Primary tumor of pancreatic cancer as a measurable target lesion in chemotherapy trials.

Background: It is unclear whether primary pancreatic cancer (PC) tumors can be accepted as measurable target lesions in chemotherapy trials. We reviewed recent PC patients to clarify the significance of their computed tomography (CT) responses of the primary tumor after chemotherapy.
Methods: The patient selection criteria were (i) having been admitted between January 2002 and December 2004, (ii) diagnosed as having histologically or cytologically proven adenocarcinoma of the pancreas, (iii) treated with chemotherapy with no previous anticancer treatment and (iv) having been evaluated by follow-up CT to assess the response according to the Response Evaluation Criteria in Solid Tumors criteria.
Results: A total of 143 patients met the selection criteria. It was possible to measure the largest diameter of the primary tumor in 119 (83%) of the 143, and primary tumor shrinkage was observed in 10 (8%) of the 119. When regarding the primary as measurable as opposed to non-measurable, the number of patients with measurable disease became 127 from 67, and the frequencies of partial response (PR), stable disease (SD) and progressive disease (PD) became 11, 74 and 15% of the 127 from 18, 52 and 30% of the 67, respectively. In the former situation, large primary tumor sometimes canceled the shrinkage or progression of small metastasis. In each setting, PR or SD represented a favorable prognosis compared with PD, however, there were no statistical differences between the PR and the SD.
Conclusion: Measuring the primary tumor is acceptable in approximately 80% of PC patients. However, we must be aware that the frequency of SD may increase compared with the PR or PD.