Biomarker analyses from a phase III, randomized, open-label, first-line study of gefitinib (G) versus carboplatin/paclitaxel (C/P) in clinically selected patients (pts) with advanced non-small cell lung cancer (NSCLC) in Asia (IPASS)

8006^

Background: IPASS demonstrated overall superiority of first-line G vs C/P for progression-free survival (PFS) in never/light ex-smokers with stage IIIB/IV adenocarcinoma NSCLC in Asia. PFS favored CP initially and then G. Outcome was correlated with biomarkers (preplanned exploratory objective). Methods: 683 patients provided tissue samples. Analyses included primary endpoint PFS (Cox proportional hazards) and secondary endpoint objective response rate (ORR; logistic regression) by biomarker status. Results: EGFR mutation (M) status was evaluable in 437 pts by Amplification Refractory Mutation System (ARMS; 60% M+). M+ pts had significantly longer PFS and higher ORR and M- pts significantly shorter PFS and lower ORR with G than C/P. In M unknown pts PFS and ORR were similar to overall population. Post hoc analysis of overall survival favored G in M+ pts (31% maturity; HR 0.78; 95% CI 0.50–1.20) and C/P in M- pts (53% maturity; HR 1.38; 95% CI 0.92–2.90); differences were not statistically significant and follow-up is ongoing. EGFR gene-copy number was evaluable in 406 pts by fluorescence in situ hybridization (FISH; 61% FISH +). Similar PFS and ORR results to analyses by M status were observed, driven by the overlap in EGFR FISH and M status. EGFR protein expression (PE) was evaluable in 365 pts by immunohistochemistry (73% PE+). PFS outcomes did not differ statistically between PE+ and PE-. ORR favored G in both PE+ and - pts. Conclusions: EGFR M status was a strong predictive biomarker for the efficacy of G vs C/P in this clinically selected first-line setting.

[Table: see text]

No significant financial relationships to disclose.

ASCO Conflict of Interest Policy and Exceptions

In compliance with the guidelines established by the ASCO Conflict of Interest Policy (J Clin Oncol. 2006 Jan 20;24[3]:519–521) and the Accreditation Council for Continuing Medical Education (ACCME), ASCO strives to promote balance, independence, objectivity, and scientific rigor through disclosure of financial and other interests, and identification and management of potential conflicts. According to the ASCO Conflict of Interest Policy, the following financial and other relationships must be disclosed: employment or leadership position, consultant or advisory role, stock ownership, honoraria, research funding, expert testimony, and other remuneration (J Clin Oncol. 2006 Jan 20;24[3]:520). The ASCO Conflict of Interest Policy disclosure requirements apply to all authors who submit abstracts to the Annual Meeting.

For clinical trials that began accrual on or after April 29, 2004, ASCO's Policy places some restrictions on the financial relationships of principal investigators (J Clin Oncol. 2006 Jan 20;24[3]:521). If a principal investigator holds any restricted relationships, his or her abstract will be ineligible for placement in the 2009 Annual Meeting unless the ASCO Ethics Committee grants an exception. Among the circumstances that might justify an exception are that the principal investigator (1) is a widely acknowledged expert in a particular therapeutic area; (2) is the inventor of a unique technology or treatment being evaluated in the clinical trial; or (3) is involved in international clinical oncology research and has acted consistently with recognized international standards of ethics in the conduct of clinical research. NIH-sponsored trials are exempt from the Policy restrictions. Abstracts for which authors requested and have been granted an exception in accordance with ASCO's Policy are designated with a caret symbol (^) in the Annual Meeting Proceedings.

For more information about the ASCO Conflict of Interest Policy and the exceptions process, please visit www.asco.org/conflictofinterest .

Evaluation of clinically selected patients (pts) with advanced non-small cell lung cancer (NSCLC) recruited in China in a phase III, randomized, open-label, first-line study in Asia of gefitinib (G) versus carboplatin/paclitaxel (C/P) (IPASS)

8041^

Background: The IRESSA Pan Asia Study (IPASS) demonstrated superiority of G vs C/P for progression-free survival (PFS) in 1,217 chemonaïve, never/light ex-smokers with WHO PS 0–2, adenocarcinoma histology and stage IIIB/IV NSCLC. PFS favored C/P initially then G, likely driven by different outcomes according to EGFR mutation (M) status. Planned analyses of pts recruited in China are reported. Methods: 372 pts in China (31% of overall population) were randomized to G 250 mg/day (n=184) or C (AUC 5 or 6)/P (200 mg/m2) (n=188). Primary objective was to assess PFS in ITT population; a treatment by country interaction test (China vs other) was performed. Secondary endpoints were overall survival (OS), objective response rate (ORR, RECIST), QoL (FACT-L, TOI), symptom improvement (LCS) and tolerability. Results: PFS results for pts in China did not significantly differ from other pts (interaction test p=0.4265). G demonstrated numerically longer PFS vs C/P; effect was not constant over time, favoring C/P initially then G. Preliminary OS (28% maturity; follow-up ongoing) was similar for G and C/P. ORR was significantly higher with G (45%) than C/P (30%). QoL improvement rates were higher with G than C/P (FACT-L 44 vs 34%; TOI 45 vs 25%); symptom improvement rates were similar (LCS 48 vs 42%). G had a more favorable tolerability profile than C/P. Conclusions: For pts in China, efficacy and tolerability data were generally consistent with the overall population. G demonstrated improved efficacy (PFS and ORR), similar OS, higher QoL and similar symptom improvement rates and more favorable tolerability profile compared with C/P in chemonaïve, never/light ex-smokers with advanced NSCLC and adenocarcinoma histology. In IPASS, EGFR mutation status appeared to be a strong predictive biomarker for G efficacy compared with C/P.

[Table: see text]

[Table: see text]

ASCO Conflict of Interest Policy and Exceptions

In compliance with the guidelines established by the ASCO Conflict of Interest Policy (J Clin Oncol. 2006 Jan 20;24[3]:519–521) and the Accreditation Council for Continuing Medical Education (ACCME), ASCO strives to promote balance, independence, objectivity, and scientific rigor through disclosure of financial and other interests, and identification and management of potential conflicts. According to the ASCO Conflict of Interest Policy, the following financial and other relationships must be disclosed: employment or leadership position, consultant or advisory role, stock ownership, honoraria, research funding, expert testimony, and other remuneration (J Clin Oncol. 2006 Jan 20;24[3]:520). The ASCO Conflict of Interest Policy disclosure requirements apply to all authors who submit abstracts to the Annual Meeting.

For clinical trials that began accrual on or after April 29, 2004, ASCO's Policy places some restrictions on the financial relationships of principal investigators (J Clin Oncol. 2006 Jan 20;24[3]:521). If a principal investigator holds any restricted relationships, his or her abstract will be ineligible for placement in the 2009 Annual Meeting unless the ASCO Ethics Committee grants an exception. Among the circumstances that might justify an exception are that the principal investigator (1) is a widely acknowledged expert in a particular therapeutic area; (2) is the inventor of a unique technology or treatment being evaluated in the clinical trial; or (3) is involved in international clinical oncology research and has acted consistently with recognized international standards of ethics in the conduct of clinical research. NIH-sponsored trials are exempt from the Policy restrictions. Abstracts for which authors requested and have been granted an exception in accordance with ASCO's Policy are designated with a caret symbol (^) in the Annual Meeting Proceedings.

For more information about the ASCO Conflict of Interest Policy and the exceptions process, please visit www.asco.org/conflictofinterest .

High-grade proteinuria associated with bevacizumab in patients with renal cell cancer and non-renal cell cancer

e16089

Background: Bevacizumab is a humanized monoclonal antibody that inhibits vascular endothelial growth factor. It is a widely used angiogenesis inhibitor in the treatment of renal cell cancer (RCC) and other solid tumors. Proteinuria is associated with significant morbidity and treatment interruptions. The overall risk for proteinuria is unclear. This study was conducted to determine the risk of developing proteinuria among RCC and non-RCC patients receiving bevacizumab. Methods: Databases from PUBMED and Web Science from January 1966 until July 2008 and abstracts presented at ASCO from January 2000 to July 2008 were searched to identify relevant studies. Studies included randomized controlled clinical trials in which standard anti-neoplastic therapy was administered with and without bevacizumab with available data for proteinuria. Summary incidence rate, relative risk (RR), and 95% confidence interval (CI) were calculated employing fixed or random effect models based upon the heterogeneity of included studies. Results: A total of 6,702 patients from 14 randomized controlled studies were included for analysis. The incidence of all-grade proteinuria in patients receiving bevacizumab was 19.3% (95% CI: 11.9–29.6%) with 2.3% (95% CI: 1.2–4.1%) being high-grade (grade 3 or 4). Patients treated with bevacizumab had an increased risk of developing high-grade proteinuria with RR of 6.3 (95% CI: 4.0–9.9) compared with controls. Risk may vary with dose of bevacizumab; significant difference may exist in patients receiving bevacizumab at 5 mg/kg/week (RR 9.1, 95% CI: 4.3–19.6, p < 0.001) and 2.5 mg/kg/week (RR = 5.1, 95%CI: 3.0–8.8, p < 0.001). The risk of high-grade proteinuria may also depend on tumor type; the incidence of high-grade proteinuria was 10.0% (95% CI: 4.3–22.4%) with a RR 48.7 (95% CI: 9.7–244.3) among 703 RCC patients compared with an incidence of 1.7% (95% CI: 0.09–3.2%) and RR of 5.2 (95% CI: 3.3–8.4) among 5,999 non-RCC patients. Conclusions: There is a significant risk for high-grade proteinuria in patients receiving bevacizumab. The risk may vary with bevacizumab dose and tumor type. RCC patients may have higher risk than non-RCC patients. Close monitoring and management are recommended for patients at high risk.

No significant financial relationships to disclose.

Concurrent blockade of platelet-activating factor and histamine prevents life-threatening peanut-induced anaphylactic reactions

BACKGROUND

Food anaphylaxis is an acute and life-threatening systemic allergic reaction. Fatality registries place peanut as the most common culprit of fatal and near-fatal reactions in North America. Because prophylaxis and treatment have advanced little in recent years, it is imperative to evaluate novel therapies.

OBJECTIVE

To investigate the impact of blocking mast cell mediators in a mouse model of peanut-induced anaphylaxis.

METHODS

Mice were sensitized with peanut protein and cholera toxin via oral gavage weekly for 4 weeks. One week after the last sensitization, separate groups of mice were treated with either a (1) 5-lypoxygenase inhibitor, (2) a platelet-activating factor (PAF) receptor antagonist, (3) histamine receptor antagonists, or (4) a PAF receptor antagonist along with histamine receptor antagonists before peanut challenge.

RESULTS

Treatment targeting either leukotrienes or histamine alone had no beneficial effects. In contrast, PAF antagonism significantly attenuated the magnitude and duration of the anaphylactic reactions. Particularly, it prevented severe reactions. Moreover, 83% of PAF-treated versus 43% of untreated mice reached recovery within 120 minutes after peanut challenge. Notably, combined blockade of PAF and histamine had a clearly greater beneficial effect. In fact, all but 1 mouse developed mild, if any, anaphylactic reactions. In addition, combination therapy was associated with a significant decrease in vascular leakage and release of vasoactive mediators after peanut challenge.

CONCLUSION

Combination therapy blocking both PAF and histamine markedly reduces the severity of peanut-induced anaphylaxis, and thus it may be a potential life-saving therapeutic approach in peanut and, likely, other food-induced anaphylaxis.

The blood oxygen level-dependent functional MR imaging signal can be used to identify brain tumors and distinguish them from normal tissue

BACKGROUND AND PURPOSE

In neuro-oncology, a major problem is clear identification of tumor from the surrounding normal tissue. We hypothesized that we could use the blood oxygen level-dependent functional MR imaging (BOLD fMRI) signals from tumors and normal brain to identify the tumors and distinguish them from the surrounding brain.

MATERIALS AND METHODS

Fourteen patients with meningiomas, gliomas, and metastatic tumors were scanned before surgery. All subjects performed a motor task; 2 subjects were also scanned while in a resting state. The BOLD signals were taken from selected points within the tumor and from the surrounding normal brain and were analyzed by using correlation analysis to determine how closely they were related.

RESULTS

The BOLD signals from all of the tumors were significantly different from those in the surrounding normal tissue. In meningiomas and gliomas, selection of a voxel in the tumor for signal-intensity analysis highlighted the entire tumor mass while excluding the normal tissue. The BOLD signal intensity was the same whether the subjects were motionless or finger tapping.

CONCLUSIONS

Analysis of the BOLD signal intensity provides a relatively simple and straightforward method for identifying brain tumors and distinguishing them from normal tissue. This approach may be of use in neurosurgery.

Biotype status and distribution of Bemisia tabaci (Hemiptera: Aleyrodidae) in Shandong province of China based on mitochondrial DNA markers

Bemisia tabaci has caused significant crop losses in China during the last decade. Recent research has shown that two potentially invasive variants, biotypes B and Q, have been found in several regions of China. Our objective was to determine the biotype status and the distribution of B. tabaci in Shandong province, an important agricultural region of China. Based on mitochondrial DNA markers, both biotypes B and Q were detected, with B being the predominant biotype. The results indicate that the more recently introduced biotype Q has not only been located in China but also has established and spread in some regions.

Stress-induced cardiomyopathy: A review

In clinical practice it is essential to bear stress-induced cardiomyopathy (SICMP) in mind as it is an insufficiently known cardiac pathology that mimics acute coronary syndromes (ACS), often with signs of cardiac failure. In the chronic phase, it poses differential diagnostic problems with regard to coronary artery pathology. Taxonomic confusion, due to the pathology also being called "takotsubo" or "ampulla cardiomyopathy", has resulted in inappropriate diagnoses and therapy. Available evidence strongly suggests that, in the presence of several cardiac risk factors, excessive sympathetic stimulation may induce this cardiomyopathy. The predilection of this cardiomyopathy for Mediterranean and Indo-Asian women, who represent 85% of cases, is probably explained by the fact that there is a significant correlation between female gender, a short (<158 cm) stature, a small (<1.9 m(2)) body surface area, and hypoplastic coronary arteries. Furthermore, 40% of SICMP patients have a hypoplastic branching of the coronary arteries in the apical region of the heart. This anomaly strongly favors the apical localization of the dyskinesia. The prognosis of SICMP is good as far as life expectancy is concerned. However, in most cases, the symptoms become chronic, medical treatment rarely improves dyspnea and chest pain, and the quality of life is, therefore, reduced. In this paper, we address diagnostic misunderstandings and we review the clinical and pathophysiological features of SICMP.

Phase II study of weekly docetaxel plus cisplatin as first-line therapy in advanced or metastatic non-small cell lung cancer (CHN TAX-206)

18173

Background: There has been increasing interest in the use of weekly administration of docetaxel as a way of reducing its hemotologic toxicity. Weekly docetaxel plus cisplatin has also shown promising efficacy and well tolerability for first-line treatment of advanced or metastatic NSCLC in our previous phase I study (2002 ASCO, abstract No 2744). We conducted this phase II trial to further evaluate this regimen’s efficacy and toxicity. Methods: Patients with histologically confirmed stage IIIB or IV NSCLC were treated with docetaxel (35 mg/m2, 30 min. iv. infusion) on days 1, 8, 15 and cisplatin (75 mg/m2, 30 min. iv. infusion) on day 1 repeated every 4 weeks for up to 6 cycles. Pts received oral dexamethasone 7.5 mg twice daily from the day before chemotherapy and consecutive two days thereafter. The primary endpoint of this phase II study is efficacy of the regimen. Results: A total of 83 patients were enrolled from July 2002 to June 2004, 75 patients were evaluable for response and 83 for safety. Median age was 55 years (range 29–70 years); and 69.9% were male; adenocarcinoma/squamous cell carcinoma/others (65/12/6); stage IIIB /IV( 47/36); ECOG PS 0/1(52/31). Median number of chemotherapy cycles was 3(1–5). One CR (complete response) and 22 PR (partial response) were achieved with an ORR of 30.7% in the evaluable patients. The 1-year survival was 48.6% with a median survival of 10.7 months (range: 3–34 months). Neutropenia was the most common adverse event, though most were mild; Grade III/IV toxicities per patient were: Neutropenia (15.6%), asthenia (11%), skin/nail toxicity (10.8%) and vomiting (9.6%). Febrile neutropenia was not observed. Conclusions: In the present study, the combination of weekly administration docetaxel combining with cisplatin appears well tolerated with very low frequency of severe hematologic toxicity and similarly efficacious as 3-weekly docetaxel in NSCLC pts.

No significant financial relationships to disclose.

Paeoniflorin inhibits TGF-beta1-mediated collagen production by Schistosoma japonicum soluble egg antigen in vitro

The main pathological characteristics of hepatic fibrosis in schistosomiasis are the proliferation of hepatic stellate cells (HSCs) and the deposition of collagen type I (Col I) and collagen type III (Col III). Transforming growth factor beta-1 (TGF-beta1) plays an important role in hepatic fibrosis. Paeoniflorin (PAE) has been reported to have immunoregulatory effects; however, the mechanism of its anti-hepatic fibrosis in S. japonicum has not been elucidated. In the present study, we found that mouse peritoneal macrophages (PMphis) stimulated by soluble egg antigen (SEA) of S. japonicum could secrete TGF-beta1, and the TGF-beta1 in the peritoneal macrophage-conditioned medium (PMCM) could induce proliferation of HSCs and secretion of Col I and III. We selected PMCM at 1 : 2 dilution as the optimum PMCM (OPMCM). Then we treated HSCs pre-incubated with OPMCM with PAE, and found that the inhibition of HSC proliferation or Col I and III production were closely correlated with the concentration of PAE. Further investigation found that PAE significantly decreased the Smad3 transcription and phosphorylation in HSCs stimulated by OPMCM. In conclusion, SEA plays a key role in hepatic fibrosis by inducing TGF-beta1 from PMphis. PAE can exert anti-fibrogenic effects by inhibiting HSCs proliferation and down-regulating Smad3 expression and phosphorylation through TGF-beta1 signalling.

Patient attitude and survival in advanced non-small cell lung cancer (NSCLC): Results of a prospective observational study

7148

Background: A physician’s ability to accurately identify a patient’s attitude toward treatment is critical. The primary objective of this study (B9E-AA-JHSH) was to evaluate patient attitudes as predictors of survival independently of currently known predictive variables, and secondarily, whether physician-assessed patient attitudes differed from patient-assessed attitudes. Methods: This was a non-interventional, prospective, observational study of patients from 19 countries of Asia, Central Eastern Europe, and Latin America. Eligible patients had stage IIIB/IV NSCLC not amenable to curative surgery/radiotherapy, gemcitabine and cis/carboplatin as part of treatment, and were chemonaive. Physicians and patients used a 7-item questionnaire to assign patient attitudes to 1 of 4 categories using a pre-defined algorithm: A = Cure; B = Maximum extension of survival with acceptance of high toxicity; C = Maximum extension of survival only if coupled with normal lifestyle; and D = Symptom relief. Enrolled patients were followed until 18 months from enrolment, death, or loss to follow up. Results: From Sept 2002 to Dec 2003, 1,985 patients were enrolled; the majority were male (73.4%), <70 yrs (83.9%), and had stage IV disease (79.2%), PS 0–1 (79.2%), and tumor-related symptoms (89.2%). Distribution of patient-assessed attitudes were A = 0%, B = 55%, C = 25%, and D = 20%. From category B-D, median survival (B = 14.6 months, C = 13.5, D = 12.5) and 1-year survival (B = 57.6%, C = 56.2%, D = 51.2%) both decreased but the differences were not statistically significant. Adjustment for known predictive variables eliminated this decreasing trend. Physician-assessed patient attitudes were lower than patient-assessed attitudes (p < .0001); however, the difference was less for patients with disease-related symptoms (p = .03). Conclusions: This is the largest analysis to date of patient attitudes when treated with gemcitabine and cis/carboplatin. Patient attitudes were not significant predictors of survival; however, physicians do underestimate patients’ desire for extended survival compared to symptom relief. Also, it was interesting to see a comparatively longer median and 1-year survival in routine practice compared to reports in clinical trial settings.

[Table: see text]

Immune response to influenza vaccination in community-dwelling Chinese elderly persons

We investigated the immune antibody response to influenza vaccine in community-dwelling Chinese elderly persons in Hong Kong. One hundred and twenty-eight subjects were recruited in a single-blind, randomized, and placebo-controlled trial. There was no significant baseline difference between the vaccine and placebo groups regarding the seroprotection rates (PR) (haemagglutination inhibition [HI] titre>or=1:40) and geometric mean titres (GMT) of the HI antibody titers. The PR, GMTs and serological response rates increased significantly in the vaccinated versus placebo groups in A-H1N1 at both weeks 4 and month 6. The GMTs and serological response rates but not the PR for A-H3N2 and influenza B increased significantly in vaccinated versus placebo group at week 4 and month 6 post-vaccination. Multivariate logistic regression analyses of the seroconversion rate for A-H3N2 within the vaccinated group showed that gender, coronary heart disease and the serum albumin level were significant predictors (p=0.018, 0.009 and 0.025, respectively). Influenza vaccination provoked a protective HI antibody response in community-living Chinese elderly persons. The mean number of unplanned hospital admissions per subject over 6 months was significantly lower in the vaccinated than in the placebo groups. Hospitalized elderly persons had poorer nutrition, 4-week post-immunization HI antibody titres and lower mini-mental state examination (MMSE) score than non-hospitalized elderly persons. Logistic regression analyses showed that chronic obstructive airway disease significantly increased the risk of hospitalization while the serum albumin level and 4-week A-H3N2 PR (HI>or=40) were independent predictors of a decreased risk of hospitalizations.

A study of radiotherapy modalities combined with continuous 5-FU infusion for locally advanced gastrointestinal malignancies

AIM

We describe the feasibility of combining infusional 5-fluorouracil (5-FU) with intraoperative radiation therapy (IORT).

METHODS

Patients with surgically resectable locally advanced gastrointestinal cancers were treated concurrently during surgery with IORT and a 72 h infusion of 5-FU. Patients without previous external beam radiation therapy (EBRT) were subsequently treated with EBRT (40-50Gy) concurrent with a 21-day continuous infusion of 5-FU. Pancreatic, gastric, duodenal, ampullary, recurrent colorectal, and recurrent anal cancer were included.

RESULTS

During IORT/5-FU, no chemotherapy-related grade III or IV hematologic or gastrointestinal toxicity was noted. Post-surgical recovery or wound healing was not affected. One of nine patients who received post-operative radiation required a treatment break. During follow-up, there were more complications in patients with pelvic tumours, especially those with previous radiation. Nine patients have had local and/or local regional recurrences, two of these in the IORT field.

CONCLUSIONS

Treatment with a combination of IORT and 5-FU followed by EBRT and 5-FU is feasible. However, long-term complications may be increased in previously irradiated recurrent pelvic tumours.

Antibacterial and antifungal activity of Indonesian ethnomedical plants

Methylene chloride and methanol extracts of 20 Indonesian plants with ethnomedical uses have been assessed for in vitro antibacterial and antifungal properties by disk diffusion method. Extracts of the six plants: Terminalia catappa, Swietenia mahagoni Jacq., Phyllanthus acuminatus, Ipomoea spp., Tylophora asthmatica and Hyptis brevipes demonstrated high activity in this bioassay system. These findings should stimulate the search for novel, natural product such as new antibacterial and antifungal agents.

The impact on clients of a community-based infant mortality reduction program: the National Healthy Start Program Survey of Postpartum Women

OBJECTIVES

This study assessed the effect of the national Healthy Start Program on its clients.

METHODS

We used a cross-sectional survey of a sample from Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) rosters of women less than 6 months postpartum who were residents of Healthy Start Program areas.

RESULTS

Healthy Start clients revealed higher sociodemographic risk, but not behavioral risk, for adverse pregnancy outcome than other area residents. They did not differ from other residents in receipt of services except for a greater likelihood of receiving case management, using birth control at the time of the interview, and rating their prenatal care more highly.

CONCLUSIONS

The Healthy Start Program succeeded in enrolling women at high risk. It had little effect on the immediately concluded pregnancy, but it might influence future outcomes.

An fMRI study of the effect of amphetamine on brain activity

Functional magnetic resonance imaging was used to evaluate the effects of oral d-amphetamine on brain activation elicited by auditory and simple motor tasks in ten normal right-handed subjects. We measured the percent signal change and number of voxels activated by a tone discrimination task and a right hand finger-tapping task after 20 mg of d-amphetamine and after placebo. Compared to placebo, amphetamine significantly increased the number of activated voxels in the left and right primary auditory cortices during the tone discrimination task and increased the number of activated voxels in the ipsilateral primary sensorimotor cortex and right middle frontal area during the motor task. Although highly specific vascular effects of drug cannot be ruled out as an explanation, these results could also mean that amphetamine increases the neuronal activity associated with each of these two tasks.

Some aspects of sound extinction by zooplankton

To address the importance of sound extinction (or the shadowing effect) in the presence of a densely aggregated zooplankton layer, acoustic scattering by weakly scattering fluid objects is studied theoretically. An analytical expression for the extinction cross section is obtained based on the forward scattering theorem and the analytical formula for the forward scattering amplitude is derived from the Modal Based-Deformed Cylinder Model (MB-DCM). The validity of the MB-DCM solution for the forward scattering amplitude and its sensitivity to geometrical and physical parameters is studied. Comparison with the PC-DWBA (Phase-Compensated-Distorted Wave Born Approximation) shows a reasonable agreement between the two models. The extinction cross section is shown to be proportional to (ka)2 and the induced attenuation is predicted for various species of zooplankton over a wide frequency range. It is shown that, under certain realistic conditions, such as the presence of a swarm of aggregated krill, sound extinction by zooplankton could influence the acoustic measurements significantly, as much as an 85% reduction in acoustic intensity for Euphausia superba with n = 5000 ind./m3 over a range of 50 m.