Long-Term Results of Induction Chemotherapy Followed by 50 Gy Radiation Therapy Alone for Low-Risk HPV-Positive Oropharynx Cancer

PURPOSE/OBJECTIVE(S)

The standard of care for non-operative management of human papillomavirus-related oropharynx cancer (HPV-OPC) consists of concurrent cisplatin chemotherapy with radiotherapy (RT) to a total dose of 70 Gy. While the oncologic outcomes of this treatment approach have been excellent, there are considerable acute and late toxicities. Here, we report the 5-year survival and toxicity outcomes of 2 prospective HPV-OPC response-adapted de-escalation trials, in which low-risk (LR) patients were treated with dose-reduced RT to 50 Gy, without concurrent chemotherapy.

MATERIALS/METHODS

Patients with LR HPV-OPC and ≥50% response to induction by RECIST 1.1 treated per 2 prospective phase II trials as well as on a prospective cohort registry were included for analysis. Patients were considered LR if the following criteria were met: T1-T3, N0-N2b (AJCC 7th edition), and ≤20 pack-year smoking history. Patients were treated with induction chemo- or chemoimmunotherapy followed by RT alone to 50 Gy. In the early trial iteration, patients underwent a planned neck dissection following RT to confirm pathologic clearance of lymph nodes. Clinicodemographic characteristics were summarized using descriptive statistics. Overall survival (OS), progression-free survival (PFS), and local control (LC) were estimated using the Kaplan-Meier method.

RESULTS

From January 2015 through March 2020, 73 patients met LR criteria, of which, 54 (74%) had ≥50% response by RECIST and were de-escalated to RT alone. The median follow-up was 58 (range 10-92) months. The median age was 58 (range 38-84) years, and 92.6% were male. 57.4% of patients never smoked, and 42.6% smoked no more than 20 pack-years. The primary site was tonsil for 53.7% and base of tongue for 46.3%. 24.1% were T1, 53.7% were T2, and 22.2% were T3. 1.9% were N0, 5.6% were N1, 11.1% were N2a, and 81.5% were N2b. The 5-year OS, PFS, and LC were 96.3% (95% CI 91.3%-100%), 96.2% (95% CI 91.2%-100%), and 98.1% (95% CI 94.6%-100%), respectively. 2 (3.7%) patients required a G-tube during RT and none at 1 year following completion of RT. Of the 30 patients with a planned neck dissection, 2 (6.7%) had residual pathologic nodal disease.

CONCLUSION

With a median follow-up of 5 years, this analysis demonstrates excellent long-term local control, survival, and swallowing function among patients with low-risk HPV+ oropharynx cancer treated with induction systemic therapy followed by radiotherapy to 50 Gy without concurrent chemotherapy, including a large proportion of patients with N2b disease. Chemo-selection provides a means of identifying a favorable cohort of HPV+ oropharynx cancer patients who can safely receive RT dose de-escalation. Further work is needed to identify this population by other means, including radiographic and genomic factors.

Definitive Chemoradiotherapy for Salivary Gland Cancers

PURPOSE/OBJECTIVE(S)

Surgical resection is the standard of care for salivary gland tumors of the head and neck. The role of radiotherapy is typically reserved for the adjuvant setting in those patients with high risk factors on surgical pathology. Surgical resection in some cases may lead to significant impairment in speech or swallowing due to location of the primary tumor. In other cases, patients may not be medically able to receive an oncologic resection. Our institution has developed a protocol for organ preservation for well-selected salivary gland malignancies. Here we report disease outcomes of salivary gland cancer patients treated with definitive chemoradiotherapy.

MATERIALS/METHODS

We retrospectively reviewed all salivary gland cancer patients at our institution who received definitive chemoradiation from January 1990 to December 2019. Chemoradiation typically consisted of 4 to 6 alternating weekly cycles of paclitaxel (100 mg/m2 on d1), infusion 5-fluorouracil (600 mg/m2/d on d0-5), hydroxyurea (500 mg PO BID), and either 1.8 Gy or 2 Gy daily or 1.5 Gy twice-daily irradiation followed by a 9-day treatment break (TFHX). The Kaplan-Meier method was used to estimate rates of locoregional control (LRC), distant metastasis-free survival (DMFS), and overall survival (OS).

RESULTS

Nineteen patients met eligibility criteria and were included for analysis. 53% of patients had adenoid cystic histology. Salivary duct, mucoepidermoid, acinic cell, and myoepithelial histologies each were represented by 10.5% of patients. About 26% of tumors were located in the nasopharynx, 21% in the base of tongue and 26% in the parotid. 74% of the patients were node negative and 53% of patients had stage IVA disease. T3 disease occurred in 26.3% while T4a and T4b disease occurred in 31.6% each. Median follow-up was 45.8 (IQR: 29-66) months. 47% of patients were treated using a twice daily approach, while 53% were treated with daily fractionation with a median dose of 72 Gy (IQR: 70-75). Three-year locoregional control (LRC), distant-metastasis free survival (DMFS), and overall survival (OS) were 93%, 76%, and 81% respectively. Eight of nine distant failures had T4a/T4b disease. Accounting for competing risk of death, local failure was 5.6% at three years. The most common acute complications were grade 2-3 mucositis (74%) and skin toxicity (47%). One patient discontinued chemoradiation due to severe hand foot mouth syndrome. 42% of patients had late toxicity of xerostomia.

CONCLUSION

Promising organ preservation is seen with concurrent chemoradiation for salivary gland cancer patients. Further prospective study of organ preservation in salivary gland cancers is warranted.

Involved Site Radiotherapy in HPV Positive Oropharyngeal Cancer: Patterns of Failure Analysis Across Prospective De-Escalation Trials

PURPOSE/OBJECTIVE(S)

HPV-associated oropharyngeal cancers (HPV+OPC) have a favorable prognosis with ongoing efforts to reduce long term toxicity while maintaining oncologic outcomes. One method under investigation includes lowering the elective radiation dose or in some cases omitting radiation to elective lymphatic nodal stations. Furthermore, pre-clinical evidence demonstrates that elective nodal irradiation blunts the anti-tumor immune response in head and neck cancer. This is a pooled secondary analysis reporting patterns of failure in patients (pts) with HPV+OPC enrolled on consecutive induction chemo- or chemoimmunotherapy (IC) based response-adaptive de-escalation trials and treated with involved-site radiotherapy (ISRT).

MATERIALS/METHODS

Pts treated on two prospective phase II trials as well as on a prospective cohort registry were included for analysis. Pts with ≥ 50% response to IC based on RECIST 1.1 who received de-escalated definitive radiotherapy (RT) or concurrent chemoradiation (CRT) with ISRT were evaluable. Pts with locally advanced low risk or high-risk HPV+OPC (LR and HR, respectively) were eligible for enrollment. Pts were considered to have HR if at least one of the following criteria was met: T4 primary, N2c-N3 disease (AJCC 7th ed.), or > 10-20 pack years smoking. In the first trial, pts with ≥ 50% response to IC received RT to gross disease plus a 1.5 cm margin (PTV1) and to the next echelon of uninvolved nodes (PTV2). Pts with LR received 50 Gy in 2 Gy daily fractions without chemotherapy; pts with HR received 30 Gy in 1.5 Gy BID fractions to PTV2 with a 15 Gy sequential boost to PTV1 with CRT. In the subsequent trial, pts with ≥ 50% response received RT to PTV1 alone to 50 Gy in 2 Gy daily fractions; concurrent CRT was included if pts had HR. Survival was estimated using the Kaplan Meier method for progression free survival (PFS), locoregional PFS (LRPFS), and overall survival (OS). Patterns of failure analysis was performed by comparing RT plans to radiographic surveillance scans.

RESULTS

Of 172 evaluable pts, 119 (69.2%) achieved a ≥ 50% response to IC and received definitive ISRT. 45 (37.8%) pts evaluated received RT to gross disease only plus margin without the next nodal echelon included. With a median follow up of 46 (IQR 34-65) months, 3-year PFS, LRPFS, and OS with their 95% confidence intervals were 96.2% (90.1-98.5%), 97.1% (91.1-99.0%), and 96.2% (90.3-98.6%), respectively. All locoregional failures were in-field and in the high dose region. No failures were observed in the RT omitted neck.

CONCLUSION

This prospective experience demonstrates feasible volume de-escalation using IC response-based selection with progressively smaller elective volumes over time. Notably, despite a marked reduction in elective treatment volume, there were no regional out-of-field failures. IC may allow for selection of pts with favorable tumor biology and microscopic disease sterilization in the regional nodes. Further efforts at elective nodal de-escalation are needed.

Radiomics Based Assessment of Tumor Infiltrating CD8 T-Cells Predicts Induction Systemic Therapy Response in HPV+ Oropharyngeal Cancer: Exploratory Analysis of Prospective Trials

PURPOSE/OBJECTIVE(S)

The adaptive immune system is increasingly recognized to be important for tumor control in HPV+ oropharyngeal cancer (HPV+OPC), and pre-clinical models suggest tumor specific T-cell priming occurs in draining lymph nodes. De-escalation strategies incorporating T-cell infiltration present a novel prognostic biomarker. The purpose of this study was to examine the utility of a validated radiomics model of CD8 T-cell infiltration within the framework of 2 prospective HPV+OPC response-adaptive de-escalation trials. We hypothesized that nodal radiomics scores (RS) would be correlated with response to induction systemic therapy.

MATERIALS/METHODS

Patients enrolled on 2 prospective phase II response adapted de-escalation trials for low- and high-risk HPV+OPC were included in the analysis. Patients received induction chemotherapy and chemoimmunotherapy in trials 1 and 2, respectively. Primary tumors and nodes were retrospectively delineated on diagnostic CT scans before and after induction therapy to ascertain volumetric tumor burden & response. RS were generated on pre-induction scans for both primary tumors and nodes. RS and tumor response were dichotomized using a 50% threshold (high vs low, responder vs non-responder, respectively). Linear regression was used to evaluate the correlation between % volume change in tumor burden and RS. Fisher's exact test was used to evaluate concordance between RS and tumor response.

RESULTS

A total of 87 patients (N = 47 Trial 1, N = 40 Trial 2) were evaluable. The mean post-induction therapy reduction in primary and nodal volumetry was 80.7% and 67% respectively. Primary and nodal RS were not associated with primary (T1/T2 vs T3/T4) or nodal stage (N1-N2b vs N2c-N, p > 0.10 both). Both primary and nodal RS were correlated with % volume change, r = 0.24 (p = 0.034) and r = 0.37 (p = 0.002), respectively. The mean difference in % volume change in primary and node, using the RS, was 11.13% (p = 0.015) and 17. 69% (p = 0.004). There was no association between primary tumor RS and total lesion responder status (p = 0.312). However, there was an association between high vs low nodal RS and total lesion responder status (p = 0.005).

CONCLUSION

This is the first report of a validated radiomics score of CD8-T cell infiltration in HPV+OPC to predict response to systemic therapy. While radiomics scores in both the primary and nodes were associated with percent volume response, this association was stronger in nodes. Higher nodal radiomics scores were associated with improved volume reduction in total lesion burden. This effect however was not observed in the primary tumor. CD8-T cell infiltration in nodes, but not in the primary tumor, was associated with overall tumor response after systemic induction therapy in HPV+ oropharyngeal cancer.

Precision of the GE Lunar Total Body-Less Head Scan for the Measurement of Three-Compartment Body Composition in Athletes

INTRODUCTION

Dual energy X-ray absorptiometry (DXA) is widely used for the assessment of lean mass (LM), fat mass (FM) and bone mineral content (BMC). When observing standardised protocols, DXA has a high level of precision for the assessment of total body composition, including the head region. However, including the head region may have limited relevance in athletes and can be problematic when positioning taller athletes who exceed scan boundaries. This study investigated the precision of a new total-body-less-head (TBLH) DXA scan for three-compartment body composition measurement in athletes, with outcomes compared to the standard total-body DXA scan.

METHODS

Precision errors were calculated from two consecutive scans with re-positioning (Lunar iDXA, GE Healthcare, Madison, WI), in male and female athletes from a range of sports. TBLH precision was determined from repeat scans in 95 athletes (male n = 55; female n = 40; age: 26.0 ± 8.5 y; body mass: 81.2 ± 20.5 kg; stature: 1.77 ± 0.11 m), and standard total-body scan precision was derived from a sub-sample of 58 athletes (male n = 19; female n = 39; age: 27.6 ± 9.9 y; body mass: 69.6 ± 14.8 kg; stature: 1.72 ± 0.94 m). Data from the sub-sample were also used to compare precision error and 3-compartment body composition outcomes between the standard total-body scan and the TBLH scan.

RESULTS

TBLH precision errors [root mean squared-standard deviation, RMS-SD (coefficient of variation, %CV)] were bone mineral content (BMC): 15.6 g (0.5%), lean mass (LM): 254.3 g (0.4%) and fat mass (FM): 199.4 g (1.3%). These outcomes compared favourably to the precision errors derived from the standard total-body scan [BMC: 12.4 g (0.4%), LM: 202.2 g (0.4%), and FM: 160.8 g (1.1%)]. The TBLH scan resulted in lower BMC (-19.5%), LM (-6.6%), and FM (-4.5%) compared to the total-body scan (BMC: 2,308 vs. 2,865 g; LM: 46,954 vs. 50,276 g; FM: 15,183 vs. 15,888 g, all p<0.005). ConclusionThe TBLH scan demonstrates high in-vivo precision comparable to that of the standard total-body scan in a heterogeneous cohort of athletes. Given the impact of head exclusion on total body composition outcomes, TBLH scans should not be used interchangeably with the standard total-body scan.

Psychological Factors in Acquired Visual Impairment: The Development of a Scale of Adjustment

A number of psychological variables bearing on the process of adjustment to acquired visual loss are examined conceptually and empirically in an attempt to clarify their relationships and to develop a testable model of adjustment which might enable rehabilitation specialists to identify clients with special problems, evaluate the effectiveness of rehabilitation programs, and determine the role of psychological factors in the context of skill acquisition. The model presented offers an alternative to existing psychodynamic models in that it is in principle a testable one. Preliminary analysis of data has resulted in the devising of a questionnaire tentatively called the Nottingham Adjustment Scale, which practitioners and researchers are encouraged to use.

Organizational uptake of NICE guidance in promoting employees' psychological health

Background

Annual costs to organizations of poor mental health are estimated to be between £33 billion and £42 billion. The UK's National Institute for Clinical Excellence (NICE) has produced evidence-based guidance on improving employees' psychological health, designed to encourage organizations to take preventative steps in tackling this high toll. However, the extent of implementation is not known outside the National Health Service.

Aims

To assess the awareness and implementation of NICE guidance on workplace psychological health.

Methods

A total of 163 organizations participated in a survey of UK-based private, public and third sector organizations employing an accumulated minimum of 322 033 workers.

Results

Seventy-seven per cent of organizations were aware of the NICE guidance for improving mental well-being in the workplace, but only 37% were familiar with its recommendations. Less than half were aware of systems in place for monitoring employees' mental well-being and only 12% confirmed that this NICE guidance had been implemented in their workplace. Where employee health and well-being featured as a regular board agenda item, awareness and implementation of NICE guidance were more likely. Significant associations were found between organizational sector and size and uptake of many specific features of NICE guidance.

Conclusions

The majority of organizations are aware of NICE guidance in general, but there is a wide gap between this and possession of detailed knowledge and implementation. The role of sector and size of organization is relevant to uptake of some features of NICE guidance, although organizational leadership is important where raised awareness and implementation are concerned.

Children sustain high levels of skin DNA photodamage, with a modest increase of serum 25-hydroxyvitamin D3 , after a summer holiday in Northern Europe

BACKGROUND

Childhood solar ultraviolet radiation (UVR) exposure increases the risk of skin cancer in adulthood, which is associated with mutations caused by UVR-induced cyclobutane pyrimidine dimers (CPD). Solar UVR is also the main source of vitamin D, essential for healthy bone development in children.

OBJECTIVES

To assess the impact of a 12-day Baltic Sea (54° N) beach holiday on serum 25-hydroxyvitamin D₃ [25(OH)D₃ ] and CPD in 32 healthy Polish children (skin types I-IV).

METHODS

Blood and urine were collected before and after the holiday and assessed for 25(OH)D₃ and excreted CPD, respectively, and personal UVR exposure was measured. Diaries were used to record sunbathing, sunburn and sunscreen use. Before- and after-holiday skin redness and pigmentation were measured by reflectance spectroscopy.

RESULTS

The average ± SD daily exposure UVR dose was 2·4 ± 1·5 standard erythema doses (SEDs), which is borderline erythemal. The mean concentration of 25(OH)D₃ increased (× 1·24 ± 0·19) from 64·7 ± 13·3 to 79·3 ± 18·7 nmol L^-1 (P < 0·001). Mean CPD increased 12·6 ± 10·0-fold from 26·9 ± 17·9 to 248·9 ± 113·4 fmol μmol^-1 creatinine (P < 0·001). Increased 25(OH)D₃ was accompanied by a very much greater increase in DNA damage associated with carcinogenic potential. Overall, skin type had no significant effects on behavioural, clinical or analytical outcomes, but skin types I/II had more CPD (unadjusted P = 0·0496) than skin types III/IV at the end of the holiday.

CONCLUSIONS

Careful consideration must be given to the health outcomes of childhood solar exposure, and a much better understanding of the risk-benefit relationships of such exposure is required. Rigorous photoprotection is necessary for children, even in Northern Europe.

Geochemically distinct carbon isotope distributions in Allochromatium vinosum DSM 180T grown photoautotrophically and photoheterotrophically

Anoxygenic, photosynthetic bacteria are common at redox boundaries. They are of interest in microbial ecology and geosciences through their role in linking the carbon, sulfur, and iron cycles, yet much remains unknown about how their flexible carbon metabolism-permitting either autotrophic or heterotrophic growth-is recorded in the bulk sedimentary and lipid biomarker records. Here, we investigated patterns of carbon isotope fractionation in a model photosynthetic sulfur-oxidizing bacterium, Allochromatium vinosum DSM180^T . In one treatment, A. vinosum was grown with CO₂ as the sole carbon source, while in a second treatment, it was grown on acetate. Different intracellular isotope patterns were observed for fatty acids, phytol, individual amino acids, intact proteins, and total RNA between the two experiments. Photoautotrophic CO₂ fixation yielded typical isotopic ordering for the lipid biomarkers: δ¹³ C values of phytol > n-alkyl lipids. In contrast, growth on acetate greatly suppressed intracellular isotopic heterogeneity across all molecular classes, except for a marked ¹³ C-depletion in phytol. This caused isotopic "inversion" in the lipids (δ¹³ C values of phytol < n-alkyl lipids). The finding suggests that inverse δ¹³ C patterns of n-alkanes and pristane/phytane in the geologic record may be at least in part a signal for photoheterotrophy. In both experimental scenarios, the relative isotope distributions could be predicted from an isotope flux-balance model, demonstrating that microbial carbon metabolisms can be interrogated by combining compound-specific stable isotope analysis with metabolic modeling. Isotopic differences among molecular classes may be a means of fingerprinting microbial carbon metabolism, both in the modern environment and the geologic record.

Abstract P5-04-01: Cell cycle dynamics at single cell level dictates response to CDK4/6 inhibition

This abstract was withdrawn by the authors.

Changes in soil organic carbon fractions after remediation of a coastal floodplain soil

Coastal floodplain soils and wetland sediments can store large amounts of soil organic carbon (SOC). These environments are also commonly underlain by sulfidic sediments which can oxidise to form coastal acid sulfate soils (CASS) and contain high concentrations of acidity and trace metals. CASS are found on every continent globally except Antarctica. When sulfidic sediments are oxidised, scalds can form, which are large bare patches without vegetation. However, SOC stocks and fractions have not been quantified in these coastal floodplain environments. We studied the changes in soil geochemistry and SOC stocks and fractions three years after remediation of a CASS scald. Remediation treatments included raising water levels, and addition of either lime (LO) or lime and mulch (LM) relative to a control (C) site. We found SOC concentrations in the remediated sites (LO and LM) were more than double than that found at site C, reflected in the higher SOC stocks to a depth of 1.6 m (426 Mg C/ha, 478 Mg C/ha and 473 Mg C/ha at sites C, LO and LM, respectively). The particulate organic C (POC) fraction was higher at sites LO and LM due to increased vegetation and biomass inputs, compared to site C. Reformation of acid volatile sulfide (AVS) occurred throughout the profile at site LM, whereas only limited AVS reformation occurred at sites LO and C. Higher AVS at site LM may be linked to the additional source of organic matter provided by the mulch. POC can also potentially contribute to decreasing acidity as a labile SOC source for Fe(3+) and SO4(2-) reduction. Therefore, coastal floodplains and wetlands are a large store of SOC and can potentially increase SOC following remediation due to i) reduced decomposition rates with higher water levels and waterlogging, and ii) high C inputs due to rapid revegetation of scalded areas and high rates of biomass production. These results highlight the importance of maintaining vegetation cover in coastal floodplains and wetlands for sequestering SOC.

Recording occupation in general practice--a second cycle audit

BACKGROUND

An audit of working age patients' records in two Cornish general practices in 2012 found infrequent and inconsistent recording of patients' occupations. A concurrent survey of general practitioners (GPs) in Cornwall found that a majority of them believed it was important to do so.

AIMS

To review occupation recording in the same practices a year later and to audit a third practice, following the introduction of the electronic fit note. To repeat the survey of attitudes to recording occupation in GPs in Cornwall.

METHODS

We manually checked 300 randomly selected patient records in Practice A and electronically searched all records of working age patients (aged 16-65 years) in Practices B and C for recorded occupation. We sent an electronic survey of attitudes to recording occupation to 202 GPs in Cornwall.

RESULTS

Recording of occupation increased from 17 to 30% of records (χ(2) = 15, P < 0.001) in Practice A and from 12 to 14% (χ(2) = 16.5, P < 0.001) in Practice B. In Practice C, 1% of records had occupation recorded and coded. The proportion of GPs in Cornwall who said that it is important to records patients' occupation increased from 70 to 90% (Fisher's exact statistic 0.01, P < 0.05).

CONCLUSIONS

Recording of patients' occupation increased in both practices from 2012 to 2013, but remains infrequent and inconsistent and the very low levels in a third practice not previously audited is of concern.

Strong influence of the littoral zone on sedimentary lipid biomarkers in a meromictic lake

Planktonic sulfur bacteria growing in zones of photic zone euxinia (PZE) are important primary producers in stratified, sulfur-rich environments. The potential for export and burial of microbial biomass from anoxic photic zones remains relatively understudied, despite being of fundamental importance to interpreting the geologic record of bulk total organic carbon (TOC) and individual lipid biomarkers. Here we report the relative concentrations and carbon isotope ratios of lipid biomarkers from the water column and sediments of meromictic Mahoney Lake. The data show that organic matter in the central basin sediments is indistinguishable from material at the lake shoreline in both its lipid and carbon isotopic compositions. However, this material is not consistent with either the lipid profile or carbon isotope composition of biomass obtained directly from the region of PZE. Due to the strong density stratification and the intensive carbon and sulfur recycling pathways in the water column, there appears to be minimal direct export of the sulfur-oxidizing planktonic community to depth. The results instead suggest that basinal sediments are sourced via the littoral environment, a system that integrates an indigenous shoreline microbial community, the degraded remains of laterally rafted biomass from the PZE community, and detrital remains of terrigenous higher plants. Material from the lake margins appears to travel downslope, traverse the strong density gradient, and become deposited in the deep basin; its final composition may be largely heterotrophic in origin. This suggests an important role for clastic and/or authigenic minerals in aiding the burial of terrigenous and mat-derived organic matter in euxinic systems. Downslope or mineral-aided transport of anoxygenic, photoautotrophic microbial mats may have been a significant sedimentation process in early Earth history.

Coupled reductive and oxidative sulfur cycling in the phototrophic plate of a meromictic lake

Mahoney Lake represents an extreme meromictic model system and is a valuable site for examining the organisms and processes that sustain photic zone euxinia (PZE). A single population of purple sulfur bacteria (PSB) living in a dense phototrophic plate in the chemocline is responsible for most of the primary production in Mahoney Lake. Here, we present metagenomic data from this phototrophic plate--including the genome of the major PSB, as obtained from both a highly enriched culture and from the metagenomic data--as well as evidence for multiple other taxa that contribute to the oxidative sulfur cycle and to sulfate reduction. The planktonic PSB is a member of the Chromatiaceae, here renamed Thiohalocapsa sp. strain ML1. It produces the carotenoid okenone, yet its closest relatives are benthic PSB isolates, a finding that may complicate the use of okenone (okenane) as a biomarker for ancient PZE. Favorable thermodynamics for non-phototrophic sulfide oxidation and sulfate reduction reactions also occur in the plate, and a suite of organisms capable of oxidizing and reducing sulfur is apparent in the metagenome. Fluctuating supplies of both reduced carbon and reduced sulfur to the chemocline may partly account for the diversity of both autotrophic and heterotrophic species. Collectively, the data demonstrate the physiological potential for maintaining complex sulfur and carbon cycles in an anoxic water column, driven by the input of exogenous organic matter. This is consistent with suggestions that high levels of oxygenic primary production maintain episodes of PZE in Earth's history and that such communities should support a diversity of sulfur cycle reactions.

Abstract P2-08-01: Analysis of PIK3CA mutation abundance in primary breast cancer with droplet digital PCR identifies frequent sub-clonal PIK3CA mutations in ER negative and / or HER2 positive breast cancer

Background: PIK3CA is the single most commonly mutated gene in breast cancer, with highest incidence reported in ER positive and HER2 negative breast cancer. Substantial data now suggests that breast cancers show intra-tumoural genetic heterogeneity, with apparently clonal tumours composed of multiple populations of tumour cells that, in addition to the founder genetic events common to all cells, harbour private genetic alterations. Tumours with mutations that are sub-clonal may respond less well to therapies targeting these mutations than cancers with clonal mutations. To assess how frequently PIK3CA mutations are clonal founder mutations, or may be subclonal, we assessed the abundance on PIK3CA mutation using digital PCR.

Methods: DNA was extracted from frozen sections of 119 primary breast cancers, following macrodissection to achieve tumour cell content of &gt;70%. PIK3CA mutations c.1624G&gt;A (E542K), c.1633G&gt;A (E545K), c.3140A&gt;T (H1047L) and c.3140A&gt;G (H1047R) were assessed by droplet digital PCR on a BioRad QX100 system. Exon 9 mutation assays were optimised to not amplify the PIK3CA pseudogene. Mutational abundance was calculated from the Poisson distribution, expressed as the portion of PIK3CA DNA in the sample that was mutant, and compared between breast cancer subtypes. A mutational abundance of &lt;20% was predefined to represent low abundance mutation, that may be subclonal.

Results: PIK3CA mutations were detected with abundance ranging from 80.4% to 0.0063%, with 26 cancers with an abundance &gt;20% and 19 cancers with low abundance &lt;20% (5 cancers with abundance 1-20%, and 14 cancer with abundance &lt;1%). There was highly correlation between repeat experiments r2 = 0.98, p&lt;0.0001, with 100% concordance for low abundance mutations in repeat analysis. High abundance mutations were numerically more common in ER positive HER2 negative cancers (18/65, 28%) than HER2 positive or triple negative (TN) cancers (7/54, 14% p = 0.07 Fishers exact test). Conversely, low abundance mutations were less common in ER positive HER2 negative cancers (4/65, 6%) than in HER2 positive or TN cancers (10/54, 19% p = 0.047). In cancers with a detectable PIK3CA mutation, mutational abundance was higher in ER positive cancer than ER negative cancers (p = 0.023 Mann-Whitney U test), and higher in ER positive HER2 negative cancers compared to HER2 positive or TN cancers (p = 0.0024). In ER positive HER2 negative cancers 82% (18/22) mutations were of high abundance, and likely clonal, whereas in TN or HER2 positive cancers 39% (7/18, p = 0.009) were of high abundance.

Conclusion: Our data suggests that hotspot PIK3CA mutations are frequently of low abundance in HER2 positive or TN breast cancer, and may be subclonal. However, we cannot exclude the possibility that these findings represent contamination. If confirmed on an independent data set, our data suggest that identification of mutational abundance may be an important component of PIK3CA mutation assessment and the potential targeting of these mutations with PI3 kinase inhibitors.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-08-01.

Microbial diversity under extreme euxinia: Mahoney Lake, Canada

Mahoney Lake, British Columbia, Canada, is a stratified, 15-m deep saline lake with a euxinic (anoxic, sulfidic) hypolimnion. A dense plate of phototrophic purple sulfur bacteria is found at the chemocline, but to date the rest of the Mahoney Lake microbial ecosystem has been underexamined. In particular, the microbial community that resides in the aphotic hypolimnion and/or in the lake sediments is unknown, and it is unclear whether the sulfate reducers that supply sulfide for phototrophy live only within, or also below, the plate. Here we profiled distributions of 16S rRNA genes using gene clone libraries and PhyloChip microarrays. Both approaches suggest that microbial diversity is greatest in the hypolimnion (8 m) and sediments. Diversity is lowest in the photosynthetic plate (7 m). Shallower depths (5 m, 7 m) are rich in Actinobacteria, Alphaproteobacteria, and Gammaproteobacteria, while deeper depths (8 m, sediments) are rich in Crenarchaeota, Natronoanaerobium, and Verrucomicrobia. The heterogeneous distribution of Deltaproteobacteria and Epsilonproteobacteria between 7 and 8 m is consistent with metabolisms involving sulfur intermediates in the chemocline, but complete sulfate reduction in the hypolimnion. Overall, the results are consistent with the presence of distinct microbial niches and suggest zonation of sulfur cycle processes in this stratified system.

Identification of risk factors by systematic review and development of risk-adjusted models for surgical site infection

BACKGROUND

Surgical site infections (SSIs) are complications of surgery that cause significant postoperative morbidity. SSI has been proposed as a potential indicator of the quality of care in the context of clinical governance and monitoring of the performance of NHS organisations against targets.

OBJECTIVES

We aimed to address a number of objectives. Firstly, identify risk factors for SSI, criteria for stratifying surgical procedures and evidence about the importance of postdischarge surveillance (PDS). Secondly, test the importance of risk factors for SSI in surveillance databases and investigate interactions between risk factors. Thirdly, investigate and validate different definitions of SSI. Lastly, develop models for making risk-adjusted comparisons between hospitals.

DATA SOURCES

A single hospital surveillance database was used to address objectives 2 and 3 and the UK Surgical Site Infection Surveillance Service database to address objective 4.

STUDY DESIGN

There were four elements to the research: (1) systematic reviews of risk factors for SSI (two reviewers assessed titles and abstracts of studies identified by the search strategy and the quality of studies was assessed using the Newcastle Ottawa Scale); (2) assessment of agreement between four SSI definitions; (3) validation of definitions of SSI, quantifying their ability to predict clinical outcomes; and (4) development of operation-specific risk models for SSI, with hospitals fitted as random effects.

RESULTS

Reviews of SSI risk factors other than established SSI risk indices identified other risk; some were operation specific, but others applied to multiple operations. The factor most commonly identified was duration of preoperative hospital stay. The review of PDS for SSI confirmed the need for PDS if SSIs are to be compared meaningfully over time within an institution. There was wide variation in SSI rate (SSI%) using different definitions. Over twice as many wounds were classified as infected by one definition only as were classified as infected by both. Different SSI definitions also classified different wounds as being infected. The two most established SSI definitions had broadly similar ability to predict the chosen clinical outcomes. This finding is paradoxical given the poor agreement between definitions. Elements of each definition not common to both may be important in predicting clinical outcomes or outcomes may depend on only a subset of elements which are common to both. Risk factors fitted in multivariable models and their effects, including age and gender, varied by surgical procedure. Operative duration was an important risk factor for all operations, except for hip replacement. Wound class was included least often because some wound classes were not applicable to all operations or were combined because of small numbers. The American Association of Anesthesiologists class was a consistent risk factor for most operations.

CONCLUSIONS

The research literature does not allow surgery-specific or generic risk factors to be defined. SSI definitions varied between surveillance programmes and potentially between hospitals. Different definitions do not have good agreement, but the definitions have similar ability to predict outcomes influenced by SSI. Associations between components of the National Nosocomial Infections Surveillance risk index and odds of SSI varied for different surgical procedures. There was no evidence for effect modification by hospital. Estimates of SSI% should be disseminated within institutions to inform infection control. Estimates of SSI% across institutions or countries should be interpreted cautiously and should not be assumed to reflect quality of medical care. Future research should focus on developing an SSI definition that has satisfactory psychometric properties, that can be applied in everyday clinical settings, includes PDS and is formulated to detect SSIs that are important to patients or health services.

FUNDING

The National Institute for Health Research Technology Assessment programme.

Raman scattering of intense, short laser pulses in modulated plasmas

We examine the exponentiation of the Raman forward scattering instability in modulated plasma channels computationally and analytically. An evolution equation for the complex phases of the Raman scattered waves treating the spatial localization and discrete nature of the channel modes is derived. Simulations with WAKE [P. Mora and T. M. Antonsen Jr., Phys. Plasmas 4, 217 (1997)] verify the theory in the linear growth regime and provide insight into the nonlinear stage of the instability when cascading and pump depletion play a role. We find that the exponentiation in modulated channels depends on two factors: the increase in coupling due to the increased plasma wavenumber in the high-density regions of the channel and a decreased coupling due to the reduced longitudinal spatial coherence. For the parameters considered, simulations show that the finite extent of the pump pulse is more significant in determining the exponentiation than phase mixing due to the transverse variation of the channel. Both the theory and simulations confirm that modulated channels allow for the stable guiding of longer pulses than nonmodulated channels.

Inverse carbon isotope patterns of lipids and kerogen record heterogeneous primary biomass

Throughout the Proterozoic δ(13)C values for preserved n-alkyl lipids are more positive than for syngenetic kerogen. This pattern is the inverse of biosynthetic expectations. It has been suggested that this isotopic inversion results from selective preservation of lipids from (13)C-enriched heterotrophic populations, while the bulk of kerogen derives from primary producers. Here, we formulate a degradation model to calculate the (13)C content of sedimentary total organic carbon and lipid. The model addresses two scenarios. The first scenario explores preferential preservation of heterotrophic lipid, thereby quantifying the existing hypothesis. In the second, we suggest that an inverse signature could be the result of prokaryotic phytoplankton contributing the majority of the total ecosystem biomass. Photosynthetic prokaryotes bearing a relative (13)C enrichment would contribute much of the resulting preserved lipids, while primary eukaryotic biomass would dominate the total organic carbon. We find that our hypothesis of a mixed primary producer community generates inverse isotopic patterns while placing far fewer requirements on specific degradation conditions. It also provides a possible explanation as to why there are large variations in the (13)C content of the isoprenoid lipids pristane and phytane relative to n-alkyl lipid, while the difference between n-alkyl lipid and kerogen is more constant. Our results suggest that the disappearance of the inverse (13)C signature in the late Ediacaran is a natural consequence of the fundamental shift to oceans in which export production has a higher ratio of eukaryotic biomass.

Abstract P5-02-01: FGFR Signalling Drives the Growth of Triple Negative and Basal-Like Breast Cancer Cell Lines Both In Vitro and In Vivo

Background: Substantial evidence now links aberrant signalling by the fibroblast growth factor receptors (FGFRs) to the development of multiple different cancer types. The oncogenic drivers of triple negative and basal-like breast cancers are largely unknown and we examined for a potential role of FGFR signalling in the oncogenesis of triple negative breast cancer.

Methods: We examined the sensitivity of a panel of 40 breast cancer cell lines to the selective fibroblast growth factor receptor (FGFR) inhibitor PD173074.

Results: Triple negative (TN) breast cancer cell lines were more sensitive to PD173074 than comparator cell lines (p=0.0028), with half (8/16) of TN cell lines demonstrating significantly reduced growth. The majority of TN cell lines demonstrated only modest sensitivity to FGFR inhibition in two-dimensional growth, but were highly sensitive in anchorage independent conditions. PD173074 inhibited down stream MAPK signalling and induced cell cycle arrest and apoptosis. Basal-like breast cancer cell lines were found to express autocrine FGF2 ligand, and RNA interference targeting of FGF2 significantly reduced anchorage independent growth. Finally, PD173074 significantly reduced the growth of basal-like breast cancer cell line xenografts.

Conclusion: Basal-like breast cancer cell lines express autocrine FGF2 and demonstrate substantial sensitivity to FGFR inhibitors, identifying a potential novel therapeutic approach for these cancers.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-02-01.