SAN ANTONIO - Radiation therapy (RT) could be more effective in African-American men with prostate cancer than previously realized, according to data presented on Monday at the American Society for Radiation Oncology (ASTRO) annual meeting.
Researchers shared data indicating that African-American men actually responded better to radiation treatment for prostate cancer than Caucasian men. That's surprising because previous research has found that black men tend to have worse outcomes from prostate cancer.
Compared with white men, black men have an incidence rate of prostate cancer that's 60% higher and mortality that's two to three times higher. The question is whether these worse outcomes are due to socioeconomic or biological factors.
Investigating the issue further, a team led by Dr. Daniel Spratt from the University of Michigan Rogel Cancer Center examined the outcomes of African-American men treated for prostate cancer. The group focused specifically on three main issues: patient outcomes, sensitivity to radiation, and outcomes in men with low androgen receptor activity.
Spratt and colleagues first analyzed genetic expression in tumors in a group of 1,953 black men with prostate cancer. They found that tumors with low androgen receptor activity were more likely to lead to distant metastases within 10 years, and African-American men were more likely to have low androgen receptor activity. Low androgen receptor activity was a statistically significant predictor of distant metastasis even after adjusting for factors such as prostate-specific antigen (PSA) level, Gleason grade, and lymph node invasion.
On the positive side, tumors in African-American men were more likely to have increased biological indicators for higher sensitivity to radiation therapy. Factors predicting this included decreased expression of the double-strand DNA repair pathway, increased expression of immune pathways, and higher radiosensitivity based on a score that the University of Michigan team developed.
In the second part of the study, the researchers examined patient outcomes in 1,129 African-American patients drawn from four randomized prostate cancer trials in the NRG Oncology/ Radiation Therapy Oncology Group (RTOG). They found that black men had lower rates of biochemical cancer recurrence than white men, with a hazard ratio of 0.82. They also had a lower rate of distant metastasis, with a hazard ratio of 0.86. Both ratios were statistically significant.
Spratt said the results support the notion that the worse outcomes reported for African-American men in the literature are due to socioeconomic factors rather than their response to treatment. In fact, if black men actually receive radiation therapy, they have the potential for better outcomes than Caucasian men.
"When you minimize the social disparities and analyze the black men treated in the context of a randomized trial, not only do they have potentially equal outcomes, we show that significantly improved outcomes are very likely," he concluded.
