Roxan Helderman

This thesis, entitled ‘Improving the HIPEC treatment delivery for colorectal cancer patients with peritoneal metastasis – THE HEAT AND TIME IS ON’ provides new insights towards treatment optimization for colorectal cancer (CRC) patients with peritoneal metastasis (PM). In the Netherlands, CRC is the third most common cancer with around 13,000 new patients each year. The survival rate at an early stage of disease is around 90%, but dramatically decreases when metastases occur in other organs. Besides the liver and lungs, metastases might develop throughout the peritoneal cavity. When left untreated, the overall survival of patients with PM is only 5 months. A valuable treatment option with the intent to prolong the survival of these patients is the combination of cytoreductive surgery (CRS) followed by hyperthermic intraperitoneal chemotherapy (HIPEC). A prolonged survival of 10-30 months was shown in several clinical studies performing CRS followed by HIPEC. During CRS, visible tumor depositions are removed, followed by a 30-90 minute HIPEC treatment, which means circulating a heated (40-43 °C) chemotherapeutic solution through the peritoneal cavity, to intentionally eradiate microscopic cancer lesions that are left behind after CRS. Although, studies showed that CRS followed by HIPEC prolonged the survival of CRC patients with PM, the role of HIPEC is currently under debate since recently randomized clinical trials did not show any survival benefit after the application of HIPEC. The goal of this thesis is to provide new insights that can help to improve the HIPEC delivery for CRC patients with PM.

In the first part of this thesis, an introduction in the world of HIPEC is provided. The efficacy of HIPEC depends on eight HIPEC treatment parameters; the choice of the type of drug, drug concentration, treatment duration, temperature of the perfusate, delivery technique, carrier solution, volume of the perfusate and patient selection. In Chapter 2 each treatment parameter is discussed and an overview of the choices per treatment parameter is provided. Overall, most CRC patient with PM were treated with oxaliplatin or mitomycin C (MMC) dissolved in dextrose or saline for a duration varying from 30-120 minutes at a temperature between 41-43 °C using the open or closed delivery technique. Worldwide, each institute has its own preference resulting in a large variation in the clinical application of HIPEC. In order to improve the HIPEC treatment outcome, it is important to optimize the treatment protocol by quantifying the effect of each parameter separately. The role and impact of each treatment parameter should be studied in an representative experimental setting, using a clinically representative animal and HIPEC model. An overview of available preclinical in vivo-models used in HIPEC research is provided in Chapter 3. Depending on the goal and treatment parameter to investigate, the desired model should be determined. Large animals, such as pigs, are ideal animal models to study the temperature distribution, pharmacokinetics, pharmacodynamics and side effects of HIPEC, because the size and anatomy are comparable to humans. However, there are currently no relevant PM pig models available, whereby the evaluation of the effect of HIPEC on tumor size or survival is hampered. Studying the effect of a HIPEC treatment parameter on the tumor lesions is much easier in small animals, such as mice, rats and rabbits. In those animals, it is rather easy to establish small tumor lesions throughout the abdominal cavity and the handling and housing of small animals is much easier and cheaper. Besides the animal model, it is important to develop an experimental HIPEC model in which the thermal and drug distribution is well-controlled, and systemic overheating of the animal is avoided. Therefore, the right delivery technique, flow rate, number of tubing, temperature and temperature control should be applied to make a fair comparison between different methods of delivering the HIPEC treatment.

In the second part the impact of the HIPEC treatment parameters type of drugs, drug concentration and temperature of the perfusate on the drug uptake, cell cycle distribution, DNA damage and apoptosis was investigated in an in vitro setting. Exposure to hyperthermia only resulted in a slightly decreased cell viability and clonogenicity of several CRC cell lines (Chapter 4). Platinum-based drugs, including oxaliplatin, showed a temperature-dependent synergy with heat resulting in increased drug uptake, a cell cycle arrest, more DNA damage and higher apoptotic levels. Same results were obtained for MMC, but without showing a synergy with heat. In conclusion, both drugs are suitable for HIPEC, although the right circumstances should be confirmed in a more representative preclinical model.

Tools to conduct HIPEC research in small animals is investigated in part 3. In Chapter 5, we present a validated semi-open HIPEC setup in which the temperature distribution is well-controlled and stable throughout a 90-minute HIPEC procedure in rats. Rats treated using a four-inflow setup resulted in a more stable and homogeneous thermal distributions compared to an one-inflow construction, with lower standard deviations and less thermal losses. The core temperatures of the rats were kept stable using occasional tail cooling. This validated design can improve accuracy in in vivo experiments investigating the impact of relevant treatment parameters on the efficacy of different HIPEC protocols. To conduct preclinical HIPEC research, it is important to use a representative animal model in which peritoneal lesions are confirmed before treatment. A major challenge for the optimal use of orthotopic animal models is non-invasive identification of tumor nodules and monitoring tumor outgrowth over time. To this end, we evaluated the use of ultrasound as a simple and easy-to-handle imaging tool for PM in small animals in Chapter 6. We were able to follow the tumor outgrowth, and to score the extent of disease using ultrasound, which was similar to ex vivo scores, thereby confirming that ultrasound is a reliable non-invasive method to detect and quantify peritoneal tumor outgrowth in rats.

Finally, in part 4, all knowledge obtained in the previous parts is coming together in the final research. After peritoneal lesions were confirmed in rats using ultrasound, HIPEC was applied using oxaliplatin or MMC at 38 °C or 42 °C for 30, 60 or 90 minutes (Chapter 7). A higher inflow temperature in combination with a longer treatment duration resulted in more drug uptake, decreased proliferation and increased apoptotic levels, demonstrating that oxaliplatin- and MMC-based HIPEC procedures are both temperature- and duration-dependent.

The overall conclusion of this thesis towards ‘Improving the HIPEC treatment delivery for colorectal cancer patients with peritoneal metastasis’ is to make sure THE HEAT AND TIME IS ON. HIPEC can be an essential part of the treatment of PMCRC patients, if applied under hyperthermic conditions with a treatment duration of at least 60 minutes. Achieving a stable and uniform drug and temperature distribution throughout the peritoneum is very important and can be accomplished by using more inflow and outflow catheters. In Chapter 8 a discussion is provided on all the studies included in this thesis to integrate all topics into the light of the latest relevant scientific literature, outlining future research directions that aim to further improve the HIPEC treatment delivery.