Combining Dual Checkpoint Immunotherapy with Ablative Radiation to All Sites of Oligometastatic Non-Small Cell Lung Cancer: Toxicity and Efficacy Results of a Phase 1b Trial

PURPOSE

Ablative local treatment of all radiographically detected metastatic sites in patients with oligometastatic non-small cell lung cancer (NSCLC) increases progression-free survival (PFS) and overall survival (OS). Prior studies demonstrated the safety of combining stereotactic body radiation therapy (SBRT) with single-agent immunotherapy. We investigated the safety of combining SBRT to all metastatic tumor sites with dual checkpoint, anticytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4), and anti-programmed cell death ligand 1 (anti-PD-L1) immunotherapy for patients with oligometastatic NSCLC.

METHODS AND MATERIALS

We conducted a phase 1b clinical trial in patients with oligometastatic NSCLC with up to 6 sites of extracranial metastatic disease. All sites of disease were treated with SBRT to a dose of 30 to 50 Gy in 5 fractions. Dual checkpoint immunotherapy was started 7 days after completion of radiation using anti-CTLA-4 (tremelimumab) and anti-PD-L1 (durvalumab) immunotherapy for a total of 4 cycles followed by durvalumab alone until progression or toxicity.

RESULTS

Of the 17 patients enrolled in this study, 15 patients received at least 1 dose of combination immunotherapy per protocol. The study was closed early (17 of planned 21 patients) due to slow accrual during the COVID-19 pandemic. Grade 3+ treatment-related adverse events were observed in 6 patients (40%), of which only one was possibly related to the addition of SBRT to immunotherapy. Median PFS was 42 months and median OS has not yet been reached.

CONCLUSIONS

Delivering ablative SBRT to all sites of metastatic disease in combination with dual checkpoint immunotherapy did not result in excessive rates of toxicity compared with historical studies of dual checkpoint immunotherapy alone. Although the study was not powered for treatment efficacy results, durable PFS and OS results suggest potential therapeutic benefit compared with immunotherapy or radiation alone in this patient population.

Radiomics-enhanced early regression index for predicting treatment response in rectal cancer: a multi-institutional 0.35 T MRI-guided radiotherapy study

PURPOSE

The accurate prediction of treatment response in locally advanced rectal cancer (LARC) patients undergoing MRI-guided radiotherapy (MRIgRT) is essential for optimising treatment strategies. This multi-institutional study aimed to investigate the potential of radiomics in enhancing the predictive power of a known radiobiological parameter (Early Regression Index, ERITCP) to evaluate treatment response in LARC patients treated with MRIgRT.

METHODS

Patients from three international sites were included and divided into training and validation sets. 0.35 T T2*/T1-weighted MR images were acquired during simulation and at each treatment fraction. The biologically effective dose (BED) conversion was used to account for different radiotherapy schemes: gross tumour volume was delineated on the MR images corresponding to specific BED levels and radiomic features were then extracted. Multiple logistic regression models were calculated, combining ERITCP with other radiomic features. The predictive performance of the different models was evaluated on both training and validation sets by calculating the receiver operating characteristic (ROC) curves.

RESULTS

A total of 91 patients was enrolled: 58 were used as training, 33 as validation. Overall, pCR was observed in 25 cases. The model showing the highest performance was obtained combining ERITCP at BED = 26 Gy with a radiomic feature (10th percentile of grey level histogram, 10GLH) calculated at BED = 40 Gy. The area under ROC curve (AUC) of this combined model was 0.98 for training set and 0.92 for validation set, significantly higher (p = 0.04) than the AUC value obtained using ERITCP alone (0.94 in training and 0.89 in validation set).

CONCLUSION

The integration of the radiomic analysis with ERITCP improves the pCR prediction in LARC patients, offering more precise predictive models to further personalise 0.35 T MRIgRT treatments of LARC patients.

A Phase 2 Randomized Clinical Trial Evaluating 4DCT Ventilation-based Functional Lung Avoidance Radiotherapy for Non-Small Cell Lung Cancer

PURPOSE

To determine whether 4-dimensional computed tomography (4DCT) ventilation-based functional lung avoidance radiotherapy preserves pulmonary function compared with standard radiotherapy for non-small cell lung cancer (NSCLC).

MATERIAL AND METHODS

This single center, randomized, phase 2 trial enrolled patients with NSCLC receiving curative intent radiotherapy with either stereotactic body radiotherapy or conventionally fractionated radiotherapy between 2016 and 2022. Patients were randomized 1:1 to standard of care radiotherapy or functional lung avoidance radiotherapy. The primary endpoint was the change in Jacobian-based ventilation as measured on 4DCT from baseline to three months post-radiation. Secondary endpoints included changes in volume of high- and low-ventilating lung, pulmonary toxicity, and changes in pulmonary function tests (PFTs).

RESULTS

A total of 122 patients were randomized and 116 were available for analysis. Median follow up was 29.9 months. Functional avoidance plans significantly (P<.05) reduced dose to high-functioning lung without compromising target coverage or organs at risk constraints. When analyzing all patients, there was no difference in the amount of lung showing a reduction in ventilation from baseline to 3 months between the two arms (1.91% vs 1.87%; P=.90). Overall grade ≥2 and grade ≥3 pulmonary toxicities for all patients were 24.1% and 8.6%, respectively. There was no significant difference in pulmonary toxicity or changes in PFTs between the two study arms. In the conventionally fractionated cohort, there was a lower rate of grade ≥2 pneumonitis (8.2% vs 32.3%; P=.049) and less of a decline in change in FEV1 (-3 vs -5; P=.042) and FVC (1.5 vs -6; P=.005) at 3 months, favoring the functional avoidance arm.

CONCLUSIONS

There was no difference in post-treatment ventilation as measured by 4DCT between the arms. In the cohort of patients treated with conventionally fractionated radiotherapy with functional lung avoidance, there was reduced pulmonary toxicity, and less decline in PFTs suggesting a clinical benefit in patients with locally advanced NSCLC.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCTXXXX Anonymized for Review XXXX.

Stereotactic MR-guided on-table adaptive radiation therapy (SMART) for borderline resectable and locally advanced pancreatic cancer: A multi-center, open-label phase 2 study

BACKGROUND AND PURPOSE

Radiation dose escalation may improve local control (LC) and overall survival (OS) in select pancreatic ductal adenocarcinoma (PDAC) patients. We prospectively evaluated the safety and efficacy of ablative stereotactic magnetic resonance (MR)-guided adaptive radiation therapy (SMART) for borderline resectable (BRPC) and locally advanced pancreas cancer (LAPC). The primary endpoint of acute grade ≥ 3 gastrointestinal (GI) toxicity definitely related to SMART was previously published with median follow-up (FU) 8.8 months from SMART. We now present more mature outcomes including OS and late toxicity.

MATERIALS AND METHODS

This prospective, multi-center, single-arm open-label phase 2 trial (NCT03621644) enrolled 136 patients (LAPC 56.6 %; BRPC 43.4 %) after ≥ 3 months of any chemotherapy without distant progression and CA19-9 ≤ 500 U/mL. SMART was delivered on a 0.35 T MR-guided system prescribed to 50 Gy in 5 fractions (biologically effective dose10 [BED10] = 100 Gy). Elective coverage was optional. Surgery and chemotherapy were permitted after SMART.

RESULTS

Mean age was 65.7 years (range, 36-85), induction FOLFIRINOX was common (81.7 %), most received elective coverage (57.4 %), and 34.6 % had surgery after SMART. Median FU was 22.9 months from diagnosis and 14.2 months from SMART, respectively. 2-year OS from diagnosis and SMART were 53.6 % and 40.5 %, respectively. Late grade ≥ 3 toxicity definitely, probably, or possibly attributed to SMART were observed in 0 %, 4.6 %, and 11.5 % patients, respectively.

CONCLUSIONS

Long-term outcomes from the phase 2 SMART trial demonstrate encouraging OS and limited severe toxicity. Additional prospective evaluation of this novel strategy is warranted.

Transcatheter Arterial Chemoembolization Imaging Features in MR-Linac Radiation Therapy Planning for the Liver

For MR-guided radiation therapy treatment planning, an MRI and CT of the intended treatment site are typically acquired. Patients' prior treatments or procedures can cause image artifacts in one or both scans, which may impact treatment planning or the radiation dose calculation. In this case report, a patient with several previous transcatheter arterial chemoembolization (TACE) procedures was planned for radiation therapy on a low-field MR-linac, and the impact of residual iodinated oil on the radiation dose calculation and MR-guided adaptive workflow was evaluated.

A Multi-Institutional Phase 2 Trial of Ablative 5-Fraction Stereotactic Magnetic Resonance-Guided On-Table Adaptive Radiation Therapy for Borderline Resectable and Locally Advanced Pancreatic Cancer

PURPOSE

Magnetic resonance (MR) image guidance may facilitate safe ultrahypofractionated radiation dose escalation for inoperable pancreatic ductal adenocarcinoma. We conducted a prospective study evaluating the safety of 5-fraction Stereotactic MR-guided on-table Adaptive Radiation Therapy (SMART) for locally advanced (LAPC) and borderline resectable pancreatic cancer (BRPC).

METHODS AND MATERIALS

Patients with LAPC or BRPC were eligible for this multi-institutional, single-arm, phase 2 trial after ≥3 months of systemic therapy without evidence of distant progression. Fifty gray in 5 fractions was prescribed on a 0.35T MR-guided radiation delivery system. The primary endpoint was acute grade ≥3 gastrointestinal (GI) toxicity definitely attributed to SMART.

RESULTS

One hundred thirty-six patients (LAPC 56.6%, BRPC 43.4%) were enrolled between January 2019 and January 2022. Mean age was 65.7 (36-85) years. Head of pancreas lesions were most common (66.9%). Induction chemotherapy mostly consisted of (modified)FOLFIRINOX (65.4%) or gemcitabine/nab-paclitaxel (16.9%). Mean CA19-9 after induction chemotherapy and before SMART was 71.7 U/mL (0-468). On-table adaptive replanning was performed for 93.1% of all delivered fractions. Median follow-up from diagnosis and SMART was 16.4 and 8.8 months, respectively. The incidence of acute grade ≥3 GI toxicity possibly or probably attributed to SMART was 8.8%, including 2 postoperative deaths that were possibly related to SMART in patients who had surgery. There was no acute grade ≥3 GI toxicity definitely related to SMART. One-year overall survival from SMART was 65.0%.

CONCLUSIONS

The primary endpoint of this study was met with no acute grade ≥3 GI toxicity definitely attributed to ablative 5-fraction SMART. Although it is unclear whether SMART contributed to postoperative toxicity, we recommend caution when pursuing surgery, especially with vascular resection after SMART. Additional follow-up is ongoing to evaluate late toxicity, quality of life, and long-term efficacy.

Toxicity and Patient-Reported Quality-of-Life Outcomes After Prostate Stereotactic Body Radiation Therapy With Focal Boost to Magnetic Resonance Imaging-Identified Prostate Cancer Lesions: Results of a Phase 2 Trial

PURPOSE

In this prospective phase 2 trial, we investigated the toxicity and patient-reported quality-of-life outcomes in patients treated with stereotactic body radiation therapy (SBRT) to the prostate gland and a simultaneous focal boost to magnetic resonance imaging (MRI)-identified intraprostatic lesions while also de-escalating dose to the adjacent organs at risk.

METHODS AND MATERIALS

Eligible patients included low- or intermediate-risk prostate cancer (Gleason score ≤7, prostate specific antigen ≤20, T stage ≤2b). SBRT was prescribed to 40 Gy in 5 fractions delivered every other day to the prostate, with any areas of high disease burden (MRI-identified prostate imaging reporting and data system 4 or 5 lesions) simultaneously escalated to 42.5 to 45 Gy and areas overlapping organs at risk (within 2 mm of urethra, rectum, and bladder) constrained to 36.25 Gy (n = 100). Patients without a pretreatment MRI or without MRI-identified lesions were treated to dose of 37.5 Gy with no focal boost (n = 14).

RESULTS

From 2015 to 2022, a total of 114 patients were enrolled with a median follow-up of 42 months. No acute or late grade 3+ gastrointestinal (GI) toxicity was observed. One patient developed late grade 3 genitourinary (GU) toxicity at 16 months. In patients treated with focal boost (n = 100), acute grade 2 GU and GI toxicity was seen in 38% and 4% of patients, respectively. Cumulative late grade 2+ GU and GI toxicities at 24 months were 13% and 5% respectively. Patient-reported outcomes showed no significant long-term change from baseline in urinary, bowel, hormonal, or sexual quality-of-life scores after treatment.

CONCLUSIONS

SBRT to a dose of 40 Gy to the prostate gland with a simultaneous focal boost up to 45 Gy is well tolerated with similar rates of acute and late grade 2+ GI and GU toxicity as seen in other SBRT regimens without intraprostatic boost. Moreover, no significant long-term changes were seen in patient-reported urinary, bowel, or sexual outcomes from pretreatment baseline.

Treatment Efficacy Outcomes Combining Dual Checkpoint Immunotherapy with Ablative Radiation to All Sites of Oligometastatic Non-Small Cell Lung Cancer: Survival Analysis of a Phase IB trial

PURPOSE/OBJECTIVE(S)

Aggressivelocal treatment to a limited number of metastatic sites in patients with oligometastatic NSCLC increases progression free survival (PFS) and overall survival (OS). Prior studies have shown the safety of combining high dose stereotactic body radiation therapy (SBRT) with single agent anti-PD1/PD-L1 therapy. Here, we report secondary survival endpoint outcomes from a phase Ib clinical trial investigating the safety of combining ablative, high dose radiation with dual checkpoint, anti-CTLA-4 and anti-PD-L1 immunotherapy for patients with oligometastatic NSCLC.

MATERIALS/METHODS

Patients with up to 6 sites of extracranial metastatic disease were eligible for trial enrollment. All sites of disease were treated with stereotactic body radiation therapy to a dose of 30 - 50 Gy in 5 fractions. Dual checkpoint immunotherapy was started 7 days following completion of radiation utilizing anti-CTLA-4 (Tremelimumab) and anti-PD-L1 (Durvalumab) immunotherapy for a total of four cycles followed by durvalumab alone until dose limiting toxicity or progression was observed. Primary toxicity outcomes were previously reported. Progression free and overall survival was analyzed using Kaplan Meier statistical methods.

RESULTS

Fifteen patients were treated with SBRT and received at least one dose of dual agent immunotherapy per protocol. The median follow up was 43 months. The median number of extracranial metastatic sites was 2. Seven patients had 3 or more sites of extracranial disease. The most commonly treated sites were separate metastatic pulmonary lesions or osseous metastatic lesions. Median progression free survival (PFS) was 42 months and median overall survival (OS) was 48 months. Seven patients remain alive without evidence of progressive disease. Prior history of brain metastases was associated with significantly worse PFS (Median PFS 4 months vs 42 months, HR 6.1 (95% CI 1.6 - 37.0) p = 0.0248), but no difference in OS (Median OS 24 vs 42 months, HR 1.9 (95% CI 0.3 - 10.4).

CONCLUSION

Ablative SBRT radiation to up to 6 sites of disease followed by dual checkpoint immunotherapy in oligometastatic NSCLC resulted in a favorable progression free survival (42 months) and overall survival (48 months) compared to historical controls. These findings suggest potential benefit to patient outcomes compared to immunotherapy or radiation alone in this patient population and warrant further investigation.

Initial Results of a Phase II Trial of Hypofractionated Radiation Therapy for Inoperable Soft Tissue Sarcoma

PURPOSE/OBJECTIVE(S)

For patients with soft tissue sarcoma (STS) who cannot or choose not to have surgery, radiation can provide local tumor control in both palliative and definitive settings. Conventionally fractionated radiation provides modest (< 50%) rates of local control (LC) for STS at 2 years. To our knowledge, no prospective studies to date have evaluated the safety and efficacy of dose-escalated hypofractionated radiation therapy as treatment of inoperable STS. We hypothesized that dose-escalated, hypofractionated radiation therapy (RT) for inoperable STS could achieve higher rates of LC than reported in trials of conventionally fractionated RT.

MATERIALS/METHODS

An IRB-approved single institution prospective phase II clinical trial of dose-escalated, hypofractionated RT as local control for STS was designed and completed planned accrual. Exclusion criteria included anti-cancer systemic therapy within the preceding two weeks. Patients underwent hypofractionated RT utilizing either CT-guided radiation (24, 50%) or MRI-guided radiation treatments (24, 50%). Data on patient characteristics, RT dose and fractionation, LC, toxicity, and overall survival (OS) was collected. The primary endpoint was local tumor control (stable, partial, or complete response according to RECIST) at 2-years after completion of radiation. Secondary endpoints were acute and late toxicity, rates of complete response, 5-year local tumor control, and progression-free and overall survival. Acute toxicity was graded on the Common Terminology Criteria for Adverse Events (CTCAE) v5.0 scale during treatment and at 3 months following RT.

RESULTS

Forty-eight patients were enrolled, 17 with non-metastatic localized disease and 31 with metastatic disease. Median patient age was 64. Twenty-five men and 23 women were treated. Ninety-six total lesions were treated (36 lung, 7 extremity, 37 abdominopelvic, 16 other). Radiation dose per fraction ranged from 6-12 Gy for a total of 1-12 fractions (median dose was 52.5 Gy in 6 fractions. Median patient follow-up is 8.6 months (range 1 - 36 months). Six patients (13%) did not complete initial 3-month follow-up imaging. Of the 40 patients who have undergone 3-month follow up imaging, 32 (80%) had stable disease, 5 (12.5%) had partial response, 0 had complete response, and 3 (7.5%) had disease progression. Median PFS was 17.2 months at time of last follow up. Median OS was 12.9 months at time of last follow up. Twenty-five patients (52%) experienced an acute toxicity likely or possibly related to radiation. Three (6%) patients experienced CTACE grade 3 or greater treatment-related toxicity (pain, weakness, decreased range of motion, dermatitis).

CONCLUSION

In this initial report of a prospective, single-institution clinical trial of hypofractionated RT for STS not undergoing resection, we report low rates of acute grade 3 or greater toxicity and high rates of tumor response. We will continue to follow these patients to assess late toxicity and durability of tumor control.

Crowdsourcing Deep Learning Algorithms to Automatically Contour GI Luminal Organs on Serial MRIs

PURPOSE/OBJECTIVE(S)

A major barrier to a sustainable real-time adaptive MR-guided radiotherapy workflow is the time-consuming process of contouring the target and organs-at-risk (OARs) before the delivery of each fraction. While auto-contouring algorithms perform relatively well for many solid organs, the performance on luminal organs in the abdomen remain difficult due to the variability between patients and variability in daily shape and position. The purpose of this study is to evaluate the performance of crowdsourced deep learning algorithms to automatically contour GI luminal organs on serial MRIs.

MATERIALS/METHODS

The stomach, small intestines, and large intestines were manually contoured on MRIs from patients who had undergone radiotherapy on an MR-Linac by a team of radiation therapists and medical physicists and were verified by a board-certified radiation oncologist. The MRIs and the contours were de-identified and uploaded to Kaggle, an online machine learning competition platform with portion of the data open to the public as training data and the remaining data hidden as a test set. Prize money was offered to teams submitting the best auto-contouring algorithms based on the Dice coefficient and Hausdorff distance evaluation metrics. The average performance of the winning algorithm and of manual contours were compared using unpaired t-test.

RESULTS

Four hundred sixty-seven MRIs were collected from 107 patients who underwent 1-5 serial MRI sessions between 2015 and 2019. The most common anatomic site of treatment was the pancreas with 41 patients, followed by the liver with 38 patients. The manual contours of the stomach, small intestines, and large intestines on 4 representative MRIs had mean and standard deviation Dice coefficient of 0.90 +/- 0.02, 0.76 +/- 0.04, and 0.85 +/- 0.03 respectively and Hausdorff distance of 18.0 +/- 6.9, 35.5 +/- 12.6, and 32.3 +/- 12.3 mm respectively. The Kaggle competition was held from April to July 2022 and 1548 teams submitted algorithms for evaluation. The auto-contouring performance of the winning solution on the stomach, small intestines, and large intestines, when evaluated on a hold-out test set with 188 MRIs, had mean and standard deviation Dice coefficient of 0.92 +/- 0.04, 0.80 +/- 0.09, 0.85 +/- 0.08 respectively and Hausdorff distance of 15.2 +/- 11.2, 33.9 +/- 15.2, 34.8 +/- 20.3 mm respectively. Unpaired t-test was performed to compare the average performance across three organs of the human (N = 120) and of the algorithm (N = 564). The results suggest that average algorithm performance was statistically superior to manual contours for Dice (p = 0.01), yet not for Hausdorff (p = 0.64).

CONCLUSION

Crowdsourced deep learning algorithms to auto-contour GI luminal organs on serial MRIs perform superiorly compared to manual contours when using a Dice coefficient metric but not when using a Haudorff distance metric. These auto-contouring algorithms may be used to efficiently adapt radiotherapy plans according to the anatomy of the day for patients with abdominal tumors on MR-Linacs.

Neoadjuvant Stereotactic MR-Guided Ablative Radiation Therapy (SMART) and Surgical Outcomes in Patients with Pancreatic Cancer

PURPOSE/OBJECTIVE(S)

The benefit of neoadjuvant radiation therapy for patients undergoing surgery for pancreatic ductal adenocarcinoma (PDAC) remains unclear. Stereotactic MR-guided adaptive radiation therapy (SMART) treatment to ablative doses is a newer technique that is well tolerated and has increased local control in unresectable pancreatic cancer. For resectable pancreatic cancer, neoadjuvant SMART has the potential to decrease local recurrence risk and positive margin rates. However, there is concern for perioperative risks associated with ablative dose treatments. We report the efficacy and safety of surgical resection in patients who have received neoadjuvant SMART at our institution.

MATERIALS/METHODS

We conducted a retrospective analysis of all consecutive patients diagnosed with PDAC who had noted vascular involvement of the celiac axis, superior mesenteric, and/or portal vessels between January 2016 and December 2022 at a single, high-volume, academic institution. Perioperative events were defined according to the Clavien-Dindo classification. The Kaplan Meier method was applied to estimate disease free survival (DFS) and overall survival (OS).

RESULTS

Seventeen patients with PDAC and vessel involvement at time of diagnosis who received SMART were included. Median follow-up time was 14.3 months; all patients underwent surgery, at a median time after radiation of 28 days (range: 15 - 90). Median length of postoperative stay was 7 days (range: 3 - 15). Five patients (29%) underwent vascular resection. Fifteen patients (88%) achieved R0 resection, with two R1 resections noted at the SMA and pancreatic neck respectively. Seven patients (41%) had adverse events attributable to surgery, with the majority being defined as abscess or infection (n = 5; 29%). One (6%) Clavien-Dindo grade III or higher toxicity was observed - a cortical cerebrovascular event following surgery. No major bleeding events requiring surgical intervention were noted. At time of event censorship, there were no observable locoregional failures. The median DFS and OS were not reached; however, 1-year DFS and OS were 62% and 87%, respectively.

CONCLUSION

Neoadjuvant SMART appears to be safe, with low rates of surgical complications and promising outcomes. Further identification of patients for this approach requires additional investigation.

The Role of Stereotactic Body Radiation Therapy in the Management of Liver Metastases

The liver is a common site for metastatic spread for various primary tumor histologies. Stereotactic body radiation therapy (SBRT) is a non-invasive treatment technique with broad patient candidacy for the ablation of tumors in the liver and other organs. SBRT involves focused, high-dose radiation therapy delivered in one to several treatments, resulting in high rates of local control. Use of SBRT for ablation of oligometastatic disease has increased in recent years and emerging prospective data have demonstrated improvements in progression free and overall survival in some settings. When delivering SBRT to liver metastases, clinicians must balance the priorities of delivering ablative tumor dosing while respecting dose constraints to surrounding organs at risk (OARs). Motion management techniques are crucial for meeting dose constraints, ensuring low rates of toxicity, maintaining quality of life, and can allow for dose escalation. Advanced radiotherapy delivery approaches including proton therapy, robotic radiotherapy, and real-time MR-guided radiotherapy may further improve the accuracy of liver SBRT. In this article, we review the rationale for oligometastases ablation, the clinical outcomes with liver SBRT, tumor dose and OAR considerations, and evolving strategies to improve liver SBRT delivery.

Surgical outcomes after neoadjuvant ablative dose radiation among patients with borderline resectable and locally advanced pancreas cancer from the multi-institutional phase 2 Stereotactic MR-Guided Adaptive Radiation Therapy (SMART) trial

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Background: Acute grade 3+ toxicity was rare in the multi-institutional phase 2 stereotactic MR-guided on-table adaptive radiation therapy (SMART) trial (NCT03621644) for locally advanced and borderline resectable pancreatic cancer (LAPC/BRPC). Surgery may be considered after ablative SMART although the feasibility and safety of this is not well understood. Postoperative outcomes of the subset of patients in the SMART trial are examined here. Methods: Trial eligibility included BRPC or LAPC without metastases after a minimum of 3 months of induction chemotherapy. All patients received SMART prescribed to 50 Gy in 5 fractions using an integrated 0.35T MR-radiation therapy device equipped with cutting edge soft tissue tracking, automatic beam gating, and on-table adaptive replanning. Surgery was permitted after SMART, often after multi-disciplinary review. Perioperative details and postoperative outcomes, including morbidity, mortality, and overall survival (OS), were analyzed. Results: 136 patients across 13 sites were enrolled between 2019-2022. 44 patients (32.4%) had surgery after SMART (33 BRPC, 11 LAPC). Surgical procedures included pancreaticoduodenectomy (81.8%), distal pancreatectomy with splenectomy (9.1%), total pancreatectomy (6.8%), and distal pancreatectomy with celiac axis resection (2.3%). 52.3% required vascular resection/reconstruction, a majority of which were venous resections (65.2%), with a smaller proportion needing both venous/arterial (21.7%), or arterial (13%). Surgery was performed after a mean 51.4 ± 52.8 days from SMART. Postoperative hospitalization was 10.5 ± 8.9 days. Nine patients (20.5%) had Clavien-Dindo complications of grade III or higher; 3 deaths resulted from post-pancreatectomy hemorrhage in patients who had portal vein resection. One-year OS in patients who had surgery versus no surgery after SMART was 66% vs. 43%, respectively. Conclusions: These are the first prospectively evaluated surgical outcomes after 5-fraction ablative SMART for BRPC/LAPC. The rate of surgery for BRPC compares favorably to radiated patients on the Alliance A021501 trial. Despite the use of ablative radiation dose and frequent need for vascular resection, the incidence of serious surgical complications was similar to what is reported after non-ablative radiation therapy. However, several deaths occurred after surgery and we therefore we urge caution when considering surgery after ablative radiation therapy. Further analysis of other variables such as the time between SMART and surgery, approaches to vascular resections, and discrete events such as delayed gastric emptying, operative duration, and post-operative pancreatic fistula are needed to better understand the surgical morbidity seen in these patients. Clinical trial information: NCT03621644 .

Phase Ib of pembrolizumab (pem) in combination with stereotactic body radiotherapy (SBRT) for resectable liver oligometastatic MMR-proficient (pMMR) colorectal cancer (CRC): Final results

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Background: SBRT is a standard treatment option for oligometastatic CRC and is associated with an increase in immunogenic antigen release and influx of immune cells. We hypothesized that radiation would enhance the immunogenicity of pMMR CRC and potentiate the effectiveness of PD-1 blockade. This phase Ib study examined the safety and efficacy of the sequential combination of SBRT and Pem in patients (pts) undergoing resection of their disease. Additionally, the accumulation and proteolysis of versican (VCAN), an immunoregulatory tumor matrix proteoglycan was examined as a novel immunotherapy biomarker. Proteolysis of VCAN results in the release of an immunostimulatory fragment, versikine. Cancers with low VCAN and high versikine (VCAN proteolysis predominant (VPP)) are hypothesized to respond better to immunotherapies. Methods: Eligibility criteria included resectable liver-confined metastatic pMMR CRC. Prior surgery and systemic chemotherapy were allowed. Subjects received sequential SBRT and cycle 1 of Pem prior to operative management and adjuvant Pem. The primary objectives were to determine the safety/tolerability of this regimen and the recurrence free survival (RFS) at 1 year following operative management. Correlative studies examined tumor infiltrating CD8+ T lymphocytes (TILs), VCAN, and versikine using immunohistochemistry. Results: 15 pts (median age 61.5 [range 39-69], 26% female) were enrolled. All pts had prior FOLFOX. The number of liver lesions ranged from 1-6. SBRT median dose was 50 Gy (40-60 Gy) to 1-2 liver lesions. Grade 3/4 AEs included one case of biliary tract injury and biloma, and one case of G3 hypophosphatemia. No grade 3/4 immune-related AEs occurred. All pts completed a minimum follow-up of 1 year post resection (median follow-up 41 months [range 15-64]). In the intention to treat analysis, the 1 year RFS was 67% (historic control 50%), 40% of patients remained cancer free, and 67% of pts are still alive. 2 of 3 pts with BRAF V600E mutations have had early recurrences. 2 pts had VCAN high tumors and both recurred prior to 1 year. 6 pts had VPP cancers and 83% were recurrence free at 1 year and 66% are currently without evidence of cancer. Conclusions: The combination of SBRT with Pem was well tolerated with no signal of increased immunotherapy-related toxicity. This study met its primary endpoint and this regimen deserves further investigation in confirmatory studies. Additionally, VCAN accumulation and proteolysis are promising biomarkers in this setting. Clinical trial information: NCT02837263 .

A Predictive Model of 2yDFS During MR-Guided RT Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer Patients

Purpose

Distant metastasis is the main cause of treatment failure in locally advanced rectal cancer (LARC) patients, despite the recent improvement in treatment strategies. This study aims to evaluate the “delta radiomics” approach in patients undergoing neoadjuvant chemoradiotherapy (nCRT) treated with 0.35-T magnetic resonance-guided radiotherapy (MRgRT), developing a logistic regression model able to predict 2-year disease-free-survival (2yDFS).

Methods

Patients affected by LARC were enrolled in this multi-institutional study. A predictive model of 2yDFS was developed taking into account both clinical and radiomics variables. Gross tumour volume (GTV) was delineated on the magnetic resonance (MR) images acquired during MRgRT, and 1,067 radiomic features (RF) were extracted using the MODDICOM platform. The performance of RF in predicting 2yDFS was investigated in terms of the Wilcoxon–Mann–Whitney test and area under receiver operating characteristic (ROC) curve (AUC).

Results

48 patients have been retrospectively enrolled, with 8 patients (16.7%) developing distant metastases at the 2-year follow-up. A total of 1,099 variables (1,067 RF and 32 clinical variables) were evaluated in two different models: radiomics and radiomics/clinical. The best-performing 2yDFS predictive model was a delta radiomics one, based on the variation in terms of area/surface ratio between biologically effective doses (BED) at 54 Gy and simulation (AUC of 0.92).

Conclusions

The results of this study suggest a promising role of delta radiomics analysis on 0.35-T MR images in predicting 2yDFS for LARC patients. Further analyses including larger cohorts of patients and an external validation are needed to confirm these preliminary results.

Combining Stereotactic Body Radiotherapy and Microwave Ablation Appears Safe and Feasible for Renal Cell Carcinoma in an Early Series

Microwave (MW) ablation and stereotactic body radiation therapy (SBRT) are both used in treating inoperable renal cell carcinoma (RCC). MW ablation and SBRT have potentially complementary advantages and limitations. Combining SBRT and MW ablation may optimize tumor control and toxicity for patients with larger (> 5 cm) RCCs or those with vascular involvement. Seven patients with RCC were treated at our institution with combination of SBRT and MW ablation, median tumor size of 6.4 cm. Local control was 100% with a median follow-up of 15 months. Four patients experienced grade 2 nausea during SBRT. Three patients experienced toxicities after MW ablation, 2 with grade 1 hematuria and 1 with grade 3 retroperitoneal bleed/collecting system injury. Median eGFR (estimated glomerular filtration rate) preceding and following SBRT and MW ablation was 69 mL/min/1.73 m² and 68 mL/min/1.73 m² (P = .19), respectively. In patients who are not surgical candidates, larger RCCs or those with vascular invasion are challenging to treat. Combination treatment with SBRT and MW ablation may balance the risks and benefits of both therapies and demonstrates high local control in our series. MW ablation and SBRT have potentially complementary advantages and limitations.

Diagnostic Performance of MRI for Esophageal Carcinoma: A Systematic Review and Meta-Analysis

Background Although CT, endoscopic US, and PET are critical in determining the appropriate management of esophageal carcinoma (squamous cell carcinoma and adenocarcinoma), previous reports show that staging accuracy remains low, particularly for nodal involvement sensitivity. Purpose To perform a systematic review and meta-analysis to determine the diagnostic performance of MRI for multiple staging thresholds in patients with biopsy-proven esophageal carcinoma (differentiation of stage T0 disease from stage T1 or higher disease, differentiation of stage T2 or lower disease from stage T3 or higher disease, and differentiation of stage N0 disease from stage N1 or higher disease [where T refers to tumor stage and N refers to nodal stage]). Materials and Methods Studies of the diagnostic performance of MRI in determining the stage of esophageal carcinoma in patients before esophagectomy and pathologic staging between 2000 and 2019 were searched in PubMed, Scopus, Web of Science, and Cochrane Library by a librarian and radiation oncologist. Pooled diagnostic performance of MRI was calculated with a bivariate random effects model. Bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies (version 2) tool. Results Twenty studies with a total of 984 patients were included in the analysis. Pooled accuracy for stage T0 versus stage T1 or higher had a sensitivity of 92% (95% CI: 82, 96) and a specificity of 67% (95% CI: 51, 81). Pooled accuracy for stage T2 or lower versus stage T3 or higher had a sensitivity of 86% (95% CI: 76, 92) and a specificity of 86% (95% CI: 75, 93). Pooled accuracy for stage N0 versus stage N1 or higher had a sensitivity of 71% (95% CI: 60, 80) and a specificity of 72% (95% CI: 64, 79). The concern for applicability was low for the patient selection, index test, and reference test domains, except for 10% of studies (two of 20) that had unclear concern for patient selection applicability. Conclusion MRI has high sensitivity but low specificity for the detection of esophageal carcinoma, which shows promise for determining neoadjuvant therapy response and for detecting locally advanced disease for potential trimodality therapy. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Leeflang in this issue.

In Silico Single-Fraction Stereotactic Ablative Radiation Therapy for the Treatment of Thoracic and Abdominal Oligometastatic Disease With Online Adaptive Magnetic Resonance Guidance

Purpose

Although SABR can improve oncologic outcomes for patients with oligometastatic disease, treatment of metastases near critical organs remains challenging. The purpose of this study is to determine the dosimetric feasibility of delivering magnetic resonance imaging (MRI)-guided adaptive SABR in a single fraction for abdominal and thoracic metastases.

Methods and Materials

Previously delivered MRI-guided radiation therapy plans for 20 patients with oligometastatic disease in the thorax or abdomen, with 70% (14/20) of the lesions within 8 mm from dose-limiting organs at risk (OARs), were used to simulate the delivery of 24 Gy in a single fraction. Planning objectives included planning target volume (PTV) V_95% >90%, optimized PTV (PTVopt) V_95% >90%, and PTVopt D_99% >20 Gy with no OAR dose violations, where PTVopt removed overlap with nearby planning organ at risk volume (PRV). Single-fraction plans were simulated on the first 5 daily setup breath-hold MRI scans, and the plans were reoptimized to consider variations in setup position and anatomy.

Results

The mean PTV V_95% for single-fraction SABR plans was lower compared with multifraction plans (mean 85.4% vs 92.6%, P = .02), but mean PTVopt V_95% was not different (95.3% vs 98.2%, P = .62). After reoptimization of the single-fraction plan to the treatment day MRI, there was an increase in mean PTV V_95% (85.0% vs 88.1%, P = .05), increase in mean PTVopt V_95% (92.7% vs 96.3%, P = .02), increase in mean PTVopt D_99% (19.7 Gy vs 23.8 Gy, P < .01), increase in mean frequency of meeting PTV D_99% >20 Gy (52% vs 87%, P < .01), and increase in mean gross tumor volume minimum dose (17.5 Gy vs 19.3 Gy, P < .01). Reoptimization decreased mean frequency of OAR dose constraint violation (48% vs 0%, P < .01).

Conclusions

Single-fraction MRI-guided SABR is a dosimetrically feasible treatment for oligometastases that allows for on-table adaptation to avoid OAR dose constraint violations, but this method requires clinical validation.

Evaluating dose constraints for radiation induced liver damage following magnetic resonance image guided Stereotactic Body radiotherapy

This study reports dose corresponding to visible radiation induced liver damage following Stereotactic Body Radiation Therapy (SBRT) for liver metastasis, and the optimal time for follow up scans using post radiation imaging. Diagnostic magnetic resonance scans of nine patients treated with liver SBRT using a 0.35 T MRI-guided radiotherapy system were analyzed. The dice coefficients between the region of visible liver damage and the delivered dose were calculated. A median dose of 35 Gy correlated most closely with the visible radiation induced liver damage. We compared scans over two to nine months and observed maximal dice coefficients at two to five months post radiation. We have presented a new method for developing treatment planning guidelines for liver SBRT.

Reduction of cardiac dose using respiratory-gated MR-linac plans for gastro-esophageal junction cancer

Treatment of locally advanced adenocarcinoma of the gastroesophageal junction (GEJ) with chemoradiation may be associated with high rates of symptomatic cardiac toxicity. Large margins are typically required to ensure coverage of GEJ tumors with free-breathing volumetric modulated arc therapy (VMAT) radiotherapy. The purpose of this study is to determine whether treatment with tighter margins enabled by maximum-inhalation breath hold (MIBH)-gated intensity modulated radiation therapy (IMRT) on an integrated MRI-linear accelerator system (MR-linac) can decrease radiation doses to the heart and cardiac substructures. Ten patients with locally advanced GEJ adenocarcinoma underwent both free breathing 4-dimensional computed tomography (4DCT) and MIBH MRI simulation scans. MR-linac IMRT plans were created with a 3 mm clinical target volume (CTV) to planning target volume (PTV) isotropic margin and 4DCT VMAT plans were created with a 11, 13, and 9 mm CTV to PTV anisotropic margins in the left-right, cranial-caudal, and anterior-posterior directions according to GEJ-specific PTV expansion recommendations by Voncken et al. Prescription dose to PTV was 50.4 Gy in 28 fractions. Dosimetry to the heart and cardiac substructures was compared with paired t test; p < 0.05 was considered significant. Mean PTV on the MR-linac IMRT plans was significantly smaller compared to the 4DCT VMAT plans (689 cm³vs 1275 cm³, p < 0.01). Mean dose to the heart and all cardiac substructures was significantly lower in the MR-linac IMRT plans compared to the 4DCT VMAT plans: heart 20.9 Gy vs 27.8 Gy, left atrium 29.6 Gy vs 39.4 Gy, right atrium 20.5 Gy vs 25.6 Gy, left ventricle 21.6 Gy vs 29.6 Gy, and right ventricle 18.7 Gy vs 25.2 Gy (all p values <0.05). MIBH-gated MR-linac IMRT treatment of locally advanced GEJ adenocarcinoma can significantly decrease doses to the heart and cardiac substructures and this may translate to reduced rates of cardiac toxicity.

A Phase 1 Dose Escalation Study of Neoadjuvant SBRT Plus Elective Nodal Radiation with Concurrent Capecitabine for Resectable Pancreatic Cancer

PURPOSE

The role of neoadjuvant radiation for resectable pancreatic adenocarcinoma is controversial. We performed a prospective dose-escalation study of neoadjuvant stereotactic body radiation therapy (SBRT) with concurrent capecitabine and elective nodal irradiation (ENI) followed by surgical resection to explore the toxicity and feasibility of this approach.

METHODS AND MATERIALS

Patients with biopsy proven, resectable cancers of the pancreatic head were enrolled. A 4 + 4 dose-escalation design was employed delivering 5 fractions of 5 to 7 Gy to primary tumor with concurrent capecitabine. The maximum tolerated dose level was expanded for an additional 4 patients. Patients at all dose levels were treated with ENI delivering 25 Gy in 5 fractions. Dose-limiting toxicity was defined as any grade ≥3 nonhematologic toxicity (National Cancer Institute Common Terminology Criteria for Adverse Events v4.0) attributable to chemoradiation occurring within 90 days of SBRT.

RESULTS

A total of 17 patients were enrolled with 16 patients evaluable and 13 patients ultimately proceeding to surgery. The most common toxicity was nausea (56%). There were no dose-limiting toxicities, and SBRT was maximally dose escalated to 35 Gy in 5 fractions for 8 patients. All patients completing surgery had R0 resections. Seven patients (54%) had moderate treatment effect identified in pathologic specimens. Three patients (23%) developed locoregional recurrences, with 2 (15%) partially included within the treated volume.

CONCLUSIONS

SBRT was safely dose escalated to 35 Gy in 5 fractions along with concurrent capecitabine and ENI. This regimen will be used in a future expansion cohort.

External Validation of Early Regression Index (ERITCP) as Predictor of Pathologic Complete Response in Rectal Cancer Using Magnetic Resonance-Guided Radiation Therapy

PURPOSE

Tumor control probability (TCP)-based early regression index (ERI_TCP) is a radiobiological parameter that showed promising results in predicting pathologic complete response (pCR) on T2-weighted 1.5 T magnetic resonance (MR) images of patients with locally advanced rectal cancer. This study aims to validate the ERI_TCP in the context of low-tesla MR-guided radiation therapy, using images acquired with different magnetic field strength (0.35 T) and image contrast (T2/T1). Furthermore, the optimal timing for pCR prediction was estimated, calculating the ERI index at different biologically effective dose (BED) levels.

METHODS AND MATERIALS

Fifty-two patients with locally advanced rectal cancer treated with neoadjuvant chemoradiation therapy were enrolled in this multi-institutional retrospective study. For each patient, a 0.35 T T2/T1-weighted MR image was acquired during simulation and on each treatment day. Gross tumor volume was contoured according to International Commission on Radiation Units Report 83 guidelines. According to the original definition, ERI_TCP was calculated considering the residual tumor volume at BED = 25 Gy. ERI was also calculated in correspondence with several BED levels: 13, 21, 32, 40, 46, 54, 59, and 67. The predictive performance of the different ERI indices were evaluated in terms of receiver operating characteristic curve. The robustness of ERI_TCP with respect to the interobserver variability was also evaluated considering 2 operators and calculating the intraclass correlation index.

RESULTS

Fourteen patients showed pCR. ERI_TCP correctly 47 of 52 cases (accuracy = 90%), showing good results in terms of sensitivity (86%), specificity (92%), negative predictive value (95%), and positive predictive value (80%). The analysis at different BED levels shows that the best predictive performance is obtained when this parameter is calculated at BED = 25 Gy (area under the curve = 0.93). ERI_TCP results are robust with respect to interobserver variability (intraclass correlation index = 0.99).

CONCLUSIONS

This study confirmed the validity and the robustness of ERI_TCP as a pCR predictor in the context of low-tesla MR-guided radiation therapy and indicate 25 Gy as the best BED level to perform predictions.

MRI-guided adaptive radiotherapy for liver tumours: visualising the future

MRI-guided radiotherapy is a novel and rapidly evolving technology that might enhance the risk-benefit ratio. Through direct visualisation of the tumour and the nearby healthy tissues, the radiation oncologist can deliver highly accurate treatment even to mobile targets. Each individual treatment can be customised to changing anatomy, potentially reducing the risk of radiation-related toxicities while simultaneously increasing the dose delivered to the tumour. MRI-guided radiotherapy offers a new tool for the radiation oncologist, and creates an opportunity to achieve durable local control of liver tumours that might not otherwise be possible. Future work will allow us to expand the population eligible for curative-intent radiotherapy, optimise and customise radiation doses to specific tumours, and hopefully create opportunities for improving outcomes through machine learning and radiomics-based approaches. This Review outlines the current and future applications for MRI-guided radiotherapy with respect to metastatic and primary liver cancers.

Investigating split-filter dual-energy CT for improving liver tumor visibility for radiation therapy

Purpose

Accurate liver tumor delineation is crucial for radiation therapy, but liver tumor volumes are difficult to visualize with conventional single‐energy CT. This work investigates the use of split‐filter dual‐energy CT (DECT) for liver tumor visibility by quantifying contrast and contrast‐to‐noise ratio (CNR).

Methods

Split‐filter DECT contrast‐enhanced scans of 20 liver tumors including cholangiocarcinomas, hepatocellular carcinomas, and liver metastases were acquired. Analysis was performed on the arterial and venous phases of mixed 120 kVp‐equivalent images and VMIs at 57 keV and 40 keV gross target volume (GTV) contrast and CNR were calculated.

Results

For the arterial phase, liver GTV contrast was 12.1 ± 10.0 HU and 43.1 ± 32.3 HU (P < 0.001) for the mixed images and 40 keV VMIs. Image noise increased on average by 116% for the 40 keV VMIs compared to the mixed images. The average CNR did not change significantly (1.6 ± 1.5, 1.7 ± 1.4, 2.4 ± 1.7 for the mixed, 57 keV and 40 keV VMIs (P > 0.141)). For individual cases, however, CNR increases of up to 607% were measured for the 40 keV VMIs compared to the mixed image. Venous phase 40 keV VMIs demonstrated an average increase of 35.4 HU in GTV contrast and 121% increase in image noise. Average CNR values were also not statistically different, but for individual cases CNR increases of up to 554% were measured for the 40 keV VMIs compared to the mixed image.

Conclusions

Liver tumor contrast was significantly improved using split‐filter DECT 40 keV VMIs compared to mixed images. On average, there was no statistical difference in CNR between the mixed images and VMIs, but for individual cases, CNR was greatly increased for the 57 keV and 40 keV VMIs. Therefore, although not universally successful for our patient cohort, split‐filter DECT VMIs may provide substantial gains in tumor visibility of certain liver cases for radiation therapy treatment planning.

The transformation of radiation oncology using real-time magnetic resonance guidance: A review

Radiation therapy (RT) is an essential component of effective cancer care and is used across nearly all cancer types. The delivery of RT is becoming more precise through rapid advances in both computing and imaging. The direct integration of magnetic resonance imaging (MRI) with linear accelerators represents an exciting development with the potential to dramatically impact cancer research and treatment. These impacts extend beyond improved imaging and dose deposition. Real-time MRI-guided RT is actively transforming the work flows and capabilities of virtually every aspect of RT. It has the opportunity to change entirely the delivery methods and response assessments of numerous malignancies. This review intends to approach the topic of MRI-based RT guidance from a vendor neutral and international perspective. It also aims to provide an introduction to this topic targeted towards oncologists without a speciality focus in RT. Speciality implications, areas for physician education and research opportunities are identified as they are associated with MRI-guided RT. The uniquely disruptive implications of MRI-guided RT are discussed and placed in context. We further aim to describe and outline important future changes to the speciality of radiation oncology that will occur with MRI-guided RT. The impacts on RT caused by MRI guidance include target identification, RT planning, quality assurance, treatment delivery, training, clinical workflow, tumour response assessment and treatment scheduling. In addition, entirely novel research areas that may be enabled by MRI guidance are identified for future investigation.

STAT-ART: The Promise and Practice of a Rapid Palliative Single Session of MR-Guided Online Adaptive Radiotherapy (ART)

This work describes a novel application of MR-guided online adaptive radiotherapy (MRgoART) in the management of patients whom urgent palliative care is indicated using statum-adaptive radiotherapy (STAT-ART). The implementation of STAT-ART, as performed at our institution, is presented including a discussion of the advantages and limitations compared to the standard of care for palliative radiotherapy on conventional c-arm linacs. MR-based treatment planning techniques of STAT-ART for density overrides and deformable image registration (DIR) of diagnostic CT to the treatment MR are also addressed.

Patient-Derived Cancer Organoid Cultures to Predict Sensitivity to Chemotherapy and Radiation

PURPOSE

Cancer treatment is limited by inaccurate predictors of patient-specific therapeutic response. Therefore, some patients are exposed to unnecessary side effects and delays in starting effective therapy. A clinical tool that predicts treatment sensitivity for individual patients is needed.

EXPERIMENTAL DESIGN

Patient-derived cancer organoids were derived across multiple histologies. The histologic characteristics, mutation profile, clonal structure, and response to chemotherapy and radiation were assessed using bright-field and optical metabolic imaging on spheroid and single-cell levels, respectively.

RESULTS

We demonstrate that patient-derived cancer organoids represent the cancers from which they were derived, including key histologic and molecular features. These cultures were generated from numerous cancers, various biopsy sample types, and in different clinical settings. Next-generation sequencing reveals the presence of subclonal populations within the organoid cultures. These cultures allow for the detection of clonal heterogeneity with a greater sensitivity than bulk tumor sequencing. Optical metabolic imaging of these organoids provides cell-level quantification of treatment response and tumor heterogeneity allowing for resolution of therapeutic differences between patient samples. Using this technology, we prospectively predict treatment response for a patient with metastatic colorectal cancer.

CONCLUSIONS

These studies add to the literature demonstrating feasibility to grow clinical patient-derived organotypic cultures for treatment effectiveness testing. Together, these culture methods and response assessment techniques hold great promise to predict treatment sensitivity for patients with cancer undergoing chemotherapy and/or radiation.

Using adaptive magnetic resonance image-guided radiation therapy for treatment of inoperable pancreatic cancer

Background

Adaptive magnetic resonance imaging‐guided radiation therapy (MRgRT) can escalate dose to tumors while minimizing dose to normal tissue. We evaluated outcomes of inoperable pancreatic cancer patients treated using MRgRT with and without dose escalation.

Methods

We reviewed 44 patients with inoperable pancreatic cancer treated with MRgRT. Treatments included conventional fractionation, hypofractionation, and stereotactic body radiation therapy. Patients were stratified into high‐dose (biologically effective dose [BED₁₀] >70) and standard‐dose groups (BED₁₀ ≤70). Overall survival (OS), freedom from local failure (FFLF) and freedom from distant failure (FFDF) were evaluated using Kaplan‐Meier method. Cox regression was performed to identify predictors of OS. Acute gastrointestinal (GI) toxicity was assessed for 6 weeks after completion of RT.

Results

Median follow‐up was 17 months. High‐dose patients (n = 24, 55%) had statistically significant improvement in 2‐year OS (49% vs 30%, P = 0.03) and trended towards significance for 2‐year FFLF (77% vs 57%, P = 0.15) compared to standard‐dose patients (n = 20, 45%). FFDF at 18 months in high‐dose vs standard‐dose groups was 24% vs 48%, respectively (P = 0.92). High‐dose radiation (HR: 0.44; 95% confidence interval [CI]: 0.21‐0.94; P = 0.03) and duration of induction chemotherapy (HR: 0.84; 95% CI: 0.72‐0.98; P = 0.03) were significantly correlated with OS on univariate analysis but neither factor was independently predictive on multivariate analysis. Grade 3+ GI toxicity occurred in three patients in the standard‐dose group and did not occur in the high‐dose group.

Conclusions

Patients treated with dose‐escalated MRgRT demonstrated improved OS. Prospective evaluation of high‐dose RT regimens with standardized treatment parameters in inoperable pancreatic cancer patients is warranted.

A phase Ib study of pembrolizumab (Pem) in combination with stereotactic body radiotherapy (SBRT) for resectable liver metastatic colorectal cancer (CRC)

680

Background: Adjunctive therapies are essential to enhance the effect of anti-PD1 therapies for the treatment of microsatellite stable (MSS) colorectal cancer. SBRT is utilized to treat liver metastatic CRC, causing an increase in immunogenic intratumoral and a rapid influx of responding immune cells. We hypothesize that radiation enhances immunogenicity of MSS CRC and potentiates effectiveness of PD-1 blockade. This phase Ib study examines the safety and efficacy of the sequential combination of SBRT and Pem in patients for whom the goal is to resect all sites of known disease. Methods: Key eligibility criteria include MSS CRC with liver-confined metastatic disease with the therapeutic goal of resection of all radiographic disease with one operation. Subjects must be a candidate for SBRT to 1-3 liver metastases. Prior surgery and systemic chemotherapy are allowed. Subjects receive sequential SBRT and cycle 1 of Pem prior to operative management. Postoperatively, patients complete cycles 2-9 of Pem followed by scheduled surveillance with imaging every 12 weeks. The primary objectives are to determine the safety of this regimen and the recurrence rate at one year following clearance of metastatic disease. Secondary objectives include time to recurrence, DFS, and OS. Results: Nine patients (median age 61.5 [range 39-69]) have completed the intended neoadjuvant therapy, operative management and at least one adjuvant cycle of Pem. All patients received prior FOLFOX. Any-grade AEs (> 20%) through cycle 2 of Pem attributable to SBRT include fatigue (44%) and nausea (22%). Any-grade AEs related to Pem include lymphopenia (25%). Postoperative AEs included one case of biliary tract injury and biloma, not related to immunotherapy. One patient developed a rash following SBRT and Pem which may be an immunotherapy-related toxicity. No grade 3/4 immunotherapy AEs have occurred. Conclusions: The combination of SBRT, Pem, and surgical resection is well tolerated with no signal of increased immunotherapy-related toxicity. Clinical trial information: NCT02837263.

Investigating a novel split-filter dual-energy CT technique for improving pancreas tumor visibility for radiation therapy

Purpose

Tumor delineation using conventional CT images can be a challenge for pancreatic adenocarcinoma where contrast between the tumor and surrounding healthy tissue is low. This work investigates the ability of a split‐filter dual‐energy CT (DECT) system to improve pancreatic tumor contrast and contrast‐to‐noise ratio (CNR) for radiation therapy treatment planning.

Materials and methods

Multiphasic scans of 20 pancreatic tumors were acquired using a split‐filter DECT technique with iodinated contrast medium, OMNIPAQUE^TM. Analysis was performed on the pancreatic and portal venous phases for several types of DECT images. Pancreatic gross target volume (GTV) contrast and CNR were calculated and analyzed from mixed 120 kVp‐equivalent images and virtual monoenergetic images (VMI) at 57 and 40 keV. The role of iterative reconstruction on DECT images was also investigated. Paired t‐tests were used to assess the difference in GTV contrast and CNR among the different images.

Results

The VMIs at 40 keV had a 110% greater image noise compared to the mixed 120 kVp‐equivalent images (P < 0.0001). VMIs at 40 keV increased GTV contrast from 15.9 ± 19.9 HU to 93.7 ± 49.6 HU and CNR from 1.37 ± 2.05 to 3.86 ± 2.78 in comparison to the mixed 120 kVp‐equivalent images. The iterative reconstruction algorithm investigated decreased noise in the VMIs by about 20% and improved CNR by about 30%.

Conclusions

Pancreatic tumor contrast and CNR were significantly improved using VMIs reconstructed from the split‐filter DECT technique, and the use of iterative reconstruction further improved CNR. This gain in tumor contrast may lead to more accurate tumor delineation for radiation therapy treatment planning.

Abstract 3146: Versican proteolysis: A novel immunostimulatory component of CD8+ T cell responses to colorectal cancer

Background: Infiltration of CD8+ T cells has shown important prognostic implications in colorectal cancers (CRC). Our group has recently correlated proteolysis of an extracellular matrix proteoglycan, versican (VCAN), with infiltration of CRCs by CD8+ T cells. Cleavage by ADAMTS proteases generates a bioactive fragment of versican, versikine (VKINE). VKINE stimulates Batf3-driven dendritic cell activation and maturation, which are critical for immunotherapy efficacy.

Methods: CT26 murine CRC cells were transfected to constitutively express VKINE. BALB/c mice between 50 and 70 days of age were orthotopically injected with either 105 empty vector (CT26-EV) or VKINE-expressing (CT26-VKINE) cells. Tumor growth was tracked weekly with colonoscopy and growth rate assessed using percent lumen occlusion. Mice were euthanized and dissected once moribund. Tissues were formalin-fixed and paraffin-embedded (FFPE). Immunohistochemical (IHC) staining was performed using standard procedures. Additionally, FFPE samples from human CRC liver metastases (n=9) were obtained under the University of Wisconsin Translational Science Biocore Institutional Review Board-approved protocol and IHC performed for VCAN, VKINE and CD8. The number of CD8+ tumor-infiltrating lymphocytes (TILs) per high-powered field (HPF) within the malignant epithelium was calculated using four separate 400x magnification fields of view.

Results: CT26-EV and CT26-VKINE injected mice both had a ~70% tumor initiation rate and these tumors averaged ~50% lumen occlusion by 14 days post injection. Survival data for each group were compared using a log-rank test. A trend towards improved survival was observed in those mice injected with CT26-VKINE (average survival of 27 days for CT26-VKINE compared to 22 days for CT26-EV, p=0.41, n=13). The average number of CD8+ TILs for each tumor were compared. For mice with CT26-VKINE, the average number of CD8+ TILs per HPF was 7.6, compared to 4.7 for mice with CT26-EV (p=0.39).

Human CRC liver metastases were analyzed for VCAN, VKINE, and CD8+ T cells. Several lesions had little to no VCAN staining, whereas others had intense pockets or peripheral staining. VKINE staining was more abundant in metastatic CRC lesions than in primary lesions. CD8+ T cells were excluded in the setting of increased VCAN staining and infiltration was noted specifically in areas of VCAN proteolysis (low VCAN and high VKINE staining). These areas of proteolysis were more often present at the tumor margin and correlated with ADAMTS1 expression.

Conclusions: Immunotherapies offer a unique treatment option for cancer patients, but their use is limited in CRC. VCAN proteolysis and the generation of bioactive VKINE has potential to influence the ability of CD8+ T cells to infiltrate the tumor in both primary and metastatic CRC, indicating the potential to utilize VCAN and VKINE as immune biomarkers or therapeutic targets.

Citation Format: Philip B. Emmerich, Susan N. Payne, Connor J. Maloney, Rosabella T. Pitera, Hanna Rainiero, Gioia Sha, Athanasios T. Papadas, Adam C. Pagenkopf, Michael F. Bassetti, Kristina A. Matkowskyj, Fotis Asimakopoulos, Dustin A. Deming. Versican proteolysis: A novel immunostimulatory component of CD8+ T cell responses to colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3146.

Abstract 5011: Patient-derived organotypic cancer spheroids (PDOCS) as predictive models for the treatment of cancer in a clinically meaningful time frame

Background: Standard two-dimensional cell cultures do not retain the key characteristics of the human cancers from which they are derived and treatment effects are not always able to be replicated in vivo, making the development of alternative culturing systems paramount. Specifically, commercially available cell lines do not fully represent the mutation profiles seen in human cancers. Here we investigate the feasibility of three-dimensional PDOCS to more accurately represent the cancers from which they are derived and to predict treatment sensitivity in a clinically meaningful time frame.

Methods: Surgical resection, core needle biopsies, paracentesis or thoracentesis samples from patients with various types of cancer were obtained under an approved IRB protocol, digested and spheroid cultures grown suspended in Matrigel. PDOCS were grown for up to two weeks and passaged at least once prior to treatment. PDOCS were imaged using brightfield imaging (4X) prior to treatment with vehicle or 5-fluorouracil (5-FU; 1, 10, or 100 µM) and/or radiation (2 or 5 Gy). After 2 days of treatment, the 5-FU was removed and the cultures were allowed to grow for an additional 2 days. PDOCS were re-imaged and the relative change in diameter was calculated using ImageJ software and compared to untreated controls. Optical metabolic imaging (OMI) was performed with a multiphoton microscope to probe the fluorescence lifetime and optical redox ratio of metabolic co-enzymes NAD(P)H and FAD. Single-cell analysis of each image was completed using Cell Profiler software to parse resistant cell populations in each PDOCS sample tested. DNA for mutation profile analysis was isolated and sequenced using a QIAseq targeted panel.

Results: PDOCS were successfully isolated from a variety of cancers including colorectal (CRC), pancreas, lung, neuroendocrine, liver, breast, and ovarian. Key phenotypic characteristics of the tumors were retained in PDOCS cultured including crypt-like structures, mucin production and Ki67 proliferation rates. Cancer hot spot sequencing was performed comparing PDOCS and the tumors from which they were derived. Over 90% of the nonsynonymous mutations were identical, except in the setting of microsatellite instability. All driver mutations were identical (i.e., APC, KRAS, PIK3CA, TP53). Differential sensitivity to chemoradiation was observed among 4 different colorectal PDOCS treated with 5-FU and radiation (Median % PDOCS diameter change vs control: Patient A 17.1, p=0.64; Patient B -3.05, p=0.02; Patient C -19.4, p=2x10-5; Patient D -31.3, p=0.002). Similar response data were determined using OMI; however, single-cell analyses identified potentially resistant cell populations.

Conclusions: PDOCS retain key characteristics of the cancers from which they are derived and can be utilized for treatment sensitivity testing in a clinically meaningful time frame.

Citation Format: Cheri A. Pasch, Peter F. Favreau, Alex E. Yueh, Kwang P. Nickel, Christopher P. Babiarz, Philip B. Emmerich, Rosabella T. Pitera, Susan N. Payne, Demetra P. Korkos, Joseph T. Sharick, Carley M. Sprackling, Linda Clipson, Kristina A. Matkowskyj, Michael A. Newton, Melissa C. Skala, Michael F. Bassetti, Randall J. Kimple, Dustin A. Deming. Patient-derived organotypic cancer spheroids (PDOCS) as predictive models for the treatment of cancer in a clinically meaningful time frame [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5011.

RTAnswers Online Patient Education Materials Deviate From Recommended Reading Levels

OBJECTIVE

Patients are turning to the Internet more often for cancer-related information. Oncology organizations need to ensure that appropriately written information is available for patients online. The aim of this study was to determine whether the readability of radiation oncology online patient information (OPI) provided by RTAnswers (RTAnswers.org, created by the American Society for Radiation Oncology) is written at a sixth-grade level as recommended by the National Institutes of Health (NIH), the U.S Department of Health and Human Services (HHS), and the American Medical Association (AMA).

METHODS

RTanswers.org was accessed and online patient-oriented brochures for 13 specific disease sites were analyzed. Readability of OPI from RTAnswers was assessed using 10 common readability tests: New Dale-Chall Test, Flesch Reading Ease Score, Coleman-Liau Index, Flesch-Kinkaid Grade Level, FORCAST test, Fry Score, Simple Measure of Gobbledygook, Gunning Frequency of Gobbledygook, New Fog Count, and Raygor Readability Estimate.

RESULTS

A composite grade level of readability was constructed using the 8 readability measures that provide a single grade-level output. The grade levels computed by each of these 8 tests were highly correlated (SI alpha = 0.98). The composite grade level for these disease site-specific brochures was 11.6 ± 0.83, corresponding to a senior in high school, significantly higher than the target sixth-grade level (p < 0.05) recommended by the NIH, HHS, and AMA.

CONCLUSION

Patient educational material provided by RTAnswers.org is written significantly above the target reading level. Simplifying and rewording this information could improve patients' understanding of radiation therapy and improve treatment adherence and outcomes.

A New Era of Image Guidance with Magnetic Resonance-guided Radiation Therapy for Abdominal and Thoracic Malignancies

Magnetic resonance-guided radiation therapy (MRgRT) offers advantages for image guidance for radiotherapy treatments as compared to conventional computed tomography (CT)-based modalities. The superior soft tissue contrast of magnetic resonance (MR) enables an improved visualization of the gross tumor and adjacent normal tissues in the treatment of abdominal and thoracic malignancies. Online adaptive capabilities, coupled with advanced motion management of real-time tracking of the tumor, directly allow for high-precision inter-/intrafraction localization. The primary aim of this case series is to describe MR-based interventions for localizing targets not well-visualized with conventional image-guided technologies. The abdominal and thoracic sites of the lung, kidney, liver, and gastric targets are described to illustrate the technological advancement of MR-guidance in radiotherapy.

Pancreatic gross tumor volume contouring on computed tomography (CT) compared with magnetic resonance imaging (MRI): Results of an international contouring conference

PURPOSE

Accurate identification of the gross tumor volume (GTV) in pancreatic adenocarcinoma is challenging. We sought to understand differences in GTV delineation using pancreatic computed tomography (CT) compared with magnetic resonance imaging (MRI).

METHODS AND MATERIALS

Twelve attending radiation oncologists were convened for an international contouring symposium. All participants had a clinical and research interest in pancreatic adenocarcinoma. CT and MRI scans from 3 pancreatic cases were used for contouring. CT and MRI GTVs were analyzed and compared. Interobserver variability was compared using Dice's similarity coefficient (DSC), Hausdorff distances, and Jaccard indices. Mann-Whitney tests were used to check for significant differences. Consensus contours on CT and MRI scans and constructed count maps were used to visualize the agreement. Agreement regarding the optimal method to determine GTV definition using MRI was reached.

RESULTS

Six contour sets (3 from CT and 3 from MRI) were obtained and compared for each observer, totaling 72 contour sets. The mean volume of contours on CT was significantly larger at 57.48 mL compared with a mean of 45.76 mL on MRI, P = .011. The standard deviation obtained from the CT contours was significantly larger than the standard deviation from the MRI contours (P = .027). The mean DSC was 0.73 for the CT and 0.72 for the MRI (P = .889). The conformity index measurement was similar for CT and MRI (P = .58). Count maps were created to highlight differences in the contours from CT and MRI.

CONCLUSIONS

Using MRI as a primary image set to define a pancreatic adenocarcinoma GTV resulted in smaller contours compared with CT. No differences in DSC or the conformity index were seen between MRI and CT. A stepwise method is recommended as an approach to contour a pancreatic GTV using MRI.

Readability of Online Patient Educational Resources Found on NCI-Designated Cancer Center Web Sites

BACKGROUND

The NIH and Department of Health & Human Services recommend online patient information (OPI) be written at a sixth grade level. We used a panel of readability analyses to assess OPI from NCI-Designated Cancer Center (NCIDCC) Web sites.

METHODS

Cancer.gov was used to identify 68 NCIDCC Web sites from which we collected both general OPI and OPI specific to breast, prostate, lung, and colon cancers. This text was analyzed by 10 commonly used readability tests: the New Dale-Chall Readability Formula, Flesch Reading Ease scale, Flesch-Kinaid Grade Level, FORCAST scale, Fry Readability Graph, Simple Measure of Gobbledygook test, Gunning Frequency of Gobbledygook index, New Fog Count, Raygor Readability Estimate Graph, and Coleman-Liau Index. We tested the hypothesis that the readability of NCIDCC OPI was written at the sixth grade level. Secondary analyses were performed to compare readability of OPI between comprehensive and noncomprehensive centers, by region, and to OPI produced by the American Cancer Society (ACS).

RESULTS

A mean of 30,507 words from 40 comprehensive and 18 noncomprehensive NCIDCCs was analyzed (7 nonclinical and 3 without appropriate OPI were excluded). Using a composite grade level score, the mean readability score of 12.46 (ie, college level: 95% CI, 12.13-12.79) was significantly greater than the target grade level of 6 (middle-school: P<.001). No difference between comprehensive and noncomprehensive centers was identified. Regional differences were identified in 4 of the 10 readability metrics (P<.05). ACS OPI provides easier language, at the seventh to ninth grade level, across all tests (P<.01).

CONCLUSIONS

OPI from NCIDCC Web sites is more complex than recommended for the average patient.

Dosimetric Comparison of Real-Time MRI-Guided Tri-Cobalt-60 Versus Linear Accelerator-Based Stereotactic Body Radiation Therapy Lung Cancer Plans

Purpose:

Magnetic resonance imaging–guided radiation therapy has entered clinical practice at several major treatment centers. Treatment of early-stage non-small cell lung cancer with stereotactic body radiation therapy is one potential application of this modality, as some form of respiratory motion management is important to address. We hypothesize that magnetic resonance imaging–guided tri-cobalt-60 radiation therapy can be used to generate clinically acceptable stereotactic body radiation therapy treatment plans. Here, we report on a dosimetric comparison between magnetic resonance imaging–guided radiation therapy plans and internal target volume–based plans utilizing volumetric-modulated arc therapy.

Materials and Methods:

Ten patients with early-stage non-small cell lung cancer who underwent radiation therapy planning and treatment were studied. Following 4-dimensional computed tomography, patient images were used to generate clinically deliverable plans. For volumetric-modulated arc therapy plans, the planning tumor volume was defined as an internal target volume + 0.5 cm. For magnetic resonance imaging–guided plans, a single mid-inspiratory cycle was used to define a gross tumor volume, then expanded 0.3 cm to the planning tumor volume. Treatment plan parameters were compared.

Results:

Planning tumor volumes trended larger for volumetric-modulated arc therapy–based plans, with a mean planning tumor volume of 47.4 mL versus 24.8 mL for magnetic resonance imaging–guided plans (P = .08). Clinically acceptable plans were achievable via both methods, with bilateral lung V20, 3.9% versus 4.8% (P = .62). The volume of chest wall receiving greater than 30 Gy was also similar, 22.1 versus 19.8 mL (P = .78), as were all other parameters commonly used for lung stereotactic body radiation therapy. The ratio of the 50% isodose volume to planning tumor volume was lower in volumetric-modulated arc therapy plans, 4.19 versus 10.0 (P < .001). Heterogeneity index was comparable between plans, 1.25 versus 1.25 (P = .98).

Conclusion:

Magnetic resonance imaging–guided tri-cobalt-60 radiation therapy is capable of delivering lung high-quality stereotactic body radiation therapy plans that are clinically acceptable as compared to volumetric-modulated arc therapy–based plans. Real-time magnetic resonance imaging provides the unique capacity to directly observe tumor motion during treatment for purposes of motion management.

Radiation Dose Escalation in Esophageal Cancer Revisited: A Contemporary Analysis of the National Cancer Data Base, 2004 to 2012

PURPOSE

To evaluate the effect of radiation dose escalation on overall survival (OS) for patients with nonmetastatic esophageal cancer treated with concurrent radiation and chemotherapy.

METHODS AND MATERIALS

Patients diagnosed with stage I to III esophageal cancer treated from 2004 to 2012 were identified from the National Cancer Data Base. Patients who received concurrent radiation and chemotherapy with radiation doses of ≥50 Gy and did not undergo surgery were included. OS was compared using Cox proportional hazards regression and propensity score matching.

RESULTS

A total of 6854 patients were included; 3821 (55.7%) received 50 to 50.4 Gy and 3033 (44.3%) received doses >50.4 Gy. Univariate analysis revealed no significant difference in OS between patients receiving 50 to 50.4 Gy and those receiving >50.4 Gy (P=.53). The dose analysis, binned as 50 to 50.4, 51 to 54, 55 to 60, and >60 Gy, revealed no appreciable difference in OS within any group compared with 50 to 50.4 Gy. Subgroup analyses investigating the effect of dose escalation by histologic type and in the setting of intensity modulated radiation therapy also failed to reveal a benefit. Propensity score matching confirmed the absence of a statistically significant difference in OS among the dose levels. The factors associated with improved OS on multivariable analysis included female sex, lower Charlson-Deyo comorbidity score, private insurance, cervical/upper esophagus location, squamous cell histologic type, lower T stage, and node-negative status (P<.01 for all analyses).

CONCLUSIONS

In this large national cohort, dose escalation >50.4 Gy did not result in improved OS among patients with stage I to III esophageal cancer treated with definitive concurrent radiation and chemotherapy. These data suggest that despite advanced contemporary treatment techniques, OS for patients with esophageal cancer remains unaltered by escalation of radiation dose >50.4 Gy, consistent with the results of the INT-0123 trial. Furthermore, these data highlight that many radiation oncologists have not embraced the concept that dose escalation does not improve OS. Although local control, not investigated in the present study, might benefit from dose escalation, novel therapies are needed to improve the OS of patients with esophageal cancer.

Online patient information from radiation oncology departments is too complex for the general population

PURPOSE

Nearly two-thirds of cancer patients seek information about their diagnosis online. We assessed the readability of online patient education materials found on academic radiation oncology department Web sites to determine whether they adhered to guidelines suggesting that information be presented at a sixth-grade reading level.

METHODS AND MATERIALS

The Association of American Medical Colleges Web site was used to identify all academic radiation oncology departments in the United States. One-third of these department Web sites were selected for analysis using a random number generator. Both general information on radiation therapy and specific information regarding various radiation modalities were collected. To test the hypothesis that the readability of these online educational materials was written at the recommended grade level, a panel of 10 common readability tests was used. A composite grade level of readability was constructed using the 8 readability measures that provide a single grade-level output.

RESULTS

A mean of 5605 words (range, 2058-12,837) from 30 department Web sites was collected. Using the composite grade level score, the overall mean readability level was determined to be 13.36 (12.83-13.89), corresponding to a collegiate reading level. This was significantly higher than the target sixth-grade reading level (middle school, t (29) = 27.41, P < .001).

CONCLUSIONS

Online patient educational materials from academic radiation oncology Web sites are significantly more complex than recommended by the National Institutes of Health and the Department of Health and Human Services. To improve patients' comprehension of radiation therapy and its role in their treatment, our analysis suggests that the language used in online patient information should be simplified to communicate the information at a more appropriate level.

Translational investigations of gastrointestinal malignancies using spheroid cultures

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Background: Spheroid cultures are now being used to investigate the biology of multiple types of cancer. This technique allows for a cost-effective, efficient and reliable means to culture tissues of interest. Recent investigations have demonstrated that spheroids maintain high mutational concordance with the cancers they are derived. We sought to determine if spheroid techniques could be utilized to perform translational investigations into subtypes of gastrointestinal malignancies. Methods: Transgenic mice carrying conditional mutations in key genes known to have important roles in colorectal cancer (CRC) tumorigenesis and progression were treated with a Cre-expressing adenovirus to initiate tumorigenesis. The mutant genes of interest included Apc, Trp53, KRAS, Pik3ca, and/or BRAF. Biopsies of these cancers were obtained with the murine endoscope and the tissue processed for spheroid culture. In addition, transgenic E6 and E7 mice were treated with DMBA and the resulting anal squamous cell carcinomas were harvested for spheroid culture. Cultured spheroids were imaged to characterize growth rate and changes in architecture. In addition, studies assessing response to therapeutics were performed and correlated with in vivo response. Human operative specimens were also obtained for culturing. Results: Multiple lines of murine CRC spheroids were able to be generated with a greater than 90% efficiency rate. These cultures maintained phenotypic characteristics of the cancers from which they were derived. Bright field imaging pre- and post-treatment was able to be utilized for quantification of treatment response. The median relative change in spheroid diameter was compared across treatment groups and correlated with response in vivo. Heterogeneity in the response of individual spheroids to treatment strategies was detected with this method. Murine squamous cell anal carcinoma was spheroid lines were generated similarly. Human CRC and anal cancers were also generated with high efficiency. Conclusions: Spheroid cultures from CRC and anal cancers can be generated with high efficiency and hold great promise for furthering treatment options for patients with cancer.

Intracellular CD24 disrupts the ARF-NPM interaction and enables mutational and viral oncogene-mediated p53 inactivation

CD24 is overexpressed in nearly 70% human cancers, whereas TP53 is the most frequently mutated tumour-suppressor gene that functions in a context-dependent manner. Here we show that both targeted mutation and short hairpin RNA (shRNA) silencing of CD24 retard the growth, progression and metastasis of prostate cancer. CD24 competitively inhibits ARF binding to NPM, resulting in decreased ARF, increase MDM2 and decrease levels of p53 and the p53 target p21/CDKN1A. CD24 silencing prevents functional inactivation of p53 by both somatic mutation and viral oncogenes, including the SV40 large T antigen and human papilloma virus 16 E6-antigen. In support of the functional interaction between CD24 and p53, in silico analyses reveal that TP53 mutates at a higher rate among glioma and prostate cancer samples with higher CD24 mRNA levels. These data provide a general mechanism for functional inactivation of ARF and reveal an important cellular context for genetic and viral inactivation of TP53.

P53 is a tumour suppressor that is frequently mutated or downregulated in cancer. Here, Wang et al. show that CD24, a molecule frequently overexpressed in cancer, promotes p53 degradation by disrupting a regulatory ARF–MDM2 interaction, and silencing CD24 prevents the downregulation of p53.

Ipilimumab and radiation therapy for melanoma brain metastases

Ipilimumab, an antibody that enhances T-cell activation, may augment immunogenicity of tumor cells that are injured by radiation therapy. We hypothesized that patients with melanoma brain metastasis treated with both ipilimumab and radiotherapy would have improved overall survival, and that the sequence of treatments may affect disease control in the brain. We analyzed the clinical and radiographic records of melanoma patients with brain metastases who were treated with whole brain radiation therapy or stereotactic radiosurgery between 2005 and 2012. The hazard ratios for survival were estimated to assess outcomes as a function of ipilimumab use and radiation type. Seventy patients were identified, 33 of whom received ipilimumab and 37 who did not. The patients who received ipilimumab had a censored median survival of 18.3 months (95% confidence interval 8.1–25.5), compared with 5.3 months (95% confidence interval 4.0–7.6) for patients who did not receive ipilimumab. Ipilimumab and stereotactic radiosurgery were each significant predictors of improved overall survival (hazard ratio = 0.43 and 0.45, with P = 0.005 and 0.008, respectively). Four of 10 evaluable patients (40.0%) who received ipilimumab prior to radiotherapy demonstrated a partial response to radiotherapy, compared with two of 22 evaluable patients (9.1%) who did not receive ipilimumab. Ipilimumab is associated with a significantly reduced risk of death in patients with melanoma brain metastases who underwent radiotherapy, and this finding supports the need for multimodality therapy to optimize patient outcomes. Prospective studies are needed and are underway.