Using transanal endoscopic microsurgery (TEM) tumors in the rectum can be removed with far greater precision and overview than other endoscopic or conventional transanal techniques allow. This provides greater confidence of complete removal of the lesion and that local recurrences are avoided. Complete resection also provides a correct histological diagnosis.
Cancer in the head of pedunculated polyp
- For T1 tumor in pedunculated polyp, Haggitt level 1 and 2, removed by endoscopic snare resection with macro- and microscopic definitely free resection margins, the treatment is considered as completed. (Similarly in colon.)
- For Haggitt level 3 the resection margins is often questionable. In rectum a resection of the area can then be performed by TEM, and histology will clarify whether this is adequate treatment. (In colon a formal resection must be performed.)
- Haggitt level 4 is treated as a sessile tumor.
Cancer of sessile polyp
TEM is the main method for removing large premalignant polyps in the rectum. Polyps up to 10-12 cm in diameter may be removed by TEM, including polyps growing around the circumference of the intestine, and are located in the area of the dentate line up to about 15 cm above the anal opening.
For infiltrating cancer local excision by TEM is a good option for curative treatment if the following criteria are met:
- The tumor is less than 2.5 to 3 cm in diameter
- The tumor is high or moderately differentiated
- The tumor does not invade deeper than the upper part of the submucosa (Kikuchi sm1)
- For sm1 there is an agreement that TEM excision is curative when performed adequately
- For sm2 there is no agreement that TEM is sufficiently radical and these patients must be considered individually
- There are no signs of infiltration in vessels or lymphatic infiltration
- The location of the rectal tumor is in an area where performing a full wall resection is possible, and one cm free margin laterally is achievable (in mucosa/intestinal wall surrounding the tumor)
It is being attempted to ascertain whether these criteria are met at the preoperative staging assessment, but a final and correct answer is only available after histological examination of the TEM sample. The TEM procedure is therefore often called a diagnostic excision biopsy and histological response will decide whether the procedure is sufficiently radical.
If all criteria are met, the risk of local recurrence is less than 10%. Patients must be carefully controlled by rectal exploration, endoscopy and possibly rectal ultrasound. Any recurrence may then be detected at an early stage, and a curative reoperation can be performed.
If all criteria are note met, patients in good general condition should be reoperated with total mesorectal excision (TME) within a few weeks. The patient should have information and be aware of this before the TEM operation.
In very old patients and patients with poor general condition TEM may be appropriate as a compromise operation also for deep T1 and at T2 tumors. The risk of local recurrence is approximately 30% for this group, but if radiation therapy is given additionally it will be reduced, possibly in combination with chemotherapy. This should be assessed individually based on the risk of side effects. Disadvantage of TEM is that the surgery usually requires general anesthesia, and therefore is more straining for the patient than other endoscopic techniques.