On December 14 2020 Davit L Aghayan defended his thesis Laparoscopic parenchyma-sparing surgery in the treatment of colorectal liver metastasis for the degree of PhD. The thesis comes out of Institute of Clinical Medicine at University of Oslo. The title of the trial lecture was The present and future perspectives of robotic resection in hepatobiliary surgery. Pricipal supervisor was professor Bjørn Edwin. 

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Colorectal cancer is one of the most common cancers in the Western World. Over half of the patients develop tumor spread to the liver (liver metastases) and surgery (liver resection) is the only potentially curative treatment for these patients. Traditionally, open surgery has been considered the only possible surgical approach, and anatomical resections (mostly formal hepatectomies: removal of the half part of the liver) had been accepted as a gold standard. 
Parenchyma-sparing approach targeting only the metastasis is balanced by two objectives: achieving complete tumor resection with negative margins (1), sparing as much healthy liver tissue as possible (2). It has shown its advantages over formal liver resections. 

With the development of minimally invasive techniques, laparoscopic (keyhole) approach to remove liver tumors has become a preferable alternative to open surgery. Despite that laparoscopic approach has been adopted by many specialized centres, there is a lack of sufficient evidence on laparoscopic liver surgery. 

This thesis aimed to investigate the role of laparoscopic parenchyma-sparing surgery in the treatment of colorectal liver metastases by highlighting its surgical and oncologic results, and comparing with conventional open approach in a randomized controlled trial.

Laparoscopic parenchyma-sparing resection in patients with colorectal liver metastases was associated with satisfactory surgical and oncological outcomes, also in patients with multiple metastases. Laparoscopic resection in the postero-superior (“difficult”) liver segments is a rational alternative to open approach providing shorter hospital stay, enhanced recovery and better health-related quality of life. In a randomized setting, laparoscopic approach was shown to be as good as open approach in terms of long-term oncologic outcomes.