The data that may predict the success of cancer treatment

How much does PSA need to drop to know that prostate cancer treatment is really working? A new study published today (Monday) in the journal CANCER of the American Cancer Society points to a clear target: a PSA level lower than 0.2 ng/mL within nine months of starting treatment was associated with better survival among patients with metastatic hormone-sensitive prostate cancer.

Researchers analyzed data from 4,890 patients in the US Veterans Health Administration system who received testosterone-lowering therapy, alone or in combination with other treatments, between 2018 and 2023. During a median follow-up period of about two years, 896 of the patients died.

54% lower risk of death

The most striking figure in the study was among patients whose PSA level dropped below 0.2 ng/mL within the first nine months of treatment. They were found to have a 54% lower risk of death compared to patients who did not reach this level. In contrast, a large percentage decrease was not sufficient on its own. Patients whose PSA level dropped by more than 90%, but still remained above 0.2, did not show the same survival advantage. The finding reinforces the possibility that the final value reached by the PSA may be more significant than the magnitude of the decrease itself.

Will there be a need to intensify treatment earlier?

PSA is a protein produced in prostate tissue and is used, among other things, to monitor the response to prostate cancer treatment. In patients with metastatic disease, a decrease in its level after starting treatment may indicate a reduction in disease activity, but it should not be relied upon alone to assess the tumor's status. The researchers suggest that patients who do not reach a PSA level lower than 0.2 within nine months may be a group where there is room to consider closer monitoring or more intensive treatment strategies. However, this is an observational study and therefore it does not prove that intensifying treatment just to lower the PSA below this threshold will necessarily improve survival.