1. Hepatocellular carcinoma (HCC) tumours located in ultrasound (US) blind spots were associated with poorer overall survival if not detected by US, larger tumour size, and greater likelihood of treatment with hepatectomy as opposed to radiofrequency ablation, compared to tumours in non-blind spots.
Evidence Rating Level: 2 (Good)
Hepatocellular carcinoma (HCC) relies on early detection for patient survival, with high-risk populations receiving half-yearly abdominal ultrasound (US), with or without serum alpha-fetoprotein (AFP), based on worldwide guidelines. However, US-based surveillance is controversial due to its substandard accuracy, in part due to inherent blind spots. These are areas with poor acoustic penetration due to anatomical limitations. Because varying tumour locations impact liver function differently, identifying lesions in blind spot areas could influence the treatments offered. Currently, there have been no studies examining the effects of US blind spot tumours on HCC prognosis. Therefore, this retrospective study based in China evaluated the characteristics of blind spot location tumours and their impact on prognosis and treatment selection. The study population consisted of 1289 participants with single-nodular BCLC stage 0-A HCC. Patients were divided into two groups: The US-detected group (n=1062) consisted of those with malignancies detected on US with or without an AFP increase, whereas the US-missed group (n=227) included those with no US lesions but an increased AFP. The ultrasounds were re-evaluated manually by researchers with greater than 5 years of US experience, and blind spots were defined as the hepatic dome, caudate lobe around the IVC, <1 cm beneath the ribs, and the left lateral segment surface. The results showed that more HCC blind spot tumours were found in the US-missed group than the US-detected group (64.3% vs 44.6%, p < 0.001). As well, a significant proportion of tumours >2 cm were within blind spot regions compared to non-blind spot regions (60.3% vs 47.1%, p = 0.001). After adjustment, factors associated with blind spot lesions include male sex, HCC size > 2 cm, cirrhosis signs, and US-missed HCC. Furthermore, there was no difference between blind spot and non-blind spot lesions in the proportion of those receiving curative treatment, even after adjusting for size. However, a greater proportion of blind spot tumours were treated with hepatectomy (60.0% vs 46.0%, p < 0.001) whereas non-blind spot tumours were more likely treated with radiofrequency ablation (30.5% vs 16.95%, p < 0.001). In terms of survival, the US-missed group had a significantly lower overall survival than the US-detected group when an HCC tumour was in a blind spot (p = 0.008), but was not different when the tumour was not in a blind spot. Overall, this study showed how blind spot location was associated with differences in tumour size, treatment type, and overall survival if not detected by US.
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