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Rohit Gosain: Managing Toxicities of Androgen Receptor Pathway Inhibitors in Prostate Cancer
Rohit Gosain/physicianresources.roswellpark.org

Rohit Gosain: Managing Toxicities of Androgen Receptor Pathway Inhibitors in Prostate Cancer

Rohit Gosain, Co-Host of Podcast Oncology Brothers, Medical Director at Roswell Park Comprehensive Cancer Center, shared on LinkedIn:

“In this ToxCheck discussion, we touched on dosing, AEs, and clinical pearls in managing these AEs from our available ARPIs in Prostate Cancer.

ENZALUTAMIDE

INDICATIONS

  • Castration-resistant prostate cancer (mCRPC and nmCRPC)

  • Metastatic castration-sensitive prostate cancer (mCSPC)

  • nmCSPC with high-risk biochemical recurrence (EMBARK)

  • Mechanism: AR antagonist

TOXICITIES

  • Fatigue/asthenia (distinctive): most prominent among ARPIs

  • Falls / fractures: falls up to 10%, fractures up to 13%

  • Cognitive/mental impairment: memory loss, confusion

  • Seizure: rare but recognized risk

  • Other: hypertension, ischemic heart disease, weight loss

DOSAGE

  • 160 mg PO QD – with or without food

  • Dose reductions: 160 – 120 – to 80 mg QD

  • No hepatic or renal dose adjustment needed

  • Strong CYP3A4 inducer, CYP2C8 substrate – avoid strong CYP2C8 inhibitors (or reduce to 80 mg); increase to 240 mg if strong CYP3A4 inducer unavoidable

KEY MANAGEMENT PEARLS

  • Highest risk of cognitive impairment and seizures among ARPIs

  • Highest fall risk

  • Avoid in seizure history, brain injury, or seizure-threshold-lowering meds

  • Fatigue is most common AE; may require dose reduction

  • Only ARPI approved for nmCSPC with high-risk BCR (EMBARK)

ABIRATERONE

INDICATIONS

  • Metastatic castration-resistant prostate cancer (mCRPC)

  • Metastatic high-risk castration-sensitive prostate cancer (mCSPC)

  • With RT for very-high-risk localized disease or positive lymph nodes

  • Mechanism: CYP17

TOXICITIES

  • Mineralocorticoid excess (distinctive): hypertension, hypokalemia, fluid retention/edema

  • Hepatotoxicity: transaminase elevations

  • Cardiac: heart failure, atrial fibrillation, ischemic heart disease

  • Adrenocortical insufficiency: if prednisone interrupted

  • GI / Other: nausea, diarrhea, fatigue, fractures, hot flushes

DOSAGE

  • 1,000 mg PO QD – empty stomach (no food 2h before/1h after)

  • Prednisone: 5 mg QD (CSPC, no docetaxel) or 5 mg BID (CSPC+docetaxel, or CRPC)

  • Dose reduction: 250 mg QD for moderate hepatic impairment (Child-Pugh B)

  • C/I in severe hepatic impairment (Child-Pugh C)

KEY MANAGEMENT PEARLS

  • LFTs: every 2 weeks × 3 months, then monthly

  • Monitor BP/K/fluid status at least monthly

  • Avoid in NYHA Class III–IV heart failure

  • Never abruptly discontinue prednisone

APALUTAMIDE

INDICATIONS

  • Non-metastatic castration-resistant prostate cancer (nmCRPC)

  • Metastatic castration-sensitive prostate cancer (mCSPC)

  • Mechanism: AR antagonist

TOXICITIES

  • Skin toxicity (distinctive): rash up to 29%, incl. SCARs, SJS/TEN

  • Falls and fractures

  • Hypothyroidism: monitor thyroid function

  • ILD/pneumonitis: rare but potentially fatal

  • Other: hypertension, fatigue, weight loss, cerebrovascular/ischemic CV events, QTc prolongation

DOSAGE

  • 240 mg QD – with or without food

  • Dose reductions: 240 – to 180 – to 120 mg QD

  • Hepatic impairment (Child-Pugh C): 120 mg QD

  • No renal dose adjustment needed

  • Strong CYP3A4/CYP2C8 inducer – significant DDIs (warfarin, statins, etc.)

KEY MANAGEMENT PEARLS

  • Rash: most common reason for discontinuation; onset typically within first months

  • Check baseline TSH; monitor every 6 months or w/symptoms

  • Permanently discontinue for confirmed SCARs or Grade 4 skin reactions

  • Stop immediately for new/worsening respiratory symptoms (ILD)

DAROLUTAMIDE

INDICATIONS

  • Non-metastatic castration-resistant prostate cancer (nmCRPC)

  • Metastatic castration-sensitive prostate cancer (mCSPC)

  • mCSPC in combination with docetaxel (triplet therapy)

  • Mechanism: AR antagonist

TOXICITIES

  • Fatigue (distinctive): lowest among ARPIs

  • Hypertension: modest increase vs placebo

  • Rash: mild (lower than apalutamide)

  • Cardiac: ischemic heart disease/coronary artery disease

  • Other: fractures (lowest risk among ARPIs), high AST/ALT/bilirubin, low neutrophils

DOSAGE

  • 600 mg (two 300 mg tabs) PO twice daily – with food

  • Dose reduction: 300 mg BID for greater than or equal to Grade 3/intolerable AEs

  • Severe renal impairment (eGFR 15–29): 300 mg BID

  • Moderate hepatic impairment (Child-Pugh B): 300 mg BID

  • Minimal drug-drug interactions (limited CYP involvement)

KEY MANAGEMENT PEARLS

  • Most favorable overall safety profile among ARPIs

  • Low BBB penetration – lowest CNS/neurocognitive toxicity

  • Minimal drug-drug interactions – preferred in polypharmacy

  • Monitor BP, CBC, LFTs periodically.”

You can also read: PSMAddition: [177Lu]Lu-PSMA-617 Improves Radiographic PFS in PSMA-Positive mAPMN/S Prostate CancerRohit Gosain: Managing Toxicities of Androgen Receptor Pathway Inhibitors in Prostate Cancer

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