Cancer Informatics for Cancer Centers: Sharing Ideas on How to Build an Artificial Intelligence-Ready Informatics Ecosystem for Radiation Oncology

In August 2022, the Cancer Informatics for Cancer Centers brought together cancer informatics leaders for its biannual symposium, Precision Medicine Applications in Radiation Oncology, co-chaired by Quynh-Thu Le, MD (Stanford University), and Walter J. Curran, MD (GenesisCare). Over the course of 3 days, presenters discussed a range of topics relevant to radiation oncology and the cancer informatics community more broadly, including biomarker development, decision support algorithms, novel imaging tools, theranostics, and artificial intelligence (AI) for the radiotherapy workflow. Since the symposium, there has been an impressive shift in the promise and potential for integration of AI in clinical care, accelerated in large part by major advances in generative AI. AI is now poised more than ever to revolutionize cancer care. Radiation oncology is a field that uses and generates a large amount of digital data and is therefore likely to be one of the first fields to be transformed by AI. As experts in the collection, management, and analysis of these data, the informatics community will take a leading role in ensuring that radiation oncology is prepared to take full advantage of these technological advances. In this report, we provide highlights from the symposium, which took place in Santa Barbara, California, from August 29 to 31, 2022. We discuss lessons learned from the symposium for data acquisition, management, representation, and sharing, and put these themes into context to prepare radiation oncology for the successful and safe integration of AI and informatics technologies.

A model for gastrointestinal tract motility in a 4D imaging phantom of human anatomy

BACKGROUND

Gastrointestinal (GI) tract motility is one of the main sources for intra/inter-fraction variability and uncertainty in radiation therapy for abdominal targets. Models for GI motility can improve the assessment of delivered dose and contribute to the development, testing, and validation of deformable image registration (DIR) and dose-accumulation algorithms.

PURPOSE

To implement GI tract motion in the 4D extended cardiac-torso (XCAT) digital phantom of human anatomy.

MATERIALS AND METHODS

Motility modes that exhibit large amplitude changes in the diameter of the GI tract and may persist over timescales comparable to online adaptive planning and radiotherapy delivery were identified based on literature research. Search criteria included amplitude changes larger than planning risk volume expansions and durations of the order of tens of minutes. The following modes were identified: peristalsis, rhythmic segmentation, high amplitude propagating contractions (HAPCs), and tonic contractions. Peristalsis and rhythmic segmentations were modeled by traveling and standing sinusoidal waves. HAPCs and tonic contractions were modeled by traveling and stationary Gaussian waves. Wave dispersion in the temporal and spatial domain was implemented by linear, exponential, and inverse power law functions. Modeling functions were applied to the control points of the nonuniform rational B-spline surfaces defined in the reference XCAT library. GI motility was combined with the cardiac and respiratory motions available in the standard 4D-XCAT phantom. Default model parameters were estimated based on the analysis of cine MRI acquisitions in 10 patients treated in a 1.5T MR-linac.

RESULTS

We demonstrate the ability to generate realistic 4D multimodal images that simulate GI motility combined with respiratory and cardiac motion. All modes of motility, except tonic contractions, were observed in the analysis of our cine MRI acquisitions. Peristalsis was the most common. Default parameters estimated from cine MRI were used as initial values for simulation experiments. It is shown that in patients undergoing stereotactic body radiotherapy for abdominal targets, the effects of GI motility can be comparable or larger than the effects of respiratory motion.

CONCLUSION

The digital phantom provides realistic models to aid in medical imaging and radiation therapy research. The addition of GI motility will further contribute to the development, testing, and validation of DIR and dose accumulation algorithms for MR-guided radiotherapy.

Abstract 6591: A universal atlas of cellular and oncogenic phenotypes

Tumors and healthy tissues exhibit gene expression variability in many of the same pathways. We propose that these commonalities result from a performance trade-off between universal cellular phenotypes; each phenotype is defined by an orthogonal gene expression profile identified using unsupervised dimensionality reduction. Using two publicly available RNA-seq datasets (n=54 normal tissues; n=1504 cancer cell lines), we show that both healthy and cancerous cells occupy a trade-off between five canonical phenotypes: OxPhos, Warburg, Fibroblastic, Immune, and Growth. Each cell is assigned a phenotype score that, as we demonstrate, predicts differential drug sensitivities and mutational signatures, even among cancers of the same tissue type. Since these phenotype scores are defined using only healthy tissues, they can be generally applied to other diseases as well.

Citation Format: Corey Weistuch, Kevin Murgas, Ken Dill, Larry Norton, Joseph Deasy, Allen Tannenbaum. A universal atlas of cellular and oncogenic phenotypes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6591.

Death without progression as an endpoint to describe cardiac radiation effects in locally advanced non-small cell lung cancer

Background and purpose

Prior studies have examined associations of cardiovascular substructure dose with overall survival (OS) or cardiac events after chemoradiotherapy (CRT) for non-small cell lung cancer (NSCLC). Herein, we investigate an alternative endpoint, death without cancer progression (DWP), which is potentially more specific than OS and more sensitive than cardiac events for understanding CRT toxicity.

Materials and methods

We retrospectively reviewed records of 187 patients with locally advanced or oligometastatic NSCLC treated with definitive CRT from 2008 to 2016 at a single institution. Dosimetric parameters to the heart, lung, and ten cardiovascular substructures were extracted. Charlson Comorbidity Index (CCI), excluding NSCLC diagnosis, was used to stratify patients into CCI low (0-2; n = 66), CCI intermediate (3-4; n = 78), and CCI high (≥5; n = 43) groups. Primary endpoint was DWP, modeled with competing risk regression. Secondary endpoints included OS. An external cohort consisted of 140 patients from another institution.

Results

Median follow-up was 7.3 years for survivors. Death occurred in 143 patients (76.5 %), including death after progression in 118 (63.1 %) and DWP in 25 (13.4 %). On multivariable analysis, increasing CCI stratum and mean heart dose were associated with DWP. For mean heart dose ≥ 10 Gy vs < 10 Gy, DWP was higher (5-year rate, 16.9 % vs 6.7 %, p = 0.04) and OS worse (median, 22.9 vs 34.1 months, p < 0.001). Ventricle (left, right, and bilateral) and pericardial but not atrial substructure dose were associated with DWP, whereas all three were inversely associated with OS. Cutpoint analysis identified right ventricle mean dose ≥ 5.5 Gy as a predictor of DWP. In the external cohort, we confirmed an association of ventricle, but not atrial, dose with DWP.

Conclusion

Cardiovascular substructure dose showed distinct associations with DWP. Future cardiotoxicity studies in NSCLC could consider DWP as an endpoint.

Abstract 6056: Activation of Sting in response to partial-tumor radiation exposure

Purpose: It has been shown that ionizing radiation can mediate antitumor immunity via the activation of the cytosolic DNA sensor cGAS/STING pathway. Therefore, the purpose of this study was to determine whether STING activation is involved in partial volume radiation therapy (RT).

Materials/Methods: We investigated 67NR murine orthotopic breast tumors in Balb/c mice and LLC cells injected in the flank of C57Bl/6, cGAS, or STING KO mice. RT was delivered to 50% or 100% of the tumor volume using a 2X2 cm collimator on a microirradiator allowing precise irradiation. Tumors were collected at different time points post-RT and assessed for different measurements.

Results: We previously showed that a single dose of radiation delivered to half of the tumor (50% RT) activated an anti-tumor immune response comparable to the response in a fully-irradiated tumor in the immunogenic 67NR murine breast carcinoma tumor model and in the less immunogenic and more radioresistant Lewis lung carcinoma (LLC) tumor model. We have also demonstrated that this immune response was due to the infiltration of CD8+ T cells along with an increased expression of ICAM adhesion molecules. Treatment with either anti-CD8 or anti-ICAM antibodies abrogated the hemi-RT response. Furthermore, a significant abscopal effect was observed after partial irradiation with a single dose of 10Gy in a bilateral 67NR tumors model. In this study, we tested whether the hemi-irradiation-mediated immune response involves the cGAS/STING canonical pathway, or a non-canonical activation of STING, in the 67NR or LLC tumor models. It has been reported that STING can be activated, independently of cGAS, via non-canonical activation of STING, involving ATM and TRAF6, among other factors. We found significant activation of the cGAS/STING pathway in the hemi-irradiated tumors as compared to control and to 100% exposed 67NR tumors. Interestingly, the increased expression of the cGAS/STING pathway was found in the hemi-irradiated tumor but, also in the non-irradiated part of this hemi-irradiated tumor. In the LLC model, a non-canonical activation of STING was involved. Using both cGAS and STING KO mice, we demonstrated that the partial exposure RT-mediated immune response is dependent on STING activation in the host while cGAS is dispensable.

Conclusions: Upstream pathways responsible for STING activation are tumor type-specific. Identifying the upstream pathways responsible for STING activation in the partial RT-mediated immune response in different tumor types would improve this therapy and its potential combination with immune checkpoint blockade.

Citation Format: Mickael Mathieu, Prerna R. Nepali, Sadna Budhu, Simon N. Powell, John Humm, Joseph Deasy, Adriana Haimovitz-Friedman. Activation of Sting in response to partial-tumor radiation exposure [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6056.

A comparison of oncological outcomes after abdominoperineal excision before and after the implementation of a selective perineal flap closure program

BACKGROUND AND OBJECTIVES

Abdominoperineal excision (APE) is the operation chosen when a patient has low rectal cancer unamenable to sphincter preserving surgery. Perineal flap reconstruction is associated with less wound morbidity but little is known about oncological outcomes. The objective was to compare outcomes in patients undergoing APE before and after the introduction of a program that utilized flap reconstruction of the perineum.

METHODS

A retrospective review of a prospectively maintained database was performed. Patients who underwent APE followed by primary closure or flap reconstruction between 1998 and 2018 were selected. The cohorts were divided according to the implementation of the flap reconstruction program in July 2009. Clinicopathological data, recurrence and survival were compared between the cohorts.

RESULTS

One hundred and forty nine patients underwent APE for rectal adenocarcinoma between 1998 and 2018. There were 57 patients in the pre-flap era and 92 in the post-flap era. Forty-six patients underwent flap reconstruction in the latter cohort (50%). More patients in the post-flap era underwent neoadjuvant chemoradiotherapy (85.9% vs. 63.2%; p < .01). Margin positivity rates decreased from 21.1% in the pre-flap era to 10.9% in the post-flap era (p = .10) and there was an associated improvement in incidence and time to local recurrence (p = .03).

CONCLUSION

The use of perineal flap reconstruction is associated with a longer median time to local recurrence. Perineal flap reconstruction may contribute to reduced margin positivity.

Enhanced super-resolution reconstruction of T1w time-resolved 4DMRI in low-contrast tissue using 2-step hybrid deformable image registration

Purpose

Deformable image registration (DIR) in low‐contrast tissues is often suboptimal because of low visibility of landmarks, low driving‐force to deform, and low penalty for misalignment. We aim to overcome the shortcomings for improved reconstruction of time‐resolved four‐dimensional magnetic resonance imaging (TR‐4DMRI).

Methods and Materials

Super‐resolution TR‐4DMRI reconstruction utilizes DIR to combine high‐resolution (highR:2x2x2mm³) breath‐hold (BH) and low‐resolution (lowR:5x5x5mm³) free‐breathing (FB) 3D cine (2Hz) images to achieve clinically acceptable spatiotemporal resolution. A 2‐step hybrid DIR approach was developed to segment low‐dynamic‐range (LDR) regions: low‐intensity lungs and high‐intensity “bodyshell” (=body‐lungs) for DIR refinement after conventional DIR. The intensity in LDR regions was renormalized to the full dynamic range (FDR) to enhance local tissue contrast. A T1‐mapped 4D XCAT digital phantom was created, and seven volunteers and five lung cancer patients were scanned with two BH and one 3D cine series per subject to compare the 1‐step conventional and 2‐step hybrid DIR using: (a) the ground truth in the phantom, (b) highR‐BH references, which were used to simulate 3D cine images by down‐sampling and Rayleigh‐noise‐adding, and (c) cross‐verification between two TR‐4DMRI images reconstructed from two BHs. To assess DIR improvement, 8‐17 blood vessel bifurcations were used in volunteers, and lung tumor position, size, and shape were used in phantom and patients, together with the voxel intensity correlation (VIC), structural similarity (SSIM), and cross‐consistency check (CCC).

Results

The 2‐step hybrid DIR improves contrast and DIR accuracy. In volunteers, it improves low‐contrast alignment from 6.5 ± 1.8 mm to 3.3 ± 1.0 mm. In phantom, it improves tumor center of mass alignment (COM = 1.3 ± 0.2 mm) and minimizes DIR directional difference. In patients, it produces almost‐identical tumor COM, size, and shape (dice> 0.85) as the reference. The VIC and SSIM are significantly increased and the number of CCC outliers are reduced by half.

Conclusion

The 2‐step hybrid DIR improves low‐contrast‐tissue alignment and increases lung tumor fidelity. It is recommended to adopt the 2‐step hybrid DIR for TR‐4DMRI reconstruction.

A super-resolution framework for the reconstruction of T2-weighted (T2w) time-resolved (TR) 4DMRI using T1w TR-4DMRI as the guidance

PURPOSE

The purpose of this study was to develop T2-weighted (T2w) time-resolved (TR) four-dimensional magnetic resonance imaging (4DMRI) reconstruction technique with higher soft-tissue contrast for multiple breathing cycle motion assessment by building a super-resolution (SR) framework using the T1w TR-4DMRI reconstruction as guidance.

METHODS

The multi-breath T1w TR-4DMRI was reconstructed by deforming a high-resolution (HR: 2 × 2 × 2 mm³ ) volumetric breath-hold (BH, 20s) three-dimensional magnetic resonance imaging (3DMRI) image to a series of low-resolution (LR: 5 × 5 × 5 mm³ ) 3D cine images at a 2Hz frame rate in free-breathing (FB, 40 s) using an enhanced Demons algorithm, namely [T1^BH →FB] reconstruction. Within the same imaging session, respiratory-correlated (RC) T2w 4DMRI (2 × 2 × 2 mm³ ) was acquired based on an internal navigator to gain HR T2w (T2^HR ) in three states (full exhalation and mid and full inhalation) in ~5 min. Minor binning artifacts in the RC-4DMRI were automatically identified based on voxel intensity correlation (VIC) between consecutive slices as outliers (VIC < VIC^mean -σ) and corrected by deforming the artifact slices to interpolated slices from the adjacent slices iteratively until no outliers were identified. A T2^HR image with minimal deformation (<1 cm at the diaphragm) from the T1^BH image was selected for multi-modal B-Spline deformable image registration (DIR) to establish the T2^HR -T1^BH voxel correspondence. Two approaches to reconstruct T2w TR-4DMRI were investigated: (A) T2^HR →[T1^BH →FB]: to deform T2w HR to T1w BH only as T1w TR-4DMRI was reconstructed, and combine the two displacement vector fields (DVFs) to reconstruct T2w TR-4DMRI, and (B) [T2^HR ←T1^BH ]→FB: to deform T1w BH to T2w HR first and apply the deformed T1w BH to reconstruct T2w TR-4DMRI. The reconstruction times were similar, 8-12 min per volume. To validate the two methods, T2w- and T1w-mapped 4D XCAT digital phantoms were utilized with three synthetic spherical tumors (ϕ = 2.0, 3.0, and 4.0 cm) in the lower or mid lobes as the ground truth to evaluate the tumor location (the center of mass, COM), size (volume ratio, %V), and shape (Dice index). Six lung cancer patients were scanned under an IRB-approved protocol and the T2w TR-4DMRI images reconstructed from the two methods were compared based on the preservation of the three tumor characteristics. The local tumor-contained image quality was also characterized using the VIC and structure similarity (SSIM) indexes.

RESULTS

In the 4D digital phantom, excellent tumor alignment after T2^HR -T1^HR DIR is achieved: ∆COM = 0.8 ± 0.5 mm, %V = 1.06 ± 0.02, and Dice = 0.91 ± 0.03, in both deformation directions using the DIR-target image as the reference. In patients, binning artifacts are corrected with improved image quality: average VIC increases from 0.92 ± 0.03 to 0.95 ± 0.01. Both T2w TR-4DMRI reconstruction methods produce similar tumor alignment errors ∆COM = 2.9 ± 0.6 mm. However, method B ([T2^HR ←T1^BH ]→FB) produces superior results in preserving more T2w tumor features with a higher %V = 0.99 ± 0.03, Dice = 0.81 ± 0.06, VIC = 0.85 ± 0.06, and SSIM = 0.65 ± 0.10 in the T2w TR-4DMRI images.

CONCLUSIONS

This study has demonstrated the feasibility of T2w TR-4DMRI reconstruction with high soft-tissue contrast and adequately-preserved tumor position, size, and shape in multiple breathing cycles. The T2w-centric DIR (method B) produces a superior solution for the SR-based framework of T2w TR-4DMRI reconstruction with highly preserved tumor characteristics and local image features, which are useful for tumor delineation and motion management in radiation therapy.

Negative Pressure Wound Therapy for Closed Laparotomy Incisions in General and Colorectal Surgery: A Systematic Review and Meta-analysis

Importance

Surgical site infections (SSIs) are common after laparotomy wounds and are associated with a significant economic burden. The use of negative pressure wound therapy (NPWT) has recently been broadened to closed surgical incisions.

Objective

To evaluate the association of prophylactic NPWT with SSI rates in closed laparotomy incisions performed for general and colorectal surgery in elective and emergency settings.

Data Sources

The PubMed, Embase, Cochrane Central Register of Controlled Trials, and Google Scholar databases were searched without language restrictions for relevant articles from inception until December 2017. The latest search was performed on December 31, 2017. The bibliographies of retrieved studies were further screened for potential additional studies.

Study Selection

Randomized clinical trials and nonrandomized studies were included. Unpublished reports were excluded, as were studies that examined NPWT (or standard nonpressure) dressings only without a comparator group. Studies that evaluated the use of NPWT in open abdominal incisions were also excluded. Disagreement was resolved by discussion, and if the question remained unsettled, the opinion of the senior author was sought. A total of 198 citations were identified, and 189 were excluded.

Data Extraction and Synthesis

This meta-analysis was conducted according to PRISMA guidelines. Data were independently extracted by 2 authors. A random-effects model was used for statistical analysis.

Main Outcomes and Measures

The primary outcome measure was SSI, and secondary outcomes included seroma and wound dehiscence rates. These outcomes were chosen before data collection.

Results

Nine unique studies (3 randomized trials and 2 prospective and 4 retrospective studies) capturing 1266 unique patients were included. Of these, 1187 patients with 1189 incisions were included in the final analysis (52.3% male among 7 studies reporting data on sex; mean [SD] age, 52 [15] years among 8 studies reporting data on age). Significant clinical and methodologic heterogeneity existed among studies. On random-effects analysis, NPWT was associated with a significantly lower rate of SSI compared with standard dressings (pooled odds ratio [OR], 0.25; 95% CI, 0.12-0.52; P < .001). However, no difference in rates of seroma (pooled OR, 0.38; 95% CI, 0.12-1.23; P = .11) or wound dehiscence (pooled OR, 2.03; 95% CI, 0.61-6.78; P = .25) was found. On sensitivity analysis, focusing solely on colorectal procedures, NPWT significantly reduced SSI rates (pooled OR, 0.16; 95% CI, 0.07-0.36; P < .001).

Conclusions and Relevance

Application of NPWT on closed laparotomy wounds in general and colorectal surgery is associated with reduced SSI rates but similar rates of seroma and wound dehiscence compared with conventional nonpressure dressings.

Introduction of a pseudo demons force to enhance deformation range for robust reconstruction of super-resolution time-resolved 4DMRI

PURPOSE

The purpose of this study was to enhance the deformation range of demons-based deformable image registration (DIR) for large respiration-induced organ motion in the reconstruction of time-resolved four-dimensional magnetic resonance imaging (TR-4DMRI) for multi-breath motion simulation.

METHODS

A demons-based DIR algorithm was modified to enhance the deformation range for TR-4DMRI reconstruction using the super-resolution approach. A pseudo demons force was introduced to accelerate the coarse deformation in a multi-resolution (n = 3) DIR approach. The intensity gradient of a voxel was applied to its neighboring (5 × 5 × 5) voxels with a weight of Gaussian probability profile (σ = 1 voxel) to extend the demons force, especially on those voxels that have little intensity gradience but high-intensity difference. A digital 4DMRI phantom with 3-8 cm diaphragmatic motions was used for DIR comparison. Six volunteers were scanned with two high-resolution (highR: 2 × 2 × 2 mm³ ) breath-hold (BH) 3DMR images at full inhalation (BHI) and full exhalation (BHE) and low-resolution (lowR: 5 × 5 × 5 mm³ ) free-breathing (FB) 3DMR cine images (2 Hz) under an IRB-approved protocol. A cross-consistency check (CCC) (BHI→FB←BHE), with voxel intensity correlation (VIC) and inverse consistency error (ICE), was introduced for cross-verification of TR-4DMRI reconstruction.

RESULTS

Using the digital phantom, the maximum deformable magnitude is doubled using the modified DIR from 3 to 6 cm at the diaphragm. In six human subjects, the first 15-iteration DIR using the pseudo force deforms 200 ± 150% more than the original force, and succeeds in all 12 cases, whereas the original demons-based DIR failed in 67% of tested cases. Using the pseudo force, high VIC (>0.9) and small ICE (1.6 ± 0.6 mm) values are observed for DIR of BHI&BHE, BHI→FB, and BHE→FB. The CCC identifies four questionable cases, in which two cases need further DIR refinement, without missing true negative.

CONCLUSIONS

The introduction of a pseudo demons force enhances the largest deformation magnitude up to 6 cm. The cross-consistency check ensures the quality of TR-4DMRI reconstruction. Further investigation is ongoing to fully characterize TR-4DMRI for potential multi-breathing-cycle radiotherapy simulation.

The significance of mucin pools following neoadjuvant chemoradiotherapy for locally advanced rectal cancer

BACKGROUND

Neoadjuvant chemo-radiotherapy is utilized for locally advanced rectal cancer to optimize local control. A subset of patients form mucin pools following radiotherapy but the association between mucin pools and pathological and oncological outcomes following curative proctectomy for rectal cancer remains unknown.

OBJECTIVE

The aim of this study was to determine the significance of mucin pool formation after neoadjuvant chemoradiotherapy for rectal cancer.

METHODS

This is a retrospective analysis of a prospectively maintained rectal cancer database. Patients who underwent curative proctectomy for rectal cancer following long course chemoradiotherapy between January 2007 and December 2016 were eligible for inclusion.

RESULTS

A total of 297 patients were eligible for inclusion; of these 36 (12.1%) had mucin pools on final histopathology. Tumors with mucin pools were less likely to be ypT3/T4 (25.0 vs 51.0%, P = 0.003), were more likely to have a good response (83.3 vs 53.6%, P < 0.001) and more likely to have a pathologic complete response (41.7 vs 19.2%, P = 0.006) to radiotherapy. The presence of mucin pools was associated with less distant recurrence ( P < 0.05) and improved overall survival ( P = 0.02).

CONCLUSIONS

The presence of mucin pools following neoadjuvant chemoradiotherapy for rectal cancer represents a surrogate marker of response to treatment and downstaging and is associated with improved survival.

Incorporating spatial dose metrics in machine learning-based normal tissue complication probability (NTCP) models of severe acute dysphagia resulting from head and neck radiotherapy

Severe acute dysphagia commonly results from head and neck radiotherapy (RT). A model enabling prediction of severity of acute dysphagia for individual patients could guide clinical decision-making. Statistical associations between RT dose distributions and dysphagia could inform RT planning protocols aiming to reduce the incidence of severe dysphagia. We aimed to establish such a model and associations incorporating spatial dose metrics. Models of severe acute dysphagia were developed using pharyngeal mucosa (PM) RT dose (dose-volume and spatial dose metrics) and clinical data. Penalized logistic regression (PLR), support vector classification and random forest classification (RFC) models were generated and internally (173 patients) and externally (90 patients) validated. These were compared using area under the receiver operating characteristic curve (AUC) to assess performance. Associations between treatment features and dysphagia were explored using RFC models. The PLR model using dose-volume metrics (PLRstandard) performed as well as the more complex models and had very good discrimination (AUC = 0.82) on external validation. The features with the highest RFC importance values were the volume, length and circumference of PM receiving 1 Gy/fraction and higher. The volumes of PM receiving 1 Gy/fraction or higher should be minimized to reduce the incidence of severe acute dysphagia.

Meta-analysis of the clinicopathological characteristics and peri-operative outcomes of colorectal cancer in obese patients

BACKGROUND

The effect of obesity on the clinicopathological characteristics of colorectal cancer (CRC) has not been clearly characterized. This meta-analysis assesses the pathological and perioperative outcomes of obese patients undergoing surgical resection for CRC.

METHODS

Meta-analysis was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Databases were searched for studies reporting outcomes for obese and non-obese patients undergoing primary CRC resection, based on body-mass index measurement. Results were reported as mean differences or pooled odds ratios (OR) with 95% confidence intervals (95% CI).

RESULTS

A total of 2183 citations were reviewed; 29 studies comprising 56,293 patients were ultimately included in the analysis, with an obesity rate of 19.3%. Obese patients with colorectal cancer were more often female (OR 1.2, 95% CI 1.1-1.2, p<0.001) but there was no difference in the proportion of rectal cancers, T4 tumours, tumour differentiation or margin positivity. Obese patients were significantly more likely to have lymph node metastases (OR 1.2, 95% CI 1.1-1.2, p<0.001), have a lower nodal yield, were associated with a longer duration of surgery, more blood loss and conversions to open surgery (OR 2.6, 95% CI 1.6-4.0, p<0.001) but with no difference in length of stay or post-operative mortality.

CONCLUSION

This meta-analysis demonstrates that obese patients undergoing resection for CRC are more likely to have node positive disease, longer surgery and higher failure rates of minimally invasive approaches. The challenges of colorectal cancer resection in obese patients are emphasized.

A novel representation of inter-site tumour heterogeneity from pre-treatment computed tomography textures classifies ovarian cancers by clinical outcome

PURPOSE

To evaluate the associations between clinical outcomes and radiomics-derived inter-site spatial heterogeneity metrics across multiple metastatic lesions on CT in patients with high-grade serous ovarian cancer (HGSOC).

METHODS

IRB-approved retrospective study of 38 HGSOC patients. All sites of suspected HGSOC involvement on preoperative CT were manually segmented. Gray-level correlation matrix-based textures were computed from each tumour site, and grouped into five clusters using a Gaussian Mixture Model. Pairwise inter-site similarities were computed, generating an inter-site similarity matrix (ISM). Inter-site texture heterogeneity metrics were computed from the ISM and compared to clinical outcomes.

RESULTS

Of the 12 inter-site texture heterogeneity metrics evaluated, those capturing the differences in texture similarities across sites were associated with shorter overall survival (inter-site similarity entropy, similarity level cluster shade, and inter-site similarity level cluster prominence; p ≤ 0.05) and incomplete surgical resection (similarity level cluster shade, inter-site similarity level cluster prominence and inter-site cluster variance; p ≤ 0.05). Neither the total number of disease sites per patient nor the overall tumour volume per patient was associated with overall survival. Amplification of 19q12 involving cyclin E1 gene (CCNE1) predominantly occurred in patients with more heterogeneous inter-site textures.

CONCLUSION

Quantitative metrics non-invasively capturing spatial inter-site heterogeneity may predict outcomes in patients with HGSOC.

KEY POINTS

• Calculating inter-site texture-based heterogeneity metrics was feasible • Metrics capturing texture similarities across HGSOC sites were associated with overall survival • Heterogeneity metrics were also associated with incomplete surgical resection of HGSOC.

C-reactive protein as a predictor of anastomotic leak in the first week after anterior resection for rectal cancer

AIM

Anastomotic leak (AL) after anterior resection results in increased morbidity, mortality and local recurrence. The aim of this study was to assess the ability of C-reactive protein (CRP) to predict AL in the first week after anterior resection for rectal cancer.

METHOD

A retrospective review of a prospectively maintained database that included all patients undergoing anterior resection between January 2008 and December 2013 was performed. The ability of CRP to predict AL was assessed using area under the receiver-operating characteristics (AUC) curves. The severity of AL was defined using the International Study Group of Rectal Cancer (ISREC) grading system.

RESULTS

Two-hundred and eleven patients were included in the study. Statistically significant differences in mean CRP values were found between those with and without an AL on postoperative days 5, 6 and 7. A CRP value of 132 mg/l on postoperative day 5 had an AUC of 0.75, corresponding to a sensitivity of 70%, a specificity of 76.6%, a positive predictive value of 16.3% and a negative predictive value of 97.5%. Multivariable analysis found that a CRP of > 132 mg/l on postoperative day 5 was the only statistically significant patient factor that was linked to an increased risk of AL (HR = 8.023, 95% CI: 1.936-33.238, P = 0.004).

CONCLUSION

Early detection of AL may minimize postoperative complications. CRP is a useful negative predictive test for the development of AL following anterior resection.

A meta-analysis of the clinicopathological characteristics and survival outcomes of inflammatory bowel disease associated colorectal cancer

PURPOSE

The current study aims to use meta-analytical techniques to compare the clinicopathological characteristics and survival outcomes of inflammatory bowel disease (IBD) associated and sporadic colorectal carcinoma (CRC). Patients with IBD have an established increased risk of developing CRC. There is no consensus, however, on the clinicopathological characteristics and survival outcomes of IBD associated CRC when compared to sporadic CRC.

METHODS

A comprehensive search for published studies comparing IBD associated and sporadic CRC was performed. Random effect methods were used to combine data. This study adhered to the recommendations of the MOOSE guidelines.

RESULTS

Data were retrieved from 20 studies describing 571,278 patients. IBD associated CRC had an increased rate of synchronous tumors (OR 4.403, 95% CI 2.320-8.359; p < 0.001), poor differentiation (OR 1.875, 95% CI 1.425-2.466; p < 0.001), and a reduced rate of rectal cancer (OR 0.827, 95% CI 0.735-0.930; p = 0.002). IBD associated CRC however did not affect the frequency of T3/T4 tumors (OR 0.931, 95% CI 0.782-1.108; p = 0.421), lymph node positivity (OR 1.061, 95% CI 0.929-1.213; p = 0.381), metastasis at presentation (OR 0.970, 95% CI 0.776-1.211; p = 0.786), sex distribution (OR 0.978, 95% CI 0.890-1.074; p = 0.640), or 5-year overall survival (OR 1.105, 95% CI 0.414-2.949; p = 0.842).

CONCLUSIONS

In this large analysis of available data, IBD associated CRC was characterized by less rectal tumors and more synchronous and poorly differentiated tumors compared with sporadic cancers, but no discernable difference in sex distribution, stage at presentation, or survival could be identified.

Liberal perioperative fluid administration is an independent risk factor for morbidity and is associated with longer hospital stay after rectal cancer surgery

INTRODUCTION Recent studies have advocated the use of perioperative fluid restriction in patients undergoing major abdominal surgery as part of an enhanced recovery protocol. Series reported to date include a heterogenous group of high- and low-risk procedures but few studies have focused on rectal cancer surgery alone. The aim of this study was to assess the effects of perioperative fluid volumes on outcomes in patients undergoing elective rectal cancer resection. METHODS A prospectively maintained database of patients with rectal cancer who underwent elective surgery over a 2-year period was reviewed. Total volume of fluid received intraoperatively was calculated, as well as blood products required in the perioperative period. The primary outcome was postoperative morbidity (Clavien-Dindo grade I-IV) and the secondary outcomes were length of stay and major morbidity (Clavien-Dindo grade III-IV). RESULTS Over a 2-year period (2012-2013), 120 patients underwent elective surgery with curative intent for rectal cancer. Median total intraoperative fluid volume received was 3680ml (range 1200-9670ml); 65/120 (54.1%) had any complications, with 20/120 (16.6%) classified as major (Clavien-Dindo grade III-IV). Intraoperative volume >3500ml was an independent risk factor for the development of postoperative all-cause morbidity (P=0.02) and was associated with major morbidity (P=0.09). Intraoperative fluid volumes also correlated with length of hospital stay (Pearson's correlation coefficient 0.33; P<0.01). CONCLUSIONS Intraoperative fluid infusion volumes in excess of 3500ml are associated with increased morbidity and length of stay in patients undergoing elective surgery for rectal cancer.

Endoscopic tattooing to aid tumour localisation in colon cancer: the need for standardisation

BACKGROUND/AIMS

An increasing number of colon and rectal tumours are being resected using laparoscopic techniques. Identifying these tumours intraoperatively can be difficult. The use of tattooing can facilitate an easier resection; however, the lack of standardised guidelines can potentially lead to errors intraoperatively and potentially result in worse outcomes for patients. The aim of this study was to identify the most reliable method of preoperative tumour localisation from the available literature to date.

METHODS

A literature review was undertaken to identify any articles related to endoscopic tattooing and tumour localisation during colorectal surgery.

RESULTS

To date there is still mixed evidence regarding tattooing techniques and the choice of ink that should be used. There are numerous studies demonstrating safe tattooing techniques and highlighting the risks and benefits of different types of ink available.

CONCLUSION

Based on the available studies we have recommended a standardised approach to endoscopic tattooing of colorectal tumours prior to laparoscopic resection.

A multiple-image-based method to evaluate the performance of deformable image registration in the pelvis

Deformable image registration (DIR) is essential for adaptive radiotherapy (RT) for tumor sites subject to motion, changes in tumor volume, as well as changes in patient normal anatomy due to weight loss. Several methods have been published to evaluate DIR-related uncertainties but they are not widely adopted. The aim of this study was, therefore, to evaluate intra-patient DIR for two highly deformable organs-the bladder and the rectum-in prostate cancer RT using a quantitative metric based on multiple image registration, the distance discordance metric (DDM). Voxel-by-voxel DIR uncertainties of the bladder and rectum were evaluated using DDM on weekly CT scans of 38 subjects previously treated with RT for prostate cancer (six scans/subject). The DDM was obtained from group-wise B-spline registration of each patient's collection of repeat CT scans. For each structure, registration uncertainties were derived from DDM-related metrics. In addition, five other quantitative measures, including inverse consistency error (ICE), transitivity error (TE), Dice similarity (DSC) and volume ratios between corresponding structures from pre- and post- registered images were computed and compared with the DDM. The DDM varied across subjects and structures; DDMmean of the bladder ranged from 2 to 13 mm and from 1 to 11 mm for the rectum. There was a high correlation between DDMmean of the bladder and the rectum (Pearson's correlation coefficient, R p  =  0.62). The correlation between DDMmean and the volume ratios post-DIR was stronger (R p  =  0.51; 0.68) than the correlation with the TE (bladder: R p  =  0.46; rectum: R p  =  0.47), or the ICE (bladder: R p  =  0.34; rectum: R p  =  0.37). There was a negative correlation between DSC and DDMmean of both the bladder (R p  =  -0.23) and the rectum (R p  =  -0.63). The DDM uncertainty metric indicated considerable DIR variability across subjects and structures. Our results show a stronger correlation with volume ratios and with the DSC using DDM compared to using ICE and TE. The DDM has the potential to quantitatively identify regions of large DIR uncertainties and consequently identify anatomical/scan outliers. The DDM can, thus, be applied to improve the adaptive RT process for tumor sites subject to motion.

A Meta-analysis of Percutaneous Drainage Versus Surgery as the Initial Treatment of Crohn's Disease-related Intra-abdominal Abscess

BACKGROUND AND AIMS

Spontaneous intra-abdominal abscess formation is a common complication of Crohn's disease. Percutaneous drainage [PD] may avoid surgery and preserve bowel length, although there is no consensus on its efficacy as the initial treatment and the associated outcomes if unsuccessful. This study uses meta-analytical techniques to compare the outcomes of PD alone versus primary surgery for Crohn's-related intra-abdominal abscess.

METHODS

A comprehensive search for comparative studies examining the use of PD and surgery for spontaneous Crohn's-related intra-abdominal abscess was performed. Each study was reviewed and data extracted. Random-effects methods were used to combine data.

RESULTS

There were six studies including a total of 333 patients that met the inclusion criteria. Surgery was performed initially in 184 patients, PD was performed in 149. Groups were similar in demographics and abscess characteristics. There was a significantly higher risk of abscess recurrence following PD (odds ratio [OR]: 6.544, 95% confidence interval [CI]: 1.783-24.010, p: 0.005]. The pooled proportion of PD patients requiring subsequent surgery was 70.7%. There was no significant difference between approaches in post-procedural complication rate [OR: 0.657, 95% CI: 0.175-2.476, p: 0.535], ultimate permanent stoma requirement [OR: 0.557, 95% CI: 0.147-2.111, p: 0.389] or length of hospital stay [difference in means: -1.006 days, 95% CI: -28.762-26.749, p: 0.943].

CONCLUSIONS

PD can avoid surgery in up to 30% of patients presenting with spontaneous Crohn's-related intra-abdominal abscesses. However, the suggested advantages over surgery in relation to complications and length of stay were not apparent. Further studies in this area are needed.

Abstract 1498: Feasibility of 2-hydroxyglutarate 1H-MR spectroscopy for routine clinical glioma imaging

The metabolic genes isocitrate dehydrogenase 1 (IDH1) or IDH2 are mutated in 70-80% of WHO grade II and III glioma. The mutant IDH enzyme gains a new function producing D-2-hydroxyglutarate (2-HG). 2-HG is a small molecule that accumulates in IDH mutant gliomas as high as 5 to 35 mM and is considered the principal effector of IDH mutation in cancers. Proton magnetic resonance spectroscopy (MRS) is an approved method in brain tumors to identify and quantify metabolites within brain lesions by using signals emitted by proton nuclei (1H). The 2-HG molecule has five nonexchangeable scalar-coupled protons that give rise to multiplet resonances in MR spectra. First attempts to measure 2-HG in IDH mutant glioma have been promising but were limited to scanners dedicated to research MRIs, long scanning times, and large tumors. The goal of this study was to explore the feasibility of performing 2HG-MRS as part of standard glioma imaging.

We developed single and multivoxel spectroscopy techniques using unique alterations of pulse sequence parameters and software routines on clinical 3Tesla MRI scanners. We added those sequences to our clinical MRI protocol. All metabolites, including 2-HG, were estimated by linear combination of model (LC Model). 107 consecutive glioma patients were evaluated, including 48 (45%) WHO grade II glioma, 40 (37%) grade III glioma and 19(18%) grade IV glioma. 80/107 (75%) patients had IDH mutant gliomas. At the time of MRS, 42(39%) patients were on active treatment with radiation or chemotherapy, 19(18%) had received such treatment in the past, and 46(43%) had never received radiation or chemotherapy. MRI tumor volume was &lt;8cc in 38 (36%) patients and ≥8cc in 69 (64%) patients. 2-HG MRS was negative in all patients with IDH-wild type tumors and in all IDH-mutant gliomas with a tumor volume &lt;8cc. In the group of IDH-mutant tumors with a tumor volume ≥8cc, 2-HG MRS was positive in approximately 35% of the untreated patients and in approximately 30% of the treated patients. For a subset of patients we measured dynamic changes in 2-HG over time (multiple times MRS). A drop in 2HG-MRS signal was associated with treatment response.

2-HG MRS in the clinical setting is feasible. Specificity was 100%. Sensitivity appears, at least in part, dependent on tumor volume with higher sensitivity in larger tumors. In patients with a detectable 2-HG peak, 2HG-MRS represents a promising non-invasive biomarker to monitor tumor growth and treatment response. Final results for the entire cohort will be presented at the meeting.

Citation Format: Macarena I. de la Fuente, Robert Young, Jennifer Rubel, Jamie Tisnado, Samuel Briggs, Andrei I. Holodny, Joseph Deasy, Lisa M. DeAngelis, Justin Cross, Ingo K. Mellinghoff, Sunitha Thakur. Feasibility of 2-hydroxyglutarate 1H-MR spectroscopy for routine clinical glioma imaging. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1498. doi:10.1158/1538-7445.AM2015-1498