The STAMPEDE2 Trial: a Site Survey of Current Patterns of Care, Access to Imaging and Treatment of Metastatic Prostate Cancer

AIMS

The forthcoming STAMPEDE2 trial has three comparisons in metastatic hormone-sensitive prostate cancer. We aim to determine clinical practices among STAMPEDE trial investigators for access to imaging and therapeutic choices and explore their interest in participation in STAMPEDE2.

MATERIALS AND METHODS

The survey was developed and distributed online to 120 UK STAMPEDE trial sites. Recipients were invited to complete the survey between 16 and 30 May 2022. The survey consisted of 30 questions in five sections on access to stereotactic ablative body radiotherapy (SABR), 177lutetium-prostate-specific membrane antigen-617 (177Lu-PSMA-617), choice of systemic therapies and use of positron emission tomography/computerised tomography and whole-body magnetic resonance imaging.

RESULTS

From 58/120 (48%) sites, 64 respondents completed the survey: 55/64 (86%) respondents were interested to participate in SABR, 44/64 (69%) in 177Lu-PSMA-617 and 56/64 (87.5%) in niraparib with abiraterone comparisons; 45/64 (70%) respondents had access to bone, spine and lymph node metastases SABR delivery and 7/64 (11%) to 177Lu-PSMA-617. In addition to androgen deprivation therapy, 60/64 (94%) respondents used androgen receptor signalling inhibitors and 46/64 (72%) used docetaxel; 29/64 (45%) respondents would consider triplet therapy with androgen deprivation therapy, androgen receptor signalling inhibitors and docetaxel. Positron emission tomography/computerised tomography was available to 62/64 (97%) respondents and requested by 45/64 (70%) respondents for disease uncertainty on conventional imaging and 39/64 (61%) at disease relapse. Whole-body magnetic resonance imaging was available to 24/64 (38%) respondents and requested by 13/64 (20%) respondents in highly selected patients. In low-volume disease, 38/64 (59%) respondents requested scans at baseline and disease relapse. In high-volume disease, 29/64 (45%) respondents requested scans at baseline, best response (at prostate-specific antigen nadir) and disease relapse; 54/64 (84%) respondents requested computerised tomography and bone scan for best response assessment.

CONCLUSION

There is noteworthy disparity in clinical practice across current study sites, however most have expressed an interest in participation in the forthcoming STAMPEDE2 trial.

Copy number architectures define treatment-mediated selection of lethal prostate cancer clones

Despite initial responses to hormone treatment, metastatic prostate cancer invariably evolves to a lethal state. To characterize the intra-patient evolutionary relationships of metastases that evade treatment, we perform genome-wide copy number profiling and bespoke approaches targeting the androgen receptor (AR) on 167 metastatic regions from 11 organs harvested post-mortem from 10 men who died from prostate cancer. We identify diverse and patient-unique alterations clustering around the AR in metastases from every patient with evidence of independent acquisition of related genomic changes within an individual and, in some patients, the co-existence of AR-neutral clones. Using the genomic boundaries of pan-autosome copy number changes, we confirm a common clone of origin across metastases and diagnostic biopsies, and identified in individual patients, clusters of metastases occupied by dominant clones with diverged autosomal copy number alterations. These autosome-defined clusters are characterized by cluster-specific AR gene architectures, and in two index cases are topologically more congruent than by chance (p-values 3.07 × 10-8 and 6.4 × 10-4). Integration with anatomical sites suggests patterns of spread and points of genomic divergence. Here, we show that copy number boundaries identify treatment-selected clones with putatively distinct lethal trajectories.

Clinical testing of transcriptome-wide expression profiles in high-risk localized and metastatic prostate cancer starting androgen deprivation therapy: an ancillary study of the STAMPEDE abiraterone Phase 3 trial

Metastatic and high-risk localized prostate cancer respond to hormone therapy but outcomes vary. Following a pre-specified statistical plan, we used Cox models adjusted for clinical variables to test associations with survival of multi-gene expression-based classifiers from 781 patients randomized to androgen deprivation with or without abiraterone in the STAMPEDE trial. Decipher score was strongly prognostic (p<2×10-5) and identified clinically-relevant differences in absolute benefit, especially for localized cancers. In metastatic disease, classifiers of proliferation, PTEN or TP53 loss and treatment-persistent cells were prognostic. In localized disease, androgen receptor activity was protective whilst interferon signaling (that strongly associated with tumor lymphocyte infiltration) was detrimental. Post-Operative Radiation-Therapy Outcomes Score was prognostic in localized but not metastatic disease (interaction p=0.0001) suggesting the impact of tumor biology on clinical outcome is context-dependent on metastatic state. Transcriptome-wide testing has clinical utility for advanced prostate cancer and identified worse outcomes for localized cancers with tumor-promoting inflammation.

Accumulation of copy number alterations and clinical progression across advanced prostate cancer

BACKGROUND

Genomic copy number alterations commonly occur in prostate cancer and are one measure of genomic instability. The clinical implication of copy number change in advanced prostate cancer, which defines a wide spectrum of disease from high-risk localised to metastatic, is unknown.

METHODS

We performed copy number profiling on 688 tumour regions from 300 patients, who presented with advanced prostate cancer prior to the start of long-term androgen deprivation therapy (ADT), in the control arm of the prospective randomised STAMPEDE trial. Patients were categorised into metastatic states as follows; high-risk non-metastatic with or without local lymph node involvement, or metastatic low/high volume. We followed up patients for a median of 7 years. Univariable and multivariable Cox survival models were fitted to estimate the association between the burden of copy number alteration as a continuous variable and the hazard of death or disease progression.

RESULTS

The burden of copy number alterations positively associated with radiologically evident distant metastases at diagnosis (P=0.00006) and showed a non-linear relationship with clinical outcome on univariable and multivariable analysis, characterised by a sharp increase in the relative risk of progression (P=0.003) and death (P=0.045) for each unit increase, stabilising into more modest increases with higher copy number burdens. This association between copy number burden and outcome was similar in each metastatic state. Copy number loss occurred significantly more frequently than gain at the lowest copy number burden quartile (q=4.1 × 10-6). Loss of segments in chromosome 5q21-22 and gains at 8q21-24, respectively including CHD1 and cMYC occurred more frequently in cases with higher copy number alteration (for either region: Kolmogorov-Smirnov distance, 0.5; adjusted P<0.0001). Copy number alterations showed variability across tumour regions in the same prostate. This variance associated with increased risk of distant metastases (Kruskal-Wallis test P=0.037).

CONCLUSIONS

Copy number alteration in advanced prostate cancer associates with increased risk of metastases at diagnosis. Accumulation of a limited number of copy number alterations associates with most of the increased risk of disease progression and death. The increased likelihood of involvement of specific segments in high copy number alteration burden cancers may suggest an order underlying the accumulation of copy number changes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00268476 , registered on December 22, 2005. EudraCT  2004-000193-31 , registered on October 4, 2004.

Proliferation index and survival in men with prostate cancer starting long-term androgen deprivation therapy in the STAMPEDE clinical trial

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Background: Treatment intensification with docetaxel or abiraterone improved survival for advanced prostate cancer starting androgen deprivation therapy (ADT) in the Systemic Therapy in Advancing or Metastatic Prostate Cancer: Evaluation of Drug Efficacy (STAMPEDE, NCT00268476) trial. However, survival and time-to-progression is highly variable on ADT, introducing the risk of unnecessary toxicity from additional treatments for some patients. Here we test the prognostic association of proliferation index using Ki67 scores in the control arm of the STAMPEDE population of high-risk localised (M0) and metastatic (M1) prostate cancer. Methods: Pre-ADT diagnostic needle biopsies were obtained from 517 men randomized in STAMPEDE arm A between 2006 and 2015. These were assessed for proliferation using an analytically optimised Ki67 immunohistochemistry assay. Ki67 was tested for associations with baseline clinico-pathological variables (Grade group, pre-ADT serum PSA and imaging metastatic burden) in univariable linear-regression models, and for associations with survival outcomes in multivariable Cox-regression models adjusted for these and additional confounding variables. Primary outcome measure was overall survival, secondary outcomes were prostate cancer-specific, failure-free, progression-free and metastatic progression-free survival. Results: Ki67 was available for 475 patients who received ADT only for at least 2 years ± radiotherapy. Of 202 M0, 74 were node positive. Of 273 M1, 116, 127 and 30 were respectively low, high and unknown radiological M1 volume. Ki67 score associated with higher Gleason (p=7.15x10-11) and presence of extra-pelvic metastases (p=1.41x10-8). Increasing Ki67 scores showed a strong linear association with poorer overall survival, with an estimated 2% increase in the hazard of death per percentage increase in the score (adjusted HR=1.02, 95% CI 1.01-1.02; p=1.04x10-5). There was also strong evidence that Ki67 associated positively with all secondary outcomes, including prostate cancer-specific survival (adjusted p=5.50x10-6) and metastatic progression-free survival (adjusted p=3.50x10-9). Conclusions: Ki67 immuno-score is strongly prognostic in clinically advanced prostate cancer independent of Gleason score and the other clinicopathological variables tested in this study. Ki67 is a clinically scalable assay that could improve selection for treatment intensification and provide a tool for screening patients most likely to benefit from further molecular investigation.

Copy number profiles of primary tumors for risk stratification of advanced prostate cancer: A biomarker study embedded in the multicenter STAMPEDE trial

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Background: Men with advanced hormone-sensitive prostate cancer (HSPC) starting long term androgen deprivation therapy (ADT) follow a highly variable clinical course. Treatment intensification with docetaxel or AR targeted therapies improves outcomes but there is a risk of overtreatment, especially in non-metastatic (M0) or metastatic (M1) low volume disease. We established a framework for biomarker evaluation in the STAMPEDE trial. We aimed to evaluate the feasibility and clinical utility of assessing the burden of copy number (CN) aberrations in newly diagnosed advanced HSPC. We hypothesised that increased percentage genome altered (PGA) would associate with higher disease burden and worse prognosis. Methods: We implemented a scalable strategy using low coverage whole genome sequencing (lpWGS) of formalin fixed paraffin embedded (FFPE) diagnostic core biopsies from STAMPEDE participants randomised to the standard of care ADT arm, between 2005 and 2016. Tissue was retrieved from 136 trial sites. 315 cases were randomly selected, aiming for a biomarker population of 300, anticipating an assay failure rate ̃5%. We defined 40% as the minimum histopathologically determined tumor cellularity (TC) for inclusion. We performed a survival analysis investigating PGA at diagnosis as a continuous measure with fractional polynomial specification in Cox models adjusting for disease burden, Gleason grade, pre-ADT PSA (log-transformed), age at randomisation and TC. We pre-specified that all hypothesis tests required evidence at the 5% significance level to consider rejecting the null hypothesis. Results: We successfully CN profiled 300/315 cases. There were no significantly different baseline clinico-pathological features between the full trial comparison n = 3106 and final biomarker population n = 300, 290/300 cases were de novo presentations. PGA in the core with highest Gleason grade and TC was median 18% (range 0%-75%; n = 300). PGA was significantly higher in M1 (n = 169) compared to M0 (n = 131) cases (median: 21% vs 14%; p = 0.00006). 284/300 were subclassified by disease burden into M0 node negative and node positive, and M1 low and high volume. PGA was significantly associated with increased disease burden (p = 0.00002). Increased PGA was significantly and non-linearly associated with an increased hazard of failure-free survival (p = 0.004), progression-free survival (p = 0.002), metastatic progression-free survival (p = 0.003), overall survival (p = 0.045) and prostate cancer-specific survival (p = 0.011). Conclusions: Evaluation of the burden of CN aberrations in archival, poor quality FFPE diagnostic tissue from men randomised in the STAMPEDE trial is feasible using lpWGS and has potential clinical utility to identify better prognosis advanced HSPC patients, who may not require treatment intensification.

Pulsed echinocandin therapy in azole intolerant or multiresistant chronic pulmonary aspergillosis: A retrospective review at a UK tertiary centre

INTRODUCTION

Chronic pulmonary aspergillosis (CPA) is a fungal disease with high mortality and morbidity. Guidelines suggest treatment with azoles as first-line therapy. However, patients often develop treatment intolerance or increasingly azole resistance.

OBJECTIVES

This retrospective review assesses outcomes in azole resistant or intolerant patients with CPA treated with cyclical echinocandin therapy.

METHODS

We retrospectively examined records of 25 patients with CPA treated with cyclical caspofungin, 6 of whom were either azole-resistant or azole intolerant. Baseline characteristics, high-resolution computed tomography severity scores, forced expiratory volume after 1 minute (FEV1), forced vital capacity (FVC), body mass index and serology (Aspergillus fumigatus-specific IgG, Aspergillus fumigatus-specific IgE, total IgE and CRP) were assessed before and after caspofungin.

RESULTS

Of the six patients, four (66%) started caspofungin due to intolerance and two (33%) due to pan-azole resistance. On treatment, there was stability in FEV1 with an overall mortality of 33% during the follow-up period with a median survival of 875.5 days (IQR 529-1024). No significant change in serology (A. fumigatus-specific IgG and CRP was seen.

CONCLUSIONS

With pulsed echinocandin therapy, azole-intolerant or pan-resistant CPA patients have similar mortality rates to azole-naïve CPA patients. Pulsed echinocandin therapy may present a strategy to stabilize CPA in patients with pan resistance or intolerance to, azole therapy.

Genomic landscape of platinum resistant and sensitive testicular cancers

While most testicular germ cell tumours (TGCTs) exhibit exquisite sensitivity to platinum chemotherapy, ~10% are platinum resistant. To gain insight into the underlying mechanisms, we undertake whole exome sequencing and copy number analysis in 40 tumours from 26 cases with platinum-resistant TGCT, and combine this with published genomic data on an additional 624 TGCTs. We integrate analyses for driver mutations, mutational burden, global, arm-level and focal copy number (CN) events, and SNV and CN signatures. Albeit preliminary and observational in nature, these analyses provide support for a possible mechanistic link between early driver mutations in RAS and KIT and the widespread copy number events by which TGCT is characterised.

Multiregion expression profiling of prostate cancer from men randomized in the STAMPEDE trial: Stage I results of a multistage biomarker analysis

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Background: The PAM50 gene expression classifier stratifies localized prostate cancer into luminal A/B and basal subtypes: luminal A have superior prognosis compared to luminal B and basal. Drug response scores built using the NCI-60 cell lines predict luminal subtypes are more taxane sensitive compared to basal; luminal B is hypothesized to be the most proliferative and hormone responsive compared to the basal subtype. The STAMPEDE trial provides a framework to validate prognostic and predictive associations of the PAM50 test in tumors from men randomized to androgen deprivation therapy (ADT) alone or with docetaxel or abiraterone. We here present multi-region whole-transcriptome expression array data at completion of Stage I designed to confirm the feasibility of molecular subtyping STAMPEDE tumor blocks. Methods: In collaboration with Decipher Biosciences we generated clinical-grade whole-transcriptome expression array data (Human Exon 1.0 ST GeneChip) performed to CLIA standards on mRNA (from three 10 micron slides) from cancer-enriched areas and applied the PAM50 classifier. Results: As of January 2019, we retrieved blocks from 2012 men from an ITT population of 3879. For Stage I feasibility assessment, we sectioned diagnostic trans-rectal biopsies of the prostate from 50 randomly selected men treated with ADT. We extracted mRNA from 109 cores; > 92% cores (101) from > 94% patients (47/50) passed quality control. The prevalence of PAM50 subtypes was: 31 basal cases (62%), 18 luminal B (36%) and 1 luminal A (2%). 26 cases (52%) were identified as ETS-related gene (ERG) positive. More than one core was interrogated from 35/50 cases (range: 1-6 cores). ERG positive cores were homogeneous across cores from the same patient but PAM50 subtyping identified intra-patient variability across cores from the same case. Conclusions: We confirm the feasibility of expression profiling STAMPEDE tumor blocks and identify a low prevalence of luminal A subtype. Whereas ERG status is consistent across multiple cores, basal and luminal subtypes co-exist in the same prostate. Multi-region analysis will enable further refinement for individual patient classification.

The development of abiraterone acetate for castration-resistant prostate cancer

Abiraterone acetate is a novel CYP17A1 inhibitor demonstrated to prolong survival in castration-resistant prostate cancer (CRPC). This review explores key stages in the almost 20-year history of abiraterone acetate׳s development, starting with a program aiming to develop inhibitors of androgen synthesis at the Institute of Cancer Research, London. Clinical development was initially slow owing to insufficient data supporting targeting of androgen synthesis as a therapeutic approach in CRPC and safety concerns of adrenocortical insufficiency from suppression of cortisol. Regulatory authorities approved abiraterone acetate in 2011 after a survival benefit was demonstrated when given in combination with prednisone as compared with prednisone alone in docetaxel-treated men. Licensing approval extended to include chemotherapy-naive patients with CRPC in 2012 following a significant increase in radiographic progression-free survival. Ongoing research focuses on identifying predictive biomarkers and understanding mechanisms of resistance to improve its administration.

Tumor clone dynamics in lethal prostate cancer

It is unclear whether a single clone metastasizes and remains dominant over the course of lethal prostate cancer. We describe the clonal architectural heterogeneity at different stages of disease progression by sequencing serial plasma and tumor samples from 16 ERG-positive patients. By characterizing the clonality of commonly occurring deletions at 21q22, 8p21, and 10q23, we identified multiple independent clones in metastatic disease that are differentially represented in tissue and circulation. To exemplify the clinical utility of our studies, we then showed a temporal association between clinical progression and emergence of androgen receptor (AR) mutations activated by glucocorticoids in about 20% of patients progressing on abiraterone and prednisolone or dexamethasone. Resistant clones showed a complex dynamic with temporal and spatial heterogeneity, suggesting distinct mechanisms of resistance at different sites that emerged and regressed depending on treatment selection pressure. This introduces a management paradigm requiring sequential monitoring of advanced prostate cancer patients with plasma and tumor biopsies to ensure early discontinuation of agents when they become potential disease drivers.

Association between PSA declines at 4 weeks and OS in patients treated with abiraterone acetate (AA) for metastatic castration resistant prostate cancer (mCRPC) after docetaxel

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Background: Falls in prostate specific antigen (PSA) levels by 50% from the baseline at 12 weeks are currently used to assess response to treatment for mCRPC (Scher et al, 2008). However PSA decline algorithms do not provide robust intermediate endpoints of overall survival (OS) benefit in mCRPC. We evaluated the association between PSA decline at 4 weeks and OS. Methods: We identified mCRPC patients who had received treatment with abiraterone acetate (AA) plus prednisolone post-docetaxel at the Royal Marsden (London, UK) between 01.01.2006 and 30.04.14. Patients were eligible for this analysis if they had PSA levels assessed at baseline, after 4 weeks and 12 weeks of treatment. PSA response at 4 weeks was defined as a ≥30% (PSA4w30) and ≥50% (PSA4w50) decline from baseline (PSABL). Association with outcome was analyzed using multivariate Cox regression and log-rank analyses. A significant p-value of 0.0167 was pre-specified to account for multiple testing. Demographics and clinical data were retrospectively collected from the hospital electronic patient record system (EPR). Results: We identified 124 patients who had received AA post-docetaxel and were eligible for this analysis. PSA4w30 was associated with longer OS (median OS 11.1 vs. 6.8 months; HR 0.50; 95% CI 0.32-0.80; p=.004). PSA4w50 was not associated with OS. A ≥50% PSA decline at 12 weeks (PSA12w50), the standard response measure, was also associated with OS (median OS 9.3 vs. 8.2; HR 0.49; 95% CI 0.29-0.80; p=.005). PSA4w30 was significantly associated with PSA12w50 (p<.001). Lack of a PSA response at 4 weeks correlated with a lack of response at 12 weeks (p=0.000), with a sensitivity of 84.9% [95% CI 75-91.4] and a specificity of 86.5% [95%CI 72–94.1]). PSA4w30 remained significantly correlated with OS (P<.001) in multivariate analyses including other established prognostic factors in mCRPC (ECOG PS, albumin, PSABL, ALP, LDH, Hemoglobin). Conclusions: Further studies to identify mCRPC patients not responding to treatment as early as possible are warranted; PSA4w30 may be useful to help identify patients unlikely to benefit from AA.

Targeting extra-gonadal androgens in castration-resistant prostate cancer

Metastatic castration resistant prostate cancer (CRPC) is associated with a rise in PSA, suggesting an increase in transcription of steroid receptor regulated genes. The efficacy of the new anti-androgen therapies abiraterone and enzalutamide, that target extra-gonadal activation of androgen signaling, confirm CRPC's addiction to genes regulated by the androgen receptor (AR). However, patients invariably progress and develop resistance. This review focuses on mechanisms of drug resistance associated with the AR and steroidogenesis in CRPC. Understanding this persistent dependency and adaptation to the androgen axis in CRPC will lead to an understanding of resistance to new licensed therapies and to novel drug discovery, ultimately improving clinical outcome in CRPC. This article is part of a Special Issue entitled 'Essential role of DHEA'.

External validation of a prognostic model predicting overall survival in metastatic castrate-resistant prostate cancer patients treated with abiraterone

A prognostic model was derived from the population of the COU-AA-301 phase 3 trial for metastatic castrate-resistant prostate cancer patients treated with abiraterone after docetaxel, and it stratifies patients into three risk groups based on clinical parameters. We validated this model in an independent cohort of patients treated with abiraterone after docetaxel outside a clinical trial (group A; n=94) and explored its utility in patients treated with abiraterone in the prechemotherapy setting (group B; n=64). For group A, median overall survival (mOS) was significantly different across the three prognostic groups (good: n=39, mOS: 21.8 mo; intermediate: n=44, mOS: 10.6 mo; poor: n=7, mOS: 6.8 mo; p<0.001; area under the curve [AUC]: 0.71). Analysis of group B confirmed the ability of the model to prognosticate for survival in the prechemotherapy setting: (good: n=44, mOS: 45.6 mo; intermediate or poor: n=20, mOS: 34.5 mo; p=0.042; AUC: 0.61). These results serve to validate the prognostic model in an independent population treated with abiraterone after docetaxel and support clinical implementation of the score. Calibration of the model was poorer in patients receiving abiraterone prechemotherapy. Prospective evaluation of this model in clinical trials is needed.

Wavelengths effective in induction of malignant melanoma

It is generally agreed that sunlight exposure is one of the etiologic agents in malignant melanoma of fair-skinned individuals. However, the wavelengths responsible for tumorigenesis are not known, although DNA is assumed to be the target because individuals defective in the repair of UV damage to DNA are several thousandfold more prone to the disease than the average population. Heavily pigmented backcross hybrids of the genus Xiphophorus (platyfish and swordtails) are very sensitive to melanoma induction by single exposures to UV. We irradiated groups of five 6-day-old fish with narrow wavelength bands at 302, 313, 365, 405, and 436 nm and scored the irradiated animals for melanomas 4 months later. We used several exposures at each wavelength to obtain estimates of the sensitivity for melanoma induction as a function of exposure and wavelength. The action spectrum (sensitivity per incident photon as a function of wavelength) for melanoma induction shows appreciable sensitivity at 365, 405, and probably 436 nm, suggesting that wavelengths not absorbed directly in DNA are effective in induction. We interpret the results as indicating that light energy absorbed in melanin is effective in inducing melanomas in this animal model and that, in natural sunlight, 90-95% of melanoma induction may be attributed to wavelengths > 320 nm--the UV-A and visible spectral regions.

DNA damage, photorepair, and survival in fish and human cells exposed to UV radiation

The effect of various wavelengths of UVB radiation on the induction of cyclobutane pyrimidine dimers in fish cells and human fibroblasts and the repair of these lesions were studied using an UV-endonuclease to measure dimers (endonuclease sensitive sites) by sedimentation of radioactive DNA, by gel electrophoresis of unlabeled DNA, and by cell survival. The data show that fish cells have an efficient photoreactivation system at wavelength > 304 nm that reverses cytotoxicity and dimer formation after exposure to filtered sunlamp irradiation of a shorter wavelength (lambda > 290 nm). Shorter wavelengths in UVB (> 304 nm) are more effective in photoreversal than longer ones (> 320 nm). As a consequence, 50-85% of dimers induced by these wavelengths in fish are photoreactivated while they are being formed. A major cytotoxicological lesion is the cyclobutane pyrimidine dimers. Cultured human fibroblasts do not possess such a repair system. These results indicate that sunlamp irradiation has wavelengths that both damage and repair DNA.

Animal model for ultraviolet radiation-induced melanoma: platyfish-swordtail hybrid

Sunlight exposure is strongly indicated as one of the important etiologic agents in human cutaneous malignant melanoma. However, because of the absence of good animal models, it has not been possible to estimate the wavelengths or wavelength regions involved. We have developed a useful animal model from crosses and backcrosses of platyfish (Xiphophorus maculatus) and swordtails (Xiphophorus helleri). Two strains of these fish are susceptible to invasive melanoma induction by exposure to filtered radiation from sunlamps in the wavelength ranges lambda greater than 290 nm and lambda greater than 304 nm. Multiple exposures on 5-20 consecutive days beginning on day 5 after birth or a single exposure of approximately 200 J/(m2.day) of lambda greater than 304 nm result in a tumor prevalence of 20% to 40% at 4 months of age compared with a background rate of 12% in one strain and 2% in another. Exposure of the fish to visible light after UV exposure reduces the prevalence to background. The melanomas are similar in many respects to mammalian melanomas, as judged by light and electron microscopy. The genetics of the crosses determined by others and the high sensitivity of the hybrids to melanoma induction indicate that the UV radiation probably inactivates the one tumor repressor gene (or a small number of tumor repressor genes) in the hybrid fish. The small size of the animals and their high susceptibility to melanoma induction make them ideal for action spectroscopy.

Established cell lines from nonmammalian vertebrates: models for DNA repair studies

Several established cell lines from different classes of vertebrates were assayed for the presence of O6-methylguanine acceptor protein. This protein is instrumental in removing adducts from DNA caused by exposure to alkylating agents. Cultured cells had levels of acceptor protein activity within the range found in fresh tissues from animals in the same class. We suggest that cells from lower vertebrates are satisfactory in vitro models for studies of this DNA repair function.

Presence of O6-methylguanine acceptor protein in the tissues of different classes of vertebrates and invertebrates

We have measured the ability of extracts of tissues from several species of mammals, birds, reptiles, amphibia and fish to demethylate adducts of O6-methylguanine in exogenous DNA by transfer of the methyl group to an acceptor protein. Our study also encompassed tissues from a smaller number of invertebrates, from arthropods, molluscs and annelids. The vertebrate tissues used were liver, brain, spleen and kidney. In the case of the invertebrates we sampled liver, neural tissue, gonads, digestive tract and hepatopancreas. There was no consistent change in the amount of acceptor activity per unit of protein or DNA going from cold-blooded to warm-blooded vertebrates. Liver invariably had the highest amount; this finding was not unexpected since metabolic processes in the liver are high, and good cellular protective mechanism important. Inter-class comparisons within the vertebrates are highly speculative, and hindered by the fact that there is little information on carcinogenesis in animals other than rodents and humans. O6-methylguanine acceptor activity was found in all the invertebrate tissues tested. The amounts were variable, 0.003-0.0051 fmol/micrograms cellular DNA, but the values fell within the range of those found in the tissues of vertebrates.

Levels of O6-methylguanine acceptor protein in tissues of rats and their relationship to carcinogenicity and aging

N-nitroso compounds react with cellular DNA to produce various damaging adducts, one of the more important being O6-alkylguanine. DNA restoration is accomplished by transfer of the alkyl group to a cysteine residue of an acceptor protein. The levels of acceptor activity were compared in several tissues from well-fed and dietary-restricted inbred SD rats 30-1,194 days of age. Striking and consistent differences were found in the levels of acceptor activity in different tissues from both groups; these levels corresponded to their sensitivity to tumorigenesis by alkylating agents. Acceptor activity levels were highest in the liver and somewhat less in the spleen; there were significantly lower levels in brain and kidney. The random loss with time in the integrity of DNA may cause alterations in cellular function or limit cellular proliferation, thus leading to senescence and death. DNA repair processes may alter the rate of accumulation of damage, thereby affecting potential longevity. There were no significant age-associated changes in the ability of cells from either dietary group to remove DNA adducts and there was no evidence of alterations in the acceptor protein with age that would compromise its functional activity.

Routine focal mollusciciding after chemotherapy to control Schistosoma mansoni in Cul de Sac valley, Saint Lucia

Concluding results of a 10-year schistosomiasis control programme in Cul de Sac valley, Saint Lucia, are described. After an area-wide mollusciciding campaign (1970-75), and a surveillance/treatment programme supplemented with selective population chemotherapy in 1975 and 1976, prevalence rates of Schistosoma mansoni were reduced to low levels. To prevent a resurgence of transmission a cost effective routine focal mollusciciding programme, suitable for public health implementation was evaluated from 1977 to 1981. Streams and main collector drains in banana fields, considered to be potential S. mansoni transmission sites, were treated every four weeks with Bayluscide 6076 emulsifiable concentrate (Clonitralide). Snail populations were effectively controlled in the treated areas but large numbers were present where no treatment was given. Only 0 X 06% of sentinel snails became infected. Prevalence of infection in the human population remained low (over-all 5%) and intensity of infection at a level not normally associated with schistosomal disease. Since control started 10 years earlier the level of potential contamination has fallen by 92% in high transmission areas. The four-year programme cost US+12,909 of which 54% was for molluscicide, 27% for labour and 19% for transport, equipment and sundries. The average annual cost per head of population was US+0 X 46.

Evaluation of chemotherapy in the control of Schistosoma mansoni in Marquis Valley, Saint Lucia. I. Results in humans

Hycanthone at a dose of 2.5 mg kg body weight was given in 1973 and 1974 to persons found by a sedimentation concentration technique to be excreting Schistosoma mansoni eggs. In a further two campaigns oxamniquine was used (15 mg/kg body weight). The last treatment was given after the 1976 survey and stools of children were re-examined annually but not further treatment was planned. In six villages prevalence remained low, at 4%, 4 years later, in two it increased to 10%, and in two others after 3 years it was 23% and further treatment was offered. Factors affecting renewed transmission and the rate prevalence builds up were investigated and found to be low attendance rate for treatment, greater use of the river water and, possibly, infected immigrants. But if prevalence builds up slowly, retreatment may be necessary only every 3-4 years at an estimated annual cost of 40 cents per person protected.

Value of individual household water supplies in the maintenance phase of a schistosomiasis control programme in Saint-Lucia, after chemotherapy

Between 1970 and 1975, the incidence of new Schistosoma mansoni infections was reduced in 5 villages after each household was provided with its individual water supply and community laundry shower units were made available. In 1975, 1976, and 1977 chemotherapy with oxamniquine was offered to persons found to be infected. Transmission was reduced further and remained at a low level for the next 4 years, with no sign of an increase in spite of the reservoir of infection remaining after therapy and a poor level of sanitation in the villages.Thus, properly maintained water supplies appear to be effective in maintaining transmission at a low level during the maintenance phase of a schistosomiasis control programme, after chemotherapy. Sporadic new infections must be anticipated among children, but these will probably be of low intensity and associated with minimal morbidity.

Reduction in transmission of Schistosoma mansoni by a four-year focal mollusciciding programme against Biomphalaria glabrata in Saint Lucia

The effect of transmission of Schistosoma mansoni of a focal snail control programme was investigated over four years amongst approximately 1250 people living in five communities in the steep-sided Soufriere river valley, St. Lucia, West Indies. Bayer 6076 was applied from constant flow drip cans to 12 stream sections at a target dose of 8 mg/litre clonitralide every four weeks. Only proven and potential transmission sites were treated; marsh habitats, where Biomphalaria glabrata were widespread, were ignored. In the stream snail numbers were reduced by 94% in the first year and by 100% thereafter. Incidence of new S. mansoni infections amongst children fell from 18% in the last year before control to 6% and 9% after three and four years respectively. Amongst children and adults in the four years of control the conversion/reversion ratio declined leading to a lowering of the over-all prevalence from 40% to 22%. Parasitologically the results were similar to those of a previously evaluated area-wide mollusciciding programme. The mean annual cost per person protected was US $2.60. This figure is atypically high because the topography of the area severely limited the population size.

Schistosoma mansoni control in Cul de Sac Valley, Saint Lucia. II. Chemotherapy as a supplement to a focal mollusciciding programme

After an intensive area-wide mollusciciding campaign, over four and a half years, transmission of Schistosoma mansoni was reduced. A cheaper scheme suitable for the follow-up or consolidation stage of control was evaluated and two selective population chemotherapy campaigns using hycanthone (2 mg/kg b.w.) and oxamniquine (15 mg/kg b.w.) were mounted. Prevalence dropped to 6% and 3% in areas with previously high and low levels of transmission respectively. Calculations suggested that these figures were falsely low and that perhaps 20% of the population were still excreting S. mansoni ova in small numbers. The unco-operative groups in the population are probably more important in maintaining a reservoir of infection in the community than persons with light infections undetected by the sedimentation concentration stool examination technique used. The benefit of more sensitive but more costly examination techniques is not clear since the importance of very light infections in transmission is uncertain. Case detection absorbs an increasing proportion of the total cost of chemotherapy programmes with fewer cases being found amongst the same number screened. Using hycanthone (649 treated) the cost per person protected was $0.74 and using oxamniquine (264 treated) $0.94. The need to develop low cost consolidation or follow-up procedures for preventing a resurgence of transmission after successful control, when the infection is no longer of public health importance, is stressed.

Evaluation of an experimental mollusciciding programme to control Schistosoma mansoni transmission in St Lucia

The size and number of colonies of Biomphalaria glabrata were reduced after four years of a surveillance/treatment snail control programme using an emulsifiable concentrate of niclosamide (25% active ingredient). Surveys among the human population showed that the incidence of new Schistosoma mansoni infections in 0-10 year-old children fell from 22% to 4.3%, while in a comparison area the incidence remained at 20%. With reduced transmission over four years, the prevalence of infection in a cohort of children examined in 1971 and 1975 fell from 34% to 23%. The fall in prevalence and intensity of infection led to a reduction of 66% in the index of potential contamination, which was reflected in a reduced rate of infection among sentinel snails and representative samples of B. glabrata collected during surveillance searches.The overall annual cost of the programme was US $3.24 per capita.

Further observations from St Lucia on control of Schistosoma mansoni transmission by provision of domestic water supplies

Individual households in five settlements were provided with piped water in a pilot scheme to investigate the effect on transmission of S. mansoni in St Lucia. Nearby comparison settlements, in the same valley, were provided with water through a public standpipe system. The incidence of S. mansoni infection among children decreased in the experimental area, leading to lower prevalence rates and lower intensity of infection in all age groups. Over the study period, indices of infection increased in the comparison settlements, but by the end of the period development was making those settlements less suitable for comparison purposes and some reduction in transmission was occurring.The changes in human infection rates were reflected in the results of studies with sentinel snails. In the experimental area, infection rates gradually fell owing to reduced water contact and consequently less contamination of the river and its banks, and possibly to the gradual reduction in contamination potential of the community with reduced prevalence and intensity of infection. It is suggested that a piped water supply be considered as a method of schistosomiasis control, but that the cost should not be debited only to the control of this disease since a clean water supply has other medical and social benefits.