Pelvic insufficiency fractures and pelvic bone metastases after neoadjuvant (chemo)radiotherapy for rectal cancer

BACKGROUND

Pelvic insufficiency fractures (PIFs) are a late complication of radiotherapy for pelvic malignancies. We evaluated the incidence, radiologic findings, clinical course, and outcome of PIFs in patients treated with neoadjuvant (chemo)radiotherapy ((C)RT) for rectal cancer.

MATERIAL AND METHODS

Data of patients diagnosed with rectal cancer from a large teaching hospital treated from 2002 to 2012 were extracted from the Dutch Cancer Registry. All hospital records were reviewed for the diagnosis of PIFs or pelvic bone metastases. An expert radiologist reassessed all imaging procedures of the lower back, abdomen, and pelvis.

RESULTS

A total of 513 rectal cancer patients were identified of whom 300 patients (58.5%) were treated with neoadjuvant (C)RT (long- vs. short-course radiotherapy: 91 patients [17.7%] vs. 209 [40.7%], respectively). Twelve PIFs were diagnosed initially according to hospital records and imaging reports of all 513 patients. These 12 patients were treated with neoadjuvant (C)RT. After reassessment of all pelvic imaging procedures done in this patient group (432 patients (84.2%)), 20 additional PIFs were detected in patients treated with neoadjuvant (C)RT, resulting in a 10.7% PIF rate in irradiated patients. One PIF was detected in the group of patients not treated with neoadjuvant (C)RT for rectal cancer. This patient had palliative radiotherapy for prostate cancer and is left out of the analysis. Median follow-up time of 32 PIF patients was 49 months. Median time between start of neoadjuvant (C)RT and diagnosis of PIF was 17 months (IQR 9-28). Overall median survival for patients with PIF was 63.5 months (IQR 44-120).

CONCLUSION

PIFs are a relatively common late complication of neoadjuvant (C)RT for rectal cancer but are often missed or misdiagnosed as pelvic bone metastases. The differentiation of PIFs from pelvic bone metastases is important because of a different treatment and disease outcome.

Towards Response ADAptive Radiotherapy for organ preservation for intermediate-risk rectal cancer (preRADAR): protocol of a phase I dose-escalation trial

INTRODUCTION

Organ preservation is associated with superior functional outcome and quality of life (QoL) compared with total mesorectal excision (TME) for rectal cancer. Only 10% of patients are eligible for organ preservation following short-course radiotherapy (SCRT, 25 Gy in five fractions) and a prolonged interval (4-8 weeks) to response evaluation. The organ preservation rate could potentially be increased by dose-escalated radiotherapy. Online adaptive magnetic resonance-guided radiotherapy (MRgRT) is anticipated to reduce radiation-induced toxicity and enable radiotherapy dose escalation. This trial aims to establish the maximum tolerated dose (MTD) of dose-escalated SCRT using online adaptive MRgRT.

METHODS AND ANALYSIS

The preRADAR is a multicentre phase I trial with a 6+3 dose-escalation design. Patients with intermediate-risk rectal cancer (cT3c-d(MRF-)N1M0 or cT1-3(MRF-)N1M0) interested in organ preservation are eligible. Patients are treated with a radiotherapy boost of 2×5 Gy (level 0), 3×5 Gy (level 1), 4×5 Gy (level 2) or 5×5 Gy (level 3) on the gross tumour volume in the week following standard SCRT using online adaptive MRgRT. The trial starts on dose level 1. The primary endpoint is the MTD based on the incidence of dose-limiting toxicity (DLT) per dose level. DLT is a composite of maximum one in nine severe radiation-induced toxicities and maximum one in three severe postoperative complications, in patients treated with TME or local excision within 26 weeks following start of treatment. Secondary endpoints include the organ preservation rate, non-DLT, oncological outcomes, patient-reported QoL and functional outcomes up to 2 years following start of treatment. Imaging and laboratory biomarkers are explored for early response prediction.

ETHICS AND DISSEMINATION

The trial protocol has been approved by the Medical Ethics Committee of the University Medical Centre Utrecht. The primary and secondary trial results will be published in international peer-reviewed journals.

TRIAL REGISTRATION NUMBER

WHO International Clinical Trials Registry (NL8997; https://trialsearch.who.int).

Impact of endorectal filling on interobserver variability of MRI based rectal primary tumor delineation

Background

Online adaptive MR-guided radiotherapy allows for the reduction of safety margins in dose escalated treatment of rectal tumors. With the use of smaller margins, precise tumor delineation becomes more critical. In the present study we investigated the impact of rectal ultrasound gel filling on interobserver variability in delineation of primary rectal tumor volumes.

Methods

Six patients with locally advanced rectal cancer were scanned on a 1.5 T MRI-Linac without (MRI_e) and with application of 100 cc of ultrasound gel transanally (MRI_f). Eight international radiation oncologists expert in the treatment of gastrointestinal cancers delineated the gross tumor volume (GTV) on both MRI scans. MRI_f scans were provided to the participating centers after MRI_e scans had been returned. Interobserver variability was analyzed by either comparing the observers' delineations with a reference delineation (approach 1) and by building all possible pairs between observers (approach 2). Dice Similarity Index (DICE) and 95 % Hausdorff-Distance (95 %HD) were calculated.

Results

Rectal ultrasound gel filling was well tolerated by all patients. Overall, interobserver agreement was superior in MRI_f scans based on median DICE (0.81 vs 0.74, p < 0.005 for approach 1 and 0.76 vs 0.64, p < 0.0001 for approach 2) and 95 %HD (6.9 mm vs 4.2 mm for approach 1, p = 0.04 and 8.9 mm vs 6.1 mm, p = 0.04 for approach 2). Delineated median tumor volumes and inter-quartile ranges were 26.99 cc [18.01-50.34 cc] in MRI_e and 44.20 [19.72-61.59 cc] in MRI_f scans respectively, p = 0.012.

Conclusions

Although limited by the small number of patients, in this study the application of rectal ultrasound gel resulted in higher interobserver agreement in rectal GTV delineation. The endorectal gel filling might be a useful tool for future dose escalation strategies.

Nationwide Validation of the 8th American Joint Committee on Cancer TNM Staging System and Five Proposed Modifications for Resected Pancreatic Cancer

BACKGROUND

The prognostic value of four proposed modifications to the 8th American Joint Committee on Cancer (AJCC) TNM staging system has yet to be evaluated. This study aimed to validate five proposed modifications.

METHODS

Patients who underwent pancreatic ductal adenocarcinoma resection (2014-2016), as registered in the prospective Dutch Pancreatic Cancer Audit, were included. Stratification and prognostication of TNM staging systems were assessed using Kaplan-Meier curves, Cox proportional hazard analyses, and C-indices. A new modification was composed based on overall survival (OS).

RESULTS

Overall, 750 patients with a median OS of 18 months (interquartile range 10-32) were included. The 8th edition had an increased discriminative ability compared with the 7th edition {C-index 0.59 (95% confidence interval [CI] 0.56-0.61) vs. 0.56 (95% CI 0.54-0.58)}. Although the 8th edition showed a stepwise decrease in OS with increasing stage, no differences could be demonstrated between all substages; stage IIA vs. IB (hazard ratio [HR] 1.30, 95% CI 0.80-2.09; p  = 0.29) and stage IIB vs. IIA (HR 1.17, 95% CI 0.75-1.83; p  = 0.48). The four modifications showed comparable prognostic accuracy (C-index 0.59-0.60); however, OS did not differ between all modified TNM stages (ns). The new modification, migrating T3N1 patients to stage III, showed a C-index of 0.59, but did detect significant survival differences between all TNM stages (p  < 0.05).

CONCLUSIONS

The 8th TNM staging system still lacks prognostic value for some categories of patients, which was not clearly improved by four previously proposed modifications. The modification suggested in this study allows for better prognostication in patients with all stages of disease.

Selected stage IV rectal cancer patients managed by the watch-and-wait approach after pelvic radiotherapy: a good alternative to total mesorectal excision surgery?

AIM

The aim of this study was to assess the clinical and oncological outcome of a selected group of stage IV rectal cancer patients managed by the watch-and-wait approach following a (near-)complete response of the primary rectal tumour after radiotherapy.

METHOD

Patients registered in the Dutch watch-and-wait registry since 2004 were selected when diagnosed with synchronous stage IV rectal cancer. Data on patient characteristics, treatment details, follow-up and survival were collected. The 2-year local regrowth rate, organ-preservation rate, colostomy-free rate, metastatic progression-free rate and 2- and 5-year overall survival were analysed.

RESULTS

After a median follow-up period of 35 months, local regrowth was observed in 17 patients (40.5%). Nine patients underwent subsequent total mesorectal excision, resulting in a permanent colostomy in four patients. The 2-year local regrowth rate was 39.9%, the 2-year organ-preservation rate was 77.1%, the 2-year colostomy-free rate was 88.1%, and the 2-year metastatic progression-free rate was 46.7%. The 2- and 5-year overall survival rates were 92.0% and 67.5%.

CONCLUSION

The watch-and-wait approach can be considered as an alternative to total mesorectal excision in a selected group of stage IV rectal cancer patients with a (near-)complete response following pelvic radiotherapy. Despite a relatively high regrowth rate, total mesorectal excision and a permanent colostomy can be avoided in the majority of these patients.

Progression-free survival in patients with 68Ga-PSMA-PET-directed SBRT for lymph node oligometastases

BACKGROUND

Prostate cancer oligometastatic disease can be treated using stereotactic body radiotherapy (SBRT) in order to postpone start of systemic treatments such as androgen deprivation therapy (ADT). 68Ga-PSMA-PET/CT imaging allows for diagnosis of oligometastases at lower PSA values. We analysed a cohort of patients with prostate cancer lymph node oligometastases detected on PSMA-PET/CT.

MATERIALS AND METHODS

Ninety patients with metachronous oligometastatic prostate cancer received SBRT for 1-3 lymph node metastases diagnosed on 68Ga-PSMA-PET/CT. The primary end point was progression free survival (PFS), with disease progression defined as occurrence of either target lesion progression, new metastatic lesion or biochemical progression. Secondary outcomes were biochemical PFS (BPFS), ADT-free survival (ADT-FS), toxicity and quality of life (QoL). Baseline patient characteristics were tested for association with PFS and a preliminary risk score was created.

RESULTS

Median follow-up was 21 months (interquartile range 10-31 months). Median PFS and BPFS were 16 and 21 months, respectively. Median ADT-FS was not reached (73% (95%-CI 62-86%) at 24 months). In multivariable analysis, younger age, higher PSA prior to SBRT and extrapelvic location were associated with shorter PFS. Grade 1 fatigue was the most predominant acute toxicity (34%). Highest grade toxicity was grade 2 for acute and late events. QoL analysis showed mild, transient increase in fatigue at 1-4 weeks after SBRT.

CONCLUSION

A median PFS of 16 months was attained after SBRT for patients with PSMA-PET positive oligometastatic lymph nodes from prostate cancer. Higher pre-SBRT PSA, younger age and extrapelvic location were found to be predictors of shorter PFS.

Magnetic Resonance Guided Radiation Therapy for Pancreatic Adenocarcinoma, Advantages, Challenges, Current Approaches, and Future Directions

Introduction

Pancreatic adenocarcinoma (PAC) has some of the worst treatment outcomes for any solid tumor. PAC creates substantial difficulty for effective treatment with traditional RT delivery strategies primarily secondary to its location and limited visualization using CT. Several of these challenges are uniquely addressed with MR-guided RT. We sought to summarize and place into context the currently available literature on MR-guided RT specifically for PAC.

Methods

A literature search was conducted to identify manuscript publications since September 2014 that specifically used MR-guided RT for the treatment of PAC. Clinical outcomes of these series are summarized, discussed, and placed into the context of the existing pancreatic literature. Multiple international experts were involved to optimally contextualize these publications.

Results

Over 300 manuscripts were reviewed. A total of 6 clinical outcomes publications were identified that have treated patients with PAC using MR guidance. Successes, challenges, and future directions for this technology are evident in these publications. MR-guided RT holds theoretical promise for the treatment of patients with PAC. As with any new technology, immediate or dramatic clinical improvements associated with its use will take time and experience. There remain no prospective trials, currently publications are limited to small retrospective experiences. The current level of evidence for MR guidance in PAC is low and requires significant expansion. Future directions and ongoing studies that are currently open and accruing are identified and reviewed.

Conclusions

The potential promise of MR-guided RT for PAC is highlighted, the challenges associated with this novel therapeutic intervention are also reviewed. Outcomes are very early, and will require continued and long term follow up. MR-guided RT should not be viewed in the same fashion as a novel chemotherapeutic agent for which dosing, administration, and toxicity has been established in earlier phase studies. Instead, it should be viewed as a novel procedural intervention which must be robustly tested, refined and practiced before definitive conclusions on the potential benefits or detriments can be determined. The future of MR-guided RT for PAC is highly promising and the potential implications on PAC are substantial.

MR-Guided Radiotherapy for Rectal Cancer: Current Perspective on Organ Preservation

Online MRI-guided radiotherapy (MRgRT) is one of the most recent technological advances in radiotherapy. MRgRT permits the visualization of tumorous and healthy tissue while the patient is on the treatment table and online daily plan adaptations following the observed anatomical changes. In the context of rectal cancer, online MRgRT is a very promising modality due to the pronounced geographical variability of tumor tissues and the surrounding healthy tissues. This current paper will discuss the possible applications of online MRgRT, in particular, in terms of radiotherapy dose escalation and response prediction in organ preservation approaches for rectal cancer.

A field strength independent MR radiomics model to predict pathological complete response in locally advanced rectal cancer

PURPOSE

Aim of this study was to develop a generalised radiomics model for predicting pathological complete response after neoadjuvant chemo-radiotherapy in locally advanced rectal cancer patients using pre-CRT T2-weighted images acquired at a 1.5 T and a 3 T scanner.

METHODS

In two institutions, 195 patients were scanned: 136 patients were scanned on a 1.5 T MR scanner, 59 patients on a 3 T MR scanner. Gross tumour volumes were delineated on the MR images and 496 radiomic features were extracted, applying the intensity-based (IB) filter. Features were standardised with Z-score normalisation and an initial feature selection was carried out using Wilcoxon-Mann-Whitney test: The most significant features at 1.5 T and 3 T were selected as main features. Several logistic regression models combining the main features with a third one selected by those resulting significant were elaborated and evaluated in terms of area under curve (AUC). A tenfold cross-validation was repeated 300 times to evaluate the model robustness.

RESULTS

Three features were selected: maximum fractal dimension with IB = 0-50, energy and grey-level non-uniformity calculated on the run-length matrix with IB = 0-50. The AUC of the model applied to the whole dataset after cross-validation was 0.72, while values of 0.70 and 0.83 were obtained when 1.5 T and 3 T patients were considered, respectively.

CONCLUSIONS

The model elaborated showed good performance, even when data from patients scanned on 1.5 T and 3 T were merged. This shows that magnetic field intensity variability can be overcome by means of selecting appropriate image features.

Gross Tumor Delineation in Esophageal Cancer on MRI Compared With 18F-FDG-PET/CT

PURPOSE

Current delineation of the gross tumor volume (GTV) in esophageal cancer relies on computed tomography (CT) and combination with 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). There is increasing interest in integrating magnetic resonance imaging (MRI) in radiation treatment, which can potentially obviate CT- or FDG-PET/CT-based delineation. The aim of this study is to evaluate the feasibility of target delineation on T2-weighted (T2W) MRI and T2W including diffusion-weighted MRI (T2W + DW-MRI) compared with current-practice FDG-PET/CT.

METHODS

Ten observers delineated primary esophageal tumor GTVs of 6 patients on FDG-PET/CT, T2W-MRI, and T2W + DW-MRI. GTVs, generalized conformity indices, in-slice delineation variation (root mean square), and standard deviations in the position of the most cranial and caudal delineated slice were calculated.

RESULTS

Delineations on MRI showed smaller GTVs compared with FDG-PET/CT-based delineations. The main variation was seen at the cranial and caudal border. No differences were observed in conformity indices (FDG-PET/CT, 0.68; T2W-MRI, 0.66; T2W + DW-MRI, 0.68) and in-slice variation (root mean square, 0.13 cm on FDG-PET/CT; 0.10 cm on T2W-MRI; 0.14 cm on T2W + DW-MRI). In the 2 tumors involving the gastroesophageal junction, addition of DW-MRI to T2W-MRI significantly decreased caudal border variation.

CONCLUSIONS

MRI-based target delineation of the esophageal tumor is feasible with interobserver variability comparable to that with FDG-PET/CT, despite limited experience with delineation on MRI. Most variation was seen at cranial-caudal borders, and addition of DW-MRI to T2W-MRI may reduce caudal delineation variation of gastroesophageal junction tumors.

Predicting the tumor response to chemoradiotherapy for rectal cancer: Model development and external validation using MRI radiomics

BACKGROUND

In well-responding patients to chemoradiotherapy for locally advanced rectal cancer (LARC), a watch-and-wait strategy can be considered. To implement organ-sparing strategies, accurate patient selection is needed. We investigate the use of MRI-based radiomics models to predict tumor response to improve patient selection.

MATERIALS AND METHODS

Models were developed in a cohort of 70 patients and validated in an external cohort of 55 patients. Patients received chemoradiation followed by surgery and underwent T2-weighted and diffusion-weighted MRI (DW-MRI) before and after chemoradiation. The outcome measure was (near-)complete pathological tumor response (ypT0-1N0). Tumor segmentation was done on T2-images and transferred to b800-images and ADC maps, after which quantitative and four semantic features were extracted. We combined features using principal component analysis and built models using LASSO regression analysis. The best models based on precision and performance were selected for validation.

RESULTS

21/70 patients (30%) achieved ypT0-1N0 in the development cohort versus 13/55 patients (24%) in the validation cohort. Three models (t2_dwi_pre_post, semantic_dwi_adc_pre, semantic_dwi_post) were identified with an area-under-the-curve (AUC) of 0.83 (95% CI 0.70-0.95), 0.86 (95% CI 0.75-0.98) and 0.84 (95% CI 0.75-0.94) respectively. Two models (t2_dwi_pre_post, semantic_dwi_post) validated well in the external cohort with AUCs of 0.83 (95% CI 0.70-0.95) and 0.86 (95% CI 0.76-0.97). These models however did not outperform a previously established four-feature semantic model.

CONCLUSION

Prediction models based on MRI radiomics non-invasively predict tumor response after chemoradiation for rectal cancer and can be used as an additional tool to identify patients eligible for an organ-preserving treatment.

Feasibility of stereotactic radiotherapy using a 1.5 T MR-linac: Multi-fraction treatment of pelvic lymph node oligometastases

Online adaptive radiotherapy using the 1.5 Tesla MR-linac is feasible for SBRT (5 × 7 Gy) of pelvic lymph node oligometastases. The workflow allows full online planning based on daily anatomy. Session duration is less than 60 min. Quality assurance tests, including independent 3D dose calculations and film measurements were passed.

MRI-based tumor inter-fraction motion statistics for rectal cancer boost radiotherapy

BACKGROUND

In patients diagnosed with rectal cancer, dose escalation is currently being investigated in a large number of studies. Since there is little known on gross tumor volume (GTV) inter-fraction motion for rectal cancer, a wide variety in margins is used. Purpose of this study is to quantify GTV inter-fraction motion statistics on different timescales and to give estimates of planning target volume (PTV) margins.

MATERIAL AND METHODS

Thirty-two patients, diagnosed with rectal cancer, were included. To investigate motion from week-to-week, 16 patients underwent a pretreatment and five weekly MRIs, prior to a radiotherapy (RT) fraction of the chemoradiotherapy treatment. To investigate motion from day-to-day, the remaining 16 patients underwent five daily MRIs before each fraction in one week of RT. GTV was delineated on all scans according to guidelines. Scans were aligned on bony anatomy with the first MRI. For both datasets separately, GTV inter-fraction motion was determined based on center-of-gravity displacement. Therefrom, systematic and random errors were determined in left/right (LR), anterior/posterior and cranial/caudal (CC) direction. PTV margin estimates were calculated and evaluated on GTV coverage.

RESULTS

Systematic and random errors were found in the range of 2.3-4.8 mm and 1.5-3.3 mm from week-to-week, and 1.8-4.5 mm and 1.8-4.0 mm from day-to-day, respectively. On both timescales, similar motion patterns were found; the most motion was observed in CC whilst the least motion was observed in LR. On the week-to-week data more systematic and less random motion was observed compared to the day-to-day data. Overall, only slight differences in margin estimates were found. Derived PTV margin estimates were found to give adequate GTV coverage.

CONCLUSION

GTV inter-fraction motion, on a week-to-week and day-to-day timescale, can be accounted for using motion statistics presented in this study.

Tumor volume regression during preoperative chemoradiotherapy for rectal cancer: a prospective observational study with weekly MRI

PURPOSE

Few data is available on rectal tumor shrinkage during preoperative chemoradiotherapy (CRT). This regression pattern is interesting to optimize timing of dose escalation on the tumor.

METHODS

Gross tumor volumes (GTV) were contoured by two observers on magnetic resonance imaging (MRI) obtained before, weekly during, 2-4 weeks after, and 7-8 weeks after a 5-week course of concomitant CRT for rectal cancer.

RESULTS

Overall, 120 MRIs were acquired in 15 patients. A statistically significant tumor volume reduction is seen from the first week, and between any two time points (p < .007). At the end of CRT, 46.3% of the initial tumor volume remained, and 32.4% at time of surgery. PTV measured 61.2% at the end of treatment. Tumor shrinkage is the fastest in the beginning of treatment (26%/week), slows down to 7%/week in the last 2 weeks of CRT, and finally to 1.3%/week in the last 5 weeks before surgery.

CONCLUSIONS

The main rectal tumor regression occurs during CRT course itself, and mostly in the first half, with shrinking speed decreasing over the course. This suggests that a sequential boost is preferably done after the elective fields, yielding an average PTV-reduction of 39%. A simultaneous integrated boost strategy could benefit from adaptive planning during the course.

Tolerability, Safety, and Outcomes of Neoadjuvant Chemoradiotherapy With Capecitabine for Patients Aged ≥ 70 Years With Locally Advanced Rectal Cancer

INTRODUCTION

In studies of colorectal cancer, the elderly have been frequently underrepresented because comorbid conditions and functional status often lead to study exclusion. For elderly patients with an indication for neoadjuvant chemoradiotherapy (nCRT), physicians usually decide using clinical factors whether nCRT should be offered. The aim of the present retrospective study was to assess the tolerability of nCRT with capecitabine and the surgical outcomes in patients aged ≥ 70 years with locally advanced rectal cancer.

PATIENTS AND METHODS

Data from 1372 rectal cancer patients diagnosed from 2002 to 2012 at 4 Dutch hospitals were used. Patients aged ≥ 70 years were included if they had received nCRT, and their data were analyzed for treatment deviations, postoperative complications, mortality, disease-free survival (DFS), and overall survival (OS). The data were stratified into 3 age groups (ie, 70-74, 75-79, and ≥ 80 years).

RESULTS

We identified 447 patients aged ≥ 70 years. Of these patients, 42 had received nCRT, and 37 (88%) had completed nCRT. Radiation dermatitis, fatigue, and diarrhea were reported in 62%, 57%, and 43% of the 42 patients, respectively. Of the 42 patients, 40 (95%) underwent surgery, 1 patient refused resection, and 1 patient died during nCRT of severe mucositis due to dihydropyrimidine dehydrogenase deficiency. The postoperative complication rate was 30%, and the 30-day mortality rate was 0%. A pathologic complete response was found in 7.5%. The 2- and 5-year DFS and OS rates were 58.5% and 40.7% and 81.0% and 58.2%, respectively.

CONCLUSION

The results of the present multicenter study have shown that if selected on clinical factors, nCRT with capecitabine is safe and well tolerated in elderly patients. No negative effect on surgical outcome was measured, and the beneficial effect (pathologic complete response, DFS, and OS) seemed comparable to that for younger age groups. We believe that elderly patients should not be excluded from nCRT on the basis of age only.

Does setup on rectal wall improve rectal cancer boost radiotherapy?

BACKGROUND

Rectal cancer patients that show a pathological complete response (pCR) after neo-adjuvant chemo-radiotherapy, have better prognosis. To increase pCR rates several studies escalate the tumor irradiation dose. However, due to lacking tumor contrast on online imaging techniques, no direct tumor setup can be performed and large boost margins are needed to ensure tumor coverage. The purpose of this study was to evaluate the feasibility of performing a setup on rectal wall for rectal cancer boost radiotherapy, thereby using rectal wall nearby the tumor as tumor position surrogate.

METHODS

For sixteen patients, daily MRI's were performed during 1 week of radiotherapy. On each of these images, tumor and rectum were delineated. Residual displacements were determined per surface voxel after setup on bony anatomy or nearby rectal wall and setup errors for both setups were compared. Furthermore for every rectal wall voxel nearby the tumor, displacement was compared with the closest tumor point and correlation was determined.

RESULTS

Mean (SD) setup error was 2.7 mm (3.3 mm) and 2.2 mm (3.2 mm) after setup on bony anatomy and rectal wall respectively. Nevertheless, similar PTV-margin estimates i.e. 95th percentile distances, were found; 8.0 mm. Also, a merely moderate correlation; ρ = 0.66 was found between rectal wall and tumor displacement. Further investigation into tumor and rectal mobility differences showed that the rectal wall lacks appropriate anatomical landmarks to find true displacements, especially to capture motion along the rectal wall.

CONCLUSIONS

Setup on rectal wall slightly reduces mean setup errors but requires a similar PTV-margin as compared to setup on bony anatomy. Rectal mobility might be similar to tumor mobility, but due the absence of anatomical landmarks in the rectum, displacements along the rectal wall are not detected on current online imaging. Therefore, to further reduce tumor position uncertainties, direct or indirect online tumor visualization is needed.

Development and validation of an MRI-based model to predict response to chemoradiotherapy for rectal cancer

BACKGROUND AND PURPOSE

To safely implement organ preserving treatment strategies for patients with rectal cancer, well-considered selection of patients with favourable response is needed. In this study, we develop and validate an MRI-based response predicting model.

METHODS

A multivariate model using T2-volumetric and DWI parameters before and 6 weeks after chemoradiation (CRT) was developed using a cohort of 85 rectal cancer patients and validated in an external cohort of 55 patients that underwent preoperative CRT.

RESULTS

Twenty-two patients (26%) achieved ypT0-1N0 response in the development cohort versus 13 patients (24%) in the validation cohort. Two T2-volumetric parameters (ΔVolume% and Sphere_post) and two DWI parameters (ADC_avg_post and ADCratio_avg) were retained in a model predicting (near-)complete response (ypT0-1N0). In the development cohort, this model had a good predictive performance (AUC = 0.89; 95% CI 0.80-0.98). Validation of the model in an external cohort resulted in a similar performance (AUC = 0.88 95% CI 0.79-0.98).

CONCLUSION

An MRI-based prediction model of (near-)complete pathological response following CRT in rectal cancer patients, shows a high predictive performance in an external validation cohort. The clinically relevant features in the model make it an interesting tool for implementation of organ-preserving strategies in rectal cancer.

Long-term health-related quality of life after pancreatic resection for malignancy in patients with and without severe postoperative complications

BACKGROUND

Surgery for pancreatic cancer yields significant morbidity and mortality risks and survival is limited. Therefore, the influence of complications on quality of life (QoL) after pancreatic surgery is important. This study compares QoL in patients with and without severe complications after surgery for pancreatic (pre-)malignancy.

METHODS

This prospective cohort study scored complications after pancreatic surgery according to the Clavien-Dindo system and the definitions of the International Study Group of Pancreatic Surgery. QoL was measured by the RAND36 questionnaire, the European Organization for Research and Treatment of Cancer core questionnaire (QLQ-C30) and the pancreas specific QLQ-PAN26. QoL in patients with severe complications was compared with QoL in patients with no or mild complications over a period of 12 months. Analysis was performed with linear mixed models for repeated measurements.

RESULTS

Between March 2012 and July 2016, 137 patients were included. Sixty-eight patients (50%) had at least 1 severe complication. There were no statistically significant and clinically relevant differences between both groups in QoL up to 12 months after surgery.

CONCLUSION

In this study, no differences in QoL between patients with and without severe postoperative complications were encountered during the first 12 months after surgery for pancreatic (pre-)malignancy.

TRIAL REGISTRATION

http://www.clinicaltrials.gov Identifier: NCT02175992.

Abstract CT067: The Prospective Dutch ColoRectal Cancer Cohort (PLCRC): a prospective nationwide observational cohort study providing the infrastructure for registry based trials

Background: Colorectal cancer (CRC) was once considered a single entity, but now appears to exist of multiple, often molecular defined, subclasses. These subclasses have implications for treatment, and hamper the feasibility of prospective randomized clinical trials which require large sample sizes. To anticipate further developments and to obtain more detailed insight in the outcome of daily practice, the Prospective Dutch CRC cohort (PLCRC) was initiated. In this prospective observational multicenter cohort, patients with all stages of colorectal cancer are included, and clinical data, tissue, blood samples and patient-reported outcome measures are collected. The cohort serves as an infrastructure for registry based trials in the Netherlands (CRC incidence approximately 16.000 patients per year).

Methods: Patients ≥18 years with histologically proven stage I-IV CRC are eligible to participate. The informed consent includes consent for systematic collection of long-term clinical data and optionally 1) standardized collection of tissue and blood samples; 2) being informed when clinically relevant DNA mutations are detected; 3) patient-reported outcome questionnaires; and 4) invitation for future interventional studies according to (amongst others) the cohort multiple randomized controlled trial design (cmRCT).

Results: In 2016 the number of participating hospitals increased from 6 to 17. The number of included patients roughly doubled to more than 1100 patients. The PLCRC infrastructure is used in the execution of fifteen studies, which amongst others focus on the prognostic value of circulating tumor DNA, the quality of life during treatment with new compounds and the influence of nutrition on treatment outcome. The studies use the option to repeatedly withdraw blood, send out PROMs and/or randomize patients according to the cmRCT design. The study populations in the substudies vary from newly diagnosed stage 2 colon cancer to non-liver limited metastatic CRC. In 2017, at least 20 hospitals which are currently in the initiation process will be added with which a 50% coverage of the Dutch hospitals will be reached.

Conclusions: PLCRC provides long-term clinical data, tissue, blood samples and patient-reported outcome measures of a large cohort of patients with colorectal cancer. The cohort will be representative of the colorectal cancer population in the Netherlands. Multiple studies are ongoing making use of the infrastructure provided. These studies will make it possible to optimize treatment for specific small subgroups.

Citation Format: Geraldine Vink, Robert Coebergh van den Braak, Haiko Bloemendal, Veerle Coupé, Marloes Elferink, Frans Erdkamp, Helma van Grevenstein, Jan-Willem de Groot, Jan Ijzermans, Martijn Intven, Maartje Los, Mirre de Noo, Martijn van Oijen, Cornelis Punt, Ron Rietbroek, Wilfried Roeloffzen, Anandi Schiphorst, Huig Schipper, Hein Stockmann, Manuel Tjin-a-Ton, Ankie van der Velden, Marlies Verhaar, Wouter Vles, David Zimmerman, Gerrit Meijer, Miriam Koopman. The Prospective Dutch ColoRectal Cancer Cohort (PLCRC): a prospective nationwide observational cohort study providing the infrastructure for registry based trials [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT067. doi:10.1158/1538-7445.AM2017-CT067

Combined T2w volumetry, DW-MRI and DCE-MRI for response assessment after neo-adjuvant chemoradiation in locally advanced rectal cancer

BACKGROUND

To assess the value of combined T2-weighted magnetic resonance imaging (MRI) (T2w) volumetry, diffusion-weighted (DW)-MRI and dynamic contrast enhanced (DCE)-MRI for pathological response prediction after neo-adjuvant chemoradiation (CRT) in locally advanced rectal cancer (LARC).

MATERIAL AND METHODS

MRI with DW-MRI and DCE-MRI sequences was performed before start of CRT and before surgery. After surgery, the tumor regression grade (TRG) was obtained based on the score by Mandard et al. Pathological complete responders (pCR, TRG 1), and pathological good responders (GR, TRG 1 + 2) were compared to non-pCR and non-GR patients, respectively.

RESULTS

In total 55 patients were analyzed, six had a pCR (10.9%) and 10 a GR (18.2%). Favorable responders had a larger decrease in tumor volume and Ktrans and a larger increase in apparent diffusion coefficient (ADC) values compared to non-responders. ADC change showed the best diagnostic accuracy for pCR. For GR, the model including ADC change and volume change showed the best diagnostic performance. However, this performance was not statistically better compared to the model with ADC change alone. Inclusion of Ktrans change did not increase the diagnostic accuracy for pathological favorable response.

CONCLUSIONS

This explorative study showed that ADC change is a promising diagnostic tool for pCR and GR. Volume decrease showed potential limited additional diagnostic value for GR while Ktrans change showed no additional diagnostic value for pCR and GR.