Is surgery the first choice for pseudomyxoma peritonei? Are there other treatments besides surgery?

Author: Li Yan, Chief Physician of Beijing Tsinghua Chang Gung Hospital affiliated to Tsinghua University

Reviewer: Ge Yuping, deputy chief physician, Peking Union Medical College Hospital

Pseudomyxoma peritonei refers to the cancerous transformation of peritoneal mucinous cells, in which tumor cells are implanted in large numbers and extensively in the peritoneum or omentum, secreting large amounts of mucus, which in turn leads to the production of a large amount of gelatinous, mucinous ascites in the abdominal cavity.

Typical clinical manifestations of pseudomyxoma peritonei include increased abdominal circumference, abdominal distension, and loss of appetite. In most cases, the diagnosis is made by finding heterogeneous or watery mucous material in the abdominal cavity during a physical examination or abdominal CT scan for other diseases.

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The treatment of pseudomyxoma peritonei has gone through a long and tortuous process, and now a comprehensive treatment plan with surgery as the main treatment has been formed. Surgery is the basis of treatment. First of all, we must ensure the success of the surgery, and then combine comprehensive treatment, including radiotherapy and chemotherapy. From a professional point of view, since pseudomyxoma peritonei involves the entire area of ​​the abdominal cavity and pelvic cavity, radiotherapy is not a commonly used treatment method.

1. Which tissues should be removed in the surgical treatment of pseudomyxoma peritonei?

The surgical treatment of pseudomyxoma peritonei is called tumor cytoreduction surgery plus hyperthermic intraperitoneal chemotherapy.

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Cytoreductive surgery is a major operation involving more than a dozen steps.

During surgical treatment of pseudomyxoma peritonei, an incision is first made from the midline of the abdomen to the pubic symphysis. After the incision, the peritoneum is peeled off, the mucus in the abdominal cavity is drained, and the tumor is completely removed.

Tumor resection includes multiple aspects: first, the greater omentum and lesser omentum need to be completely removed; second, the peritoneum on the surface of the liver and its substantial surface, as well as the peritoneum on the surface of the diaphragm need to be removed; sometimes it is also necessary to remove the peritoneum of the spleen and its area, and even the spleen itself; the next step is to remove the peritoneum of the pelvic cavity, and if necessary, the rectum needs to be removed. For female patients, the uterus, bilateral ovaries and rectum may also need to be removed; in addition, the appendix area also needs to be removed; finally, the tumor on the surface of the small intestinal mesentery needs to be removed.

After the abdominal tumor is cleaned, hot perfusion chemotherapy is performed. The international standard hot perfusion chemotherapy uses 43°C normal saline plus chemotherapy drugs, such as cisplatin, 5-fluorouracil, oxaliplatin, taxanes, etc. At a temperature of 43°C, high-concentration chemotherapy drugs circulate continuously in the abdominal cavity for 60-90 minutes, thoroughly flushing out residual tumor cells.

After the completion of the hyperthermic chemotherapy, the gastrointestinal reconstruction is performed and the operation is complete. The operation is relatively complicated and involves many tissues and organs, so the technical operation requirements are very high.

According to the scope of surgical resection, a lot of tumors are removed during surgery, and it is necessary to take representative samples of the tumors in each part, that is, to take pathological samples, and conduct a more in-depth and detailed pathological examination of the tumors in each part. Through pathological examination, a lot of tumor-related information can be obtained, and based on this information, it can be determined which type of drug or which type of drug combination is more sensitive, providing a basis for chemotherapy and molecular targeted therapy after surgery.

2. Do all patients with pseudomyxoma peritonei need surgical treatment?

For patients with pseudomyxoma peritonei who are initially diagnosed, the functions of important organs such as the heart, liver, lungs, kidneys, and brain are good; patients can tolerate surgery and have the ability to cooperate with the surgery. Surgery is the first choice for treatment because no other treatment method can achieve the same therapeutic effect as surgery.

If the disease progresses and the best time for surgical treatment is missed, surgery cannot be considered first. For example, if the obstruction is particularly severe and the physical condition is particularly weak, the symptoms should be controlled first, such as nutritional support and effective puncture and drainage. Or if the physical condition is particularly poor and cannot tolerate surgery, appropriate tumor reduction surgery can be performed first to drain the ascites, significantly reduce abdominal distension and abdominal pain, and improve appetite before standardized surgical treatment.

For patients who are not suitable for surgery, other treatments should be adopted. Currently, the most important methods are chemotherapy and targeted therapy.

3. Are chemotherapy and targeted therapy for pseudomyxoma peritonei effective?

Pseudomyxoma peritonei is not very sensitive to traditional chemotherapy drugs, mainly because the tumor is surrounded by a thick layer of mucus, which acts as a barrier to prevent chemotherapy drugs from penetrating into the tumor cells. In order to improve the treatment effect, people have improved the chemotherapy method and adopted a combination of techniques: first, take specific drugs orally to dissolve the mucus layer on the surface of tumor cells. Once the mucus is dissolved, chemotherapy drugs can directly act on tumor cells. This method currently seems to be more effective and has become one of the most effective means of treating pseudomyxoma peritonei besides surgery.

In addition to chemotherapy, molecular targeted therapy can also be used. By detecting relevant gene targets and selecting corresponding molecular targeted drugs, this method has also achieved good results in some patients and can delay the progression of the disease.

In addition to surgery, progress in the treatment of pseudomyxoma peritonei is mainly reflected in chemotherapy and molecular targeted therapy.

Similar to other types of tumors, pseudomyxoma peritonei also has the risk of recurrence and metastasis, which mainly occurs in the abdominal cavity. Tumor cell reduction surgery combined with hot perfusion chemotherapy, coupled with comprehensive treatment, can significantly reduce the risk of metastasis and recurrence, and significantly delay the time of metastasis and recurrence.