Radiation therapy approaches — including external beam radiation therapy (EBRT) and brachytherapy — for prostate cancer patients with aggressive disease are better at extending the time to metastasis or cancer recurrence than prostate surgery, a study shows.
The findings were presented at the American Society for Radiation Oncology (ASTRO) 2018 Annual Meeting, held Oct. 21-24 in San Antonio, Texas. The study was titled “Comparative Effectiveness of Prostatectomy and Radiation Therapy (RT) in Gleason 9-10 Prostate Cancer.”
Prostate cancer with a Gleason score — a measure of how aggressive a cancer is — of 9 or 10 is an aggressive cancer with a high likelihood of spreading. Patients usually have a radical prostatectomy — where the prostate and surrounding tissues are surgically removed — but recent studies suggest that EBRT with a brachytherapy boost is better at delaying biochemical relapse, deemed as rising PSA levels.
EBRT is a type of radiation therapy where high-energy radiation beams are delivered into tumors, accounting for their contours. This is better than traditional radiation treatments, as it helps reduce damage to healthy tissue and nearby organs.
Brachytherapy consists of small radiation “seeds” that are implanted directly into tumors. This kind of internal radiation therapy — which can be implanted temporarily or permanently — allows the use of higher total radiation doses delivered in shorter periods than EBRT.
To see whether these kinds of radiation therapy outperformed radical prostatectomy, researchers examined the Veterans Administration system for patients with Gleason score 9 or 10 diagnosed between 2000 and 2010.
During that period, 1,951 patients had been treated for aggressive prostate cancer, including 682 who received surgery, 1,146 who were given EBRT, 62 who received a combination of EBRT and brachytherapy, and 61 who were treated with brachytherapy only.
Most patients also received androgen deprivation therapy, either before surgery (55%) if they were in the radical prostatectomy group, or concomitant with radiation treatment (73-77%). Also, 11% of patients in the surgery group also received EBRT after the procedure.
After a median follow-up of six years and two months, patients receiving radiation approaches had lived longer without experiencing biochemical recurrence or metastasis, researchers found.
After adjusting for parameters including age at diagnosis, Gleason score, cancer stage, and PSA levels at baseline, patients receiving EBRT were 39% less likely to experience a biochemical recurrence or death, and 65% less likely to experience metastasis or death. The combination of EBRT and brachytherapy was even better at improving these measures, reducing the risk of biochemical recurrence and metastasis by 46% and 74%, respectively.
Brachytherapy alone, on the other hand, only extended the time to metastasis or death, compared to surgery.
Overall, researchers found that patients who opted for radical prostatectomy lived longer than those on radiation treatments, but researchers deemed these overall survival measures as “unreliable, given a historical preference to recommend [radical prostatectomy] in patients with longer life expectancies,” they stated.
Researchers also found that EBRT and EBRT plus brachytherapy delayed the need for salvage therapies, defined as additional radiation and/or androgen deprivation therapy.
“Radiation therapy-based approaches for patients with GS 9-10 prostate cancer were associated with superior [biochemical failure-free survival], [metastasis-free survival], and prolonged time to salvage therapy compared to RP,” researchers concluded. “The costs and consequences of upfront RP for patients with GS 9-10 prostate cancer warrant further investigation.”
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