Stereotactic MR-Guided Radiotherapy for Pancreatic Tumors: Dosimetric Benefit of Adaptation and First Clinical Results in a Prospective Registry Study

Morgan Michalet; Karl Bordeau; Marie Cantaloube; Simon Valdenaire; Pierre Debuire; Sebastien Simeon; Fabienne Portales; Roxana Draghici; Marc Ychou; Eric Assenat; Marie Dupuy; Sophie Gourgou; Pierre-Emmanuel Colombo; Sebastien Carrere; François-Regis Souche; Norbert Aillères; Pascal Fenoglietto; David Azria; Olivier Riou

doi:10.3389/fonc.2022.842402

Stereotactic MR-Guided Radiotherapy for Pancreatic Tumors: Dosimetric Benefit of Adaptation and First Clinical Results in a Prospective Registry Study

Front Oncol. 2022 Mar 9:12:842402. doi: 10.3389/fonc.2022.842402. eCollection 2022.

Authors

Morgan Michalet¹, Karl Bordeau¹, Marie Cantaloube¹, Simon Valdenaire¹, Pierre Debuire¹, Sebastien Simeon¹, Fabienne Portales², Roxana Draghici¹, Marc Ychou², Eric Assenat³, Marie Dupuy³, Sophie Gourgou⁴, Pierre-Emmanuel Colombo⁵, Sebastien Carrere⁵, François-Regis Souche⁶, Norbert Aillères¹, Pascal Fenoglietto¹, David Azria¹, Olivier Riou¹

Affiliations

¹ University Federation of Radiation Oncology of Mediterranean Occitanie, Montpellier Cancer Institute (ICM), Univ Montpellier, INSERM U1194 Institut de Recherche en Cancérologie de Montpellier (IRCM), Montpellier, France.
² Medical Oncology Department, Institut du Cancer de Montpellier (ICM), Montpellier Cancer Institute, Univ Montpellier, Montpellier, France.
³ Medical Oncology Department, Centre Hospitalier Universitaire (CHU) St Eloi, Montpellier, France.
⁴ Biometrics Unit Institut du Cancer de Montpellier (ICM), Montpellier Cancer Institute, Univ Montpellier, Montpellier, France.
⁵ Digestive Surgery Department, Institut du Cancer de Montpellier (ICM), Montpellier Cancer Institute, Univ Montpellier, Montpellier, France.
⁶ Surgical Department, Centre Hospitalier Universitaire (CHU) St Eloi, Montpellier, France.

Abstract

Introduction: Stereotactic MR-guided adaptive radiotherapy (SMART) is an attractive modality of radiotherapy for pancreatic tumors. The objectives of this prospective registry study were to report the dosimetric benefits of daily adaptation of SMART and the first clinical results in pancreatic tumors.

Materials and methods: All patients treated in our center with SMART for a pancreatic tumor were included. Patients were planned for five daily-adapted fractions on consecutive days. Endpoints were acute toxicities, late toxicities, impact of adaptive treatment on target volume coverage and organs at risk (OAR) sparing, local control (LC) rate, distant metastasis-free survival (DMFS), and overall survival (OS).

Results: Thirty consecutive patients were included between October 2019 and April 2021. The median dose prescription was 50 Gy. No patient presented grade > 2 acute toxicities. The most frequent grade 1-2 toxicities were asthenia (40%), abdominal pain (40%), and nausea (43%). Daily adaptation significantly improved planning target volume (PTV) and gross tumor volume (GTV) coverage and OAR sparing. With a median follow-up of 9.7 months, the median OS, 6-month OS, and 1-year OS were 14.1 months, 89% (95% CI: 70%-96%), and 75% (95% CI: 51%-88%), respectively, from SMART completion. LC at 6 months and 1 year was respectively 97% (95% CI: 79-99.5%) and 86% (95% CI: 61%-95%). There were no grade > 2 late toxicities. With a median follow-up of 10.64 months, locally advanced pancreatic cancer (LAPC) and borderline resectable pancreatic cancer (BRPC) patients (22 patients) had a median OS, 6-month OS, and 1-year OS from SMART completion of 14.1 months, 76% (95% CI: 51%-89%), and 70% (95% CI: 45%-85%), respectively. Nine patients underwent surgical resection (42.1% of patients with initial LAPC and 33.3% of patients with BRPC), with negative margins (R0). Resected patients had a significantly better OS as compared to unresected patients (p = 0.0219, hazard ratio (HR) = 5.78 (95% CI: 1.29-25.9)).

Conclusion: SMART for pancreatic tumors is feasible without limiting toxicities. Daily adaptation demonstrated a benefit for tumor coverage and OAR sparing. The severity of observed acute and late toxicities was low. OS and LC rates were promising. SMART achieved a high secondary resection rate in LAPC patients. Surgery after SMART seemed to be feasible and might increase OS in these patients.

Keywords: adaptive radiotherapy; borderline resectable pancreatic cancers; image guided radiotherapy (IGRT); locally advanced pancreatic cancer; pancreatic cancer; pancreatic tumors; stereotactic MR-guided adaptive radiotherapy; stereotactic body radiation therapy.