CT Muscle Measure Guides Treatment Benefit in New Prostate Cancer: STAMPEDE Findings

Skeletal muscle index measured from regular CT scans works as a simple marker to predict outcomes and treatment response in newly diagnosed hormone-sensitive prostate cancer, based on this STAMPEDE study review.
Low muscle, or sarcopenia, is common in advanced prostate cancer and gets worse with hormone therapy, but skeletal muscle index (SMI) uses psoas muscle area at the L3 spine level divided by height squared from scans patients already have.
The research team looked at 2,267 men from STAMPEDE trials on docetaxel and AR pathway inhibitors: 1,578 with spread cancer at average skeletal muscle index 47.2 square cm per square meter, 689 high-risk no-spread at 48.2. They compared usual care to adding docetaxel with zoledronic acid or abiraterone with prednisolone, with or without enzalutamide. For men with spread cancer, higher skeletal muscle index cut death risk by 15 percent for every 10-unit rise, separate from tumor load (hazard ratio 0.85, 95 percent confidence interval 0.79 to 0.92, p less than 0.001) for overall survival. No such link held for no-spread cases on time to spread.

The big find was prediction: men with high skeletal muscle index got more benefit in time to spread from abiraterone plus prednisolone with or without enzalutamide over usual care (hazard ratio 0.44 versus 0.59 for low skeletal muscle index). Tests showed adding the muscle-treatment match improved predictions (chi-square 4.67, p=0.03), with gains strongest between skeletal muscle index 41 to 63 (chi-square 9.95, p=0.006). One in five men fell outside that sweet spot, 13 percent too low and 7 percent too high, and saw no extra benefit from the add-on. Docetaxel groups showed nothing similar. Averages ran mid-40s to low-50s, typical for low muscle in cancer.

​CT muscle checks could help pick who gains from stronger upfront combos like abiraterine plus enzalutamide in high-risk no-spread cancer, avoiding side effects for low muscle men. Needs checking in everyday patients, but highlights keeping muscle up with your training during hormone therapy.

Source.