 447-454, 1999), are independent of the size and the shape of the implant target volume and are independent of the number and the locations of the seeds implanted. It also showed that the magnitude of relative dosimetric effects is independent of the location of dose evaluation point within the edematous target volume. It implies that the relative dosimetric effects of prostate edema are universal with respect to a given isotope and edema characteristic. A set of master tables for the relative dosimetric effects of edema were obtained for a wide range of edema characteristics for both (125)I and (103)Pd prostate seed implants.

CONCLUSIONS

A rigorous analytic solution of the relative dosimetric effects of prostate edema has been derived for a class of edema characterized by Waterman et al. The solution proved that the dosimetric effects caused by the edema are universal functions of edema characteristics for a given isotope. It provides an efficient tool to examine the relative dosimetric effects of edema for any given edema characteristics and for any isotopes that may be considered for prostate implants.

Isotope selection for permanent prostate implants? An evaluation of 103Pd versus 125I based on radiobiological effectiveness and dosimetry

Transperineal interstitial permanent prostate brachytherapy (TIPPB) has become an increasingly popular treatment for early-stage/favorable-risk adenocarcinoma of prostate. Within TIPPB, permanent implants often use either (103)Pd (T(1/2) = 17 days) or (125)I (T(1/2) = 60 days). This review compares the radiobiological and treatment planning effectiveness of (103)Pd and (125)I implants by using the linear-quadratic model with recently published data regarding: prostate tumor cell doubling times, T(pot), alpha and alpha/beta, ratio. The tumor potential doubling times (T(pot)) were determined based on recently published proliferation constants (K(p)). The initial slope of the cell radiation dose survival curve, alpha, the terminal slope beta and the alpha/beta ratio were taken from recent published clinical and cellular results. The total dose delivered from each isotope was the dose used clinically, that is, 120 Gy for (103)Pd and 145 Gy for (125)I. Dale's modified linear-quadratic equation was used to estimate the biological effective dose, the cell-surviving fraction, the effective treatment time, and the wasted radiation dose for different values of T(pot). Treatment plans for peripherally loaded implants were compared. The T(pot) reported for organ-confined prostate carcinomas varied from 16 to 67 days. At short T(pot) both isotopes were less effective, but (103)Pd had much less dependence on T(pot) than (125)I. However, at long T(pot) both isotopes produced similar effects. The minimum surviving fraction for exposure to (103)Pd decreased from 1.40 x 10(-4) to 1.31 x 10(-5) as the T(pot) increased from 16 to 67 days. By contrast for exposure to (125)I, the minimum surviving fraction decreased from 3.98 x 10(-3) to 1.98 x 10(-5) over the same range of T(pot). A comparison of treatment plans revealed that (103)Pd plans required more needles and seeds; however, this was a function of seed strength. Both isotopes had similar dose-volume histograms for prostate, urethra, and rectum. The theoretical prediction of effectiveness using the linear quadratic equation for the common clinically prescribed total radiation doses indicated that (103)Pd should be more effective than (125)I because it had less dependence on T(pot). The greatest benefit of (103)Pd was shown to be with tumors with a short T(pot). Although the regrowth delay would be longer with (125)I, the benefit was inconsequential compared with the very slow doubling times of localized prostate cancer. Treatment planning with either isotope revealed no significant differences. These findings may explain why clinically there seemed to be no clear difference in treatment outcome with either isotope. Based on these predictions, we recommend a clinical trial to compare the efficacy of the two isotopes.

Transient elevation of serum prostate-specific antigen following (125)I/(103)Pd brachytherapy for localized prostate cancer

Based on suggestions by anecdotal evidence to date, an attempt is made to estimate the occurrence of non-disease-related prostate-specific antigen (PSA) spiking in the serum PSA profiles of a series of men treated by (125)I/(103)Pd brachytherapy with or without external beam irradiation. Five hundred ninety-one patients treated between January 1988 and December 1993 were eligible for study. Patients whose clinical status was described as equivocal (declining PSA > 1.0 ng/mL or rising PSA without documented disease [9.6% of the cohort]) were not considered. Evidence of PSA increases that were followed by decline were identified. Treatment and disease-specific parameters were examined for influence of the occurrence of spiking. In patients judged biochemical successes at last follow-up (serum PSA < or = 1.0 ng/mL), 35.8% exhibited a temporary increase of 0.2 ng/mL or more. Seventy-five percent of these patients exhibited a temporary increase between 0.3 and 3.4 ng/mL. The average time of the temporary increases was 24.8 months after implant. Spiking was not associated with a higher risk of clinical failure in this data set. Conventional risk factors for recurrent disease were not associated with benign PSA spiking. Low-magnitude serum PSA spiking may occur in up to one third of patients following permanent, low-dose rate brachytherapy of the prostate. Most of these observations occur up to 3 years after implant and do not appear to be related to disease recurrence. Caution should be taken before initiating further therapy pursuant to the observation of PSA spiking of less than 2 to 3 ng/mL shortly following brachytherapy. Frequent serum PSA sampling following prostate brachytherapy with early follow-up may overestimate biochemical failure rates.

Brachytherapy for prostate cancer: summary of American Brachytherapy Society recommendations

This article summarizes recent American Brachytherapy Society (ABS) recommendations for permanent prostate brachytherapy. The ABS recommends treating patients with high probability of organ-confined disease with brachytherapy alone. Brachytherapy candidates with a significant risk of extraprostatic extension should be treated with supplemental external beam radiation therapy (EBRT). The recommended prescription doses for monotherapy are 145 Gy for (125)I and 125 Gy for (103)Pd. The corresponding boost doses (after 40 to 50 Gy EBRT) are 110 Gy and 100 Gy, respectively. The ABS recommends that post-implant dosimetry should be performed on all patients undergoing permanent prostate brachytherapy for optimal patient care. A dose-volume histogram (DVH) of the prostate should be performed and the D(90) (dose to 90% of the prostate gland) reported by all centers. Additionally, the D(80) D(100), the fractional V(80), V(90), V(100), V(150), V(200) (ie, the percentage of prostate volume receiving 80%, 90%, 100%, 150%, and 200% of the prescribed dose, respectively), the rectal and urethral doses should be reported and ultimately correlated with clinical outcome in the research environment. On-line, real-time dosimetry, the effects of dose heterogeneity, and the effects of tissue heterogeneity need further investigation.

Toward a statistically relevant calibration end point for prostate seed implants

Interstitial brachytherapy for carcinoma of the prostate is achieved through the use of a configuration of radioactive seeds placed in a manner that delivers a customized, reasonably uniform dose to the target volume. Accurate dose delivery depends on both precise seed placement and reliable seed strength in the implanted configuration. This study assumes the independence of the two issues, and quantifies the reduction in the minimum dose to the surface of the gland due only to variability in individual seed strengths. Current AAPM guidelines pertaining to the acceptable limits on seed-to-seed variability are prudent for small configurations of seeds, yet are likely to be overly stringent for applications such as prostate seed implantation. In this study we determine the reduction in the minimum peripheral dose (mPD) caused by the introduction of source strength variability, and provide statistical insight into this effect. It is concluded that the current guidelines limit the reduction in mPD to < or =0.4% relative to the prescription value, for an average configuration, due to the inclusion of strength variability. The maximum observed reduction in mPD would be < or =1.5%. This value is an order of magnitude lower than the recommendations of the AAPM Task Group 40 for the overall accuracy of brachytherapy procedures, which suggests that seed strength variability is of limited concern and that constraints on this factor should perhaps be reevaluated.

[Focal morphological changes in the bone tissue of the mandible and tibia of rabbits under the influence of different metal inclusions]

Morphological changes in bone tissue were studied in an experimental model with electrochemical polarization of the bone, which was achieved by applying electrodes (anode made of silver-palladium alloy SPS-250 and cathode of copper-aluminum alloy manufactured as orthodontic ligature wire) on the mandibular periosteum and tibial bone of rabbits. Macroscopic changes were as follows: osseous tissue hypertrophy at the zone of cathode polarization with a corresponding increase in the area of transverse section of the mandible and atrophy of the bone under the anode, all this causing pronounced asymmetry of the jaw bones. Microscopic changes in the bone were adequate to the macroscopic and characterized by sharp activation of its apposition (under cathode) and resorption (under anode).

Long-term complications with prostate implants: iodine-125 vs. palladium-103

The linear quadratic model predicts that the normal tissue biologically effective dose (BED) will be lower with palladium-103 (Pd-103) vs. iodine-125 (I-125) for the currently prescribed minimum tumor doses (MTD) used for I-125 (160 Gy) and Pd-103 (115 Gy) prostate cancer brachytherapy. The predicted BEDs for I-125 and Pd-103 suggest that the long-term complication rates should be lower with Pd-103 vs. I-125 in clinical practice. A review of 123 early stage T1c and T2 prostate cancer patients implanted at Yale University with I-125 (82 patients) or Pd-103 (41 patients) reveals a significantly lower overall complication rate with Pd-103 (0%) vs. I-125 (13%). Most important, the grade III-IV complication rate for Pd-103 was 0% vs. 6% for I-125. The 3-year actuarial probability of remaining free of a long-term complication was 100% for Pd-103 vs. 82% for I-125 (P<0.01). A review of the literature for 992 patients implanted with I-125 vs. 540 patients implanted with Pd-103 shows a consistently higher complication rate for I-125 vs. Pd-103. Assuming that the MTD for Pd-103 may be increased to produce an equivalent late-reacting normal tissue BED to that for I-125, then the radiobiology model predicts the log10 cell kill for Pd-103 implant will be greater than that of an I-125 implant for all tumor doubling times (high-grade tumors and low-grade tumors). The implications of these findings are discussed in terms of future research directions for prostate implants.

Dosimetric considerations for catheter-based beta and gamma emitters in the therapy of neointimal hyperplasia in human coronary arteries

PURPOSE

Recent data indicate that intraluminal irradiation of coronary arteries following balloon angioplasty reduces proliferation of smooth muscle cells, neointima formation, and restenosis. We present calculations for various isotopes and geometries in an attempt to identify suitable source designs for such treatments.

METHODS AND MATERIALS

Analytical calculations of dose distributions and dose rates are presented for 192Ir, 125I, 103Pd, 32P, and 90Sr for use in intracoronary irradiation. The effects of source geometry and positioning accuracy are studied.

RESULTS

Accurate source centering, high dose rate, well-defined treatment volume, and radiation safety are all of concern; 15-20 Gy are required to a length of 2-3 cm of vessel wall (2-4 mm diameter). Dose must be confined to the region of the angioplasty, with reduced doses to normal tissues. Beta emitters have radiation safety advantages, but may not have suitable ranges for treating large diameter vessels. Gamma emitters deliver larger doses to normal tissues and to staff. Low energy x-ray emitters such as 125I and 103Pd reduce these risks but are not available at high enough activities. The feasibility of injecting a radioactive liquid directly into the angioplasty balloon is also explored.

CONCLUSIONS

Accurate source centering is found to be of great importance. If this can be accomplished, then high energy beta emitters such as 90Sr would be ideal sources. Otherwise, gamma emitters such as 192Ir may be optimal. A liquid beta source would have optimal geometry and dose distribution, but available sources, such as 32P are unsafe for use with available balloon catheters.

Feasibility study of the treatment of primary unresectable carcinoma of the pancreas with 103Pd brachytherapy

PURPOSE

The purpose of this study was to assess the feasibility of 103Pd brachytherapy in the management of primary unresectable carcinoma of the pancreas.

METHODS AND MATERIALS

Between August 1988 and January 1992, 11 patients with biopsy-proven primary unresectable adenocarcinoma of the pancreas were treated with 103Pd brachytherapy during laparotomy. The median age was 66 (range 57-70). The most common presenting symptoms were weight loss (eight patients), pain (six patients), and nausea/vomiting (four patients). Less common symptoms were jaundice (two patients), early satiety (two patients), and ascites (one patient). All patients underwent laparotomy and surgical staging. Eight patients had T3N0M0 disease, two patients had T3N1M0 disease, and one patient had T3N1M1 disease. The surgical procedure performed was biliary bypass in six patients, biopsy only in four patients, and gastric bypass in one patient. The average tumor dimension was 4.0 cm. The median activity, matched peripheral dose (MPD) and implanted volumes were 95.3 mCi, 124.4 Gy, and 33 cm3, respectively. The median initial dose rate was 0.21 Gy per hour. Five patients received postoperative external beam radiation therapy (median 45 Gy) and seven patients received chemotherapy postoperatively. The median follow-up was 7 months (range 1-19).

RESULTS

The median survival for the entire group of patients was 6.9 months. Ten of 11 patients have died, with 1 patient presently alive and receiving chemotherapy for metastatic disease to the liver, but without local progression radiographically. Five of 11 patients (45%) were locally controlled, defined as either a complete response or freedom from progression at the site of the implant as evaluated by computed tomography scan. In the other six patients, the median time to local progression was 6.9 months. Five patients developed distant metastases (four liver, one subcutaneous nodule). Two patients failed in regional sites (one omentum, one paraaortic lymph node). Four of 11 patients (36%) developed acute postoperative complications that included one gastric outlet obstruction, one duodenal perforation, and two with sepsis. One of 11 patients (9%) developed a late complication of radiation enteritis 5 months after implantation. The median survival for patients experiencing complications was 1.7 months as compared to 8.4 months for the patients who did not develop a complication (p = 0.10). Pain relief was obtained in five out of six (83%) of the patients presenting with pain for a median duration of 24 weeks. Local control did not appear to be related to the MPD, dose rate, implanted volume, treatment with external beam irradiation, or the use of chemotherapy. Patients were more likely to develop a complication if the MPD was greater than 115 Gy (four out of six patients) as compared to those whose MPD was less than 115 Gy (one out of five patients) (p = 0.12).

CONCLUSIONS

Because there was no improvement in median survival over conventional modalities, and the complication rate was high; we do not recommend 103Pd brachytherapy as a component of the treatment of unresectable adenocarcinoma of the pancreas.

Palladium-103: a new radioactive source in the treatment of unresectable carcinoma of the pancreas: a phase I-II study

Palladium-103 (Pd-103) is introduced in brachytherapy procedures because of its favorable physical properties, including its low energy, rapid dose fall-off, short half-life, and total cumulative dose delivery at a higher dose rate than iodine-125 (I-125) isotope. Intraoperative brachytherapy using I-125 pellets was reported to provide significant palliation and meaningful prolongation of life in highly selected patients with unresectable carcinoma of the pancreas. After considering some of the advantages of Pd-103 over I-125, we designed a phase I-II clinical trial to assess the feasibility of intraoperative Pd-103 in unresectable carcinoma of the pancreas to study the related morbidity when combined with chemotherapy and external beam radiation, and to evaluate the impact on palliation and local control rates. Between December 1989 and December 1993, 15 patients with biopsy-proven unresectable adenocarcinoma of the pancreas were treated with interstitial Pd-103 implants during laparotomy. In 13 patients the lesion was located in the head of the pancreas, in one patient in the uncinate process, and in one patient in the body of the pancreas. The stage distribution was as follows: T1 = 2; T2 = 6, and T3 = 7. In addition, all patients underwent biliary and gastric bypass. The mean number of Pd-103 pellets was 45; the mean total activity to obtain a matched peripheral dose (MPD) of 11,000 cGy was 68.9 mCi. The mean tumor volume encompassing the MPD was 16.5 cc. All patients received postoperative external beam radiation (4,500 cGy over 4 1/2 weeks) and chemotherapy (5-fluorouracil and mitomycin C). This combined treatment, consisting of intraoperative brachytherapy using Pd-103 and postoperative external beam radiation with chemotherapy, was well tolerated in all patients. These were no treatment-related mortalities, and no serious complications, such as bleeding or fistula formation. Pain relief was obtained within 3-6 weeks in 10 out of 12 patients presenting with pain. Survival ranged from 6 to 24 months (median 10 months). The study suggests that Pd-103 can be considered an alternative to I-125 for interstitial brachytherapy for unresectable carcinoma of the pancreas. Symptom relief appeared to occur faster and complications are significantly less. However, this study did not show any improvement in the median survival rate over I-125 due to the advanced stage cancer in the majority of patients in the study.

Response of L-929 fibroblasts, human gingival fibroblasts, and human tissue mast cells to various metal cations

Recent data suggest that under certain conditions, various metal cations are released from dental alloys. These ions may produce adverse effects in various cell types in vivo. In this study, the cytopathogenic effects of 13 metal cations on murine L-929 fibroblasts, human gingival fibroblasts, and human tissue mast cells were analyzed in vitro. Several metal cations (dose range, from 0.0033 to 1.0 mmol/L) were found to induce dose-dependent inhibition of 3H-thymidine incorporation into cultured fibroblasts. The rank order of potency (lowest observed effect level, LOEL) for L-929 fibroblasts was: Ag+ > Pt4+ > Co2+ > In3+ > Ga3+ > Au3+ > Cu2+ > Ni2+ > Zn2+ > Pd2+ > Mo5+ > Sn2+ > Cr2+. A similar rank order of potency was obtained for primary human gingival fibroblasts: Pt4+ > Ag+ > Au3+ > In3+ > Ga3+ > Ni2+ > Co2+ > Zn2+ > Cu2+ > Cr2+ > Pd2+ > Mo5+ > Sn2+. In primary human mast cells, Ag+ and Au3+ caused dose-dependent toxic histamine release, whereas the other metal cations were ineffective over the dose range tested. To investigate the mechanism of metal cation-induced effects, we performed DNA as well as electron microscopic analyses on cultured fibroblasts. Both the DNA pattern and the ultrastructure of L-929 cells and gingival fibroblasts after exposure to cytopathogenic metal cations revealed signs of necrosis but no signs of apoptosis. Together, our data provide evidence that various metal cations produce dose-dependent cytopathogenic effects in distinct cell types, including human gingival fibroblasts and human tissue mast cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative nephrotoxic effects of cis-platinum (II), cis-palladium (II), and cis-rhodium (III) metal coordination compounds in rat kidneys

A Sprague-Dawley rat kidney perfusion technique was used in situ to study the effects of cis-dichloro-diamine platinum, PdCl2 (2,6-diaminopyridine), and RhCl3 (2,6-diaminopyridine) on sodium and calcium retention in the whole kidney. The technique involves perfusion of both kidneys via the abdominal aorta and then through the right and left renal arteries and dorsal aorta. Compared to controls, kidneys perfused independently with the three coordination compounds showed approximately equal to 45% decrease and approximately equal to 117% increase in Na+ and Ca2+ retention, respectively. Perfusates containing the coordination compounds in addition to 15 mM ouabain showed approximately equal to 76% decrease in Na+ and insignificant increase in renal Ca2+ retention. Hence, one can rule out the presence of voltage-gated Ca(2+)-channels at the basolateral side due to membrane depolarization. These results suggest that the three metal coordination compounds showed identical nephrotoxic effects on the handling of Na+ and Ca2+ ions by inhibiting both the Na(+)-Ca(2+)-anti-porter and the Na(+)-H(+)-exchanger with laxing effects on nonvoltage-gated Ca(2+)-channels at the basolateral side. However, their effects on the Na(+)-K(+)-ATPase and the Na(+)-Ca2+ symporter was insignificant.