Hepatocellular carcinoma (HCC) patients have chronic liver disease with functional deterioration and multicentric oncogenicity. Liver surgeries for the patients should be planned on both oncological effects and sparing liver function. In colorectal patients with post-chemotherapy liver injury and multiple bilateral tumors, handling multiple tumors in a fragile/easy-to-bleed liver is an important issue. Liver surgery for biliary tract cancers is often performed as a resection of large-volume functioning liver with extensive lymphadenectomy and bile duct resection/reconstruction. Minimally invasive liver surgery (MILS) for HCC is applied with the advantages of laparoscopic for cases of cirrhosis or repeat resections. Small anatomical resections using the Glissonian, indocyanine green-guided, and hepatic vein-guided approaches are under discussion. In many cases of colorectal liver metastases, MILS is applied combined with chemotherapy owing to its advantage of better hemostasis. Two-stage hepatectomy and indocyanine green-guided tumor identification for multiple bilateral tumors are under discussion. In the case of biliary tract cancers, MILS with extensive lymphadenectomy and bile duct resection/reconstruction are developing. A robot-assisted procedure for dissection of major vessels and handling fragile livers may have advantages, and well-simulated robot-assisted procedure may decrease the difficulty for biliary tract cancers.

Liver surgery for cancer is mainly performed in patients with hepatocellular carcinoma (HCC), liver metastasis of colorectal carcinoma (CRCLM), or biliary tract carcinomas (BTC)[1-4]. It is usually performed as curative-intent liver resection (LR) without other comparable alternatives, except for ablation therapy for small HCC and liver transplantation for patients with severe cirrhosis and non-advanced HCC. However, LR for each disease has its own specificity based on disease characteristics and background liver condition. This editorial describes the characteristics of LR for each disease. Thereafter, the advantages, disadvantages, and current status of the minimally invasive approach for each disease, and its potential are discussed.

Patients with HCC mostly have a history of chronic liver disease (CLD), which causes functional deterioration and multicentric oncogenicity in the injured liver[1]. Therefore, depending on the tumor and pre-existing liver conditions, LR, ablation therapy, trans-arterial chemoembolization, liver transplantation, or recently emerged systemic chemo-immune therapy are chosen. The rates of LR application to primary HCC cases and the 5 year-survival rate thereafter are approximately 30% and 50%, respectively[1]. However, after a successful first treatment, many patients eventually enter a long-term treatment course with repeated treatments for recurrent/multicentric metachronous HCC raised from an oncogenic CLD background. One of the above-listed treatment options is selected based on the tumor and liver conditions of the patients at the time of each treatment. On LR indication, an evaluation of the liver function and, accordingly, estimation of resectable functional liver volume should be performed preoperatively[5], since HCC patients with CLD have a potential risk factor for postoperative morbidity and liver failure. Furthermore, potential repeated treatments over a long period of the treatment course should be considered in the treatment strategy of patients with HCC/CLD.

However, dissemination of cancer cells within the same portal territory as HCC tumors is well known, and anatomical resection of HCC is recommended[6]. Hemi-hepatectomy, sectionectomy, and sometimes segmentectomy, are widely accepted anatomical resections. However, since clear margins of segments one, five, six, and seven have sometimes been difficult to define, the Tokyo 2020 terminology of liver anatomy and resections was recently issued for segment or smaller anatomical resections[7]. These small anatomical resections and their combinations are under discussion for their oncological advantages. Liver surgeries for HCC patients should be planned to be appropriate in terms of both oncological effects on the currently existing HCC and sparing function of the liver with CLD, not only to minimize postoperative morbidity but also from the long-term perspective of potential repeated treatments.

LR is the only curative-intent treatment for patients with CRCLM, with a 5-year overall survival rate of approximately 40%-50%[3]. However, due to the advancement of chemotherapy over the last few decades, combination strategies with chemotherapy, including adjuvant, neoadjuvant, and conversion strategies, for expanding indications and improving outcomes have become increasingly common[3]. Based on the current situation, patients with multiple tumors in the bilateral lobes often undergo LR. Several procedures are advocated to ensure that extended LR for multiple tumors is feasible and safer, such as residual liver hypertrophy with percutaneous transhepatic portal embolization (PTPE)[8,9], two-stage hepatectomy[10], or associating liver partition or portal vein embolization for staged hepatectomy (ALPPS)[11]. In contrast, parenchymal-sparing LR is recommended for tumors occurring in small numbers, since tumor cell spreading via the portal vein system is rare, contrary to HCC[12]. Repeat LR for resectable recurrences improves long-term outcomes[13], and parenchymal-sparing LR reportedly improves salvageability and survival at recurrence within the liver[14]. The background liver condition is usually not fibrotic without CLD but is often associated with post-chemotherapy liver injury, such as steatosis and congestion of microcirculation with sinusoidal obstructive syndrome[15,16]. Liver steatosis can lead to liver fragility during surgery and postoperative elevation of transaminase levels. Congestion of microcirculation with sinusoidal obstruction can cause increased blood loss during surgery and, sometimes, postoperative morbidity, including ascites, similar to portal hypertension in patients with cirrhosis[17].

Liver surgery (LS) for BTC is performed in intrahepatic cholangiocarcinoma (ICC; peripheral and central types), perihilar cholangiocarcinoma, and gall bladder carcinoma[4]. Small peripheral ICC of the mass-forming type, often with CLD backgrounds and rarely with lymph node metastases, can be treated with an HCC-like approach, though it usually lacks an HCC-like tumor capsule with more invasive features than HCC[18]. Others have more aggressive features like spreading along the Glissonian pedicle with perineural, lymphatic, and venous invasions, as well as direct liver parenchymal invasion and lymph node metastases[4,18]. Since the invasion often involves hilar and intrahepatic Glissonian pedicles, LRs for those diseases sacrifice large volumes of functioning non-cancerous liver parenchyma to remove the cancer cells deeply infiltrated from the hilum into the peripheral Glissonian pedicle. PTPE is sometimes applied in such cases to enlarge the residual liver volume preoperatively[8]. Extensive lymphadenectomy and bile duct (sometimes including vasculature: Portal vein and hepatic artery) resection plus reconstruction are required. The patients mostly have a normal liver; however, sometimes damage from biliary obstruction may be present. In cases with jaundice, preoperative biliary drainage is needed[19].

Laparoscopic liver resection (LLR) emerged in the early 1990s, and its indications have expanded thereafter[20,21]. The cancers previously mentioned are all within the indication of LLR. Less intraoperative blood loss, shorter hospital stays, and less morbidity in some conditions with comparable long-term outcomes have been generally reported with LLR for HCC and CRCLM[22,23]. LLRs for BTC, especially for those requiring extensive lymphadenectomy and bile duct (and vasculature) resection plus reconstruction, are now in the developmental stage with some early reports[24]. Although laparoscopic techniques for liver parenchymal transection, mobilization, and hemostasis have been established, those for extensive lymphadenectomy and bile duct (and vasculature) resection plus reconstruction are performed only in specialized centers. Robot-assisted LLR is also in its developmental stage and is performed mainly in specialized centers[25]. Moreover, devices that can be used in robotic procedures are still limited. However, some of the robotic procedures, such as bile duct/ vasculature resection plus reconstruction, are expected to have advantages due to increased dexterity from stable endo-wrist instruments and stable high-definition three-dimensional visualization.

MILS for HCC with CLD background and recommendation for anatomical resection has been established and applied to most cases with advantages in cirrhotic patients and repeat LR by laparoscopic specific “caudal approach”. Small anatomical resections using Glissonian approach, ICG-guided approach, landmark (i.e., hepatic vein)-guided approach are under discussion and developments. Robot-assisted procedure for long range dissection of major vessels may have advantages.

MILS for CRCLM with combination treatments to chemotherapy has been established and applied to many cases with the advantage in better hemostasis by pneumoperitoneum and optimal visualization. LLRs with two-stage hepatectomy, ALPPS, ICG-guided tumor identification are under discussion and developments. Robot-assisted procedure for handling the fragile liver after chemotherapy may have advantages.

MILS for BTC with spreading invasion along Glissonian pedicle, lymph node metastases and direct invasion to liver parenchyma is developing, especially for extensive lymphadenectomy and bile duct (vasculatures) resection /reconstruction, and possible in experienced center. Well simulated and planned robot-assisted procedure may decrease the difficulty in setting tumor free resection line and reconstruction of small bile duct orifice (Table 1).