PCWG4 replaces terms like "castration-resistant" with "Androgen Pathway Modulation (APM) resistant." This change is driven by patient feedback finding the term "castration" insensitive and by the need for language that reflects modern treatments that don't always involve medical or surgical castration.
The NCI working group concluded that neither metastasis-directed therapy (MDT) nor systemic hormonal therapy should be required as a control arm in trials for biochemically recurrent (BCR) prostate cancer. This facilitates testing novel non-hormonal agents and reflects that surveillance is often a reasonable standard of care.
For an older patient population, the ultimate goal in prostate cancer treatment might not be a traditional cure, but rather turning it into a quiescent, chronic disease manageable with well-tolerated therapy, similar to HIV. This reframes success as long-term control until a patient dies of other causes.
Unlike bladder cancer, prostate cancer has highly effective androgen-pathway inhibitors (ARPIs) that extend survival. This success has pushed chemotherapy and, by extension, ADC development to later treatment lines as clinicians prioritize other novel mechanisms of action first.
After years of successfully intensifying hormonal therapy, the focus in prostate cancer is shifting toward de-intensification. Researchers are exploring intermittent therapy for top responders and developing non-hormonal approaches like radioligands to spare patients the chronic, life-altering side effects of permanent castration.
The term "hormone resistance" was misleading. Researchers discovered that even in a castrate state, prostate cancer tumors produce their own testosterone locally. This maintained androgen receptor signaling, proving the disease was still "androgen addicted" and opening the door for new targeted therapies.
The rapid advancement of ARPIs wasn't just a scientific breakthrough. It was a rare convergence of FDA interest in new endpoints, a deeper biological understanding of castration resistance, and intense industry and academic collaboration that created a uniquely fertile ground for innovation.
Experts believe molecular tests like Decipher and PTEN status are superior to simply counting bone lesions for guiding treatment. While not yet standard practice for all decisions, this represents a significant shift towards using underlying tumor biology to determine therapy, like adding docetaxel.
Clinical trials use arbitrary, time-based definitions (e.g., relapse within 2 years) for endocrine resistance. This isn't a perfect biological classification but a practical necessity to create homogeneous patient groups for testing, which may not fully reflect the diverse patient population in clinical practice.
Counterintuitively, administering super-physiologic levels of testosterone can induce responses in certain castration-resistant prostate cancers. This strategy, called Bipolar Androgen Therapy, exploits the tumor's overexpressed receptors, turning a growth signal into a therapeutic vulnerability, though it remains a risky approach.
The IMbark trial demonstrated that an ARPI (enzalutamide), either alone or with ADT, outperformed ADT monotherapy in high-risk patients. This pivotal finding raises the question of whether giving ADT alone in any setting, such as with radiation for localized disease, is now an outdated and inferior approach.