For patients diagnosed with CRLM, ablation and surgery are preferred treatment options. However, with the continuous improvement of comprehensive treatment, the treatment of CRLM is gradually moving towards interventional minimally invasive procedures, especially for patients who are not suitable for surgery. Ablation therapy is a minimally invasive treatment method that has gradually become popular in the treatment of CRLM. It can achieve effective treatment of small tumors without the need for major surgery and has the advantages of being less painful and reducing hospital stays8–10,27. However, due to the specific characteristics of ablation therapy, there are certain risks involved in treatment, such as incomplete ablation or tumor recurrence28. Therefore, accurate individualized risk assessment of local tumor progression (LTP) is crucial for monitoring protocols and therapeutic decision-making in CRLM patients undergoing ablation therapy. In this study, we developed a radiomics model for early prediction of LTP after ablation and demonstrated its high performance.
Due to the rich vascularity of the liver, the infiltration of intrahepatic malignant tumors into surrounding tissues via microvascular invasion is an important factor in tumor recurrence29. Shan et al 30 studied peri-tumoral 2cm radiomics features of hepatocellular carcinoma (HCC) based on CT images and found that they were more effective at predicting recurrence of HCC compared to radiomics features of the tumor. Xia et al 31 also found that tumors extracted from preoperative CT images through radiomic features of the surrounding region contributed to the microvascular invasion status of HCC. The peri-tumor area can be seen to provide effective information in predicting early recurrence. LTP was defined as the appearance of a new tumor within 10 mm of the tumor periphery on the image. Staal et al 32 evaluated that the radiomics features of the 10 mm margin around the postoperative AZ were also valuable markers for predicting LTP after thermal ablation of CRLM. To obtain complete and valid information around the AZ, we studied 0–5 mm, 0–10 mm, and 5–15 mm around the AZ. The best AUC was obtained for the radiomics model of 0–10 mm around the AZ, which is consistent with the definition of LTP. However, when assessing the dilatation around the AZ, it is not necessarily better to have a closer or farther outcome variable. We speculate that the 0–10 mm region around the AZ, representing the area where tumor molecules diffuse after ablation, may be the area with the greatest variation in capillary and immune factor content and the most diverse imaging information. Combining both AZ and PAZ showed superior efficacy in predicting early recurrence after CRLM ablation, with good sensitivity and specificity, helping clinicians to be more objective and individualized in evaluating early efficacy and designing treatment strategies for CRLM ablation.
The square root of GLCM_Correlation in both PAZ1 and PAZ2 models was one of the important features in their respective models with a weighting factor > 0.4. Previous studies have also found that the derived feature of GLCM_Correlation is an important predictor of recurrence after hepatectomy for CRLM33,34, but based on CRLM lesions rather than PAZ. Our study, however, is based on PAZ. We speculate that this may represent the high recurrence rate due to the presence of tumor infiltration around the ablation zone and high malignancy. It is evident that some derived features based on GLCM_Correlation are important in predicting recurrence of some malignant tumors.
It has been shown that the type of thermal ablation does not determine the success and survival of ablation35, so this study does not differentiate between ablation modalities. Lesions with a diameter greater than 3 cm have been shown to have significantly worse ablation results compared to lesions smaller than 3 cm36. Therefore, only lesions with a diameter of less than 3 cm were included in this study. However, it was found that tumor size remains an independent predictor of local tumor progression (LTP) after thermal ablation in patients with CRLM, and the results showed that the larger the tumor, the greater the risk of LTP. This may be due to the fact that as the diameter of the lesion increases, the probability of tumor infiltration into the surrounding microvasculature increases, and the probability of complete ablation of the lesion decreases, leading to an increased risk of residual or recurrent tumor.
This study still has some limitations. Firstly, it is a single institution retrospective study with a small sample size, which may lead to some statistical bias and the inability to perform external validation analysis. It is necessary to further expand the sample size and validate the results. Secondly, the follow-up period of at least 6 months is rather short. Although local tumor progression usually occurs early in the follow-up period, and the majority of patients were followed up for > 12 months (37/53, 69%), some patients with short follow-up may still develop local tumor progression later. Finally, it was not possible to clearly interpret the impact of adjuvant and neoadjuvant chemotherapy before and after ablation on preventing local tumor progression in patients with CRLM.