CT‑Measured Muscle Quality Predicts Survival in Men with Non‑Metastatic Castration‑Resistant Prostate Cancer

Researchers in Japan have found that muscle “quality,” not just size, is linked to how long men with non‑metastatic castration‑resistant prostate cancer (nmCRPC) live, even when they are treated with androgen receptor signaling inhibitors. The study analyzed 344 men using standard CT scans to measure muscle quantity and the amount of fat inside the muscle, represented as the psoas–lumbar vertebral index (PLVI) and intramuscular adipose tissue content (IMAC). Higher IMAC means more fat infiltration and poorer muscle quality.

Over a median follow‑up of about 4 years, roughly 40% of patients died. In unadjusted analyses, both lower muscle quantity and higher IMAC were associated with shorter survival. After adjusting for age, comorbidities, Gleason score, whether the patient received an ARSI during nmCRPC, and PSA doubling time, muscle quantity no longer predicted survival independently. In contrast, higher IMAC remained significant, with a hazard ratio of about 1.8 (95% CI 1.1–2.8), meaning an approximately 80% higher risk of death compared with those with better muscle quality, even after accounting for other factors.

The study also showed no clear link between either muscle quantity or quality and treatment response or safety. There were no meaningful differences in PSA declines of ≥50% or ≥90%, PSA‑progression‑free survival, metastasis‑free survival, or rates of ARSI‑related side effects based on IMAC or PLVI. Practical takeaways are that CT‑measured muscle quality may help refine prognosis in nmCRPC and support discussions about physical activity, nutrition, and exercise, but it should not be used alone to change systemic therapy choices, since it appears more as a marker of overall patient resilience than of drug response.

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