In a set of three presentations highlighted by ASTRO on the first day of the meeting, researchers from across the U.S. presented new findings that have implications for treating prostate and lung cancers while minimizing the adverse side effects of radiation therapy.
In his presentation, Dr. Mark Buyyounouski from Stanford University said his team found that using fewer but higher doses of radiation doesn't increase long-term side effects or lower the quality of life of men with prostate cancer who had their prostates removed.
Buyyounouski et al wanted to test whether an accelerated approach is also acceptable for men after undergoing prostatectomy, looking at data from 245 patients. They compared patient-reported genitourinary and gastrointestinal side effects experienced by men who either had hypofractionated postoperative radiation therapy delivered over five weeks or conventionally fractionated radiation delivered over seven weeks.
The researchers found that immediately after treatment, the average change to genitourinary scores in patients did not differ between treatment groups, but patients treated with shortened radiation initially reported worse gastrointestinal symptoms. By six months, however, there were no differences in genitourinary or gastrointestinal impacts reported by the two groups. The quality of life for patients remained comparable until the end of the 24 months.
Buyyounouski said other benefits for hypofractionated radiotherapies include shorter time commitment for patients, improved productivity for staff, and lower costs.
In a second presentation, Dr. Paul Nguyen from Harvard Medical School presented his team's findings on a genetic biomarker test that he said accurately predicts how men with high-risk prostate cancer will respond to treatment with radiation and hormone therapy.
Nguyen and colleagues analyzed the activity of 22 genes in prostate tumors to produce a score reflecting how aggressive a patient's cancer is. They calculated scores using RNA extracted from archived biopsy samples collected in three major prostate cancer trials. The trials had 90, 172, and 123 patients respectively, with some samples as old as 29 years. Then, the researchers looked at how closely these scores were associated with long-term outcomes.
The genetic classifier predicted which patients were more likely to develop distant metastases (hazard ratio [HR], 1.24), which were more likely to die of their prostate cancer (HR, 1.27), and which were more likely to die from any cause (HR, 1.12).
Nguyen said that for example, the rate of distant cancer metastasis at 10 years was 29% for patients whose scores indicated they had more aggressive cancer, compared with 13% for those whose scores signaled lower risk.
"High-risk prostate cancer is a heterogeneous disease state and the genomic classifier can improve risk stratification to help personalize shared decision-making," Nguyen said.
In her presentation, Dr. Jillian Tsai from the Memorial Sloan Kettering Cancer Center in New York City led a team that found that high-dose radiation therapy can be used to lengthen progression-free survival for people with advanced lung cancer.
Tsai said this stereotactic body radiation therapy is useful for when systemic therapy does not fully halt the growth or spread of metastases.
Of the 106 patients enrolled in the team's study, 59 had non-small cell lung cancer and 47 had breast cancer. All participants in the trial had between one and five progressing metastatic sites that had not responded to systemic therapy.
Patients were randomized into two groups: half received stereotactic body radiation therapy to all progressive sites, and half were treated with the standard of care, which allowed physicians to choose whether to continue their current systemic therapy or switch to another drug.
Patients were followed for a median of 45 weeks, by which time 78 (74%) had experienced further tumor progression and 39 (37%) had died. The median progression-free survival was 44 weeks for patients with non-small cell lung cancer treated with stereotactic body radiation therapy, compared with nine weeks for those who received standard care (p = 0.001).
However, no significant difference was found in progression-free survival between the two groups of patients with breast cancer.
"Stereotactic body radiation therapy had pretty acceptable toxicity profiles in this patient population. We want to study the mechanisms of the differential benefits for our future analysis," Tsai said.
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