Pretreatment diagnostic studies
LAPAROTOMY SHOULD BE THERAPEUTIC, NOT DIAGNOSTIC.
If the primary tumor cannot be resected completely, surgery (pancreaticoduodenectomy) for pancreatic cancer offers no survival advantage. However, only 16% to 30% of patients who undergo operation with curative intent have their tumors successfully removed; the remaining patients are found to have unsuspected liver or peritoneal metastases or local tumor extension to the mesenteric vessels. Therefore, most patients who undergo surgical exploration for presumed cancer of the pancreatic head receive no survival benefit, yet the laparotomy results in a perioperative morbidity rate of 20% to 30%, a mean hospital stay of 14 to 20 days, and a median survival after surgery of only 6 months. Further, in patients whose tumors are resected with positive margins (Table 32.4-8) (Table Not Available) , the survival duration is less than 1 year and no different from the survival duration achieved with palliative chemotherapy and irradiation in patients who have locally advanced, unresectable disease. Therefore, in contrast to the case for selected patients with colorectal or gastric cancer, there are no data in support of palliative (positive-margin) resection for adenocarcinoma of the pancreas.
RESECTABILITY SHOULD BE DETERMINED PREOPERATIVELY.
Accurate preoperative assessment of resectability will increase resectability rates and minimize positive-margin resections. A common misconception in pancreatic tumor surgery is that resectability is determined best at laparotomy. In fact, however, resectability is most accurately determined preoperatively by imaging studies, not at the time of “exploratory” laparotomy. Surgeons will declare a tumor to be unresectable at the time of laparotomy when unsuspected liver metastases, peritoneal implants, or, most commonly, locally advanced disease is found. The term locally advanced is often poorly defined, leaving the patient, the medical oncologist, and the radiation oncologist without a clear understanding of why the primary tumor was not resected. Data from MDACC have demonstrated improved rates of resectability when high-quality CT is combined with objective preoperative criteria for resectability. CT criteria for resectability include (1) the absence of extrapancreatic disease, (2) a patent superior mesenteric-portal vein (SMPV) confluence, and (3) no direct tumor extension to the celiac axis or SMA. Patients whose tumors are deemed unresectable by these radiographic criteria are not considered candidates for a potentially curative resection.
Improved CT technology over the past decade has resulted in CT being the study of choice to determine extent of disease and resectability status in patients with pancreatic cancer. Image resolution has improved considerably with the use of dynamic scanning, whereby intravenous contrast material is delivered by an automatic injector. The development of helical or spiral scanning has improved scan speed through continuous rotation of the x-ray tube around the gantry. This allows the entire pancreas to be imaged during the bolus phase of contrast enhancement. In addition, scan data can be processed to display images in three-dimensional and multiplanar formats. Helical CT performed with contrast enhancement and a thin-section technique can accurately assess the relationship of the low-density tumor to the celiac axis, SMA, and SMPV confluence. However, design of the scanning protocol and interpretation of scans must be done by experienced physicians who understand the clinical importance of accurate staging and assessment of resectability in patients with pancreatic cancer.
Controversy Over Fine-Needle Aspiration and Intraoperative Biopsy
CT-guided percutaneous fine-needle aspiration (FNA) is the diagnostic procedure of choice for establishing a cytologic diagnosis in patients with locally advanced and metastatic pancreatic cancer. The wisdom of percutaneous biopsy has recently been questioned, and several authors have suggested that the use of preoperative FNA results in peritoneal contamination by tumor cells–contamination that otherwise would not have occurred. However, only in the subgroup of patients with resectable disease are fears of FNA-induced tumor dissemination worthy of consideration; patients who have unresectable disease or who undergo a positive-margin resection have a median survival of only 6 to 12 months, and it is unlikely that microscopic contamination of the peritoneal cavity by tumor cells during biopsy would influence survival of such a short duration. In addition, the majority of patients with unresectable disease require tissue confirmation of adenocarcinoma to enable appropriate counseling and treatment planning. Given the currently available minimally invasive methods of tissue acquisition and biliary decompression, it is unrealistic to consider laparotomy with intraoperative biopsy as an alternative to CT-guided FNA in patients with advanced disease. In patients with potentially resectable disease, the concern about biopsy-induced peritoneal contamination by tumor cells has led to the recommendation that patients with clinical and radiographic findings suggestive of a malignant neoplasm of the pancreas or periampullary region undergo pancreaticoduodenectomy without tissue diagnosis. In one report, CT-guided-FNA was proposed as a cause of positive peritoneal washings in six patients. However, each of these patients appears to have had advanced, unresectable disease, which could have been the source of positive washings. Five of the six reports on the cytologic analysis of peritoneal washings have involved patients with locally advanced or unresectable adenocarcinoma of the pancreas. None of the 38 patients found to have positive washings in these five published series underwent a potentially curative pancreaticoduodenectomy; one patient underwent a palliative resection with grossly positive margins.