The 58th Annual Meeting of the American Society for Radiation Oncology
The annual meeting of the American Society for Radiation Oncology was held from Sept. 25 to 28 in Boston and attracted approximately 11,000 participants from around the world, including physicians, oncology nurses, radiation therapists, biologists, physicists, and other cancer researchers. The conference featured educational courses focusing on radiation, surgical, and medical oncology.
In a randomized controlled trial, Paul D. Brown, M.D., of the Mayo Clinic in Rochester, Minn., and colleagues compared the efficacy of stereotactic radiosurgery (SRS) to the historic standard of care, whole brain radiotherapy (WBRT), in patients with cancer that had metastasized to the brain.
“In our trial, there was no difference in survival between the treatment groups. The patients treated with SRS had better quality of life, better cognitive function, and less toxicity. Furthermore, due to less time commitment and a quicker recovery after SRS, patients treated with SRS can restart systemic therapies more rapidly,” Brown said. “Our results confirm that postoperative SRS should be a standard of care since there is no significant difference in survival whether a patient receives postoperative SRS or WBRT, and SRS avoids the well-known toxicities of WBRT and provides better preservation of cognitive function and quality of life.”
In another study, Anita Mahajan, M.D., of the MD Anderson Cancer Center in Houston, and colleagues found that postoperative SRS significantly reduces the risk of local relapse after a complete surgical resection of a brain metastasis. The investigators randomized 128 patients who had one to three metastatic brain tumors (of which at least one was completely surgically resected) to either SRS to the surgical cavity or observation.
“At one year, there was an almost 50 percent reduction in local failures (28 versus 55 percent) in the SRS versus observation arm. There was no difference in the number of patients who developed new lesions at one year (62 percent) or overall survival (median, 17 months) between the two arms. The median time to WBRT was 15 months in both arms,” Mahajan said.
When evaluating risk factors that predicted local failure, the investigators found that smaller tumors (<2.5 cm) had a 91 percent local control at one year in both arms. Tumor histology, number of metastases, and systemic disease status did not influence local control.
“Clinicians now have level-one evidence for the benefit of postoperative SRS after complete resection of a brain metastasis. Patients remain at risk for additional metastases, which can be managed after detection,” Mahajan said. “This approach allows delay or avoidance of WBRT with no obvious compromise in overall survival.”
Dan Spratt, M.D., of the University of Michigan in Ann Arbor, and colleagues identified three intrinsic molecular subtypes of prostate cancer, which independently predict the risk of developing distant metastasis, and may predict which men will benefit most from postoperative radiotherapy.
“Our group has performed the largest genomic analysis of primary prostate cancer to date and has identified the intrinsic molecular subtypes of prostate cancer,” Spratt said. “We analyzed over 4,200 men’s tumors and found three distinct subtypes. Each subtype has unique biology and each subtype provides a patient a different prognosis.”
The investigators found that patients with subtype A have the most favorable prognosis in regards to the development of distant metastases. However, patients with subtypes B and C have the most favorable response to post-prostatectomy radiotherapy.
“Therefore, these subtypes provide important biologic information about each patient’s tumor to personalize the management of each man with prostate cancer,” Spratt said. “Future studies are already ongoing that incorporate genomic testing before treatment to help guide treatment selection and inform prognosis to validate our findings.”
Robert Meier, M.D., of the Swedish Medical Center in Seattle, and colleagues aimed to determine if high-dose stereotactic body radiotherapy (SBRT) could be safely employed (across multiple institutions) for men with newly diagnosed prostate cancer. The researchers also sought to determine if cancer recurrence rates could be improved, compared to historic controls.
“The treatment was very effective. In low-risk patients, cancer control at five years was 97.3 percent, and was superior to the historic control rate seen with conventional external beam radiotherapy (i.e., 93 percent). In intermediate-risk patients, five-year cancer control was 97.1 percent,” Meier said. “This study shows that SBRT is appropriate treatment for low- and intermediate-risk prostate cancer, and may be preferable to other treatments.”
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