Posted: Tuesday, November 8, 2022
Alan Dal Pra, MD, of the University of Miami/Sylvester Comprehensive Cancer Center, and colleagues presented data at the 2022 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 160) on the prognostic value of the 24-gene Postoperative Radiation Therapy Outcome Score (PORTOS) classifier in predicting the benefit of postoperative radiotherapy in patients with biochemically recurrent prostate cancer.
Because the recent SAKK 09/10 phase III clinical trial showed that dose-intensified salvage radiotherapy was not superior to conventional dose salvage radiotherapy for recurrent prostate cancer after radical prostatectomy, the researchers sought a different predictive model. They evaluated the PORTOS classifier, an expression signature of 24 DNA damage repair and immune pathway genes previously shown to predict benefit from postoperative radiotherapy.
Tumors from 226 patients from the SAKK 09/10 trial with transcriptome data were evaluated for PORTOS. Of these patients, 16% had a high PORTOS radiation response, and 84% had a lower PORTOS radiation response. A high PORTOS was predictive of improved outcomes in patients receiving dose-intensified salvage radiation therapy. Patients with a high PORTOS who received a 70-Gy dose had a 5-year clinical progression-free survival rate of 94%, compared with 49% for patients receiving a 64-Gy dose (P = .006). In an interaction analysis, PORTOS had a statistically significant interaction with radiation therapy dose for multiple endpoints: freedom from biochemical disease progression (P = .04), clinical progression-free survival (P = .003), and metastasis-free survival (P = .037).
“In a phase III trial testing salvage radiation therapy dose intensification after radical prostatectomy, patients with [a] high PORTOS had significantly better outcomes with dose-intensified treatment, suggesting that higher doses should be considered in this subgroup,” the investigators concluded.
Disclosure: To view Dr. Dal Pra’s disclosures, visit plan.core-apps.com.