By Manisha Palta, MD, and Albert Koong, MD, PhD
The role of radiation therapy (RT) in pancreatic cancer is rapidly evolving. Until recently, 3-D conformal RT was the primary technique for treating patients. However, the emergence of intensity-modulated radiation therapy (IMRT) has allowed greater dose conformality, resulting in reduced dose to organs at risk. Together with advancements in simulation and image guidance, these developments have facilitated the use of hypofractionated RT, including stereotactic body RT. Simultaneously, more effective systemic therapies have also been developed. As these systemic therapies improve overall survival, local regional treatments like RT and surgery have become more important.
To address the questions surrounding RT for patients with pancreatic cancer, ASTRO launched a guideline on this topic, published online in Practical Radiation Oncology on August 29. The guideline task force comprised of not only radiation oncologists, including those working in community practice and Veterans Affairs and a resident representative, but also members from medical and surgical oncology, medical physics and the patient community. The guideline considered indications for RT in the adjuvant, neoadjuvant and definitive settings, along with doses, target volumes and sequencing with systemic therapies. It also made recommendations on simulation and treatment planning, technique and use of prophylactic medications to mitigate toxicity. Recommendations are rated as either strong or conditional, and the quality of the evidence is also graded for each recommendation.
For conventionally fractionated RT, the task force made a conditional recommendation supporting its use in the adjuvant setting if patients have high-risk features such as positive lymph nodes and margins. It conditionally recommended neoadjuvant RT in patients with borderline resectable tumors following chemotherapy, as well as RT as an option for definitive therapy in those with locally advanced disease. In addition, for borderline and locally advanced pancreatic cancer, SBRT is conditionally recommended. However, the task force recognized that ongoing clinical trials, including the Alliance for Clinical Trials in Oncology study, may provide new data for patients with borderline pancreatic cancer.
For RT simulation, the guideline recommends that patient-specific motion assessment should be utilized along with image guidance. Use of IMRT is recommended for treatment delivery.
Finally, there was strong consensus, even with limited clinical data, that patients undergoing RT for pancreatic cancer should receive prophylactic anti-nausea medications and agreement that patients may benefit from anti-acid or acid-reducing drugs.
Throughout the guideline, the task force sought to promote a patient-centered approach that integrates the patient's values, preferences and ability to tolerate short and late toxicities, and how those considerations are balanced against outcomes like local control. Given the many controversies and nuances of RT, it is especially important that every patient who might be appropriate for RT have a nuanced discussion with a radiation oncologist about the risks and benefits of RT, ideally in a multidisciplinary setting that also includes a surgeon and a medical oncologist.
Although many of the current guideline recommendations are conditional recommendations, reflecting limitations in the available data, ongoing and recently completed trials continue to add to the evidence available to make decisions on RT for pancreatic cancer and may alter the guideline in future years.