By Laura Williamson, Science Writer
This year’s Plenary session included the presentation of five abstracts with four discussants, and focused largely on promising new advances in delivering radiation therapy faster and more effectively while better preserving patients’ quality of life. The session was moderated by Andrea Ng, MD, MPH, FASTRO, Dana-Farber Brigham Cancer Center in Boston and Kenneth Rosenzweig, MD, FASTRO, Icahn School of Medicine, Mount Sinai in New York City.
Dr. Ng introduced the first presenter, Vinai Gondi, MD, as one of two recipients of the 2023 Leibel Memorial Award, given to early- to mid-career American Board of Radiology-certified or board-eligible principal investigators. Dr. Gondi presented his study, “Primary endpoint results of NRG CC003: Phase IIR/III trial of prophylactic cranial irradiation (PCI) with or without hippocampal avoidance (HA) for small cell lung cancer (SCLC).” The study found hippocampal avoidance — a common practice in treating people with small cell lung cancer whose cancer has spread to the brain — was non-inferior for intracranial relapse risk following prophylactic cranial irradiation (PCI) and prevented first failure in any cognitive domain.
Discussant Debra Yeboa, MD, MD Anderson Cancer Center in Houston, noted that prior investigations of the neuroprotective efficacy of hippocampal avoidance during PCI had led to conflicting results. “This study essentially serves as the tie breaker,” she said.
Next, Jiayi Yu, PhD, presented the abstract, “High dose Hyperfractionated Thoracic Radiotherapy vs Standard Dose for Limited Stage Small-Cell Lung Cancer: a Multicenter, Open Label, Randomized Phase 3 Trial.” This study, conducted at 16 public hospitals in China, found that compared to a standard radiotherapy dose of 45 Gy, a twice-daily, higher dose of 54 Gy improved overall survival and progression-free survival without increasing toxicities in people with limited stage small-cell lung cancer over a median follow-up time of 45 months.
Discussant Kristin Higgins, MD, Winship Cancer Institute of Emory University in Atlanta, noted that this was an important study because it was the first phase 3 trial of twice-daily dose escalation for people with small-cell lung cancer. However, unlike people with this type of cancer in the U.S., the majority of patients in this study were not smokers and were under 70 years old. They also experienced low levels of esophagitis, which she found “puzzling.”
“It was a carefully selected patient population,” Dr. Higgins said, “and not representative of most limited stage small cell lung cancer patients. Optimizing the radiotherapy component of treatment is very important in cancers that are treated with combined modality paradigms. As further data emerges, integration of 54 Gy will be important, but we need more details and it may not be applicable to all patients.”
Next, Nicholas van As, MD, MBBS, The Royal Marsden NHS Foundation Trust in London, presented “5-year outcomes from PACE B: An International phase III randomised controlled trial comparing stereotactic body radiotherapy (SBRT) vs conventionally fractionated or moderately hypo fractionated external beam radiotherapy for localised prostate cancer.” This study found people with intermediate-risk, localized prostate cancer can be treated as effectively using fewer and higher doses of radiation delivered over five days as they can with lower doses delivered over several weeks. Not only was SBRT non-inferior, it demonstrated a five-year 96% disease control rate, compared to 95% for conventional radiation without significantly higher toxicity.
“The outcomes for patients in both study arms were better than we expected,” said the study’s principal investigator, Dr. van As. “To be able to sit with a patient and say, ‘We can treat you with a low toxicity treatment in five days and your chance of keeping the cancer at bay for five years is 96%,’ it’s a positive conversation to have.”
Discussant Alejandro Berlin, MD, MS, Princess Margaret Cancer Center in Toronto, said he agreed that SBRT should be considered the standard of care for localized, intermediate-risk prostate cancers. “SBRT is better, it’s cheaper and it’s faster,” he said.
Mitchell Machtay, MD, FASTRO, Penn State Hershey Medical Center in Hershey, PA next presented “Randomized phase III trial of postoperative radiotherapy with or without cetuximab for intermediate-risk squamous cell carcinoma of the head and neck (SCCHN): NRG/RTOG 0920.” While the study did not reach statistical significance for its primary endpoint of overall survival, it did show radiation plus cetuximab increased disease-free survival after five years for people with intermediate-risk head and neck cancer. Acute toxicity was worse with this treatment but there were no differences in late toxicities. “It may therefore be considered an appropriate treatment for this patient population,” Dr. Machtay said, “but only after a very careful, thorough discussion of the benefits and risks. And we believe that the absolute magnitude of this benefit is likely to be greater for the HPV negative population.”
The final presentation was delivered by Søren Bentzen, DSc, PhD, FASTRO, University of Maryland School of Medicine in Baltimore, who discussed findings from his study, “Randomized controlled trial of hypofractionated vs. normo-fractionated sccelerated radiation therapy with or without cisplatin for locally advanced head and neck squamous cell carcinoma (HYPNO).” The findings suggest an accelerated radiation regimen could reduce the burden in low- and middle-income countries of alcohol and tobacco-related head and neck cancers.
The large, international, phase III study – involving patients from 10 countries across four continents – found delivering a course of radiation in 20 rather than 33 treatment sessions was just as effective for patients with locally advanced disease, without increasing side effects. “This is a trial that directly informs how you can effectively deliver radiation therapy to patients in a resource-scarce environment,” Dr. Bentzen said.
Christina Chapman, MD, MS, Baylor College of Medicine in Houston, Texas, discussed both of the head and neck trials, concluding that together they make an important contribution by bringing attention to “the global burden of head and neck cancer, to the suboptimal outcomes in HPV negative patients, the need for renewed conversation on our endpoints, including whether overall survival versus progression-free and local control should be preferred, and also emphasized the importance of collecting data on toxicity and quality of life.”
These studies can be found in the Proceedings of the 2023 ASTRO Annual Meeting.
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