Survival variability of controls and definition of imaging endpoints for longitudinal follow-up of pancreatic ductal adenocarcinoma in rats.
BACKGROUND
The 3Rs guideline is the gold standard for ethics in animal experimentation. Two of those rules, namely refinement and reduction, require further improvement. The objective of this study was to define pathways to better compliance with these prerequisites. Two methods which move us in this direction are: (1) using small animal imaging techniques for pancreatic ductal adenocarcinoma (PDAC) follow-up and (2) reduction of the number of control animals included in a study of PDAC progression under treatment.


METHODS
Firstly, we used MicroCT scan to diagnose events showing PDAC progression prior to any clinical symptoms to thereby define more humane endpoints identifiable before any painful phenomenon is observed. Secondly, in order to test the hypothesis of using a reference control group in all preclinical studies of a new treatment of PDAC, we investigated the stability of the results obtained with the control groups in three successive identical studies comparing placebo and gemcitabine in tumor-bearing Lewis rats.


RESULTS
Two imaging endpoints were found. The first was the observation of a liver metastasis assessing PDAC diffusion and, earlier than liver metastasis, the presence of bands of fluid along the flanks, with more or less a medial displacement of bowel and solid viscera, reflecting a peritoneal ascites. Results of the longitudinal follow-up of rats in the gemcitabine study revealed heterogeneity in the survival rate in the three control groups, as opposed to the survival rate in the three treated groups which did not differ statistically. As a result, the significance of improved survival with chemotherapy varied greatly according to the control group used for the comparison, ranging from no impact to a highly significant effect.


CONCLUSIONS
The early detection by the means of animal imaging of one or more signs indicating the onset of a critical step in the development of the disease (e.g., ascites or/and metastasis) allows the researcher to prevent the occurrence of animal pain, thereby ensuring better animal welfare. However, using a single standard control group in an effort to use fewer animals for a given model runs such a significant risk of false results that it mars the entire study. Although reducing the number of animals in a study remains the gold standard of our experimental practice, in this case it would come at the price of a loss of validity of the results.
IRCAD, University Hospital of Strasbourg, 1 place de l'hôpital, Strasbourg, France. cherif.akladios@gmail.com.
Cherif
C
Akladios
Department of Digestive and Endocrine Surgery, IRCAD, IHU, University Hospital of Strasbourg, 1 place de l'hôpital, Strasbourg, France.
Mihaela
M
Ignat
Department of Digestive and Endocrine Surgery, IRCAD, IHU, University Hospital of Strasbourg, 1 place de l'hôpital, Strasbourg, France.
Didier
D
Mutter
IRCAD, University Hospital of Strasbourg, 1 place de l'hôpital, Strasbourg, France.
Marc
M
Aprahamian
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology / Q000627:therapeutic use*; D021441:Carcinoma, Pancreatic Ductal / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000401:mortality; D045744:Cell Line, Tumor; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D004354:Drug Screening Assays, Antitumor; D005500:Follow-Up Studies; D008137:Longitudinal Studies; D008297:Male; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000401:mortality; D011917:Rats, Inbred Lew; D015996:Survival Rate; D055114:X-Ray Microtomography; D000093542:Gemcitabine
D000964:Antimetabolites, Antineoplastic; D003841:Deoxycytidine; D000093542:Gemcitabine
3Rs; Ductal adenocarcinoma; Humane endpoints; MicroCT scan; Pancreas; Rat