Outcomes of Moderately Dose Escalated Hypofractionated Chemoradiation for Pancreatic Cancer

PURPOSE/OBJECTIVE(S)

A modestly hypofractionated course of chemoradiation (CRT) consisting of 36 Gy/15 fractions (F) concurrent with gemcitabine used in PREOPANC and phase II trials has become increasingly common for the treatment of borderline resectable (BR) and locally advanced (LA) pancreatic cancer (PC). Achieving an R0 resection remains a key prognostic factor in PC. We tested whether escalating dose beyond standard dosing (SD) of 36-39 Gy/15 F (or 50-54 Gy/25-30 F) would improve R0 resection rates and outcomes while respecting nearby organs at risk.

MATERIALS/METHODS

This was a retrospective analysis of consecutive patients at our institution from 2012-2022 with BR/LA PC treated with moderate dose escalated (MDE) (45 Gy/15 F, N = 45) or SD (36-39 Gy/15 F, N = 68 or 50-54 Gy/25-30 F, N = 25) CRT. For MDE, a 5 mm expansion from the duodenum, small bowel, and stomach was created (GI_PRV); PTV was cropped from this structure and prescribed 45 Gy/15 F. The primary endpoint was R0 resection rate with secondary endpoints of cumulative incidence of local progression (LP, recurrence after surgery/imaging progression if no surgery) with death as a competing risk (LP after occurrence of distant metastasis [DM] were still captured), cumulative incidence of DM, and overall survival (OS). Univariable and multivariable competing risks regression analyses were performed to determine the association between baseline covariates and LP.

RESULTS

We identified 45 patients treated with MDE and 93 treated with SD. Most patients presented with BR disease (55.6% MDE; 54.8% SD) and received neoadjuvant chemotherapy with FOLFIRINOX (98% MDE; 99% SD). All patients in the MDE group and 99% in the SD group received concurrent chemotherapy with gemcitabine used most often (96% MDE; 77% SD). Median follow-up was 17 m (IQR 13-27 m). Surgical resection rates were similar between groups (33.3% MDE vs. 39.8% SD, p = 0.46). Amongst patients that had surgery, R0 resection rates were non-significantly higher in the MDE group (73.3% vs. 47.4%, p = 0.09). Cumulative incidence of LP at 18 m was significantly lower in the MDE group (9.0% vs. 24.8%, p = 0.04). No difference in rates of DM (51.2% MDE vs. 59.6% SD, p = 0.92) or OS at 18 m (53.9% vs. 53.6%, p = 0.89) were observed. On multivariable analysis, MDE (HR = 0.39, p = 0.03) and pancreatic head location (HR = 0.51, p = 0.04) were the only factors independently associated with LP. Rates of grade 2+ gastrointestinal toxicity during CRT (20% MDE vs. 20.9% SD, p = 0.91) and ≤90 days of completing CRT (11.6% MDE vs. 14.8%, p = 0.62) were similar between groups, as were rates of grade 3+ hematologic toxicity (52.3% MDE vs. 41.3% SD, p = 0.23).

CONCLUSION

In this single institutional study, we found MDE is a simple, safe, and effective strategy associated with improved local control, higher R0 resection rates, and similar toxicity to SD CRT for patients with BR/LA PC. Further prospective data is needed to clarify the role of dose-escalated RT in the management of this lethal malignancy.

Added Value of Next Generation over Sanger Sequencing in Kenyan Youth with Extensive HIV-1 Drug Resistance

HIV-1 drug resistance testing in children and adolescents in low-resource settings is both important and challenging. New (more sensitive) drug resistance testing technologies may improve clinical care, but evaluation of their added value is limited. We assessed the potential added value of using next-generation sequencing (NGS) over Sanger sequencing for detecting nucleoside reverse transcriptase inhibitor (NRTI) and nonnucleoside reverse transcriptase inhibitor (NNRTI) drug resistance mutations (DRMs). Participants included 132 treatment-experienced Kenyan children and adolescents with diverse HIV-1 subtypes and with already high levels of drug resistance detected by Sanger sequencing. We examined overall and DRM-specific resistance and its predicted impact on antiretroviral therapy and evaluated the discrepancy between Sanger sequencing and six NGS thresholds (1%, 2%, 5%, 10%, 15%, and 20%). Depending on the NGS threshold, agreement between the two technologies was 62% to 88% for any DRM, 83% to 92% for NRTI DRMs, and 73% to 94% for NNRTI DRMs, with more DRMs detected at low NGS thresholds. NGS identified 96% to 100% of DRMs detected by Sanger sequencing, while Sanger identified 83% to 99% of DRMs detected by NGS. Higher discrepancy between technologies was associated with higher DRM prevalence. Even in this resistance-saturated cohort, 12% of participants had higher, potentially clinically relevant predicted resistance detected only by NGS. These findings, in a young, vulnerable Kenyan population with diverse HIV-1 subtypes and already high resistance levels, suggest potential benefits of more sensitive NGS over existing technology. Good agreement between technologies at high NGS thresholds supports their interchangeable use; however, the significance of DRMs identified at lower thresholds to patient care should be explored further. IMPORTANCE HIV-1 drug resistance in children and adolescents remains a significant problem in countries facing the highest burden of the HIV epidemic. Surveillance of HIV-1 drug resistance in children and adolescents is an important public health strategy, particularly in resource-limited settings, and yet, it is limited due mostly to cost and infrastructure constraints. Whether newer and more sensitive next-generation sequencing (NGS) adds substantial value beyond traditional Sanger sequencing in detecting HIV-1 drug resistance in real life settings remains an open and debatable question. In this paper, we attempt to address this issue by performing a comprehensive comparison of drug resistance identified by Sanger sequencing and six NGS thresholds. We conducted this study in a well-characterized, vulnerable cohort of children and adolescents living with diverse HIV-1 subtypes in Kenya and, importantly, failing antiretroviral therapy (ART) with already extensive drug resistance. Our findings suggest a potential added value of NGS over Sanger even in this unique cohort.