Acrometastasis of the Lower Limb Carries a Poorer Prognosis: A Retrospective Cohort Study.

BACKGROUND: Bony metastasis distal to the knee is rare and often reported alongside metastasis distal to the elbow. We sought to provide empirical evidence of the epidemiology, presentation, and prognosis of lower limb acrometastasis, alongside investigation of the distribution of metastases present while lower limb acrometastases form.

METHODS: This retrospective cohort study identified 44 radiologically confirmed cases of lower limb acrometastasis from a single region. Case note review facilitated the extraction of data relating to the stated aims. Patients were grouped by extent of metastasis at primary diagnosis. Mann-Whitney U test compared metastatic burden, and Kaplan-Meier analysis compared survival.

RESULTS: Prostate and breast carcinoma were the most commonly diagnosed primary tumors. Sixty-eight acrometastatic lesions were identified, of which 70% presented asymptomatically. Lower limb acrometastasis was associated with metastatic disease at a significantly greater number of sites than those presenting with metastasis proximal to the knee only (P = .007) and conveyed a significantly worse survival than metastasis proximal to the knee or nil metastasis (P < .001). Median survival from diagnosis of lower limb acrometastasis was 1.0 year.

CONCLUSION: Lower limb acrometastasis is associated with a large metastatic burden and occurs in the terminal year of disease. Radiological identification of cases reveals a distinct cohort of acrometastatic lesions, more likely to present asymptomatically, and arises from alternate primary carcinomas than those in previous literature.

LEVELS OF EVIDENCE: Level IV: Case series.