As a patient who understands every prostate cancer tumor is different, I will offer the information that I've learned over the years.

Chemotherapy does not kill all cancer cells, because it targets rapidly dividing cells (affects the cell division process). However, prostate tumors often also contain slow-growing and/or dormant cancer cells.

Also, regarding the change in size of a PCa tumor after being treated with chemotherapy, my understanding is that a PCa tumor is composed of actual cancer cells and non-cancerous elements. For example, the percentage of cancer cells within a PCa tumor can range from 30% to 60% of the cell mass (that number changes depending on the doctor explaining). Therefore, even if all cancer cells within a tumor are killed, the prostate cancer tumor does not necessarily disappear from an ultrasound view, and especially not in the near term.

When the combination of ADT and ARSI treatments are used, they effectively force rapidly dividing cancer cells into a state of more slowly dividing or becoming dormant. As a result, the tissue supporting the previously rapidly growing cancer cells also reduces in size.

Just in case helpful, our longer-term hope for the systematic treatment of PCa is to leverage the developments in other types of cancer, which also seek to target the slow-growing and/or dormant cells.