San Francisco, CA—Today, patients who receive stereotactic body radiation therapy (SBRT) for intermediate- or high-risk localized prostate cancer are not receiving concurrent androgen-deprivation therapy (ADT), despite national guideline recommendations that support the concurrent use of ADT with radiation therapy.
Among patients aged >40 years with localized prostate cancer who received radiation therapy between 2004 and 2015, ADT use decreased for patients who were considered low risk or intermediate risk (favorable or unfavorable), according to an analysis of data from the National Cancer Database.
ADT use increased only in men with high-risk disease, reported Trevor J. Royce, MD, MPH, MS, Assistant Professor, Department of Radiation Oncology, University of North Carolina at Chapel Hill, and colleagues at the 2020 Genitourinary Cancers Symposium.
“In general, because there is the potential for quality-of-life effects from ADT, best practice is to use it when there is a proved benefit,” said Dr Royce.
“To be clear, ADT is an extraordinarily effective approach to treating prostate cancer; it’s just that as clinicians we aim to be judicious with its application,” he emphasized.
Randomized clinical trials have demonstrated improved survival by adding ADT to fractionated radiotherapy for men with unfavorable intermediate-risk or high-risk localized prostate cancer. As a result, guidelines from the National Comprehensive Cancer Network recommend the use of ADT with radiation therapy in these patient populations.
Although SBRT is noninferior to conventional radiation for tumor control and toxicity, and noninferior to moderate hypofractionation for toxicity, the benefit of ADT with SBRT is unknown.
Using the National Cancer Database, Dr Royce and colleagues identified men aged >40 years with localized prostate cancer who received treatment with radiation (excluding brachytherapy) between 2004 and 2015. ADT prescribed for ≤180 days of radiation was considered combined modality therapy. SBRT was defined as ≥5 Gy per fraction. Non-SBRT external beam radiation therapy (EBRT) was defined as ≤3 Gy per fraction and a total dose ≥60 Gy per fraction. Of the 141,384 men included in the study, 7599 patients received SBRT and 133,825 received EBRT.
The use of SBRT increased markedly for all risk groups from 2004 to 2015, from 0.9% to 10.3% (P <.001). The use of SBRT increased in the low-risk group from 0.9% to 21.6% during this time, from 1.1% to 13.7% in the favorable intermediate-risk group, from 0.6% to 10.8% in the unfavorable intermediate-risk group, and from 0.8% to 2.8% in the high-risk group.
However, the use of ADT declined during that period for all groups, except the high-risk group (P <.001). The use of ADT decreased from 60.8% to 39.2% among all patients. By contrast, in the high-risk group, the use of ADT increased from 78.9% to 84.2%.
These trends, the investigators noted, were in part driven by declining use of ADT and the increasing use of SBRT.
Patients who received EBRT were more likely to receive ADT than those who received SBRT across all risk groups (P <.001). Overall, the use of ADT was 49.2% among men who received EBRT and 15.4% among patients who received SBRT. When stratified by risk group, the use of ADT was 13.1% among men who received EBRT versus SBRT in the low-risk group, 42.7% versus 14.9% in the favorable intermediate-risk group, 48.2% versus 19.2% in the unfavorable intermediate-risk group, and 81.2% versus 41.5% in the high-risk group.
On multivariable analysis, the use of ADT was significantly less likely among men who received SBRT versus men who received EBRT across all risk groups (P <.001).
“ADT use has likely decreased over time, because we have a greater appreciation for its quality of life effects, and prostate cancer risk stratification has improved, and we have a better sense of who stands to receive the most benefit with ADT,” Dr Royce indicated.