Sparing the surgical area with stereotactic body radiotherapy for combined treatment of spinal metastases: a treatment planning study.

INTRODUCTION: Decreasing the radiation dose in the surgical area is important to lower the risk of wound complications when surgery and radiotherapy are combined for the treatment of spinal metastases. The purpose of this study was to compare the radiation dose in the surgical area for spinal metastases between single fraction external beam radiotherapy (EBRT), single fraction stereotactic body radiotherapy (SBRT) and single fraction SBRT with active sparing (SBRT-AS) of the posterior surgical area. METHODS: Radiotherapy treatment plans for EBRT, SBRT and SBRT-AS of the posterior surgical area were created for 13 patients with spinal metastases. A single fraction of 8Gy was prescribed to the spinal metastasis in the EBRT plan. For the SBRT treatment plans, a single fraction of 18Gy was prescribed to the metastasis and 8Gy to the rest of the vertebral body. For the SBRT plan with active sparing the dose in the designated surgical area was minimized without compromising the dose to the organs at risk. RESULTS: The median dose in the surgical area was 2.6Gy (1.6-5.3Gy) in the SBRT plan with active sparing of the surgical area compared to a median dose of 3.7Gy (1.6-6.3Gy) in the SBRT plan without sparing and 6.5Gy (3.5-9.1Gy) in the EBRT plans (p < .001). The radiation doses to the spinal metastases and organs at risk were not significantly different between the SBRT plan with and without sparing the surgical area. CONCLUSIONS: The radiation dose to the surgical area is significantly decreased with the use of SBRT compared to EBRT. Active sparing of the surgical area further decreased the mean radiation dose in the surgical area without compromising the dose to the spinal metastasis and the organs at risk.

Preoperative Chemoradiotherapy Versus Perioperative Chemotherapy for Patients With Resectable Esophageal or Gastroesophageal Junction Adenocarcinoma.

BACKGROUND: This study compares neoadjuvant chemoradiotherapy (nCRT) with perioperative chemotherapy (pCT) for patients with resectable esophageal or gastroesophageal junction (GEJ) adenocarcinoma in terms of toxicity, postoperative complications, pathologic response, and survival. METHODS: This study retrospectively analyzed and compared 313 patients with resectable esophageal or GEJ adenocarcinoma treated with either nCRT (carboplatin/paclitaxel 41.4 Gy, n = 176) or pCT (epirubicin, cisplatin and capecitabine, n = 137). RESULTS: The baseline and tumor characteristics were similar in both groups. The ability to deliver all planned preoperative cycles was greater in the nCRT group (92.0 vs. 76.6%). Whereas nCRT was associated with a higher rate of grades 3 and 4 esophagitis, pCT was associated with a higher rate of grades 3 and 4 thromboembolic events, febrile neutropenia, nausea, vomiting, diarrhea, hand-foot syndrome, mucositis, cardiac complications, and electrolyte imbalances. Two patients in the pCT group died during neoadjuvant treatment due to febrile neutropenia. More postoperative cardiac complications occurred in the nCRT group. All other postoperative complications and the in-hospital mortality rate (nCRT, 4.7%; pCT, 2.3%) were comparable. The pathologic complete response (pCR) rate was 15.1% after nCRT and 6.9% after pCT. Radicality of surgery was comparable (R0: 93.0 vs. 91.6%). The median overall survival was 35 months after nCRT versus 36 months after pCT. CONCLUSION: For patients with esophageal or GEJ adenocarcinoma, chemoradiotherapy with paclitaxel, carboplatin and concurrent radiotherapy, and perioperative chemotherapy with epirubicin, cisplatin, and capecitabin lead to equal oncologic outcomes in terms of radical resection rates, lymphadenectomy, patterns of recurrent disease, and (disease-free) survival. However, neoadjuvant chemoradiotherapy is associated with a considerably lower level of severe adverse events and should therefore be the preferred protocol until a well-powered randomized controlled trial provides different insights.

Redefining radiotherapy for early-stage breast cancer with single dose ablative treatment: a study protocol.

BACKGROUND: A shift towards less burdening and more patient friendly treatments for breast cancer is currently ongoing. In low-risk patients with early-stage disease, accelerated partial breast irradiation (APBI) is an alternative for whole breast irradiation following breast-conserving surgery. MRI-guided single dose ablative APBI has the potential to offer a minimally burdening, non-invasive treatment that could replace current breast-conserving therapy. METHODS: The ABLATIVE study is a prospective, single arm, multicenter study evaluating preoperative, single dose, ablative radiation treatment in patients with early-stage breast cancer. Patients with core biopsy proven non-lobular invasive breast cancer, (estrogen receptor positive, Her2 negative, maximum tumor size 3.0 cm on diagnostic MRI) and a negative sentinel node biopsy are eligible. Radiotherapy (RT) planning will be performed using a contrast enhanced (CE) planning CT-scan, co-registered with a CE-MRI, both in supine RT position. A total of twenty-five consecutive patients will be treated with a single ablative RT dose of 20 Gy to the tumor and 15 Gy to the tumorbed. Follow-up MRIs are scheduled within 1 week, 2, 4 and 6 months after single-dose RT. Breast-conserving surgery is scheduled at six months following RT. Primary study endpoint is pathological complete response. Secondary study endpoints are the radiological response and toxicity. Furthermore, patients will fill out questionnaires on quality of life and functional status. Cosmetic outcome will be evaluated by the treating radiation oncologist, patient and 'Breast Cancer Conservation Treatment cosmetic results' software. Recurrence and survival rates will be assessed. The patients will be followed up to 10 years after diagnosis. If patients give additional informed consent, a biopsy and a part of the irradiated specimen will be stored at the local Biobank and used for future research on radiotherapy response associated genotyping. DISCUSSION: The ABLATIVE study evaluates MRI-guided single dose ablative RT in patients with early-stage breast cancer, aiming at a less burdening and non-invasive alternative for current breast-conserving treatment. TRIAL REGISTRATION: ClinicalTrials.gov registration number NCT02316561 . The trial was registrated prospectively on October 10th 2014.

Health-related quality of life after pancreatic resection for malignancy.

BACKGROUND: Health-related quality of life (QoL) is of major importance in pancreatic cancer, owing to the limited life expectation. The aim of this prospective longitudinal study was to describe QoL in patients undergoing resection for pancreatic or periampullary malignancy. METHODS: QoL was measured on a scale of 0-100 in patients who underwent pancreatic resection for malignancy or premalignancy at the University Medical Centre Utrecht before resection, and 1, 3, 6 and 12 months after surgery. Measures consisted of the RAND-36, the European Organization for Research and Treatment of Cancer (EORTC) core questionnaire (QLQ-C30) and the EORTC pancreatic cancer-specific module (QLQ-PAN26). RESULTS: Between March 2012 and November 2013, 68 consecutive patients with a malignancy (59 patients) or premalignancy (9) were included. Physical role restriction, social and emotional domains showed a significant and clinically relevant deterioration directly after operation in 53 per cent (RAND-36, P < 0.001), 63 and 78 per cent (QLQ-C30 and RAND-36 respectively, P < 0.001) and 37 per cent (RAND-36, P < 0.001) of patients respectively. Most domains demonstrated recovery to preoperative values or better at 3 months, except for physical functioning. Emotional functioning at 3, 6 and 12 months was better than at baseline (P < 0.001). Symptom scores revealed a deterioration in vitality, pain (P = 0.002), fatigue (P < 0.001), appetite loss (P < 0.001), altered bowel habit (P = 0.001) and side-effects (P < 0.001) after 1 month. After 3 months, only side-effects were worse than preoperative values (P < 0.001). CONCLUSION: QoL after pancreatic resection for malignant and premalignant tumours decreased considerably in the early postoperative phase. Full recovery of QoL took up to 6 months after the operation.

Focal salvage therapy for local prostate cancer recurrences after primary radiotherapy: a comprehensive review.

BACKGROUND/AIM: Patients with locally recurrent prostate cancer after primary radiotherapy can be eligible for salvage treatment. Whole-gland salvage techniques carry a high risk of toxicity. A focal salvage approach might reduce the risk of adverse events while maintaining cancer control in carefully selected patients. The aim of this review was to evaluate current literature to assess whether focal salvage leads to a comparable or favourable recurrence rate and less toxicity compared to whole-gland salvage. METHODS: A literature search was performed using PubMed, Embase and the Cochrane Library. A total of 3015 articles were screened and assessed for quality. Eight papers [on focal cryoablation (n = 3), brachytherapy (n = 3) and high-intensity focused ultrasound (n = 2)] were used to report outcomes. RESULTS: One-, 2-, 3- and 5-year biochemical disease-free survival (BDFS) ranges for focal salvage are, respectively, 69-100, 49-100, 50-91 and 46.5-54.5 %. Severe genitourinary, gastrointestinal and sexual function toxicity rates are 0-33.3 %. One study directly compares focal to whole-gland salvage cryotherapy, showing 5-year BDFS of, respectively, 54.4 and 86.5 % with lower toxicity rates for focal salvage patients. CONCLUSION: Provisional data suggest that BDFS rates of focal salvage are in line with those of whole-gland approaches. There is evidence that focal salvage could decrease severe toxicity and preserve erectile function.

Imaging of oesophageal cancer with FDG-PET/CT and MRI.

Integrated 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG) PET/CT and magnetic resonance imaging (MRI) with functional features of diffusion-weighted imaging (DWI) are advancing imaging technologies that have current and future potential to overcome important limitations of conventional staging methods in the management of patients with oesophageal cancer. PET/CT has emerged as an important part of the standard work-up of patients with oesophageal cancer. Besides its important ability to detect unsuspected metastatic disease, PET/CT may be useful in the assessment of treatment response, radiation treatment planning, and detection of recurrent disease. In addition, high-resolution T2-weighted MRI and DWI have potential complementary roles. Recent improvements in MRI protocols and techniques have resulted in better imaging quality with the potential to bring improvement in staging, radiation treatment planning, and the assessment of treatment response. Optimal use and understanding of PET/CT and MRI in oesophageal cancer will contribute to the impact of these advancing technologies in tailoring treatment to the individual patient and achieving best possible outcomes. In this article, we graphically outline the current and potential future roles of PET/CT and MRI in the multidisciplinary management of oesophageal cancer.

Temporal B0 field variation effects on MRSI of the human prostate at 7 T and feasibility of correction using an internal field probe.

Spectral degradations as a result of temporal field variations are observed in MRSI of the human prostate. Moving organs generate substantial temporal and spatial field fluctuations as a result of susceptibility mismatch with the surrounding tissue (i.e. periodic breathing, cardiac motion or random bowel motion). Nine patients with prostate cancer were scanned with an endorectal coil (ERC) on a 7-T MR scanner. Temporal B0 field variations were observed with fast dynamic B0 mapping in these patients. Simulations of dynamic B0 corrections were performed using zero- to second-order shim terms. In addition, the temporal B0 variations were applied to simulated MR spectra causing, on average, 15% underestimation of the choline/citrate ratio. Linewidth distortions and frequency shifts (up to 30 and 8 Hz, respectively) were observed. To demonstrate the concept of observing local field fluctuations in real time during MRSI data acquisition, a field probe (FP) tuned and matched for the (19) F frequency was incorporated into the housing of the ERC. The data acquired with the FP were compared with the B0 field map data and used to correct the MRSI datasets retrospectively. The dynamic B0 mapping data showed variations of up to 30 Hz (0.1 ppm) over 72 s at 7 T. The simulated zero-order corrections, calculated as the root mean square, reduced the standard deviation (SD) of the dynamic variations by an average of 41%. When using second-order corrections, the reduction in the SD was, on average, 56%. The FP data showed the same variation range as the dynamic B0 data and the variation patterns corresponded. After retrospective correction, the MRSI data showed artifact reduction and improved spectral resolution. B0 variations can degrade the MRSI substantially. The simple incorporation of an FP into an ERC can improve prostate cancer MRSI without prior knowledge of the origin of the dynamic field distortions.

Composite slice-selective adiabatic excitation for prostate MRSI.

Higher magnetic field strengths, such as 7 T, offer increased spectral resolution and higher signal-to-noise ratio. These properties can be very advantageous for MRSI. In particular, signals that generally overlap at lower fields, such as choline, polyamines and creatine, can be resolved at 7 T. However, higher magnetic field strengths suffer from strong radiofrequency (RF) field nonuniformities. These nonuniformities become even stronger when using surface transceivers, such as an endorectal coil for prostate imaging. In order to obtain uniform excitations for accurate MRSI measurements, adiabatic sequences are therefore recommended. Conventional adiabatic MRS sequences (i.e. localization by adiabatic selective refocusing, LASER) have relatively long TEs, especially when optimized to measure the strongly coupled spins of citrate in the prostate. The semi-LASER (sLASER) sequence has a significantly shorter TE, although it does not provide adiabatic excitation. Therefore, we propose an adiabatic sLASER sequence that either has a composite adiabatic slice-selective excitation (cLASER) or a non-slice-selective adiabatic excitation (nsLASER), allowing for shorter TEs, whilst maintaining the adiabatic spin excitation. Furthermore, the spatial properties of the composite adiabatic excitation allow for a high slice excitation bandwidth, resulting in negligible chemical shift displacement artifacts. Exclusion of the slice selection can be considered once the field of view extends beyond the transmit field of the RF coil. The use of a transceiver at high magnetic field strengths has shown that the cLASER and nsLASER sequences are suitable for MRSI of the prostate in both phantom and in vivo validations.

Improving SNR and B1 transmit field for an endorectal coil in 7 T MRI and MRS of prostate cancer.

Higher magnetic field strengths like 7 T and above are desirable for MR spectroscopy given the increased spectral resolution and signal to noise ratio. At these field strengths, substantial nonuniformities in B(1)(+/-) and radiofrequency power deposition become apparent. In this investigation, we propose an improvement on a conventionally used endorectal coil, through the addition of a second element (stripline). Both elements are used as transceivers. In the center of the prostate, approximately 40% signal to noise ratio increase is achieved. In fact, the signal to noise ratio gain obtained with the quadrature configuration locally can be even greater than 40% when compared to the single loop configuration. This is due to the natural asymmetry of the B(1)(+/-) fields at high frequencies, which causes destructive and constructive interference patterns. Global specific absorption rate is reduced by almost a factor of 2 as expected. Furthermore, approximately a 4-fold decrease in local specific absorption rate is observed when normalized to the B(1) values in the center of the prostate. Because of the 4-fold local specific absorption rate decrease obtained with the dual channel setup for the same reference B(1) value (20 µT at 3.5 cm depth into the prostate) as compared to the single loop, the transmission power B(1) duty cycle can be increased by a factor 4. Consequently, when using the two-element endorectal coil, the radiofrequency power deposition is significantly reduced and radiofrequency intense sequences with adiabatic pulses can be safely applied at 7 T for (1)H magnetic resonance spectroscopy and MRI in the prostate. Altogether, in vivo (1)H magnetic resonance spectroscopic imaging of prostate cancer with a fully adiabatic sequence operated at a minimum B(1)(+) of 20 µT shows insensitivity to the nonuniform transmit field, while remaining within local specific absorption rate guidelines of 10 W/kg.

Comparison of seed brachytherapy or external beam radiotherapy (70 Gy or 74 Gy) in 919 low-risk prostate cancer patients.

PURPOSE: The aim of this analysis was to compare the biochemical no evidence of disease (bNED) rates in low-risk prostate cancer patients treated at two centers of excellence using different approaches: seed brachytherapy (BT) and external beam radiotherapy (EBRT). MATERIALS AND METHODS: A total of 919 low-risk prostate cancer patients, treated from 1998-2008, were identified in the two databases. In Utrecht, 667 patients received I-125 BT applying a dose of 144 Gy. In Vienna, 252 patients were treated with EBRT, applying a local dose of 70 Gy in 82 patients and 74 Gy in 170 patients. bNED rates (Phoenix definition) were assessed. RESULTS: The median follow-up was 46 months (range 1-148 months). The 5-year actuarial bNED rates were 94% for BT patients and 88% for EBRT patients (p = 0.002)-84% for patients receiving 70 Gy and 91% for patients receiving 74 Gy, respectively. In the univariate analysis, patients receiving 70 Gy showed significantly worse outcome compared to BT (p = 0.001) and a difference close to significance compared to 74 Gy (p = 0.06). In the multivariate analysis including tumor stage, Gleason score, initial PSA, hormonal therapy, and dose, patients receiving 70 Gy EBRT showed significantly worse bNED rates compared to BT patients. CONCLUSION: Low-risk prostate cancer patients receiving 74 Gy by EBRT show comparable biochemical control rates to patients receiving seed brachytherapy, whereas patients receiving 70 Gy show significantly worse outcome.

Model-Based Selection for Proton Therapy in Breast Cancer: Development of the National Indication Protocol for Proton Therapy and First Clinical Experiences.

AIMS: Proton therapy is a radiation technique that yields less dose in normal tissues than photon therapy. In the Netherlands, proton therapy is reimbursed if the reduced dose to normal tissues is predicted to translate into a prespecified reduction in toxicity, based on nationally approved validated models. The aim of this paper is to present the development of a national indication protocol for proton therapy (NIPP) for model-based selection of breast cancer patients and to report on first clinical experiences. MATERIALS AND METHODS: A national proton therapy working group for breast cancer (PWG-BC) screened the literature for prognostic models able to estimate the individual risk of specific radiation-induced side-effects. After critical appraisal and selection of suitable models, a NIPP for breast cancer was written and subjected to comments by all stakeholders. The approved NIPP was subsequently introduced to select breast cancer patients who would benefit most from proton therapy. RESULTS: The model of Darby et al. (N Engl J Med 2013; 368:987-82) was the only model fulfilling the criteria prespecified by the PWG-BC. The model estimates the relative risk of an acute coronary event (ACE) based on the mean heart dose. The absolute lifetime risk of ACE <80 years was calculated by applying this model to the Dutch absolute incidence of ACE for female and male patients, between 40 and 70 years at breast cancer radiotherapy, with/without cardiovascular risk factors. The NIPP was approved for reimbursement in January 2019. Based on a threshold value of a 2% absolute lower risk on ACE for proton therapy compared with photons, 268 breast cancer patients have been treated in the Netherlands with proton therapy between February 2019 and January 2021. CONCLUSION: The NIPP includes a model that allows the estimation of the absolute risk on ACE <80 years based on mean heart dose. In the first 2 years, 268 breast cancer patients have been treated with proton therapy in The Netherlands.

Excised and irradiated volumes in relation to the tumor size in breast-conserving therapy.

In early-stage breast cancer and DCIS patients, breast-conserving therapy is today's standard of care. The purpose of this study was to evaluate the relation between the microscopic tumor diameter (mTD), the excised specimen (ES) volume, and the irradiated postoperative complex (POC) volume, in patients treated with breast-conserving therapy. In 186 patients with pTis-2N0 breast cancer, the mTDs, ES, and POC volumes (as delineated on the radiotherapy-planning CT scan), were retrospectively determined. Linear regression analysis was performed to study the association between the mTD, and the ES and POC volumes. The explained variance (r (2)) was calculated to establish the proportion of variation in the outcome variable that could be explained by the determinant (P ≤ 0.05). Moreover, the influence of tumor characteristics, age, surgical procedures, and breast size was studied. Median mTD was 1.2 cm (range 0.1-3.6 cm), median ES volume was 60 cm(3) (range 6-230 cm(3)) and median POC volume was 15 cm(3) (range 0.5-374 cm(3)). The POC was not clearly visible on the majority of the CT scans, based on a median assigned cavity visualization score of 3 (range 1-5). The explained variance for the mTD on the ES volume was low (r(2) = 0.08, P < 0.001). A slightly stronger association was observed in palpable tumors (r(2) = 0.23, P < 0.001) and invasive lobular carcinomas (r(2) = 0.39, P = 0.01). Furthermore, weak associations were observed between POC volume and mTD (r(2) = 0.04, P = 0.01), and POC and ES volume (r(2) = 0.23, P < 0.001). A weak association was observed between breast volume and ES volume (r(2) = 0.27, P < 0.001). In conclusion, both the excised and the irradiated POC volumes did not show a clinically relevant association with the mTD in women with early-stage breast cancer treated with breast-conserving therapy. Future studies should focus on improvement of surgical localization, development of image-guided, minimally invasive operation techniques, and more accurate image-guided target volume delineation in radiotherapy.

Integrating a 1.5 T MRI scanner with a 6 MV accelerator: proof of concept.

At the UMC Utrecht, The Netherlands, we have constructed a prototype MRI accelerator. The prototype is a modified 6 MV Elekta (Crawley, UK) accelerator next to a modified 1.5 T Philips Achieva (Best, The Netherlands) MRI system. From the initial design onwards, modifications to both systems were aimed to yield simultaneous and unhampered operation of the MRI and the accelerator. Indeed, the simultaneous operation is shown by performing diagnostic quality 1.5 T MRI with the radiation beam on. No degradation of the performance of either system was found. The integrated 1.5 T MRI system and radiotherapy accelerator allow simultaneous irradiation and MR imaging. The full diagnostic imaging capacities of the MRI can be used; dedicated sequences for MRI-guided radiotherapy treatments will be developed. This proof of concept opens the door towards a clinical prototype to start testing MRI-guided radiation therapy (MRIgRT) in the clinic.

A novel method for comparing 3D target volume delineations in radiotherapy.

When comparing delineations it is often useful to obtain a local measure of distance between the volume surfaces. Commonly used methods for analysing local distance exhibit fundamental drawbacks which may cause overestimation of the distance or lead to asymmetry in the measure. This paper describes a new method that aims to solve these problems. The new method finds corresponding points between two delineations by traversing a vector field based on the combined gradient of the distance transforms. The proposed method provides a fundamentally more reliable, symmetric measure of distance. This is supported by an illustrative example of observer variation in prostate delineation. An implementation of the method is available on request to the author.

Variation in target and rectum dose due to prostate deformation: an assessment by repeated MR imaging and treatment planning.

In daily clinical practice, implanted fiducial markers are used to correct for prostate motion, but not for prostate deformation. The aim of this study is to investigate the variation in target and rectum dose due to the deformation of the prostate gland (without seminal vesicles). Therefore, we performed five to six MRI scans of eight healthy volunteers that exhibited large variation in rectal volume and thus prostate deformation. Prostate motion was corrected by a mask-based rigid registration which uses the delineation as well as the internal structures of the prostate gland. Per MRI scan, one IMRT plan with a PTV margin of 4 mm was created, resulting in 41 IMRT plans. The dose distribution of the IMRT plan based on the MRI scan with the minimum rectal volume was applied to the other rigidly registered MRI scans to evaluate the impact of prostate deformation. In conclusion, pre-treatment planning on the minimum rectal volume can cause a fraction dose increase (up to 15%) to the rectum due to prostate deformation. The impact on the total dose increase to the rectum depends on the intrapatient rectum variation during treatment, but is negligible with the currently used PTV margins in a fractionated treatment.

Adaptive cone-beam CT planning improves long-term biochemical disease-free survival for 125I prostate brachytherapy.

PURPOSE: Determining the independent effect of additional intraoperative adaptive C-arm cone-beam CT (CBCT) planning vs. transrectal ultrasound (TRUS)-guided interactive planning alone in 125I brachytherapy for prostate cancer (PCa) on biochemical disease-free survival (BDFS). METHODS AND MATERIALS: T1/T2-stage PCa patients receiving TRUS-guided brachytherapy from 2000 to 2014 were analyzed. From October 2006, patients received additional intraoperative adaptive CBCT planning for dosimetric evaluation and subsequent remedial seed placement in underdosed areas. Patients were stratified according to the National Comprehensive Cancer Network (NCCN) risk classification. Kaplan-Meier analysis was used to estimate BDFS (primary outcome), overall survival, and PCa-specific survival (secondary outcomes). Cox regression was used to assess the relation between CBCT use and biochemical failure (BF) and overall mortality. RESULTS: In all, 1623 patients were included. Median followup was 99 months (interquartile range 70-115) for TRUS patients (n = 613) and 51 months (interquartile range 29-70) for CBCT patients (n = 1010). BF occurred 203 times and 206 patients died, 26 from PCa. For TRUS and CBCT patients, 7-year BDFS was 87.2% vs. 93.5% (log rank: p = 0.04) for low, 75.9% vs. 88.5% (p < 0.001) for intermediate, and 57.1% vs. 85.0% for high-risk patients (p < 0.001). For TRUS and CBCT patients, 7-year PCa-specific survival was 96.0% vs. 100% (p < 0.0001). After Cox regression, CBCT patients had lower hazard of BF: hazard ratio (HR) 0.25 (95% confidence interval [CI]: 0.18-0.33; p < 0.0001). Corrected for confounders, CBCT remained a predictor of BF: HR 0.51 (95% CI: 0.31-0.86; p = 0.01) but not for overall mortality: HR 0.66 (95% CI: 0.40-1.07; p = 0.09). CONCLUSIONS: Additional intraoperative adaptive CBCT planning in 125I prostate brachytherapy leads to a significant increase in BDFS in all NCCN risk groups.

Recommendations for MRI-based contouring of gross tumor volume and organs at risk for radiation therapy of pancreatic cancer.

PURPOSE: Local recurrence is a common and morbid event in patients with unresectable pancreatic adenocarcinoma. A more conformal and targeted radiation dose to the macroscopic tumor in nonmetastatic pancreatic cancer is likely to reduce acute toxicity and improve local control. Optimal soft tissue contrast is required to facilitate delineation of a target and creation of a planning target volume with margin reduction and motion management. Magnetic resonance imaging (MRI) offers considerable advantages in optimizing soft tissue delineation and is an ideal modality for imaging and delineating a gross tumor volume (GTV) within the pancreas, particularly as it relates to conformal radiation planning. Currently, no guidelines have been defined for the delineation of pancreatic tumors for radiation therapy treatment planning. Moreover, abdominal MRI sequences are complex and the anatomy relevant to the radiation oncologist can be challenging. The purpose of this study is to provide recommendations for delineation of GTV and organs at risk (OARs) using MRI and incorporating multiple MRI sequences. METHODS AND MATERIALS: Five patients with pancreatic cancer and 1 healthy subject were imaged with MRI scans either on 1.5T or on 3T magnets in 2 separate institutes. The GTV and OARs were contoured for all patients in a consensus meeting. RESULTS: An overview of MRI-based anatomy of the GTV and OARs is provided. Practical contouring instructions for the GTV and the OARs with the aid of MRI were developed and included in these recommendations. In addition, practical suggestions for implementation of MRI in pancreatic radiation treatment planning are provided. CONCLUSIONS: With this report, we attempt to provide recommendations for MRI-based contouring of pancreatic tumors and OARs. This could lead to better uniformity in defining the GTV and OARs for clinical trials and in radiation therapy treatment planning, with the ultimate goal of improving local control while minimizing morbidity.

Adaptive planning strategy for high dose rate prostate brachytherapy­a simulation study on needle positioning errors.

The development of magnetic resonance (MR) guided high dose rate (HDR) brachytherapy for prostate cancer has gained increasing interest for delivering a high tumor dose safely in a single fraction. To support needle placement in the limited workspace inside the closed-bore MRI, a single-needle MR-compatible robot is currently under development at the University Medical Center Utrecht (UMCU). This robotic device taps the needle in a divergent way from a single rotation point into the prostate. With this setup, it is warranted to deliver the irradiation dose by successive insertions of the needle. Although robot-assisted needle placement is expected to be more accurate than manual template-guided insertion, needle positioning errors may occur and are likely to modify the pre-planned dose distribution.In this paper, we propose a dose plan adaptation strategy for HDR prostate brachytherapy with feedback on the needle position: a dose plan is made at the beginning of the interventional procedure and updated after each needle insertion in order to compensate for possible needle positioning errors. The introduced procedure can be used with the single needle MR-compatible robot developed at the UMCU. The proposed feedback strategy was tested by simulating complete HDR procedures with and without feedback on eight patients with different numbers of needle insertions (varying from 4 to 12). In of the cases tested, the number of clinically acceptable plans obtained at the end of the procedure was larger with feedback compared to the situation without feedback. Furthermore, the computation time of the feedback between each insertion was below 100 s which makes it eligible for intra-operative use.