A Multiplexed Approach to Assess Small Cell Lung Cancer Subtype Heterogeneity in Primary and Patient-Derived Tumor Samples.

Unlocking the heterogeneity of cancers is crucial for developing therapeutic approaches that effectively eradicate disease. As our understanding of markers specific to cancer subclones or subtypes expands, there is a growing demand for advanced technologies that enable the simultaneous investigation of multiple targets within an individual tumor sample. Indeed, multiplex approaches offer distinct benefits, particularly when tumor specimens are small and scarce. Here we describe the utility of two fluorescence-based multiplex approaches; fluorescent Western blots, and multiplex immunohistochemistry (Opal™) staining to interrogate heterogeneity, using small cell lung cancer as an example. Critically, the coupling of Opal™ staining with advanced image quantitation, permits the dissection of cancer cell phenotypes at a single cell level. These approaches can be applied to patient biopsies and/or patient-derived xenograft (PDX) models and serve as powerful methodologies for assessing tumor cell heterogeneity in response to therapy or between metastatic lesions across diverse tissue sites.

Molecular and Pathologic Characterization of YAP1-Expressing Small Cell Lung Cancer Cell Lines Leads to Reclassification as SMARCA4-Deficient Malignancies.

PURPOSE: The classification of small cell lung cancer (SCLC) into distinct molecular subtypes defined by ASCL1, NEUROD1, POU2F3, or YAP1 (SCLC-A, -N, -P, or -Y) expression, paves the way for a personalized treatment approach. However, the existence of a distinct YAP1-expressing SCLC subtype remains controversial. EXPERIMENTAL DESIGN: To better understand YAP1-expressing SCLC, the mutational landscape of human SCLC cell lines was interrogated to identify pathogenic alterations unique to SCLC-Y. Xenograft tumors, generated from cell lines representing the four SCLC molecular subtypes, were evaluated by a panel of pathologists who routinely diagnose thoracic malignancies. Diagnoses were complemented by transcriptomic analysis of primary tumors and human cell line datasets. Protein expression profiles were validated in patient tumor tissue. RESULTS: Unexpectedly, pathogenic mutations in SMARCA4 were identified in six of eight SCLC-Y cell lines and correlated with reduced SMARCA4 mRNA and protein expression. Pathologist evaluations revealed that SMARCA4-deficient SCLC-Y tumors exhibited features consistent with thoracic SMARCA4-deficient undifferentiated tumors (SMARCA4-UT). Similarly, the transcriptional profile SMARCA4-mutant SCLC-Y lines more closely resembled primary SMARCA4-UT, or SMARCA4-deficient non-small cell carcinoma, than SCLC. Furthermore, SMARCA4-UT patient samples were associated with a YAP1 transcriptional signature and exhibited strong YAP1 protein expression. Together, we found little evidence to support a diagnosis of SCLC for any of the YAP1-expressing cell lines originally used to define the SCLC-Y subtype. CONCLUSIONS: SMARCA4-mutant SCLC-Y cell lines exhibit characteristics consistent with SMARCA4-deficient malignancies rather than SCLC. Our findings suggest that, unlike ASCL1, NEUROD1, and POU2F3, YAP1 is not a subtype defining transcription factor in SCLC. See related commentary by Rekhtman, p. 1708.

Inhibition of cellular RNA methyltransferase abrogates influenza virus capping and replication.

Orthomyxo- and bunyaviruses steal the 5' cap portion of host RNAs to prime their own transcription in a process called "cap snatching." We report that RNA modification of the cap portion by host 2'-O-ribose methyltransferase 1 (MTr1) is essential for the initiation of influenza A and B virus replication, but not for other cap-snatching viruses. We identified with in silico compound screening and functional analysis a derivative of a natural product from Streptomyces, called trifluoromethyl-tubercidin (TFMT), that inhibits MTr1 through interaction at its S-adenosyl-l-methionine binding pocket to restrict influenza virus replication. Mechanistically, TFMT impairs the association of host cap RNAs with the viral polymerase basic protein 2 subunit in human lung explants and in vivo in mice. TFMT acts synergistically with approved anti-influenza drugs.

Healthcare worker stress, anxiety and burnout during the COVID-19 pandemic in Singapore: A 6-month multi-centre prospective study.

AIM: The long-term stress, anxiety and job burnout experienced by healthcare workers (HCWs) are important to consider as the novel coronavirus disease (COVID-19) pandemic stresses healthcare systems globally. The primary objective was to examine the changes in the proportion of HCWs reporting stress, anxiety, and job burnout over six months during the peak of the pandemic in Singapore. The secondary objective was to examine the extent that objective job characteristics, HCW-perceived job factors, and HCW personal resources were associated with stress, anxiety, and job burnout. METHOD: A sample of HCWs (doctors, nurses, allied health professionals, administrative and operations staff; N = 2744) was recruited via invitation to participate in an online survey from four tertiary hospitals. Data were gathered between March-August 2020, which included a 2-month lockdown period. HCWs completed monthly web-based self-reported assessments of stress (Perceived Stress Scale-4), anxiety (Generalized Anxiety Disorder-7), and job burnout (Physician Work Life Scale). RESULTS: The majority of the sample consisted of female HCWs (81%) and nurses (60%). Using random-intercept logistic regression models, elevated perceived stress, anxiety and job burnout were reported by 33%, 13%, and 24% of the overall sample at baseline respectively. The proportion of HCWs reporting stress and job burnout increased by approximately 1·0% and 1·2% respectively per month. Anxiety did not significantly increase. Working long hours was associated with higher odds, while teamwork and feeling appreciated at work were associated with lower odds, of stress, anxiety, and job burnout. CONCLUSIONS: Perceived stress and job burnout showed a mild increase over six months, even after exiting the lockdown. Teamwork and feeling appreciated at work were protective and are targets for developing organizational interventions to mitigate expected poor outcomes among frontline HCWs.

NOTCH Your Usual Suspect: MYC Charged with Controlling Neuroendocrine Cell-Fate in Small Cell Lung Cancer.

Small cell lung cancer (SCLC) is highly heterogeneous. In this issue of Cancer Cell, Ireland et al. demonstrate that MYC mediates neuroendocrine cell plasticity in SCLC by activating NOTCH signaling. This MYC-NOTCH axis controls the dynamic behavior of tumor cells, resulting in the co-existence of SCLC subtypes within individual tumors.

Genetic polymorphisms of ATG16L1 and IRGM genes in Malaysian patients with Crohn's disease.

OBJECTIVE: To investigate the association between genetic polymorphisms in ATG16L1 and IRGM genes and the development of Crohn's disease (CD) in Malaysian patients. METHODS: Altogether 335 participants were recruited, including 85 patients with CD and 250 unrelated healthy controls, and their informed consent was obtained. Genomic DNA was extracted via a conventional phenol-chloroform extraction method. Six single nucleotide polymorphisms (SNPs) in ATG16L1 and IRGM genes were genotyped using TaqMan SNP genotyping assays. Associations between SNP and CD were determined using Fisher's exact test, odds ratio, and 95% confidence interval. Statistical power and the Hardy-Weinberg equilibrium were also calculated. RESULTS: Two SNPs (rs2241880 and rs6754677) in the ATG16L1 gene were significantly associated with the onset of CD in the Malaysian population. The A allele and homozygous A/A genotype of the rs2241880 A/G polymorphism were protective against CD in the overall Malaysian and Malay population. The G allele and homozygous G/G genotype of the rs6754677 G/A polymorphism were protective in the Indian population, whereas the homozygous A/A genotype showed a risk of developing CD. The homozygous G/G genotype of IRGM rs11747270 was significantly present in the controls. However, this significance was not observed in a race-stratified analysis. All three ATG16L1 SNPs were associated with inflamed terminal ileum. IRGM rs4958847 and rs11747270 increased the risk of developing arthritis in patients with CD. CONCLUSION: We found a significant association between SNP, which are located in autophagy-related genes, and CD in a Malaysian population.

Site-specific glycation of Aß1-42 affects fibril formation and is neurotoxic.

Aß1-42 is involved in Alzheimer's disease (AD) pathogenesis and is prone to glycation, an irreversible process where proteins accumulate advanced glycated end products (AGEs). Nϵ-(Carboxyethyl)lysine (CEL) is a common AGE associated with AD patients and occurs at either Lys-16 or Lys-28 of Aß1-42. Methyglyoxal is commonly used for the unspecific glycation of Aß1-42, which results in a complex mixture of AGE-modified peptides and makes interpretation of a causative AGE at a specific amino acid residue difficult. We address this issue by chemically synthesizing defined CEL modifications on Aß1-42 at Lys-16 (Aß-CEL16), Lys-28 (Aß-CEL28), and Lys-16 and -28 (Aß-CEL16&28). We demonstrated that double-CEL glycations at Lys-16 and Lys-28 of Aß1-42 had the most profound impact on the ability to form amyloid fibrils. In silico predictions indicated that Aß-CEL16&28 had a substantial decrease in free energy change, which contributes to fibril destabilization, and a increased aggregation rate. Single-CEL glycations at Lys-28 of Aß1-42 had the least impact on fibril formation, whereas CEL glycations at Lys-16 of Aß1-42 delayed fibril formation. We also tested these peptides for neuronal toxicity and mitochondrial function on a retinoic acid-differentiated SH-SY5Y human neuroblastoma cell line (RA-differentiated SH-SY5Y). Only Aß-CEL16 and Aß-CEL28 were neurotoxic, possibly through a nonmitochondrial pathway, whereas Aß-CEL16&28 showed no neurotoxicity. Interestingly, Aß-CEL16&28 had depolarized the mitochondrial membrane potential, whereas Aß-CEL16 had increased mitochondrial respiration at complex II. These results may indicate mitophagy or an alternate route of metabolism, respectively. Therefore, our results provides insight into potential therapeutic approaches against neurotoxic CEL-glycated Aß1-42.

Efficient synthesis and characterisation of the amyloid beta peptide, Aß1-42, using a double linker system.

The amyloidogenic Aß42 peptide was efficiently prepared using a double linker system, markedly improving solubility and chromatographic peak resolution, thus enabling full characterisation using standard techniques. The tag was readily cleaved with sodium hydroxide and removed by aqueous extraction, affording Aß42 in high purity and yield for biophysical characterisation studies.

Real-time intrafraction prostate motion during linac based stereotactic radiotherapy with rectal displacement.

BACKGROUND: Kilovoltage Intrafraction Monitoring (KIM) is a method which determines the three-dimensional position of the prostate from two-dimensional kilovoltage (kV) projections taken during linac based radiotherapy treatment with real-time feedback. Rectal displacement devices (RDDs) allow for improved rectal dosimetry during prostate cancer treatment. This study used KIM to perform a preliminary investigation of prostate intrafraction motion observed in patients with an RDD in place. METHODS: Ten patients with intermediate to high-risk prostate cancer were treated with a Rectafix RDD in place during two boost fractions of 9.5-10 Gy delivered using volumetric modulated arc therapy (VMAT) on Clinac iX and Truebeam linacs. Two-dimensional kV projections were acquired during treatment. KIM software was used following treatment to determine the displacement of the prostate over time. The displacement results were analyzed to determine the percentage of treatment time the prostate spent within 1 mm, between 1 and 2 mm, between 2 and 3 mm and greater than 3 mm from its initial position. RESULTS: KIM successfully measured displacement for 19 prostate stereotactic boost fractions. The prostate was within 1 mm of its initial position for 84.8%, 1-2 mm for 14%, 2-3 mm 1.2% and ≥3 mm only 0.4% of the treatment time. CONCLUSIONS: In this preliminary study using KIM, KIM was successfully used to measure prostate intrafraction motion, which was found to be small in the presence of a rectal displacement device. TRIAL REGISTRATION: The Hunter New England Human Research Ethics Committee reference number is 14/08/20/3.01.

Performance assessment of a programmable five degrees-of-freedom motion platform for quality assurance of motion management techniques in radiotherapy.

Inter-fraction and intra-fraction motion management methods are increasingly applied clinically and require the development of advanced motion platforms to facilitate testing and quality assurance program development. The aim of this study was to assess the performance of a 5 degrees-of-freedom (DoF) programmable motion platform HexaMotion (ScandiDos, Uppsala, Sweden) towards clinically observed tumor motion range, velocity, acceleration and the accuracy requirements of SABR prescribed in AAPM Task Group 142. Performance specifications for the motion platform were derived from literature regarding the motion characteristics of prostate and lung tumor targets required for real time motion management. The performance of the programmable motion platform was evaluated against (1) maximum range, velocity and acceleration (5 DoF), (2) static position accuracy (5 DoF) and (3) dynamic position accuracy using patient-derived prostate and lung tumor motion traces (3 DoF). Translational motion accuracy was compared against electromagnetic transponder measurements. Rotation was benchmarked with a digital inclinometer. The static accuracy and reproducibility for translation and rotation was <0.1 mm or <0.1°, respectively. The accuracy of reproducing dynamic patient motion was <0.3 mm. The motion platform's range met the need to reproduce clinically relevant translation and rotation ranges and its accuracy met the TG 142 requirements for SABR. The range, velocity and acceleration of the motion platform are sufficient to reproduce lung and prostate tumor motion for motion management. Programmable motion platforms are valuable tools in the investigation, quality assurance and commissioning of motion management systems in radiation oncology.

Quantification of intrafraction prostate motion and its dosimetric effect on VMAT.

Intrafraction prostate motion degrades the accuracy of radiation therapy (RT) delivery. Whilst a number of metrics in the literature have been used to quantify intrafraction prostate motion, it has not been established whether these metrics reflect the effect of motion on the RT dose delivered to the patients. In this study, prostate motion during volumetric modulated arc therapy (VMAT) treatment of 18 patients and a total of 294 fractions was quantified through novel metrics as well as those available in the literature. The impact of the motion on VMAT dosimetry was evaluated using these metrics and dose reconstructions based on a previously validated and published method. The dosimetric impact of the motion on planning target volume (PTV) and clinical target volume (CTV) coverage and organs at risk (OARs) was correlated with the motion metrics, using the coefficient of determination (R 2 ), to evaluate their utility. Action level threshold for the prostate motion metric that best described the dosimetric impact on the PTV D95% was investigated through iterative regression analysis. The average (range) of the mean motion for the patient cohort was 1.5 mm (0.3-9.9 mm). A number of motion metrics were found to be strongly correlated with PTV D95%, the range of R 2 was 0.43-0.81. For all the motion measures, correlations with CTV D99% (range of R 2 was 0.12-0.62), rectum V65% (range of R 2 was 0.33-0.58) and bladder V65% (range of R 2 was 0.51-0.69) were not as strong as for PTV D95%. The mean of the highest 50% of motion metric was one of the best indicator of dosimetric impact on PTV D95%. Action level threshold value for this metric was found to be 3.0 mm. For an individual fraction, when the metric value was greater than 3.0 mm then the PTV D95% was reduced on average by 6.2%. This study demonstrated that several motion metrics are well correlated with the dosimetric impact (PTV D95%) of individual fraction prostate motion on VMAT delivery and could be used for treatment course adaptation.

Association of NOD1, CXCL16, STAT6 and TLR4 gene polymorphisms with Malaysian patients with Crohn's disease.

Crohn's disease (CD) is a prominent type of inflammatory bowel disease (IBD) that can affect any part of the gastrointestinal tract. CD is known to have higher prevalence in the Western countries, but the number of cases has been increasing in the past decades in Asia, including Malaysia. Therefore, there is a need to investigate the underlining causes of CD that may shed light on its prevention and treatment. In this study, genetic polymorphisms in NOD1 (rs2075820), CXCL16 (rs2277680), STAT6 (rs324015) and TLR4 (rs4986791) genes were examined in a total of 335 individuals (85 CD patients and 250 healthy controls) with PCR-RFLP approach. There was no significant association observed between NOD1 rs2075820 and STAT6 rs324015 with the onset of CD in the studied cohort. However, the G allele of CXCL16 rs2277680 was found to have a weak association with CD patients (P = 0.0482; OR = 1.4310). The TLR4 rs4986791 was also significantly associated to CD. Both the homozygous C genotype (P = 0.0029; OR = 0.3611) and C allele (P = 0.0069; OR = 0.4369) were observed to confer protection against CD. On the other hand, the heterozygous C/T genotype was a risk genotype (P = 0.0015; OR = 3.1392). Further ethnic-stratified analysis showed that the significant associations in CXCL16 rs2277680 and TLR4 rs4986791 were accounted by the Malay cohort. In conclusion, the present study reported two CD-predisposing loci in the Malay CD patients. However, these loci were not associated to the onset of CD in Chinese and Indian patients.

Real-Time 3D Image Guidance Using a Standard LINAC: Measured Motion, Accuracy, and Precision of the First Prospective Clinical Trial of Kilovoltage Intrafraction Monitoring-Guided Gating for Prostate Cancer Radiation Therapy.

PURPOSE: Kilovoltage intrafraction monitoring (KIM) is a new real-time 3-dimensional image guidance method. Unlike previous real-time image guidance methods, KIM uses a standard linear accelerator without any additional equipment needed. The first prospective clinical trial of KIM is underway for prostate cancer radiation therapy. In this paper we report on the measured motion accuracy and precision using real-time KIM-guided gating. METHODS AND MATERIALS: Imaging and motion information from the first 200 fractions from 6 patient prostate cancer radiation therapy volumetric modulated arc therapy treatments were analyzed. A 3-mm/5-second action threshold was used to trigger a gating event where the beam is paused and the couch position adjusted to realign the prostate to the treatment isocenter. To quantify the in vivo accuracy and precision, KIM was compared with simultaneously acquired kV/MV triangulation for 187 fractions. RESULTS: KIM was successfully used in 197 of 200 fractions. Gating events occurred in 29 fractions (14.5%). In these 29 fractions, the percentage of beam-on time, the prostate displacement was >3 mm from the isocenter position, reduced from 73% without KIM to 24% with KIM-guided gating. Displacements >5 mm were reduced from 16% without KIM to 0% with KIM. The KIM accuracy was measured at <0.3 mm in all 3 dimensions. The KIM precision was <0.6 mm in all 3 dimensions. CONCLUSIONS: Clinical implementation of real-time KIM image guidance combined with gating for prostate cancer eliminates large prostate displacements during treatment delivery. Both in vivo KIM accuracy and precision are well below 1 mm.

Isolating dividing neural and brain tumour cells for gene expression profiling.

BACKGROUND: The characterisation of dividing brain cells is fundamental for studies ranging from developmental and stem cell biology, to brain cancers. Whilst there is extensive anatomical data on these dividing cells, limited gene transcription data is available due to technical constraints. NEW METHOD: We focally isolated dividing cells whilst conserving RNA, from culture, primary neural tissue and xenografted glioma tumours, using a thymidine analogue that enables gene transcription analysis. RESULTS: 5-ethynyl-2-deoxyuridine labels the replicating DNA of dividing cells. Once labelled, cultured cells and tissues were dissociated, fluorescently tagged with a revised click chemistry technique and the dividing cells isolated using fluorescence-assisted cell sorting. RNA was extracted and analysed using real time PCR. Proliferation and maturation related gene expression in neurogenic tissues was demonstrated in acutely and 3 day old labelled cells, respectively. An elevated expression of marker and pathway genes was demonstrated in the dividing cells of xenografted brain tumours, with the non-dividing cells showing relatively low levels of expression. COMPARISON WITH EXISTING METHOD: BrdU "immune-labelling", the most frequently used protocol for detecting cell proliferation, causes complete denaturation of RNA, precluding gene transcription analysis. This EdU labelling technique, maintained cell integrity during dissociation, minimized copper exposure during labelling and used a cell isolation protocol that avoided cell lysis, thus conserving RNA. CONCLUSIONS: The technique conserves RNA, enabling the definition of cell proliferation-related changes in gene transcription of neural and pathological brain cells in cells harvested immediately after division, or following a period of maturation.

Prostate motion during radiotherapy of prostate cancer patients with and without application of a hydrogel spacer: a comparative study.

BACKGROUND AND PURPOSE: The use of a tissue expander (hydrogel) for sparing of the rectum from increased irradiation during prostate radiotherapy is becoming popular. The goal of this study is to investigate the effect of a tissue expander (hydrogel) on the intrafraction prostate motion during radiotherapy. METHODS AND MATERIAL: Real time prostate motion was analysed for 26 patients and 742 fractions; 12 patients with and 14 patients without hydrogel (SpaceOAR™). The intra-fraction motion was quantified and compared between the two groups. RESULTS: The average (±standard deviation) of the mean motion during the treatment for patients with and without hydrogel was 1.5 (±0.8 mm) and 1.1 (±0.9 mm) respectively (p < 0.05). The average time of motion >3 mm for patients with and without hydrogel was 7.7 % (±1.1 %) and 4.5 % (±0.9 %) respectively (p > 0.05). The hydrogel age, fraction number and treatment time were found to have no effect (R (2) < 0.05) on the prostate motion. CONCLUSIONS: Differences in intrafraction motion in patients with hydrogel and without hydrogel were within measurement uncertainty (<1 mm). This result confirms that the addition of a spacer does not negate the need for intrafraction motion management if clinically indicated.

Knowledge of Human Papillomavirus Infection, Cervical Cancer and Willingness to pay for Cervical Cancer Vaccination among Ethnically Diverse Medical Students in Malaysia.

The primary objective of this study was to assess the knowledge of medical students and determine variation between different cultural groups. A secondary aim was to find out the willingness to pay for cervical cancer vaccination and the relationships between knowledge and attitudes towards Human Papillomavirus vaccination. A cross-sectional survey was conducted in a private medical university between June 2014 and November 2014 using a convenient sampling method. A total of 305 respondents were recruited and interviewed with standard questionnaires for assessment of knowledge, attitudes and practice towards human papilloma virus and their willingness to pay for HPV vaccination. Knowledge regarding human papilloma virus, human papilloma virus vaccination, cervical cancer screening and cervical cancer risk factors was good. Across the sample, a majority (90%) of the pupils demonstrated a high degree of knowledge about cervical cancer and its vaccination. There were no significant differences between ethnicity and the participants' overall knowledge of HPV infection, Pap smear and cervical cancer vaccination. Some 88% of participants answered that HPV vaccine can prevent cervical cancer, while 81.5% of medical students said they would recommend HPV vaccination to the public although fewer expressed an intention to receive vaccination for themselves.

The first clinical treatment with kilovoltage intrafraction monitoring (KIM): a real-time image guidance method.

PURPOSE: Kilovoltage intrafraction monitoring (KIM) is a real-time image guidance method that uses widely available radiotherapy technology, i.e., a gantry-mounted x-ray imager. The authors report on the geometric and dosimetric results of the first patient treatment using KIM which occurred on September 16, 2014. METHODS: KIM uses current and prior 2D x-ray images to estimate the 3D target position during cancer radiotherapy treatment delivery. KIM software was written to process kilovoltage (kV) images streamed from a standard C-arm linear accelerator with a gantry-mounted kV x-ray imaging system. A 120° pretreatment kV imaging arc was acquired to build the patient-specific 2D to 3D motion correlation. The kV imager was activated during the megavoltage (MV) treatment, a dual arc VMAT prostate treatment, to estimate the 3D prostate position in real-time. All necessary ethics, legal, and regulatory requirements were met for this clinical study. The quality assurance processes were completed and peer reviewed. RESULTS: During treatment, a prostate position offset of nearly 3 mm in the posterior direction was observed with KIM. This position offset did not trigger a gating event. After the treatment, the prostate motion was independently measured using kV/MV triangulation, resulting in a mean difference of less than 0.6 mm and standard deviation of less than 0.6 mm in each direction. The accuracy of the marker segmentation was visually assessed during and after treatment and found to be performing well. During treatment, there were no interruptions due to performance of the KIM software. CONCLUSIONS: For the first time, KIM has been used for real-time image guidance during cancer radiotherapy. The measured accuracy and precision were both submillimeter for the first treatment fraction. This clinical translational research milestone paves the way for the broad implementation of real-time image guidance to facilitate the detection and correction of geometric and dosimetric errors, and resultant improved clinical outcomes, in cancer radiotherapy.

Six degrees-of-freedom prostate and lung tumor motion measurements using kilovoltage intrafraction monitoring.

PURPOSE: Tumor positional uncertainty has been identified as a major issue that deteriorates the efficacy of radiation therapy. Tumor rotational movement, which is not well understood, can result in significant geometric and dosimetric inaccuracies. The objective of this study was to measure 6 degrees-of-freedom (6 DoF) prostate and lung tumor motion, focusing on the more novel rotation, using kilovoltage intrafraction monitoring (KIM). METHODS AND MATERIALS: Continuous kilovoltage (kV) projections of tumors with gold fiducial markers were acquired during radiation therapy for 267 fractions from 10 prostate cancer patients and immediately before or after radiation therapy for 50 fractions from 3 lung cancer patients. The 6 DoF motion measurements were determined from the individual 3-dimensional (3D) marker positions, after using methods to reject spurious and smooth noisy data, using an iterative closest point algorithm. RESULTS: There were large variations in the magnitude of the tumor rotation among different fractions and patients. Various rotational patterns were observed. The average prostate rotation angles around the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) axes were 1.0 ± 5.0°, 0.6 ± 3.3°, and 0.3 ± 2.0°, respectively. For 35% of the time, the prostate rotated more than 5° about the LR axis, indicating the need for intrafractional adaptation during radiation delivery. For lung patients, the average LR, SI, and AP rotation angles were 0.8 ± 4.2°, -0.8 ± 4.5°, and 1.7 ± 3.1°, respectively. For about 30% of the time, the lung tumors rotated more than 5° around the SI axis. Respiration-induced rotation was detected in 2 of the 3 lung patients. CONCLUSIONS: The prostate and lung tumors were found to undergo rotations of more than 5° for about a third of the time. The lung tumor data represent the first 6 DoF tumor motion measured by kV images. The 6 DoF KIM method can enable rotational and translational adaptive radiation therapy and potentially reduce treatment margins.

The first clinical implementation of electromagnetic transponder-guided MLC tracking.

PURPOSE: We report on the clinical process, quality assurance, and geometric and dosimetric results of the first clinical implementation of electromagnetic transponder-guided MLC tracking which occurred on 28 November 2013 at the Northern Sydney Cancer Centre. METHODS: An electromagnetic transponder-based positioning system (Calypso) was modified to send the target position output to in-house-developed MLC tracking code, which adjusts the leaf positions to optimally align the treatment beam with the real-time target position. Clinical process and quality assurance procedures were developed and performed. The first clinical implementation of electromagnetic transponder-guided MLC tracking was for a prostate cancer patient being treated with dual-arc VMAT (RapidArc). For the first fraction of the first patient treatment of electromagnetic transponder-guided MLC tracking we recorded the in-room time and transponder positions, and performed dose reconstruction to estimate the delivered dose and also the dose received had MLC tracking not been used. RESULTS: The total in-room time was 21 min with 2 min of beam delivery. No additional time was needed for MLC tracking and there were no beam holds. The average prostate position from the initial setup was 1.2 mm, mostly an anterior shift. Dose reconstruction analysis of the delivered dose with MLC tracking showed similar isodose and target dose volume histograms to the planned treatment and a 4.6% increase in the fractional rectal V60. Dose reconstruction without motion compensation showed a 30% increase in the fractional rectal V60 from that planned, even for the small motion. CONCLUSIONS: The real-time beam-target correction method, electromagnetic transponder-guided MLC tracking, has been translated to the clinic. This achievement represents a milestone in improving geometric and dosimetric accuracy, and by inference treatment outcomes, in cancer radiotherapy.

Kilovoltage intrafraction monitoring for prostate intensity modulated arc therapy: first clinical results.

PURPOSE: Most linear accelerators purchased today are equipped with a gantry-mounted kilovoltage X-ray imager which is typically used for patient imaging prior to therapy. A novel application of the X-ray system is kilovoltage intrafraction monitoring (KIM), in which the 3-dimensional (3D) tumor position is determined during treatment. In this paper, we report on the first use of KIM in a prospective clinical study of prostate cancer patients undergoing intensity modulated arc therapy (IMAT). METHODS AND MATERIALS: Ten prostate cancer patients with implanted fiducial markers undergoing conventionally fractionated IMAT (RapidArc) were enrolled in an ethics-approved study of KIM. KIM involves acquiring kV images as the gantry rotates around the patient during treatment. Post-treatment, markers in these images were segmented to obtain 2D positions. From the 2D positions, a maximum likelihood estimation of a probability density function was used to obtain 3D prostate trajectories. The trajectories were analyzed to determine the motion type and the percentage of time the prostate was displaced ≥ 3, 5, 7, and 10 mm. Independent verification of KIM positional accuracy was performed using kV/MV triangulation. RESULTS: KIM was performed for 268 fractions. Various prostate trajectories were observed (ie, continuous target drift, transient excursion, stable target position, persistent excursion, high-frequency excursions, and erratic behavior). For all patients, 3D displacements of ≥ 3, 5, 7, and 10 mm were observed 5.6%, 2.2%, 0.7% and 0.4% of the time, respectively. The average systematic accuracy of KIM was measured at 0.46 mm. CONCLUSIONS: KIM for prostate IMAT was successfully implemented clinically for the first time. Key advantages of this method are (1) submillimeter accuracy, (2) widespread applicability, and (3) a low barrier to clinical implementation. A disadvantage is that KIM delivers additional imaging dose to the patient.