Early ctDNA dynamics as a surrogate for progression-free survival in advanced breast cancer in the BEECH trial.

BACKGROUND: Dynamic changes in circulating tumour DNA (ctDNA) levels may predict long-term outcome. We utilised samples from a phase I/II randomised trial (BEECH) to assess ctDNA dynamics as a surrogate for progression-free survival (PFS) and early predictor of drug efficacy. PATIENTS AND METHODS: Patients with estrogen receptor-positive advanced metastatic breast cancer (ER+ mBC) in the BEECH study, paclitaxel plus placebo versus paclitaxel plus AKT inhibitor capivasertib, had plasma samples collected for ctDNA analysis at baseline and at multiple time points in the development cohort (safety run-in, part A) and validation cohort (randomised, part B). Baseline sample ctDNA sequencing identified mutations for longitudinal analysis and mutation-specific digital droplet PCR (ddPCR) assays were utilised to assess change in ctDNA abundance (allele fraction) between baseline and 872 on-treatment samples. Primary objective was to assess whether early suppression of ctDNA, based on pre-defined criteria from the development cohort, independently predicted outcome in the validation cohort. RESULTS: In the development cohort, suppression of ctDNA was apparent after 8 days of treatment (P = 0.014), with cycle 2 day 1 (4 weeks) identified as the optimal time point to predict PFS from early ctDNA dynamics. In the validation cohort, median PFS was 11.1 months in patients with suppressed ctDNA at 4 weeks and 6.4 months in patients with high ctDNA (hazard ratio = 0.20, 95% confidence interval 0.083-0.50, P < 0.0001). There was no difference in the level of ctDNA suppression between patients randomised to capivasertib or placebo overall (P = 0.904) nor in the PIK3CA mutant subpopulation (P = 0.071). Clonal haematopoiesis of indeterminate potential (CHIP) was evident in 30% (18/59) baseline samples, although CHIP had no effect on tolerance of chemotherapy nor on PFS. CONCLUSION: Early on-treatment ctDNA dynamics are a surrogate for PFS. Dynamic ctDNA assessment has the potential to substantially enhance early drug development. CLINICAL REGISTRATION NUMBER: NCT01625286.

The National Lung Matrix Trial: translating the biology of stratification in advanced non-small-cell lung cancer.

BACKGROUND: The management of NSCLC has been transformed by stratified medicine. The National Lung Matrix Trial (NLMT) is a UK-wide study exploring the activity of rationally selected biomarker/targeted therapy combinations. PATIENTS AND METHODS: The Cancer Research UK (CRUK) Stratified Medicine Programme 2 is undertaking the large volume national molecular pre-screening which integrates with the NLMT. At study initiation, there are eight drugs being used to target 18 molecular cohorts. The aim is to determine whether there is sufficient signal of activity in any drug-biomarker combination to warrant further investigation. A Bayesian adaptive design that gives a more realistic approach to decision making and flexibility to make conclusions without fixing the sample size was chosen. The screening platform is an adaptable 28-gene Nextera next-generation sequencing platform designed by Illumina, covering the range of molecular abnormalities being targeted. The adaptive design allows new biomarker-drug combination cohorts to be incorporated by substantial amendment. The pre-clinical justification for each biomarker-drug combination has been rigorously assessed creating molecular exclusion rules and a trumping strategy in patients harbouring concomitant actionable genetic abnormalities. Discrete routes of pathway activation or inactivation determined by cancer genome aberrations are treated as separate cohorts. Key translational analyses include the deep genomic analysis of pre- and post-treatment biopsies, the establishment of patient-derived xenograft models and longitudinal ctDNA collection, in order to define predictive biomarkers, mechanisms of resistance and early markers of response and relapse. CONCLUSION: The SMP2 platform will provide large scale genetic screening to inform entry into the NLMT, a trial explicitly aimed at discovering novel actionable cohorts in NSCLC. CLINICAL TRIAL ISRCTN: 38344105.

Cortical activation during rhythmic hand movements performed under three types of control: an fMRI study.

Echoplanar fMRI was used to measure changes in cortical activation during the performance of a simple hand movement task under three types of voluntary control. Each of three imaging series alternated a task with rest: passive (in which the experimenter moved the hand), voluntary against low resistance, and voluntary against higher resistance. Contralateral activation was observed in the supplementary motor area (SMA), the primary motor cortex (M1), and the somatosensory cortex (S1) in all three tasks in each subject, whereas ipsilateral activation differed in each cortical region for each task. SMA had the widest prevalence of ipsilateral activation in all three tasks. In the M1, ipsilateral activation was observed in all but 1 subject in the two voluntary tasks but in only a few subjects in the S1 in any of the tasks. Quantitative changes in signal intensity and spatial extent of activation differentiated the voluntary tasks from the passive task and were most pronounced in the S1.

On the fragility of skilled performance: what governs choking under pressure?

Experiments 1-2 examined generic knowledge and episodic memories of putting in novice and expert golfers. Impoverished episodic recollection of specific putts among experts indicated that skilled putting is encoded in a procedural form that supports performance without the need for step-by-step attentional control. According to explicit monitoring theories of choking, such proceduralization makes putting vulnerable to decrements under pressure. Experiments 3-4 examined choking and the ability of training conditions to ameliorate it in putting and a nonproceduralized alphabet arithmetic skill analogous to mental arithmetic. Choking occurred in putting but not alphabet arithmetic. In putting, choking was unchanged by dual-task training but eliminated by self-consciousness training. These findings support explicit monitoring theories of choking and the popular but infrequently tested belief that attending to proceduralized skills hurts performance.

Neural mechanisms of visual attention: object-based selection of a region in space.

Objects play an important role in guiding spatial attention through a cluttered visual environment. We used event-related functional magnetic resonance imaging (ER-fMRI) to measure brain activity during cued discrimination tasks requiring subjects to orient attention either to a region bounded by an object (object-based spatial attention) or to an unbounded region of space (location-based spatial attention) in anticipation of an upcoming target. Comparison between the two tasks revealed greater activation when attention selected a region bounded by an object. This activation was strongly lateralized to the left hemisphere and formed a widely distributed network including (a) attentional structures in parietal and temporal cortex and thalamus, (b) ventral-stream object processing structures in occipital, inferior-temporal, and parahippocampal cortex, and (c) control structures in medial- and dorsolateral-prefrontal cortex. These results suggest that object-based spatial selection is achieved by imposing additional constraints over and above those processes already operating to achieve selection of an unbounded region. In addition, ER-fMRI methodology allowed a comparison of validly versus invalidly cued trials, thereby delineating brain structures involved in the reorientation of attention after its initial deployment proved incorrect. All areas of activation that differentiated between these two trial types resulted from greater activity during the invalid trials. This outcome suggests that all brain areas involved in attentional orienting and task performance in response to valid cues are also involved on invalid trials. During invalid trials, additional brain regions are recruited when a perceiver recovers from invalid cueing and reorients attention to a target appearing at an uncued location. Activated brain areas specific to attentional reorientation were strongly right-lateralized and included posterior temporal and inferior parietal regions previously implicated in visual attention processes, as well as prefrontal regions that likely subserve control processes, particularly related to inhibition of inappropriate responding.

Expression of the Arabidopsis G-protein GP alpha1: purification and characterisation of the recombinant protein.

The Arabidopsis G alpha subunit, GP alpha1, was expressed within Escherichia coli by co-transformation with the expression vector and the dnaY gene which encodes tRNA(Arg)(AGA/AGG) Isolation of the recombinant GP alpha1 in a highly pure form could be achieved by a combination of anion exchange and dye affinity chromatography or by a single step affinity procedure via chromatography on 4-amino-anilido-GTP agarose. The recombinant protein yielded by both procedures was highly active and bound GTPgammaS with an apparent Kd in the nM range. GTPgammaS binding was stimulated two-fold in the presence of Zn2+ compared with that in the presence of Mg2+, Mn2+ or Ca2+.

Word, pseudoword, and nonword processing: a multitask comparison using event-related brain potentials.

Event-related brain potentials (ERPs) to words, pseudowords, and nonwords were recorded in three different tasks. A letter search task was used in Experiment 1. Performance was affected by whether the target letter occurred in a word, a pseudoword, or a random nonword. ERP results corroborated the behavioral results, showing small but reliable ERP differences between the three stimulus types. Words and pseudowords differed from nonwords at posterior sites, whereas words differed from pseudowords and nonwords at anterior sites. Since deciding whether the target letter was present or absent co-occurred with stimulus processing in Experiment 1, a delayed letter search task was used in Experiment 2. ERPs to words and pseudowords were similar and differed from ERPs to nonwords, suggesting a primary role of orthographic and phonological processing in the delayed letter search task. To increase semantic processing, a categorization task was used in Experiment 3. Early differences between ERPs to words and pseudowords at left posterior and anterior locations suggested a rapid activation of lexico-semantic information. These findings suggest that the use of ERPs in a multiple task design makes it possible to track the time course and the activation of multiple sources of linguistic information when processing words, pseudowords, and nonwords. The task-dependent nature of the effects suggests that the language system can use multiple sources of linguistic information in flexible and adaptive ways.

Automaticity and word perception: evidence from Stroop and Stroop dilution effects.

The Stroop effect is cut in half by adding a neutral word to the display. D. Kahneman and D. Chajczyk's (1983) "attention capture" account of "Stroop dilution" holds word recognition to be involuntary but strictly serial. The authors compared attention capture to 3 alternatives involving parallel rather than serial processing: In the lexicon, activation is divided among multiple words; postlexically, multiple words race for access to response processes; or prelexically, feature processing is degraded by multiple patterns whether or not they are words. Results support the latter. Multiple patterns are processed in parallel. If any are color words, Stroop effects occur but are reduced because any color word's input to lexical memory is lower in quality than if a single color word were the only pattern. Thus, lexical encoding is involuntary but can operate on several input representations in parallel, with effectiveness determined by input quality.

Lexical access and the brain: anatomical constraints on cognitive models of word recognition.

Recent studies in the cognitive psychology of reading and many other skilled performances have been dominated by models inspired by neural connectivity (e.g., McClelland & Rumelhart, 1986). Such models have not yet begun to consider the accumulating evidence of considerable anatomical localization of component cognitive operations in the human brain (e.g., Posner, Petersen, Fox, & Raichle, 1988). In this article we apply anatomical findings to the job of building computational models of visual word recognition. Brain imaging studies already provide important constraints on how lexical access should be defined in terms of isolable encoding operations that compute the visual form, phonology, and semantics of words. Brain imaging studies also speak to issues of modularity versus interaction between these encoding operations, distribution versus localization of processing within the operations, and orchestration of operations to accomplish different word processing tasks. We conclude that a combined cognitive and anatomical analysis may be of considerable benefit in developing more adequate models of human information processing.

Automaticity and cognitive anatomy: is word recognition "automatic"?

Recent progress in neural imaging technologies such as positron emission tomography and dense-array recording of event-related potentials has greatly increased the capacity for in vivo measurement of cognitively relevant processing activity within the human brain. Data from these neural imaging technologies can be combined with behavioral data from standard chronometric techniques to enhance computational modeling of human cognition. Applications of neural data to issues of attention and automaticity are illustrated in the domain of visual word recognition, addressing the question "Is word recognition automatic?"

The level-of-focal-attention hypothesis in oral reading: influence of strategies on the context specificity of lexical repetition effects.

Two experiments examined the influence of level of focal attention--text or lexical--on benefits from lexical repetition in speeded oral reading of coherent texts and random word lists. Experiment 1 showed that with coherent targets, direction of attention to the text level resulted in benefit only from a previous reading of the same coherent paragraph. However, when attention was directed to the lexical level, equal benefit resulted from a previous reading of either the same coherent paragraph or a scrambled version of the paragraph. Experiment 2 showed that level of focal attention did not influence benefit with scrambled targets. Thus, the linguistic structure of the target is important to repetition benefits and their modulation by attentional strategies.

Adding new information to semantic memory: how much learning is enough to produce automatic priming?

A series of experiments investigated the integration of new vocabulary words into semantic memory and the creation of new associations between preexisting, but previously unrelated, words. The ability of the newly learned vocabulary words and associations to facilitate lexical decisions when serving as primes under conditions associated with automatic processing was used to index integration. The results indicate that very extensive study is necessary for such integration to occur and that it is easier to add a new word to semantic memory than to establish a link between two formerly unconnected words already in semantic memory. The implications of these results for models of semantic memory and the episodic/semantic distinction are considered.

Semantic priming and repetition priming from masked words: evidence for a center-surround attentional mechanism in perceptual recognition.

Two lexical decision experiments compared semantic and repetition priming by masked words. Experiment 1 established prime-mask stimulus onset asynchronies (SOAs) with presence-absence detection judgments. Primes presented at detection-threshold SOAs produced equal facilitation for repeated and semantically related targets: 26 ms and 24 ms. Experiment 2 established SOAs with semantic judgments. Primes presented at 70% of the semantic-threshold SOA to mimic the exposure conditions of Experiment 1 produced slightly greater facilitation for repeated targets but a tendency toward inhibition for semantically related targets: 38 ms and -6 ms. These results confirm Dagenbach, Carr, and Wilhelmsen's (1989) report that strategies induced by threshold-setting tasks can influence masked priming. In addition, Experiment 2 suggests a mechanism for retrieving weakly activated semantic codes into consciousness that relies on the center-surround principle to enhance activation of sought-for codes and to inhibit related codes stored nearby in the semantic network.

Strategic hand use preferences and hemispheric specialization in tactual reading: impact of the demands of perceptual encoding.

Four reading-related, information-processing tasks were administered to right-handed blind readers of braille who differed in level of reading skill and in preference for using the right hand or the left hand when required to read text with just one hand. The tasks were letter identification, same-different matching of letters that differed in tactual similarity, short-term memory for lists of words that varied in tactual and phonological similarity, and paragraph reading with and without a concurrent memory load of digits. The results showed interactions between hand preference and the hand that was actually used to read the stimulus materials, such that left preferrers were significantly faster and more accurate with their left hands than with their right hands whereas right preferrers were slightly but usually not significantly faster with their right hands than with their left hands. In all cases, the absolute magnitude of the left-hand advantage among left preferrers was substantially larger than the right-hand advantage among right preferrers. The results suggest that encoding strategies for dealing with braille are reflected in hand preference and that such strategies operate to modify an underlying but somewhat plastic superiority of the right hemisphere for dealing with the perceptual requirements of tactual reading. These requirements are not the same as those of visual reading, leading to some differences in patterns of hemispheric specialization between readers of braille and readers of print.

Words, pictures, and priming: on semantic activation, conscious identification, and the automaticity of information processing.

We investigated the encoding mechanisms involved in the perceptual recognition of words and pictures. Latencies in naming word and picture targets were analyzed as a function of several characteristics of a preceding prime, including whether it was a word or a picture, its duration of exposure, the interval between the prime and target onset, and whether or not the prime was consciously identified and reported by the subject. Results indicated that a common semantic code is available that can represent the meaning of either a word or a picture. This semantic representation, however, appears to be more easily activated by picture primes than by word primes and seems to benefit the naming of picture targets more than the naming of word targets. Despite the advantage for pictures with respect to semantic activation, overall processing in the naming task was slower and more attention demanding for pictures than for words. Comparison of our data with data on classification, in which an opposite pattern occurs (overall processing appears to be slower and more attention demanding for words than for pictures), suggests that, on the average, pictures have faster and more automatic access to their meanings than to their names but that words have faster and more automatic access to their names than to their meanings. This conclusion concerning the relative ability of stimuli to activate different kinds of internal representations has implications for a theory of the basis and development of automaticity.

Early extraction of meaning from pictures and its relation to conscious identification.

Two experiments were conducted in which subjects labeled target pictures preceded by either semantically related or unrelated prime pictures. The exposure duration of each prime was varied around a threshold value, established separately for each subject, that represented the minimum viewing time necessary to identify the prime picture with 100% accuracy. The results of the first study indicated that semantic-priming effects can be obtained with pictures at prime exposure durations too brief for conscious identification of the prime to occur. Data from the second experiment provided an estimate of the minimum exposure time necessary for priming under these conditions. There was evidence from both experiments that attaching a name to a picture is an attended operation that can interfere with naming a subsequent picture, independent of any semantic priming that might occur. This indicates that extracting the meaning from a picture and consciously identifying it may be separate processes. The results are discussed in terms of current models of picture perception.

Orthography and familiarity effects in word processing.

Both orthographic regularity and visual familiarity have been implicated as contributors to the efficiency of processing visually presented words. Our studies sought to determine which of the internal codes representing words in the nervous system are facilitated by these two variables. To do this, sets of letter strings in which orthography and familiarity were factorially combined were used as the basis for physical, phonetic, semantic, and lexical judgments. The data indicated consistent effects of orthography on the activation of all codes. These effects were seen in same-different matching and in judgments of stimulus orientation, which are based on visual codes; in judgments of pronounceability based on phonetic codes; in judgments of meaningfulness based on semantic codes; and in lexical decisions, which are based on phonetic and semantic codes together. Familiarity, on the other hand, had a clear influence on the activation of semantic codes and to a lesser extent affected phonetic codes. Despite previous positive results found in matching letter strings, however, no influence of familiarity occurred in judgments based on visual codes once evidence for criterion shifting was eliminated. Our negative results included direct tests of facilitation in matching acronyms (e.g., FBI) and in matching both regular and irregular strings familiarized by specific training. It now appears that earlier findings of visual familiarity effects may be attributed to response biases resulting from the activation of higher level codes sensitive to familiarity, and to the use of small sets of training stimuli that allowed subjects to induce orthographic-like rules. The results obtained so far with our methods seem to reconcile an inconsistent literature by showing that speeded decisions based on visual codes are most strongly influenced by rule-governed processing mechanisms sensitive to orthographic structure, whereas decisions based on phonetic and semantic codes are affected about equally by rule-governed mechanisms and by stimulus-specific mechanisms sensitive to familiarity. This conclusion may lead to changes in notions of how effective various kinds of visual training are likely to be at different stages in the acquisition of reading skill.