Characterization of DNA Damage Response-Associated Somatic Mutations in Borderline Resectable and Locally Advanced Pancreatic Cancer

PURPOSE/OBJECTIVE(S)

The role of radiation for pancreatic cancer remains controversial, with recent studies showing conflicting results, highlighting the need to develop biomarkers of radiation response. Despite its potential utility in predicting radiosensitivity, the landscape of somatic mutations in borderline resectable pancreatic cancer (BRPC) and locally advanced pancreatic cancer (LAPC), as related to DNA damage response (DDR), has not been well characterized. This study aimed to characterize the frequency of such mutations in a cohort of patients with BRPC/LAPC treated with neoadjuvant chemotherapy and stereotactic body radiotherapy (SBRT).

MATERIALS/METHODS

Mutational data was collected from patients with BRPC/LAPC treated at a single institution with neoadjuvant chemotherapy and SBRT, followed by surgical resection from 2016-2021. Chemotherapy consisted of modified FOLFIRINOX or gemcitabine/nab-paclitaxel, and patients were treated with SBRT in 33 Gy in 5 fractions. Genomic data was obtained from either endoscopic biopsy or surgical specimens, and next-generation sequencing was performed either in-house with a Solid Tumor Panel or with FoundationOne CDx. Specific emphasis was placed on the characterization of double-strand DNA break (DSB) repair genes, as this is the type of tumor cell damage traditionally induced by radiation therapy. Genes associated with the two main pathways of DSB repair, non-homologous end joining (NHEJ) and homologous repair (HR), were analyzed. Specific HR pathway mutations assessed were BLM, BRCA1/2, MRE11, NBN, PALB2, RAD50, RAD51B-D, and RAD54L, while PRKDC mutations were assessed for the NHEJ pathway. Mutations in ATM, an important initiator of DDR pathways, were also analyzed. Additionally, the frequency of mutations in TP53, CDKN2A and SMAD4 in patients with concomitant KRAS mutations was assessed.

RESULTS

Eighty-five patients were included in the study. Five (5.9%) patients had mutations in the NHEJ pathway of the PRKDC gene. Twenty (23.5%) patients had mutations in the HR pathway, including BRCA2 (10/85; 11.8%), PALB2 (5/85; 5.9%), BRCA1 (3/85; 3.5%), and RAD50 (1/85; 1.2%). Six (7.1%) patients had mutations in ATM. No patients were found to have mutations in BLM, RAD51B-D, RAD54L, or NBN. Amongst patients with KRAS mutations (72/85), concomitant mutations were observed in TP53 (47/85; 55.3%), CDKN2A (16/85; 18.8%), and SMAD4 (9/85; 10.6%).

CONCLUSION

Herein, we characterized the frequency of somatic mutations associated with DSB repair genes in patients with BRPC/LAPC. Data analysis on outcomes related to radiation response in patients with mutations in DDR pathways is ongoing, but will likely also benefit from multi-institutional efforts to increase the power to answer this question.

Pancreas Cancer Learning Health Network Established to Share Best Practice Across 14 Centers and Improve Patient Outcomes

PURPOSE/OBJECTIVE(S)

Pancreas cancer (PC) survival is among the lowest of all malignancies. Clinical trials have failed to significantly improve outcomes. Individual and institutional biases in care result in significant variation in practice, further hindering progress. Learning health networks (LHNs) prospectively collect real world data across centers and test improvements that can rapidly be expanded across centers if deemed successful. Herein, we report preliminary progress from the Pancreas Cancer Canopy Cancer Collective (PC-CCC), the first oncology LHN, established to improve duration and quality of survival in PC.

MATERIALS/METHODS

In 2019, we established the PC-CCC with six care centers who engaged in a collaborative design process to create a set of improvement aims, change ideas, and outcome measures. Center team members receive training and coaching in collaborative quality improvement methods, applied to local improvement efforts. Eight more centers joined in 2021, and a shared Canopy outcomes database was built and implemented to inform center-specific and network-wide improvement efforts and allow the LHN to undertake research using real-world data. Current improvement efforts are focused on proactively screening new PC patients for: (1) Clinical trials, (2) pancreas enzymes, (3) palliative care needs, and (4) goals of care conversations.

RESULTS

Currently, 14 care centers are active participants in the PC-CCC LHN. Data on a total of 2,002 PC patients are available to date. At presentation to the care center, most patients are female (51%) and have biopsy proven PC (83.9%). Average age is 68 years, and presenting disease status is metastatic (14.5%), resectable (11.4%), locally advanced (10.9%), borderline resectable (8.1%), or not yet staged (40%). For those who received radiation, 75.8% received stereotactic body radiation therapy. Among patients whose chemotherapy regimen was documented, most received 5-fluorouracilbased treatment (52%). Descriptive follow up data (including treatment and outcomes) are being actively updated, to be reported at time of presentation.

CONCLUSION

Creation of a cancer LHN for PC is feasible and has set the stage for improving patient and provider outcomes through iterative community-building, continuous improvement, and sharing of data and multidisciplinary best practices. Additionally, the data obtained from the CCC database can rapidly inform the network how variation in clinical practice across centers can influence outcomes.

Correlation of DPC4 status with outcomes in pancreatic adenocarcinoma patients receiving adjuvant chemoradiation

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Background: In an autopsy series of patients with advanced pancreatic cancer (PCA), loss of DPC4 was highly correlated with disseminated metastasis. The purpose of this study was to determine if DPC4 gene status predicts for survival and patterns of recurrence following adjuvant (adj) chemoradiation (CRT).

Methods: 101 patients who underwent surgery followed by adjuvant 5-FU or gemcitabine-based CRT were studied. Imaging studies were reviewed to assess patterns of recurrence and tumor tissue obtained to determine DPC4 immunolabeling status. DPC4 status was graded as intact or lost/mutated. Kaplan-Meier estimates were used to compute survival and Cox proportional hazards were used to compare risk factors.

Results: Median overall (mOS) and progression-free survival (PFS) was 22.6 mos (95% CI 18.8 to 31.6) and 14.0 mos (95% CI 11.5 to 18.4). The mOS and 1-yr OS for patients with DPC4 intact vs. lost status was 21.9 mos (95% CI 16.8-32.4) and 78.4% vs. 22.6 mos (95% CI 18.4-32.6) and 78.2%, respectively (HR: 1.05, p=0.82). After adjusting for node, margin status, tumor grade, tumor size, and age, DPC4 status did not predict for mOS (RR 1.04, 95% CI: 0.62-1.74, p=0.89). Time to first progression at any site for PCA with DPC4 intact vs. lost status was 13.8 vs. 14.0 mos (p=0.79). Local recurrence was more common in PCA with DPC4 loss than with intact status (34.4% vs. 13.7%, p=0.012). There was no difference in the rates of distant recurrence in PCA with intact vs. loss of DPC4 expression (62.8% vs. 55.7%, p=0.45); however, DPC4 loss was more commonly associated with liver recurrence (27.9% vs. 19.6%, p=0.31).

Conclusions: In pancreatic cancer patients receiving adj CRT, loss of DPC4 labeling in their resected PCA indicates a greater likelihood of developing local recurrence despite having received adj CRT. Efforts to improve loco-regional control are therefore needed for these patients following surgery and adj CRT.

No significant financial relationships to disclose.