Grape seed extract, a supplement derived from wine grape seeds and rich in antioxidant proanthocyanidins, has been studied for cardiovascular benefits. Recently, researchers explored whether it could also slow the growth of prostate cancer in men who have already undergone treatment but then experienced a recurrence without metastasis.
Paul Maroni, MD, of the University of Colorado Cancer Center, and colleagues conducted a phase II trial involving men with recurrent prostate cancer who had been treated previously but showed rising PSA levels without metastasis. The goal was to determine whether grape seed extract could modestly delay cancer progression during a period when doctors often opt for careful observation rather than immediate systemic therapy.
In the study, 41 men received 150 mg of grape seed extract twice daily for up to 12 months. The researchers tracked PSA doubling time, defined as the months required for PSA levels to double, to gauge tumor activity. This measure was compared with each patient’s PSA doubling time before starting the extract.
Results indicated that, on average, PSA doubling time lengthened from 5.71 months to 6.86 months with grape seed extract. Approximately 78% of participants experienced an increased PSA doubling time, and about 37% had a substantial improvement of at least 30% in their PSA doubling time. Notably, patients with higher baseline PSA and higher testosterone levels tended to respond more favorably. The treatment was generally well tolerated, with few adverse effects observed.
Maroni stressed that these findings are encouraging but not definitive. “This is not ready for prime time yet. People should not just start taking grape seed extract on the assumption that it’s going to work for them,” he noted. Nevertheless, the data suggest a potential role for grape seed extract as a supplementary approach to slow cancer progression during surveillance in select patients.
The study team—whose work was supported by the CU Cancer Center and several foundations—emphasizes the need for larger, randomized trials to confirm efficacy and gather more information on which patients might benefit most. Collaboration included researchers across CU’s Department of Surgery and Cancer Center, with additional contributions from Rajesh Agarwal, PhD, who has long investigated the extract’s cancer-related properties.
Clinical context remains important. Prostate cancer is the second most common cancer among men in the United States and a leading cause of cancer death, with screening and early detection improving outcomes. Initial treatment decisions vary by disease risk, ranging from active surveillance for low-risk cases to radical prostatectomy or radiation for more advanced disease. When cancer recurs after local therapy, androgen deprivation therapy (ADT) is commonly used, though it carries potential quality-of-life effects. In slower, non-metastatic recurrences, delaying systemic therapy while exploring low-risk adjuvant approaches may be reasonable in carefully selected patients.
Patients considering supplements should consult their healthcare providers, as supplements can interact with treatments or affect PSA interpretation. Further research will determine whether grape seed extract can become a reliable component of management for non-metastatic, recurrent prostate cancer.
Authors and collaborators include CU Cancer Center members Elizabeth Kessler, Thomas Flaig, Elaine Lam, and Dexiang Gao, among others. This work extends the ongoing exploration of integrative strategies to improve quality of life and potentially slow disease progression in men with prostate cancer.
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