Prostate Cancer: From Watchful Waiting to Castration Resistance

Reading the risk: PSA and the Gleason grade

Before any treatment, prostate cancer is sorted by how dangerous it looks. Three tools estimate risk. PSA (prostate-specific antigen), a blood marker, hints at tumour burden and later tracks response. The Gleason score — now simplified into Grade Groups 1 to 5 — reads how disordered the cells look under the microscope; the more they lose their normal architecture, the more aggressive the cancer. And the clinical stage says how far it has physically spread (confined to the gland, breaching its capsule, or in lymph nodes and bone). Together these place a patient into low-, intermediate-, or high-risk localised disease, or beyond into metastatic disease — and that bucket, more than anything, dictates the plan.

Localised, low-risk: the courage to watch

For low-risk localised disease, the guideline-preferred option is active surveillance: no immediate surgery or radiation, just structured monitoring with periodic PSA, examinations, imaging, and repeat biopsies. Treatment is deferred — sometimes indefinitely — and triggered only if the cancer shows signs of progression. This is not neglect; it is a deliberate strategy to spare men the incontinence and erectile dysfunction that radical treatment can cause, for a cancer that may never threaten their life. When treatment IS chosen for localised disease, the two curative mainstays are radical prostatectomy (surgery) and radiotherapy (external-beam or brachytherapy), which have broadly comparable cancer outcomes but different side-effect profiles.

Locally advanced and high-risk: radiation plus hormones

When the cancer is high-risk or has grown beyond the gland but not yet to distant sites, cure is still the goal — but a single weapon is not enough. The standard is radiotherapy combined with androgen-deprivation therapy (ADT), given for months to years around the radiation. Prostate cancer is fundamentally fuelled by androgens (male hormones), so starving the tumour of testosterone while irradiating it markedly improves survival compared with radiation alone. Exactly HOW we deprive the tumour of androgens — GnRH agonists and antagonists, anti-androgens, and testosterone-synthesis blockers like abiraterone — is the subject of its own dedicated chapter, "Prostate cancer and androgen deprivation," in the hormone-therapy section. Here, the point to hold is strategic: at this stage ADT is the partner that makes local treatment work.

Metastatic hormone-sensitive: hit hard, hit early

Once the cancer has spread but still responds to hormone withdrawal, the philosophy has shifted. For decades, metastatic hormone-sensitive prostate cancer (mHSPC) was treated with ADT alone, adding more drugs only when it failed. Modern practice does the opposite: it intensifies up-front. ADT remains the backbone, but from the start it is combined with either docetaxel chemotherapy, or an androgen-receptor pathway agent (abiraterone or enzalutamide) — and, for many patients, all three as a triplet. Trial after trial has shown that this combination beats ADT alone, delaying progression and extending survival. The lesson is timing: adding the second (and third) agent early, while the disease is still hormone-sensitive, buys far more than saving it for later.

Castration-resistant: the receptor is still the target

Eventually many cancers learn to grow despite castrate-level testosterone — this is castration-resistant prostate cancer (CRPC). The name misleads students into thinking hormones are now useless. They are not. The tumour has usually found ways to keep signalling through the androgen receptor (amplifying it, mutating it, or making its own androgens), so androgen-pathway agents still work: abiraterone (which blocks androgen synthesis) and enzalutamide (which blocks the receptor) remain frontline. Beyond them the ladder widens: taxane chemotherapy with docetaxel first and cabazitaxel after it; radium-223, a bone-seeking radioactive isotope for men with symptomatic bone metastases; PARP inhibitors for tumours carrying BRCA or other homologous-recombination-repair (HRR) mutations; and PSMA-targeted radioligand therapy — lutetium-177-PSMA — which links a radioactive payload to a molecule that homes to the prostate-specific membrane antigen (PSMA) studding the cancer's surface.

Each of these tools belongs to a mechanism family covered elsewhere. This chapter deliberately stays at the level of strategy, not molecules. The detailed mechanism of the androgen-pathway agents — abiraterone, enzalutamide, and the GnRH drugs behind ADT — lives in the "Prostate cancer and androgen deprivation" hormone chapter. How the taxanes docetaxel and cabazitaxel freeze the mitotic spindle belongs to the microtubule-agents chapter. Why PARP inhibitors are lethal specifically to BRCA/HRR-mutant cancers (synthetic lethality) is developed in the kinase-inhibitors and precision-oncology chapters. Follow those cross-links when you want the pharmacology; here, simply anchor WHICH tool answers WHICH clinical situation.

Don't forget the bones

Prostate cancer loves bone: it is the commonest site of metastasis, and the skeleton is under threat from two directions at once. The metastases themselves erode bone and cause fractures and pain, while long-term ADT — by stripping away testosterone — accelerates bone loss and osteoporosis. So supportive bone protection is part of good prostate-cancer care: bone-targeted agents (bisphosphonates or the RANK-ligand antibody denosumab) reduce skeletal complications from bone metastases and counter treatment-induced bone loss, alongside calcium and vitamin D. The dosing and safety of these bone-protective drugs (including osteonecrosis of the jaw and hypocalcaemia) are covered in the endocrine bone chapter.