The long-term follow up of the NRG Oncology trial RTOG 9408, studying the addition of short-term androgen-deprivation therapy (ADT) to radiotherapy (RT) for men with early, localized prostate adenocarcinoma, indicated that RT combined with ADT is superior to RT alone for overall survival (OS) up to 10.4 years following treatment.
Radiation therapy (in North America), or radiotherapy (in the UK and Australia) also called radiation oncology, and sometimes abbreviated to XRT, is the medical use of ionizing radiation as part of cancer treatment to control malignant cells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis).
Cancer cells can be distinguished from normal cells in the body, as they tend to replicate more quickly and take over tissue with healthy cells. Radiation therapy manipulates this characteristic of cancer cells by attacking the DNA of cells that are in the process of replicating, rendering the cells unable to multiply sufficiently and eventually leading to their death.
However, when researchers assessed these results up to 18 years, the benefits of adding ADT to RT dissipated. The results were presented at the American Society for Radiation Oncology's Annual Meeting in San Antonio, TX on October 22, 2018, during the Genitourinary 2: Long-Term Updates of Prospective Prostate Cancer Clinical Trials session.
The study was also awarded a "Best of ASTRO" designation. The primary aim of NRG-RTOG 9408 was to determine if the addition of four months of ADT before and during RT would improve the overall survival of men with prostate adenocarcinoma.
Secondary objectives included determining the difference in disease-specific mortality (DSM), biochemical failure (BF), the incidence of distant metastases (DM) and local progression (LP). 1974 men were randomly assigned to either receive RT alone (990 patients) or RT plus four months of ADT (984 patients).
"After concluding that the addition of ADT did provide benefit for both primary and secondary aims, we continued to survey results up to 18 years from treatment. The median follows up for surviving patients was 14.8 years," stated Dr. Christopher U. Jones of Sutter Cancer Centers and Lead Author of NRG-RTOG 9408.
"Our study team noticed that overall survival data began to favor the radiotherapy alone arm over the experimental, androgen-deprivation therapy arm following the first ten years after treatment," said Jones.
"However, disease-specific mortality, biochemical failure, the incidence of distant metastases and local progression continued to show long-term benefit," stated Jones. The incidence of late grade 3, 4, and 5 genitourinary and gastrointestinal toxicities were low and similar between the ADT and RT arms.