Researchers have discovered that a combination of blood tests and advanced imaging can detect hidden prostate cancer that standard PSA (prostate-specific antigen) tests might miss, potentially changing how doctors decide whether to intensify or reduce treatment for metastatic hormone-sensitive prostate cancer. In a new analysis presented at the 2026 American Society of Clinical Oncology Annual Meeting, scientists found that all 20 patients studied still had detectable cancer on imaging scans six months into treatment, even when their PSA levels dropped significantly.

What Is PSMA-PET Imaging and Why Does It Matter?

PSMA-PET is an advanced imaging scan that uses a radioactive tracer to light up prostate cancer cells throughout the body. Unlike a standard PSA blood test, which only measures a protein level, PSMA-PET actually shows where cancer cells are hiding. Researchers at Dana-Farber Cancer Institute and Harvard Medical School analyzed data from the PSMAtrack trial to understand what this imaging reveals about treatment response.

The findings were striking: even patients whose PSA dropped to very low levels (below 0.2 ng/mL, which doctors consider an excellent response) still showed cancer on their PSMA-PET scans. Specifically, residual disease appeared in 100% of patients in the blood pool and 85% in the liver. The most common sites where cancer persisted included the prostate itself (90% of patients), bone (80%), pelvic lymph nodes (55%), and other lymph nodes throughout the body (50%).

How Do PSA Levels and Imaging Results Compare?

The research revealed an important distinction between what PSA blood tests show and what imaging reveals. Among the 20 participants, the median PSA level at six months was 0.29 ng/mL, with 55% of patients achieving that favorable PSA level of 0.2 ng/mL or lower. However, the amount of cancer visible on PSMA-PET scans differed dramatically between these two groups.

Patients with PSA levels below 0.2 ng/mL had significantly smaller tumor volumes on imaging (median 7.7 milliliters) compared to those with PSA levels of 0.2 ng/mL or higher (median 147 milliliters). The intensity of the cancer signal on the scans also differed markedly, with the higher PSA group showing much more avid disease. This suggests that PSA and imaging provide complementary information about how well treatment is working.

How Could This Change Treatment Decisions?

The real-world implication of these findings is that doctors may soon use both PSA levels and PSMA-PET imaging at the six-month mark to decide whether to intensify, maintain, or reduce treatment. According to Praful Ravi, assistant professor of medicine at Harvard Medical School and medical director of Genitourinary Theranostics at Dana-Farber Cancer Institute, this represents a major shift in precision oncology.

"All patients had residual PSMA-avid disease after 6 months of systemic therapy for metastatic hormone-sensitive prostate cancer. There was a significantly higher 6-month PSMA tumor volume and intensity in patients with PSA of 0.2 ng/mL or greater at 6 months versus a PSA of less than 0.2 ng/mL at 6 months. Six-month PSMA-PET and 6-month PSA may identify patients for consolidative therapy after initial systemic therapy," said Praful Ravi, assistant professor of medicine at Harvard Medical School.

Praful Ravi, Assistant Professor of Medicine at Harvard Medical School and Medical Director of Genitourinary Theranostics at Dana-Farber Cancer Institute

In an interview at the conference, Ravi elaborated on how clinicians might use this information to personalize treatment strategies. For patients with favorable PSA levels and limited disease on imaging, doctors might consider de-escalation strategies, potentially stopping intensive therapy after a period of time. Conversely, for patients with PSA levels above 0.2 ng/mL who have significant PSMA-avid disease, doctors could consider escalating therapy with additional treatments like PSMA radiopharmaceutical therapy or other targeted approaches.

Steps to Understanding Your Prostate Cancer Treatment Plan

• Ask About Both Tests: Request that your doctor use both PSA blood tests and PSMA-PET imaging at the six-month mark to get a complete picture of how your cancer is responding to treatment, rather than relying on PSA levels alone.
• Understand Your PSA Target: Know that a PSA level of 0.2 ng/mL or lower at six months is considered an excellent response, but this should be combined with imaging results to guide next steps in your treatment plan.
• Discuss Treatment Adjustments: Have a conversation with your oncology team about whether your results suggest de-escalation (reducing treatment intensity) or escalation (intensifying therapy), based on both your PSA level and imaging findings.
• Consider Clinical Trials: Ask whether you might be eligible for clinical trials testing new approaches to treatment intensification or de-escalation based on six-month imaging and PSA results.

What Does This Mean for Prostate Cancer Patients?

The study involved 20 patients with a median age of 72 years who were receiving standard treatment with androgen deprivation therapy (ADT), which suppresses testosterone to slow cancer growth, often combined with additional medications that block androgen receptor signaling. About 60% received ADT with an additional drug called an androgen receptor pathway inhibitor (ARPI), while others also received chemotherapy with docetaxel.

The key takeaway is that achieving a low PSA level, while important, may not tell the whole story about treatment response. Ravi noted that patients who fail to achieve a PSA below 0.2 ng/mL at six months have a median survival of only three to four years, compared to eight to nine years for those who reach that target. However, even patients who do achieve this favorable PSA level still have detectable cancer on imaging, suggesting that additional interventions might improve long-term outcomes.

The researchers initiated this analysis because historical data on how PSMA-PET imaging changes during the early months of metastatic prostate cancer treatment was limited. By prospectively tracking changes in imaging from baseline through six months, they aimed to establish whether imaging metrics could help guide treatment decisions earlier in the disease course, before patients develop biochemical recurrence.

While these findings are promising, they represent early research from a single trial. Larger studies and clinical trials testing whether treatment escalation or de-escalation based on six-month imaging and PSA results actually improves survival are ongoing. For now, the message for patients is to discuss both PSA levels and imaging results with your oncology team and ask how these findings might apply to your individual treatment plan.