Approximate Bayesian computation for spatial SEIR(S) epidemic models

Approximate Bayesia n Computation (ABC) provides an attractive approach to estimation in complex Bayesian inferential problems for which evaluation of the kernel of the posterior distribution is impossible or computationally expensive. These highly parallelizable techniques have been successfully applied to many fields, particularly in cases where more traditional approaches such as Markov chain Monte Carlo (MCMC) are impractical. In this work, we demonstrate the application of approximate Bayesian inference to spatially heterogeneous Susceptible-Exposed-Infectious-Removed (SEIR) stochastic epidemic models. These models have a tractable posterior distribution, however MCMC techniques nevertheless become computationally infeasible for moderately sized problems. We discuss the practical implementation of these techniques via the open source ABSEIR package for R. The performance of ABC relative to traditional MCMC methods in a small problem is explored under simulation, as well as in the spatially heterogeneous context of the 2014 epidemic of Chikungunya in the Americas.

An empirically adjusted approach to reproductive number estimation for stochastic compartmental models: A case study of two Ebola outbreaks

The various thresholding quantities grouped under the "Basic Reproductive Number" umbrella are often confused, but represent distinct approaches to estimating epidemic spread potential, and address different modeling needs. Here, we contrast several common reproduction measures applied to stochastic compartmental models, and introduce a new quantity dubbed the "empirically adjusted reproductive number" with several advantages. These include: more complete use of the underlying compartmental dynamics than common alternatives, use as a potential diagnostic tool to detect the presence and causes of intensity process underfitting, and the ability to provide timely feedback on disease spread. Conceptual connections between traditional reproduction measures and our approach are explored, and the behavior of our method is examined under simulation. Two illustrative examples are developed: First, the single location applications of our method are established using data from the 1995 Ebola outbreak in the Democratic Republic of the Congo and a traditional stochastic SEIR model. Second, a spatial formulation of this technique is explored in the context of the ongoing Ebola outbreak in West Africa with particular emphasis on potential use in model selection, diagnosis, and the resulting applications to estimation and prediction. Both analyses are placed in the context of a newly developed spatial analogue of the traditional SEIR modeling approach.

A spatial epidemic model for disease spread over a heterogeneous spatial support

Data from the Iowa mumps epidemic of 2006 were collected on a spatial lattice over a regular temporal interval. Without access to a person-to-person contact graph, it is sensible to analyze these data as homogenous within each areal unit and to use the spatial graph to derive a contact structure. The spatio-temporal partition is fine, and the counts of new infections at each location at each time are sparse. Therefore, we propose a spatial compartmental epidemic model with general latent time distributions (spatial PS SEIR) that is capable of smoothing the contact structure, while accounting for spatial heterogeneity in the mixing process between locations. Because the model is an extension of the PS SEIR model, it simultaneously handles non-exponentially distributed latent and infectious time distributions. The analysis within focuses on the progression of the disease over both space and time while assessing the impact of a large proportion of the infected people dispersing at the same time because of spring break and the impact of public awareness on the spread of the mumps epidemic. We found that the effect of spring break increased the mixing rate in the population and that the spatial transmission of the disease spreads across multiple conduits.

Survival of non-small cell lung cancer (NSCLC) patients with and without diabetes mellitus (DM): Findings from the Cancer Care Outcomes Research and Surveillance Consortium (CanCORS)

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Background: DM increases all-cause mortality in the general population. It is also associated with more complications from chemotherapy, increased risk of radiation pneumonitis and worse surgical-wound healing. In this study, we explored the effect of DM on NSCLC overall survival. Methods: This study utilized the surveys and abstracted medical record resources of NSCLC patients studied by CanCORS, an inception cohort of newly diagnosed lung and colon cancer patients from the United States. Patients with NSCLC stage I-IV were included. The log-rank test was used to compare the survival curves of patients with and without DM. Cox proportional hazard models were used to adjust for other variables in the survival model. Results: Of the 2243 NSCLC patients, 359 (16%) had DM. Survival for patients diagnosed with DM was significantly worse than patients without DM [hazard ratio (HR) 1.28; 95% confidence interval (CI) 1.13-1.45]. The median overall survival for patients with and without DM was 561 and 833 days, respectively. DM was also associated with poorer survival (HR 1.20; 95% CI 1.05, 1.36) after adjusting for age, smoking status, stage, treatment (radiation, chemotherapy), brain metastasis, severity of respiratory symptoms at diagnosis, and comorbidities. While a significant interaction between stage and DM was not detectable after adjusting for the above, the estimated Kaplan-Meier plots present more prominent differences in stages I-III, with virtually overlapping plots in stage IV. Conclusions: DM was associated with worse survival in NSCLC patients. Although this finding can be utilized when counseling diabetic NSCLC patients, it is unknown if improving DM care will result in a better survival. The effect of DM on survival in the various stages of NSCLC needs further study.

A path-specific SEIR model for use with general latent and infectious time distributions

Most current Bayesian SEIR (Susceptible, Exposed, Infectious, Removed (or Recovered)) models either use exponentially distributed latent and infectious periods, allow for a single distribution on the latent and infectious period, or make strong assumptions regarding the quantity of information available regarding time distributions, particularly the time spent in the exposed compartment. Many infectious diseases require a more realistic assumption on the latent and infectious periods. In this article, we provide an alternative model allowing general distributions to be utilized for both the exposed and infectious compartments, while avoiding the need for full latent time data. The alternative formulation is a path-specific SEIR (PS SEIR) model that follows individual paths through the exposed and infectious compartments, thereby removing the need for an exponential assumption on the latent and infectious time distributions. We show how the PS SEIR model is a stochastic analog to a general class of deterministic SEIR models. We then demonstrate the improvement of this PS SEIR model over more common population averaged models via simulation results and perform a new analysis of the Iowa mumps epidemic from 2006.

Do patients with advanced-stage non-small cell lung cancer (AS NSCLC) live longer if managed within a clinical trial setting?

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Background: Treatment outcomes of AS NSCLC (stages IIIB and IV) are poor. There is an argument that participation in a clinical trial (CT) may confer survival benefit, probably, through enhancing quality of care. In this study, we explore the survival outcomes and perceived care quality for AS NSCLC patients (pts) treated within vs outside a CT. Methods: Data were obtained from surveys of newly diagnosed AS NSCLC pts studied by the Cancer Care Outcomes Research and Surveillance Consortium (CanCORS), a large cohort of pts across the United States. Pts who did not complete the baseline survey were excluded as this was associated with worse performance status (PS). Baseline characteristics according to CT participation were determined. Association between CT enrollment and survival was explored utilizing univariate and multivariate survival analysis after adjusting for age, comorbidities and self-reported PS. Results: Of 815 AS NSCLC pts, 56 (7%) were enrolled on a CT. Chemotherapy trials comprised 67% of all trials. Of the 815 pts, 697 (86%) died. Median survival for pts within vs outside a CT was 62 vs 64 months. Neither age, comorbidities nor recalled PS differed significantly between pts within vs outside a CT (P=0.2085, 0.5818 and 0.1678 respectively). On the multivariate survival model, CT enrollment did not correlate with longer survival (P=0.8811) and only presence of comorbidities was associated with worse survival (P=0.0021). Comparing pts according to CT enrollment, there was no significant difference in symptom management, receiving hospice care (P=0.606), death location (P=0.2018), or following pts’ wishes (P=0.8321). However, perception of the overall cancer care quality was greater among CT enrollees (P=0.0171). Conclusions: Management of AS NSCLC pts within a CT setting conveyed a perception of superior care that did not translate into survival benefit after adjusting for differences in age, comorbidities, and self-reported PS. These findings suggest that providing cancer care within a CT should not imply a survival benefit when counseling AS NSCLC pts about entering CTs.

Prostate cancer DNA ploidy and response to salvage hormone therapy after radiotherapy with or without short-term total androgen blockade: an analysis of RTOG 8610

PURPOSE

DNA ploidy has consistently been found to be a correlate of prostate cancer patient outcome. However, a minority of studies have used pretreatment diagnostic material and have involved radiotherapy (RT)-treated patients. In this retrospective study, the predictive value of DNA ploidy was evaluated in patients entered into Radiation Therapy Oncology Group protocol 8610. The protocol treatment randomization was RT alone versus RT plus short-course (approximately 4 months) neoadjuvant and concurrent total androgen blockade (RT+TAB).

PATIENTS AND METHODS

The study population consisted of 149 patients, of whom 74 received RT alone and 75 received RT+TAB. DNA content was determined by image analysis of Feulgen stained tissue sections; 94 patients were diploid and 55 patients were nondiploid. Kaplan-Meier univariate survival, the cumulative incidence method, and Cox proportional hazards multivariate analyses were used to evaluate the relationship of DNA ploidy to distant metastasis and overall survival.

RESULTS

DNA nondiploidy was not associated with any of the other prognostic factors in univariate analyses. In Kaplan-Meier analyses, 5-year overall survival was 70% for those with diploid tumors and 42% for nondiploid tumors. Cox proportional hazards regression revealed that nondiploidy was independently associated with reduced overall survival. No correlation was observed between DNA ploidy and distant metastasis. The diminished survival in the absence of an increase in distant metastasis was related to a reduction in the effect of salvage androgen ablation; patients treated initially with RT+TAB and who had nondiploid tumors had reduced survival after salvage androgen ablation.

CONCLUSIONS

Nondiploidy was associated with shorter survival, which seemed to be related to reduced response to salvage hormone therapy for those previously exposed to short-term TAB.

Neoadjuvant estramustine and etoposide followed by concurrent estramustine and definitive radiotherapy for locally advanced prostate cancer: feasibility and preliminary results

PURPOSE

Current therapy for locally advanced prostate cancer is suboptimal. A treatment regimen was designed to improve systemic control by neoadjuvant targeting of hormone-sensitive and -insensitive micrometastatic disease and to improve local control by escalating the biologic effective dose to the prostate using estramustine (EMP) concurrently with radiotherapy.

PATIENTS AND METHODS

Eighteen patients with locally advanced prostate cancer (Stages T3/T4 or T1c/T2b/T2c with a Gleason score of > or =7 and a serum PSA >15 ng/ml) were entered onto this trial. Therapy consisted of two 21-day cycles of oral estramustine (10 mg/kg/day) in three divided doses and oral etoposide (50 mg/m(2)/day, in two divided doses), followed by concurrent estramustine (10 mg/kg/day, PO) and three-dimensional conformal radiotherapy.

RESULTS

Two patients required discontinuation of chemotherapy due to development of Grade 3 and 4 toxicity. All others completed both components of therapy per protocol guidelines. Minor toxicities included alopecia (100% of patients), anemia (69%), leukopenia (37%), thrombocytopenia (19%), and nausea (6%) but did not require dose modifications. There were no fatalities. Actuarial 3-year overall survival and disease-free survival (DFS) were 88% and 73%, respectively. Local control rate, assessed by repeated prostate biopsies at 18 months post completion of therapy, was 71%.

CONCLUSION

The described regimen is well tolerated, and preliminary efficacy data are encouraging. The underlying concepts of early targeting of both hormone-sensitive and -insensitive micrometastatic clones, in combination with aggressive local therapy, warrant further investigation.

Therapeutic Strategies for Localized Prostate Cancer II: Perineal Prostatectomy, X-Rays, Protons, Neutrons, and Combination Brachytherapy

Application of improved imaging, diagnostic, and computer techniques is beginning to have an impact on the management of localized prostate cancer. It is possible to perform a range of surgical and radiation procedures with less morbidity than in the past. The changes in therapy for patients with localized disease derive from better knowledge of anatomy for invasive procedures and optimization of virtual planning for noninvasive methods. Perineal prostatectomy and combinations of beam and seed radiation offer both patient and physician reasonable therapeutic options.

The impact of race on biochemical disease-free survival in early-stage prostate cancer patients treated with surgery or radiation therapy

PURPOSE

To assess the impact of race on biochemical freedom from recurrence in patients with early-stage prostate cancer treated either by radical prostatectomy or radiation therapy.

METHODS

Between July 1989 and December 1994, 693 patients with early-stage prostate cancer were treated with radiation (302 patients) or by radical prostatectomy (391 patients) at Barbara Ann Karmanos Cancer Institute/Wayne State University. Stage, Gleason score, race, pretreatment PSA, and follow-up PSA values were abstracted. There were 387 Caucasian males (CM) and 306 African-American males (AAM). None of the patients received hormone therapy. Radiation therapy was delivered using photon irradiation (249 patients, median dose 69 Gy) or mixed neutron/photon irradiation (53 patients, median dose 10 NGy + 38 PGy). Median follow-up was 36 months (range 2-70) for CM and 35 months (range 1-70) for AAM.

RESULTS

Thirty-seven percent of patients treated surgically were AAM, compared to 53% in the radiation group (p = 0001). AAM had a higher median prostate-specific antigen (PSA) than CM (9.78 ng/ml vs. 8.0 ng/ml, p = 0.01). Thirty-three percent of AAM had a pretreatment PSA greater than 15 ng/ml compared to 20% of CM (p = 0.00001). Disease-free survival (DFS) by race was equivalent at 36 months, 81% for CM and 77% for AAM (p = NS). For patients with PSA < or =15, DFS rates were 87% and 85% for CM and AAM, respectively. DFS rates for patients with PSA >15 were 61% for CM and 64% for AAM (p = NS). Significant prognostic factors on multivariate analysis included pretreatment PSA (p = 0.0001) and Gleason score (p = 0.0001).

CONCLUSION

Race does not appear to adversely affect biochemical disease-free survival in males treated for early-stage prostate cancer. African-American males with early-stage prostate cancer should expect similar biochemical disease-free survival rates to those seen in Caucasian males.

External beam radiotherapy for painful osseous metastases: pooled data dose response analysis

PURPOSE

Although the effectiveness of external beam irradiation in palliation of pain from osseous metastases is well established, the optimal fractionation schedule has not been determined. Clinical studies to date have failed to demonstrate an advantage for higher doses. To further address this issue, we conducted a pooled dose response analysis using data from published Phase III clinical trials.

METHODS AND MATERIALS

Complete response (CR) was used as an endpoint because it was felt to be least susceptible to inconsistencies in assessment.The biological effective dose (BED) was calculated for each schedule using the linear-quadratic model and an alpha/beta of 10. Using SAS version 6.12, the data were fitted using a weighted linear regression, a logistic model, and the spline technique. Finally, BED was categorized, and odds ratios for each level were calculated.

RESULTS

CR was assessed early and late in 383 and 1,007 patients, respectively. Linear regression on the early-response data yielded a poor fit and a nonsignificant dose coefficient. With the late-response data, there was an excellent fit (R-square = 0.842) and a highly significant dose coefficient (p = 0.0002). Fitting early CR to a logistic model, we could not establish a significant dose response relationship. However, with the late-response data there was an excellent fit and the dose coefficient was significantly different from zero (0.017 +/- 0.00524; p = 0.0012). Application of the spline technique or removal of an outlier resulted in an improved fit (p = 0.048 and p = 0.0001, respectively). Using BED of < 14.4 Gy as a reference level, the odds ratios for late CR were 2.29-3.32 (BED of 19.5-51.4 Gy, respectively).

CONCLUSION

Our results demonstrate a clear dose-response for pain relief. Further testing of high intensity regiments is warranted.

Apoptosis induction by a novel anti-prostate cancer compound, BMD188 (a fatty acid-containing hydroxamic acid), requires the mitochondrial respiratory chain

We recently developed a class of novel anti-prostate cancer compounds, cyclic hydroxamates that elicit a potent apoptotic response in many tumor cells cultured in vitro (D.G. Tang et al., Biochem. Biophys. Res. Commun., 242: 380-384, 1998). The lead compound, termed BMD188, induces programmed cell death in a variety of prostate cancer cells in vitro as well as in vivo (L. Li et al., Anticancer Res., 19: 51-70, 1999). BMD188 kills androgen-independent prostate cancer cells as well as prostate cancer cells with a multidrug-resistance phenotype. The apoptotic effect of BMD188 in prostate cancer cells does not depend on cell cycle, p53 status, or its purported target, arachidonate 12-lipoxygenase, but does require caspase activation and seems to involve mitochondria. To synthesize more specific and effective anti-prostate cancer hydroxamic acid compounds, it is important to understand their mechanism(s) of action. In the present study, we studied the role of mitochondrial respiratory chain (MRC) in BMD188-induced apoptosis in androgen-independent prostate cancer PC3 cells and compared its effect with that of staurosporine (STS), a widely used apoptosis inducer. Several lines of evidence indicate that BMD188-induced cell death depends on MRC: (a) the death could be significantly inhibited by several complex-specific respiration inhibitors; (b) respiration-deficient rho0 cells were more resistant than wild-type parent cells to apoptosis induction by BMD188; and (c) BMD188 induced a rapid increase in reactive oxygen species in mitochondria, an up-regulation of cytochrome c oxidase subunits, a biphasic alteration (i.e., an early hyperpolarization, followed by later hypopolarization) in the mitochondrial membrane potential (delta psi(m)), dramatic changes in mitochondrial morphology and distribution prior to caspase activation, and an abnormal proliferation of mitochondria at the ultrastructural level. By contrast, STS-induced PC3 apoptosis seemed not to depend on MRC. Taken together, the data suggest that the MRC represents a functional target for anti-prostate cancer hydroxamates.

The cost-effectiveness of mixed beam neutron-photon radiation therapy in the treatment of adenocarcinoma of the prostate

The results of clinical trials in the treatment of adenocarcinoma of the prostate using, mixed beam neutron/photon therapy, neutrons alone and photon therapy in combination with hormone treatment are compared. These trials indicate that neutron therapy is superior to photon/hormone therapy in achieving local control. The costs of delivering these two different therapies in a large US academic radiation oncology center at Wayne State University (WSU) are compared. The cost of a full course of mixed beam therapy is $20,142 compared to $18,871 for the photon/hormone treatment. Although the WSU neutron facility is a state-of-the-art installation, it is also a prototype device; it is estimated that a modern neutron facility based on this design would operate more cost effectively reducing the cost of a course of mixed beam therapy to $18,532.

Hormone-refractory prostate cancer cells express functional follicle-stimulating hormone receptor (FSHR)

PURPOSE

Understanding growth regulation in hormone-refractory prostate cancer may provide avenues for novel treatment interventions. This study was conducted to characterize the expression of the receptor (FSHR) for follicle-stimulating hormone (FSH) in androgen-independent prostate cancer cell lines and in human malignant prostate tissues.

MATERIALS AND METHODS

Western blotting, immunohistochemistry (IHC), and flow cytometric analysis were used to study the expression of FSHR. The effect of FSH on cell growth and clonogenicity was studied using proliferation and clonogenic assays.

RESULTS

Immunohistochemistry revealed expression of FSH in PC3 and Du145 cells. FSHR was identified in PC3 and Du145 cells, as well as in human adenocarcinoma of the prostate. The specificity of the FSHR detected on prostate cancer tissues or cells by IHC and Western blotting was confirmed by preabsorbing the antibodies with the immunizing antigens. Stimulation of these hormone-refractory cells with FSH triggered a proliferative response in vitro, suggesting that the receptor is biologically active.

CONCLUSION

Hormone-refractory prostate cancer cells express FSH and biologically active FSHR. Our results suggest that FSHR and its ligand may play a role in the regulation of the growth of hormone-refractory prostate cancers.

Prostate secretory protein (PSP94) suppresses the growth of androgen-independent prostate cancer cell line (PC3) and xenografts by inducing apoptosis

BACKGROUND

PSP94 (prostate secretory protein of 94 aa; also called PIP), one of the predominant proteins secreted into the seminal fluid, was proposed as an independent diagnostic/prognostic marker for prostate cancers. It was also shown to inhibit rat prostate cancer growth. In this study, we investigated the effect of purified PSP94 on the growth of androgen-independent human prostate cancer cells (PC3) and its potential mechanism of action.

METHODS AND RESULTS

PSP94, in a dose- and time-dependent manner, inhibited the growth of PC3 cells. The protein demonstrated a stronger inhibitory effect on the colony-forming ability of PC3 cells in soft agar. A daily injection of PSP94 at 5 microg/kg/body weight resulted in a 50-60% inhibition in the growth of PC3 xenografts in athymic mice. PC3 cell growth inhibition by PSP94 resulted from cell death characteristic of morphological apoptosis, which was confirmed by dual fluorescence microscopy, electron microscopy, and DNA fragmentation assays. Mechanistic studies indicated that PSP94 enhanced the expression of proapoptotic protein Bax without affecting Bcl-2 levels.

CONCLUSIONS

This study suggests that PSP94 may represent a novel, apoptosis-based, antitumor agent applicable to the treatment of hormone-refractory human prostate cancers.

A novel hydroxamic acid compound, BMD188, demonstrates anti-prostate cancer effects by inducing apoptosis. I: In vitro studies

BACKGROUND

Prostate cancer is the most frequently diagnosed malignancy in the Western countries. Apoptosis-targeted drug development could represent a specific and effective weapon against the disease (Tang and Porter, 32: 284-293, 1997). We previously demonstrated that the arachidonate 12-lipoxygenase and its metabolic products could function as survival factors for many solid tumors (Tang et al., Proc. Natl. Acad. Sci. USA 93: 5241-5246, 1996; Tang and Honn, J. Cell. Physiol. 172: 155-170, 1997).

MATERIALS AND METHODS

In this study, we synthesized a series of novel cyclic hydroxamic acid compounds that demonstrated varying degrees of inhibitory effects on the arachidonate 12-lipoxygenase. Subsequently we studied the effects of these novel compounds on human prostate cancer cells. First, all these compounds were screened on androgen-independent PC3 adenocarcinoma cells. Second, based on the results (i.e., the LD50 values) of the primary, secondary and tertiary screening, lead compounds were determined. Third, the lead compounds were utilized to study their cytotoxic effects on various prostate cancer cells as well as several types of normal cells. Finally, the molecular nature of the cell death was thoroughly characterized and the potential mechanisms of cell death were determined.

RESULTS

About 30% of the compounds screened induced a strong apoptotic death of androgen-independent prostate cancer cells, PC3, with an LD50 mostly at 10-20 microM. A lead compound, BMD188 [cis-1-hydroxy-4-(1-naphthyl)-6-octylpiperidine-2-one], was subsequently identified which inhibited the growth of PC3 cells with an LD50 at approximately 10 microM. Comparative studies indicated that BMD188 induced a more potent apoptotic response in PC3 cells than several conventional chemotherapeutic drugs. Furthermore, unlike the above drugs, BMD188 could induce 100% apoptosis in tumor cells. BMD188 also caused apoptosis of other types of prostate cancer cells including cells with multidrug resistance phenotype, independent of the androgen-dependence and p53 status. By contrast, BMD188 generally demonstrated 2-5 fold lower cytotoxicity towards several normal cell types including normal prostate epithelial cells. The growth inhibition by BMD188 was due to apoptosis induction as evidenced by DNA ladder formation, PARP [poly(ADP-ribose)polymerase] cleavage, and typical apoptotic morphology. BMD188-induced apoptosis does not depend on its inhibitory effects on lipoxygenase since target cells (i.e., PC3 and Du145) did not express the lipoxygenase mRNA and protein. In contrast, the apoptosis-inducing effect of BMD188 in PC3 cells could be significantly inhibited by serine protease inhibitors TPCK and TLCK as well as by caspase inhibitors DEVD and zVAD. The involvement of caspases in the apoptotic effects of BMD188 was further confirmed by the activation of caspase-3 (CPP32). In the accompanying paper, we show that BMD188 also inhibits the primary growth and local invasion of Du145 prostate cancer cells orthotopically implanted into the SCID or athymic nude mice.

CONCLUSION

The data presented here suggest that these novel cyclic hydroxamic acid compounds, via induction of apoptotic death, may find potential clinical applications in the treatment of human prostate cancers.

A novel hydroxamic acid compound, BMD188, demonstrates anti-prostate cancer effects by inducing apoptosis. II: In vivo efficacy and pharmacokinetic studies

BACKGROUND

In the preceding paper, we demonstrated that, BMD188 [cis-1-hydroxy-4-(1-naphthyl)-6-octylpiperidine-2-one], a newly synthesized cyclic hydroxamic acid compound, induces potent apoptotic death of prostate cancer cells in vitro. In this project, we studied the in vivo pharmacokinetic behavior and anti-tumor efficacy of this novel compound.

MATERIALS AND METHODS

A bioavailability/elimination study was first performed using radiolabeled BMD188 administered to rats through intraperitoneal (i.p.), intravenous (i.v). or oral (p.o.) routes. Based on these pharmacokinetic data as well as pilot experiments on in vivo toxicity, two sets of efficacy studies, with i.p. administered BMD188, were performed in SCID mice or athymic nude mice which had been orthotopically transplanted with Du145 human prostate cancer cells. Tumor growth rate was measured and the final tumor weights and sizes determined. Subsequently, histopathological data were obtained and tumor tissue sections were used for apoptosis (i.e., TUNEL) staining.

RESULTS

The pharmacokinetic studies revealed low (approximately 8%) absorption through the p.o. route and high (approximately 70%) absorption through the i.p. route. The average plasma half life (T1/2) of BMD188 was approximately 50 h. Post-absorption, plasma elimination of radioactivity was similar to that in animals given [3H]-188 intravenously. The in vivo efficacy results indicate that i.p. administered BMD188 significantly inhibited the primary growth and local invasion of Du145 prostate cancer cells orthotopically implanted into SCID or athymic nude mice. The tumor-inhibitory effect of BMD188 was due to apoptosis induction in vivo, as revealed by histological analysis as well as TUNEL staining of the tumor tissue sections.

CONCLUSION

Collectively, the preceding in vitro and the current in vivo studies suggest that BMD188 and its analogs may find clinical applications in the treatment of prostate cancer patients by inducing apoptotic death of prostate cancer cells.

The influence of race on the efficacy of curative radiation therapy for carcinoma of the prostate

The purpose of this study was to examine the effect of race on the outcome of patients treated curatively with external beam irradiation for carcinoma of the prostate. The study was performed between January 1980 and December 1993 of 1,529 men with prostate cancer. Similar percentages of Caucasian men (CM) and African-American men (AAM) had localized disease (stages T1 and T2) and advanced stage disease (stage T3). There was no difference in crude survival by race (P = .13). At 5 years, crude survival by race was 75% for CM and 73% for AAM. At 10 years, the crude survivals, were 50% and 40%, respectively. Disease-specific survival rates were equivalent for AAM and CM (P = .66). The 5-year disease-specific survival was 83% for CM and 85% for AAM. At 10 years, the disease-specific survival was 65% for CM and 69% for AAM. There was no difference in disease-specific survival by race when stage-for-stage comparisons were made. Among those patients referred for curative radiation therapy, AAM and CM had a similar age, stage, and grade distribution. This study demonstrated that there was no difference in disease-specific survival between CM and AAM treated curatively with radiation for prostate cancer.

Systemic bone-seeking radionuclides for palliation of painful osseous metastases: current concepts

Bone metastases require multidisciplinary treatment, the primary goal of which is to relieve pain and improve quality of life. Among the options available, bone-seeking radioisotopes are attractive because they can treat several symptomatic metastases simultaneously. This therapy may have antitumor efficacy in addition to analgesic properties. Although the ultimate place of systemic radionuclides in the treatment of bone metastases has not been firmly established, some patients clearly benefit from these modalities.

Extended survivability of prostate cancer cells in the absence of trophic factors: increased proliferation, evasion of apoptosis, and the role of apoptosis proteins

This project was undertaken to study the survival properties of various prostate cells, including normal (NHP), BPH (benign prostate hyperplasia), primary carcinoma (PCA), and metastatic prostate cancer cells (LNCaP, PC3, and Du145), in the absence of trophic factors. Cell proliferation and cell death were quantitated by enumerating the number of live cells using MTS/PMS kit and of dead (apoptotic) cells using 4',6-diamidino-2-phenylindole dihydrochloride nuclear staining. These cells demonstrated an overall survivability in the order of BPH < NHP < LNCaP < PC3 < PCA < Du145. Upon growth factor deprivation, NHP/BPH cells rapidly underwent apoptosis, leading to a decreased number of live cells. PCA/PC3/Du145 cells, in contrast, demonstrated an initial phase of aggressive growth during which apoptosis rarely occurred, followed by a "plateau" phase in which cell loss by apoptosis was compensated by cell proliferation, followed by a later phase in which apoptosis exceeded the cell proliferation. LNCaP cells demonstrated survival characteristics between those of NHP/BPH and PCA/PC3/Du145 cells. We concluded that the increased survivability in prostate cancer cells results from enhanced cell proliferation as well as decreased apoptosis. The molecular mechanisms for evasion of apoptosis in prostate cancer cells were subsequently investigated. Quantitative Western blotting was used to examine the protein expression of P53 and P21WAF-1, Bcl-2 and Bcl-X(L) (anti-apoptotic proteins), and Bax, Bak, and Bad (proapoptotic proteins). The results revealed that, upon trophic factor withdrawal, NHP and BPH cells upregulated wild-type p53 and proapoptotic proteins Bax/Bad/Bak and down-regulated the expression of P21. Furthermore, NHP and BPH cells endogenously expressed little or no Bcl-2. In sharp contrast, prostate cancer cells expressed nonfunctional P53 and various amounts of Bcl-2 proteins. Upon deprivation, these cancer cells up-regulated P21 and Bcl-2 and/or BclX(L), lost response to withdrawal-induced up-regulation of Bax/Bad/Bak or decreased or even completely lost Bax expression and expressed some novel proteins such as P25 and P54/55 complex. These data together suggest that prostate cancer cells may use multiple molecular mechanisms to evade apoptosis, which, together with increased proliferation, contribute to extended survivability of prostate cancer cells in the absence trophic factors.

Impact of postprostatectomy prostate-specific antigen nadir on outcomes following salvage radiotherapy

OBJECTIVES

To evaluate the relationship between the postprostatectomy prostate-specific antigen (PSA) nadir and the outcome of patients treated with salvage radiotherapy.

METHODS

Seventy-eight patients received definitive external beam radiation for recurrence following radical prostatectomy (RP). The PSA nadir was undetectable in 41 patients (less than 0.05 ng/mL). All patients received salvage radiotherapy (median dose 66 Gy) for a median of 19 months (range 2 to 149) following prostatectomy. The median follow-up time was 25 months (range 1 to 59) from the date of completion of radiation.

RESULTS

Among patients having an undetectable or detectable postoperative PSA, 78% and 68% were free of disease, respectively, at the last follow-up. At 3 years, the disease-free survival rates were 65% and 60%, respectively (P = 0.6). Overall, the disease-free survival rate at 3 years was 78% in patients with a PSA level 2 ng/mL or less at the time of radiotherapy compared to 31% with a PSA greater than 2 ng/mL (P < 0.0001).

CONCLUSIONS

Many patients who never achieve an undetectable postprostatectomy PSA level may still be salvaged with therapeutic radiotherapy. The best predictor of a favorable outcome is a low (2 ng/mL or less) PSA level at the time of radiation.

Role of alphaII(b)beta3 integrin in prostate cancer metastasis

BACKGROUND

Integrins participate in cell-cell and cell-matrix interactions. In this study we determined whether alphaII(b)beta3 integrin is involved in metastasis of human prostate adenocarcinoma cells.

METHODS

Prostate adenocarcinoma PC-3 and DU-145 cell lines express alphaII(b)beta3. Northern blotting, 5'-RACE, and immunofluorescent localization confirmed expression of alphaIIb integrin in prostate adenocarcinoma cells. We used orthotopic/ectopic site of implantation and lung colonization assays in SCID mice to determine whether alphaII(b)beta3 participates in metastatasis of tumor cells.

RESULTS

Immunofluorescent localization of alphaIIb integrin in fibronectin-adherent DU-145 and PC-3 cells is remarkably different. In DU-145 cells the integrin localizes to focal contact sites, whereas it is predominantly intracellular in PC-3 cells. Both tumor cell lines are tumorigenic when implanted subcutaneously or intraprostatically in SCID mice, but only DU-145 cells injected intraprostatically metastasize. Flow cytometry with a mAb directed to alphaII(b)beta3 revealed higher expression of alphaII(b)beta3 in DU-145 tumor cell suspensions isolated from the prostate when compared to DU-145 tumor cells from the subcutis. Function-blocking mAbs to alphaII(b)beta3 inhibit lung colonization of tail vein-injected DU-145 cells.

CONCLUSIONS

Altogether, the data suggest that alphaII(b)beta3 integrin participates in the metastatic progression of prostatic adenocarcinoma.

12(S)-HETE increases the motility of prostate tumor cells through selective activation of PKC alpha

Prostate carcinoma has become the second most fatal cancer in American men. In rat Dunning prostate adenocarcinoma cells, increased cellular motility has been associated positively with their increased metastatic potential. However, the mechanism(s) responsible for regulation of tumor cell motility is poorly understood. We have reported that a lipoxygenase metabolite of arachidonic acid 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] augments tumor cell metastatic potential through activation of protein kinase C (PKC). We report here that 12(S)-HETE increased the motility of AT2.1 cells and this 12(S)-HETE increased motility was inhibited by PKC inhibitor calphostin C. Western blot analysis revealed that AT2.1 cells expressed the Ca(2+)-dependent PKC isoform alpha and Ca(2+)-independent PKC isoform delta. Pretreatment of cells with a Ca2+ chelator BAPTA blocked the 12(S)-HETE increased motility. Further, the motility of AT2.1 cells was increased in a dose dependent manner by thymelea toxin, a selective PKC alpha activator. Our data demonstrate that 12(S)-HETE augments the motility of AT2.1 cells via its selective activation of PKC alpha which may serve as a key target for the development of antimetastatic drugs useful for combating prostate cancers.

Radiation therapy for endometrial cancer in patients treated for postoperative recurrence

PURPOSE

To retrospectively evaluate the outcome and risk factors in patients treated with radiation for endometrial cancer at time of recurrence.

MATERIALS AND METHODS

Three hundred ninety-nine women were treated with radiation therapy for endometrial cancer at KCI/WSU from January 1980 to December 1994. Of these, 26 patients treated primarily with surgery received radiation therapy at the time of recurrence. Median time to recurrence after surgery was 8 months, with all recurrences occurring within 24 months. Twenty-four patients had recurrences in the vaginal cuff, vagina, or pelvis. These patients received external-beam radiation to the pelvis (45.00-50.40 Gy) and periaortic lymph nodes (45.00-50.00 Gy), along with a boost given by external-beam radiation or brachytherapy (16.00-30.00 Gy). Mean follow-up was 15 months (range 1-85 months).

RESULTS

The 2-year survival was 50% and median survival was 16 months (survival range 1-85 months). Of 26 patients, 54% (14) failed locally following radiation therapy. Factors indicative of poor survival included histology (sarcoma, poorly differentiated adenocarcinoma), grade, and lymph node positivity. Histological differentiation influenced local control; lymphovascular space invasion was of borderline significance with regard to local control.

CONCLUSION

Local control and survival for surgically treated endometrial cancer patients who receive radiation at the time of recurrence are poor, with the exception of those patients with recurrent disease limited to the vagina. Early detection of recurrence may improve outcome. Pathologic risk factors may identify those patients at risk for extrapelvic recurrence. Alternative treatment modalities need to be developed for this high-risk group of patients.

Radiotherapeutic management of osseous metastases: a survey of current patterns of care

PURPOSE

Radiotherapy plays a major role in the management of painful osseous metastases. This survey was conducted to study the current approaches to this clinical problem in the radiotherapy community.

METHODS AND MATERIALS

A questionnaire was sent to 2500 members of the American Society for Therapeutic Radiology and Oncology. It consisted of 30 multiple-choice questions regarding four hypothetical clinical scenarios likely to be encountered in daily practice. Questions related to the technique of choice [local field (LF) vs. hemibody radiotherapy (HBI)], the use of systemic radionuclides (SR), fractionation schemes, dose, the integration of modalities, and the follow-up of these patients. The analysis is based on 817 (33%) responses received regarding 3268 cases.

RESULTS

Local field is the most common form of therapy. Overall, LF was used, alone or in combination with other forms of therapy, in 54% and 74% of patients, respectively. LF was used more frequently in patients with breast cancer than in patients with prostate cancer (79% vs. 45%; p = 0.0001). Long fractionation schemes were used by 90% of physicians in 96% of cases. Short fractionation schemes were used by 7% of physicians in 4% of cases. This tendency was more pronounced in private practice than in the university or government/ multidisciplinary settings (p = 0.008) and in physicians starting their practice before 1982 (p = 0.05). The most common schedule was 30 Gy in 10 fractions, used by 77% of physicians in 64% of cases. HBI was used, alone or in combination with other forms of therapy, in 1% and 2% of patients, respectively. It was used more frequently in patients with prostate cancer than in patients with breast cancer (1.2% vs. 0.1%, respectively; p < 0.0001). SR were used alone or in combination with local-field irradiation in 21% and 40% of cases, respectively. SR were used more frequently in patients with prostate cancer than in those with breast cancer (28% vs. 0.2%, respectively;p < 0.00001). The most common radionuclide in use is Sr-89 (99%) at a dose of 4 mCi (73%) or 10.8 mCi (26%).

CONCLUSIONS

Although LF remains the mainstay of therapy, our results demonstrate the emergence of a new pattern of practice: LF to the painful site in combination with SR for clinically occult metastases. Despite an ongoing academic debate regarding fractionation schemes, the vast majority of American practitioners advocate long schedules.

The current role of radiotherapy in the treatment of invasive bladder cancer

Invasive bladder cancer remains a therapeutic challenge. Approximately 50% of patients treated with radical cystectomy die of metastatic disease. External beam radiation therapy when given alone has results inferior to that of surgery, and although it has shown some benefit when given in the preoperative setting, this was not verified by randomized trials. Altered fractionation radiation schemes and combined modality using a cisplatin-based combination chemotherapy with radiation have resulted in up to 60% bladder preservation.

Sociodemographic analysis of patients in radiation therapy oncology group clinical trials

PURPOSE

To assess the degree to which the sociodemographic characteristics of patients enrolled in Radiation Therapy Oncology Group (RTOG) clinical trails are representative of the general population.

METHODS AND MATERIALS

Sociodemographic data were collected on 4016 patients entered in 33 open RTOG studies between July 1991 and June 1994. The data analyzed included educational attainment, age, gender, and race. For comparison, we obtained similar data from the U.S. Department of Census. We also compared our RTOG data with Surveillance Epidemiology and End Results (SEER) data for patients who received radiation therapy, to determine how RTOG patients compared with cancer patients in general, and with patients with cancers at sites typically treated with radiotherapy.

RESULTS

Overall, the sociodemographic characteristics of patients entered in RTOG trials were similar to those of the Census data. We found that, in every age group of African-American men and at nearly every level of educational attainment, the proportion of RTOG trial participants mirrored the proportion in the census data. Significant differences were noted only in the youngest category of African-American men, where the RTOG accrues more in the lower educational categories and fewer with college experience. For African-American women, we found a similar pattern in every age group and at each level of educational attainment. As with men, RTOG trials accrued a considerably larger proportion of younger, less educated African-American women than the census reported. Using SEER for comparison, the RTOG enrolled proportionately more African-American men to trials all cancer sites combined, and for prostate and head and neck cancer. In head and neck trials, the RTOG enrolled nearly twice as many African-American men than would be predicted by SEER data. In lung cancer trials, RTOG underrepresented African-American men significantly; however, there was no difference for brain cancer trials. There were no racial differences in RTOG accrual and SEER incidence data for women on trials in brain, lung, and head and neck cancer. However, the RTOG trials accrued nearly twice the proportion of African-American women in cervical cancer trials and in all sites combined, compared to the SEER data.

CONCLUSIONS

Comparisons with the U.S. Census and SEER show that African-Americans are proportionally well represented in cancer clinical trials conducted by the Radiation Therapy Oncology Group. The comparative analysis indicates that all educational levels in each age group of African-Americans generally mirror the U.S. Census, with one exception. The exception is a significant overrepresentation of less-educated African-Americans in the youngest age category. This exception is counter to the expectation that better-educated patients are more likely to enroll in trials. When compared with SEER data, the RTOG trials either parallel or overrepresent African-American men and women, with the only exception being in lung cancer, where men are underrepresented. These results show that, in comparison to the Census and SEER data, the RTOG has fulfilled its commitment to enroll African-American patients in its clinical trials.

BMD188, A novel hydroxamic acid compound, demonstrates potent anti-prostate cancer effects in vitro and in vivo by inducing apoptosis: requirements for mitochondria, reactive oxygen species, and proteases

A newly synthesized cyclic hydroxamic acid compound, BMD188 [cis-1-hydroxy-4-(1-naphthyl)-6-octylpiperidine-2-one], was found to induce the apoptotic death of cultured prostate cancer cells by activating caspase-3. Orally administered BMD188 significantly inhibited the primary growth of prostate cancer cells (Du145) orthotopically implanted into SCID mice. Mechanistic studies indicated that BMD188 did not alter the protein levels of several Bcl-2 family members. In contrast, the BMD188 effect required three essential factors: reactive oxygen species (ROS), the mitochondrial respiratory chain function, and proteases. First, the apoptosis-inducing effect of BMD188 could be blocked by ROS scavengers such as Desferal. Second, both BMD188-induced PARP cleavage as well as PC3 cell apoptosis could be dramatically inhibited by several complex-specific mitochondrial respiration blockers. The involvement of mitochondria was also supported by the observations that BMD188 dramatically altered the mitochondrial distribution and morphology without affecting the cellular ATP levels. Finally, the apoptosis-inducing effect of BMD188 in PC3 cells could be significantly inhibited by serine protease inhibitors (TPCK and TLCK) as well as by caspase inhibitors (zVAD-fmk and DEVD-CHO). Collectively, the present study suggests that BMD188 and its analogs may find clinical applications in the treatment of prostate cancer patients by inducing apoptotic death of prostate cancer cells.

A rational approach to the treatment of prostate cancer with radiation therapy: lessons for the future

The widespread use of prostate-specific antigen (PSA) has revealed that radiation therapy cures adenocarcinoma of the prostate less frequently than previously believed. Biologic factors (such as the complex nature of this disease) and technical factors (geographic miss, inadequate dose to the tumor volume) affect the ability of radiation to effectively treat all patients with prostate cancer. To improve treatment outcome, patients with virulent forms of the disease must be identified. The use of prognostic markers (PSA, prostate-specific membrane antigen, prostate-specific antigen doubling time) and genetic markers (12 lipoxygenase, p53, bcl-2, ploidy) may aid in the development of treatments for these patients. Technical modifications have been made to increase the total dose delivered to the prostate and the accuracy of dose delivery. Brachytherapy, proton therapy and conformal radiation therapy have been used to increase the relative integral dose. Improved prostate targeting may be achieved with the use of fiducial markers, on-line portal imaging, and endorectal magnetic resonance imaging. High linear energy transfer radiation, radiosensitizers and altered fractionation have been used in an attempt to increase the biologic equivalent dose to the tumor. Lastly, hormonal therapy and chemotherapy have been shown to decrease tumor burden and improve local control. All of these methods may improve outcome in patients with adenocarcinoma of the prostate. However, further work must be completed to translate these methods into standards of care.

Hyperbaric oxygen therapy for radiation-induced brain injury in children

BACKGROUND

Radiation-induced necrosis (RIN) of the brain is a complication associated with the use of aggressive focal treatments such as radioactive implants and stereotactic radiosurgery. In an attempt to treat patients with central nervous system (CNS) RIN, ten patients received hyperbaric oxygen treatment (HBOT).

METHODS

Patients presented with new or increasing neurologic deficits associated with imaging changes after radiotherapy. Necrosis was proven by biopsy in eight cases. HBOT was comprised of 20-30 sessions at 2.0 to 2.4 atmospheres, for 90 minutes-2 hours. Sites of RIN included the brain stem (n = 2), posterior fossa (n = 1), and supratentorial fossa (n 7). Histologic types included brain stem glioma (n = 2), ependymoma (n = 2), germinoma (n = 2), low grade astrocytoma (n = 1), oligodendroglioma (n = 1), glioblastoma multiforme (n = 1), and arteriovenous malformation (n = 1).

RESULTS

Initial improvement or stabilization of symptoms and/or imaging findings were documented in all ten patients studied and no severe HBOT toxicity was observed. Four patients died, with the cause of death attributed to tumor progression. Five of six surviving patients were improved by clinical and imaging criteria; one patient was alive with tumor present at last follow-up.

CONCLUSIONS

HBOT may prove to be an important adjunct to surgery and steroid therapy for CNS RIN.

The experience with neutron irradiation in locally advanced adenocarcinoma of the prostate

Patients with locally advanced adenocarcinoma of the prostate, defined as those with extraprostatic disease, a Gleason score of 7 or higher, or a PSA of 15 ng/mL or higher, have a significantly worse prognosis with standard external beam radiotherapy. Post-treatment PSA and biopsy data confirm that most patients have residual local disease as a component of failure in most cases. Two randomized trials of neutron irradiation mixed with photon irradiation and neutron irradiation alone compared with standard photon irradiation to a dose of 70 cGy have both confirmed an improvement in the disease-free survival of patients treated with neutron irradiation. The high complication rate in the second study and the limited number of neutron facilities led to a dramatic decline in the utilization of neutrons in prostate cancer. However, at Wayne State University, using a super conducting cyclotron, a number of clinical studies have been performed to demonstrate the safety and efficacy of neutron irradiation. Chronic complication rates have been low. Biochemical freedom from relapse rates have been excellent. For patients with a pretreatment PSA <10 ng/mL, 10 to 20 ng/mL or >20 ng/mL, 92%, 85%, and 38% of patients have no evidence of disease at 4 years. Thus, neutron irradiation has been proven to be a safe method of dose intensification that can lead to a significant improvement in the overall outcome of patients with nonmetastatic adenocarcinomas of the prostate.

Involvement of the multiple tumor suppressor genes and 12-lipoxygenase in human prostate cancer. Therapeutic implications

We performed a detailed and comprehensive study of the involvement of tumor suppressor genes in human prostate cancer. We utilized primers flanking either the restriction fragment length polymorphism (RFLP) or variable number of tandem repeat [VNTR; microsatellite or simple repeat site (SRS)] polymorphic sites to polymerase chain reaction (PCR) amplify the genomic DNA and detect loss of heterozygosity of the target genes. Quantitative reverse transcription (RT)-PCR was performed to measure the mRNA expression levels and PCR/single strand conformational polymorphism (SSCP) and DNA sequencing carried out to detect mutation of the tumor suppressor genes. We found that multiple tumor suppressor genes (e.g., p53, DCC, APC, MCC, BRCA1, and WAF1/CIP1) were inactivated at different frequencies via various mechanisms [e.g., loss of heterozygosity (LOH), loss of expression (LOE), mutation, and inactivation by cellular binding protein]. Several important and novel findings are as following: LOH and LOE of the DCC gene, LOH, LOE, and possible mutation of the APC/MCC genes, LOH of the BRCA1 locus, and mutation of the WAF1/CIP1 gene. For p53 tumor suppressor gene alone, multiple inactivation mechanisms (i.e., LOH, LOE, mutation, and amplification of the cellular inactivating protein MDM2) were identified. A possible involvement of genomic instability or mutator phenotype in human prostate cancer was investigated by microsatellite typing using PCR. A high frequency of microsatellite instability was detected and the microsatellite instability found to correlate with advanced stage and poor differentiation of prostate cancer, suggesting that genes functioning in DNA mismatch repair or general stabilization of the genome may be involved in prostate cancer. The results obtained in this study suggested that multiple tumor suppressor genes (both known and unknown genes) may share the role in prostate cancer; a pattern which has been found in a number of human malignancies such as cancers of the esophagus, colon and breast. In fact, we performed deletion studies aimed at localizing potential tumor suppressor loci on various chromosomal regions. A number of chromosomal regions (i.e., 6p12-24 and 17q21) were found to potentially harbor unidentified tumor suppressor genes. Detailed deletion mapping has localized the potential tumor suppressor loci to a < 2 Mb region centromeric to the BRCA1 gene on chromosome 17q. In addition, we identified a number of novel mechanisms of tumor suppressor gene inactivation, in prostate cancer such as loss of mRNA expression of the DCC, APC, MCC and p53 gene, and mutator phenotype. And for the very first time, we identified somatic mutations of the WAF1/CIP1 gene in primary human malignancy-human prostate cancer. This finding provides the first evidence in primary tumor that the WAF1/CIP1 gene may be a tumor suppressor gene and may be involved in prostate cancer. We identified 12-lipoxygenase (12-LOX) as a potential prognostic marker for human prostate cancer. mRNA expression levels of the 12-LOX gene was measured by quantitative reverse transcription-polymerase chain reaction (RT-PCR) and semi-quantitative in situ hybridization (ISH) in 122 pairs of matched normal and tumor tissues from prostate cancer patients. We found that 12-LOX expression levels were elevated in approximately half of the patients analyzed and the 12-LOX elevation correlates with advanced stage, poor differentiation, and surgical margin positivity. Our data suggest that 12-LOX may serve as a correlative marker for a more aggressive phenotype of prostate cancer and therefore for poor prognosis. We are currently refining our assays for possible clinical applicability. Since not all patients with loss of expression of the DCC gene showed LOH of the DCC locus, there must be other mechanism(s) responsible for loss of expression of the DCC gene. When we analyzed the relationship between DCC loss of expression and 12-LOX elevation in prostate cancer pati

Therapeutic irradiation for patients with an elevated post-prostatectomy prostate specific antigen level

PURPOSE

This study was initiated to determine the efficacy of post-prostatectomy therapeutic radiation for patients with elevated prostate specific antigen (PSA).

MATERIALS AND METHODS

A total of 47 patients received 66 Gy. therapeutic irradiation to the prostate bed for a PSA level greater than 0 ng./ml. postoperatively. Univariate and multivariate survival analyses were performed to identify prognostic variables.

RESULTS

At a median followup of 36 months (range 18 to 48) 83 and 33% of the patients with PSA 2 ng./ml. or less and 2 ng./ml. or greater, respectively, had no evidence of disease (p = 0.001). Pathological stage and a complete biochemical response (PSA less than 0.05 ng./ml.) were also significant prognostic variables.

CONCLUSIONS

Therapeutic irradiation for patients with elevated PSA postoperatively is highly effective. At a median followup of 36 months 64% of the patients remain disease-free.

Modeling of internal dose distributions during SR-89 treatment of a patient with bone metastases

METHODS

A model of strontium biodistribution similar to the one created by the International Commission on Radiological Protection (ICRP) was applied for activity and absorbed dose calculations in a patient with bone metastases treated with Sr-89 strontium chloride. Metastases are represented just like all other organs and tissues collecting strontium. Data from the ICRP's standard Reference Man were used.

RESULTS

Results include calculated time-activity data for all model compartments and for relevant target organs. Absorbed doses per unit administered activity were calculated for blood (0.036 cGy/MBq), soft tissues (0.046 cGy/MBq), bone marrow (1.15 cGy/MBq), bone surface (1.45 cGy/MBq), upper large intestine (ULI) (0.13 cGy/MBq), lower large intestine (LLI) (0.38 cGy/MBq), bladder (0.12 cGy/MBq), and metastases (37.5 cGy/MBq).

CONCLUSIONS

Results of the absorbed dose calculations are comparable with results presented in references for specific clinical cases. Discrepancies in dose values may be effected by the size of metastases and the patient's condition.