Backscatter measurements for NIF ignition targets (invited)

Backscattered light via laser-plasma instabilities has been measured in early NIF hohlraum experiments on two beam quads using a suite of detectors. A full aperture backscatter system and near backscatter imager (NBI) instrument separately measure the stimulated Brillouin and stimulated Raman scattered light. Both instruments work in conjunction to determine the total backscattered power to an accuracy of ∼15%. In order to achieve the power accuracy we have added time-resolution to the NBI for the first time. This capability provides a temporally resolved spatial image of the backscatter which can be viewed as a movie.

Stage 2 Genome-Wide Association Study of Candidate Low Penetrance Genes Implicated in Breast Cancer Risk

The risk of breast cancer in the first-degree female relatives of breast cancer cases is approximately double the risk in the general population. BRCA1 and BRCA2 account for less than 20% of this excess risk; the majority is probably due to the multiplicative effects of large numbers of low penetrance risk alleles. Genome-wide association studies (GWAS) have successfully identified 13 low-penetrance breast cancer risk alleles (Easton et al 2007, Hunter et al 2007, Stacey et al 2007, Zheng et al 2009, Ahmed et al 2009, Thomas et al 2009) but power calculations suggest that many more are still to be discovered.We have recently conducted a genome wide association study of 1,500 bilateral breast cancer cases, 200 cases with at least two affected first degree relatives and 1,450 controls from the 1958 birth cohort (WTCCC, 2007) using the Illumina HumanHap 370 chip. Based on these data and publicly available data from the Cancer Genetic Markers of Susceptibility (CGEMS) study we have selected 1,200 of the most significant SNPs to genotype in a stage 2 study comprising 5,500 breast cancer cases and 4,500 controls. All 13 of the known loci were replicated in this 2-stage analysis.Additional candidates at novel genomic loci are being genotyped in a replication study of 6,000 cases and 6,000 controls.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6136.

Does Having Primary Breast Reconstruction Influence Chest-Wall Radiotherapy Rates?

BACKGROUND: Immediate breast reconstuction should be discussed with all patient's who require mastectomy. The immediate recontruction may interfere with postmactectomy chest wall radiotherapy (RT) .The adverse impact of chest-wall radiotherapy on the reconstructed breast is widely reported. Predicting who will require chest-wall RT prior to surgery can be difficult, limited to the knowledge of full pathological staging and often only known after mastectomy. Does having primary reconstruction influence in chest-wall RT decision making? Are women who opt for primary reconstruction less likely to receive RT than those who choose no reconstruction?METHODS: From 1st Jan 2008 to 31st March 2009, we performed 430 mastectomies 226 were mastectomy only (M0), 204 were mastectomy with immediate reconstruction (MIR). Data were prospectively recorded on chest wall recurrence risk adjuvant chest wall radiotherapy, type of breast reconstruction (tissue expander, fixed volume implant, autologous reconstruction only and autologous reconstruction implant assisted).Chest-wall recurrence risk was calculated from pathology.RESULTS:Performed 430 mastectomies, 335 for invasive disease, 53 for DCIS, 6 for ALH/LCIS, 36 benign (for risk reduction or symmetry purposes).Two hundred and twenty-six (52%) were mastectomy only (M0), 204 (48%) were mastectomy with immediate reconstruction (MIR).Chest wall radiotherapy + MO vs. MIRTotal RT 130(30%), of which 88 (67%, 88/130) and 44 (33%, 44/130) were MO and MIR respectively. MOMO+RTMIRMIR+RTLow Risk (ASCO pN-ve/T<50mm)42 (18%,42/226)4 (9%,4/42)44 (21%,44/204)2 (4%,2/44)Moderate Risk (SUPREMO pN+ (1-3) and/or pT2)89 (39%)31 (34%,31/89)59 (29%)23 (39%,23/59)High Risk (ASCO pT_>50mm and/or pN+_> 4)77 (32%)53 (73%,53/77)29 (14%)19(65%,19/29) RT and Type of Reconstruction: Of the 204 MIR, 85 (42%) were autologous and 119 (58%) implant based of which 16 autologous (18%,16/85) and 30 (25%,30/119 ) implants received RT.CONCLUSION:Chest wall RT rates are broadly comparable across the three risk groups for MIR and MO suggesting MIR doesn't influence decision making regarding RT.The number of high risk MIR was small (14%) suggesting successful preoperative selection.Slightly higher radiotherapy rate for implant based reconstruction may be explained by staged reconstruction.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3119.

Pooled Analysis of Cardiac Safety in Patients Treated with Pertuzumab

Background: Pertuzumab, a monoclonal antibody, is a human epidermal growth factor receptor 2 (HER2)-dimerisation inhibitor directed to the dimerisation epitope of HER2, with promising activity when given with trastuzumab to patients with HER2-positive metastatic breast cancer following progression on trastuzumab.1 As anti-HER2 treatment has been associated with cardiac dysfunction, we investigated the incidence of reduced left ventricular ejection fraction (LVEF) and congestive heart failure (CHF) in patients treated with pertuzumab as single agent or in combination with cytotoxic or anti-HER therapy.Methods: We analysed patients in completed Phase II studies with pertuzumab. Cardiac dysfunction was defined as: 1) reduced LVEF (baseline normal: LVEF reduced ≥10% absolute and to below 50%); 2) symptomatic CHF: any symptoms suggestive of CHF counted (severity then classified according to New York Heart Association).Results: In 554 patients analysed, the overall incidence of reduced LVEF was 5.8% and of CHF 0.7%. Individual data for patients in different treatment protocols are shown in Table 1. PatientsReduced LVEFCHF (n)(n/%)(n/%)Pertuzumab as single agent (24% with prior anthracyclines)30221/7.01/0.3Pertuzumab with cytotoxic therapy1756/3.42/1.1Pertuzumab with trastuzumab (71% with prior anthracyclines)775/6.51/1.3 The majority of patients with reduced LVEF or symptomatic CHF had significant improvement or return to baseline function on follow-up or with standard cardiac medication.Conclusions: Overall, the incidence of cardiac dysfunction in Phase II studies of patients treated with pertuzumab was low. When combined with trastuzumab in selected patients, there is no apparent indication that pertuzumab exacerbates the known risk of reduced LVEF and CHF with trastuzumab.2 These data suggest that the combination of pertuzumab with trastuzumab or chemotherapy for HER2-positive breast cancer appears safe from a cardiac perspective with appropriate monitoring in ongoing studies.References1. Gelmon K et al. Poster 1026 presented at the 44th ASCO Annual Meeting, Chicago, Illinois, USA, 30 May-3 June, 20082. Muehlbauer S et al. Abstract presented at SABCS 2008; abs 6136

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5088.

Pertuzumab and Trastuzumab: Re-Responses to 2 Biological Agents in Patients with HER2-Positive Breast Cancer Which Had Previously Progressed during Therapy with Each Agent Given Separately: A New Biological and Clinical Observation

Background: Pertuzumab, a fully humanised IgG1 monoclonal antibody, is a human epidermal growth factor receptor 2 (HER2)-dimerisation inhibitor directed to the dimerisation epitope of HER2 (trastuzumab binds to the juxta-membrane epitope). Pertuzumab has demonstrated promising activity when given with trastuzumab to patients with HER2-positive metastatic breast cancer (mBC) which had progressed during therapy with trastuzumab in a 2-step Phase II study.1Methods: The protocol was amended to include a 3rd cohort of patients to determine the activity of pertuzumab when given without trastuzumab.2 Patients recruited into this 3rd cohort were allowed to have trastuzumab re-introduced in combination with pertuzumab if there was inadequate response to pertuzumab alone or response followed by relapse.Results: Twenty-nine patients were recruited into this 3rd cohort. Patients had reached their 3rd line of treatment for mBC. To date, 15 patients have had trastuzumab re-introduced after disease progression on trastuzumab therapy and pertuzumab monotherapy. Among these 15 patients, at the time of this analysis there have been 3 patients with confirmed responses. There are also 4 patients who had not yet undergone 8 cycles of assessments to reach the overall best response end point, of which at least 2 were experiencing stablisation of disease. Updated data on activity and toxicity will be presented.Conclusions: We believe this is the first time that anti-tumour activity has been reported in patients when 2 biological agents have been used together after the disease has progressed during therapy with each agent alone. There are several mechanisms which might explain this phenomenon. Trastuzumab prevents proteolytic cleavage of the extracellular domain of HER2, keeping the receptor in situ. The addition of a second antibody to a separate epitope increases the potential for antibody-dependent cell-mediated cytotoxicity and prevents dimerisation between HER2 and other HER family members, such as HER1 and HER3. The combined antibodies might increase the efficiency of inhibition of signal transduction. There are wide-ranging and potentially significant biological and clinical implications.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5114.

Pertuzumab monotherapy following trastuzumab-based treatment: Activity and tolerability in patients with advanced HER2- positive breast cancer

1022

Background: Pertuzumab binds to the dimerization epitope of the HER2 receptor, inhibits HER dimerization and signal transduction, and induces ADCC. In 2 cohorts of pts (n = 66) with HER2-positive metastatic breast cancer which had progressed during trastuzumab therapy after ≤3 lines of chemotherapy with or without trastuzumab, pertuzumab plus trastuzumab has been shown to be active (CR 7.6%, PR 16.7%, SD ≥6/12 25.8%) (Gelmon et al. ASCO 2008, Abs 1026). To assess the activity of pertuzumab monotherapy in this clinical setting, the protocol was amended to include a 3rd cohort of pts. Methods: Pt selection was not changed except that ≥1 month between the last dose of trastuzumab and study start was required. Pts received pertuzumab monotherapy. If the tumor failed to respond or responded and then progressed, trastuzumab could be added to pertuzumab. 27 pts were to be recruited to ensure that ≥24 were fully evaluable for objective response and stabilization of disease ≥6 months. Standard 21-day schedules of the antibodies were given. Results: 29 pts were recruited. Tolerability was good: the major adverse events were mild diarrhea and rash with no clinical cardiac events. To date, 2 responses have been reported, and several pts have ongoing stabilization of disease. 14 pts have received trastuzumab plus pertuzumab following inadequate response (or response then relapse) on pertuzumab monotherapy. Of these 14, 2, having progressed during trastuzumab, failed to respond to pertuzumab monotherapy but underwent confirmed response when trastuzumab was added to the pertuzumab –possibly the first report of such a phenomenon and providing good evidence of an enhanced effect when the antibodies are combined. Updated results will be presented. Conclusions: Pertuzumab monotherapy is active against HER2-positive breast cancer which has progressed during trastuzumab-based therapy. The combination of the two antibodies appears to be more active than either antibody alone. The combination is also active in patients that had failed both antibodies given separately. In clinical studies, the use of the two antibodies combined is justified.

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Association of paediatric mastocytosis with a polymorphism resulting in an amino acid substitution (M541L) in the transmembrane domain of c-KIT

BACKGROUND

The receptor tyrosine kinase c-KIT plays a key role in normal mast cell development. Point mutations in c-KIT have been associated with sporadic or familial mastocytosis.

OBJECTIVES

Two unrelated pairs of apparently identical twins affected by cutaneous mastocytosis attending the Mastocytosis Clinic at the Royal Children's Hospital, Melbourne, provided an opportunity to assess the possible contribution of c-KIT germline mutations or polymorphisms in this disease.

METHODS

Tissue biopsy, blood and/or buccal swab specimens were collected from 10 children with mastocytosis. To detect germline mutations/polymorphisms in c-KIT, we studied all coding exons by denaturing high pressure liquid chromatography. Exons showing mismatches were examined by direct sequencing. The influence of the substitution identified was further examined by expressing the variant form of c-KIT in factor-dependent FDC-P1 cells.

RESULTS

In both pairs of twins, a heterozygous ATG to CTG transition in codon 541 was observed, resulting in the substitution of a methionine residue in the transmembrane domain by leucine (M541L). In each case, one parent was also heterozygous for this allele. Expression of M541L KIT in FDC-P1 cells enabled them to grow in human KIT ligand (stem cell factor, SCF) but did not confer factor independence. Compared with cells expressing wild-type KIT at a similar level, M541L KIT-expressing cells displayed enhanced growth at low levels of SCF, and heightened sensitivity to the KIT inhibitor, imatinib mesylate.

CONCLUSIONS

The data suggest that the single nucleotide polymorphism resulting in the substitution M541L may predispose to paediatric mastocytosis.