Office of Research Integrity
Monitoring & Endpoints
Animals on a tumor study must be monitored by protocol personnel on a model-appropriate schedule (typically ranging from daily to weekly) until tumor development is established. After tumor development is confirmed through the presence of visible/palpable tumors or appropriate imaging assessment for internal tumors, animals must be monitored and the tumors measured at least twice weekly. More frequent observations (including weekends and holidays) may be necessary based on tumor growth rate, study parameters, or general condition of the animal. The overall wellbeing of the animal should take priority over precise tumor measurements in decisions regarding euthanasia or other interventions. Clinical signs and body condition score must be incorporated into the endpoints of the study.
Experimental endpoints for primary tumors should be based on size and/or weight. The tumor size endpoint is recommended for spherical tumors while the tumor weight endpoint should be applied to oblong tumors. Growth of internal tumors such as metastases or lung tumors can be monitored and measured using a variety of imaging modalities. Visible or palpable tumors may be measured via imaging or with calipers.
Tumor weight can be calculated with the following formula (length and width in mm):
(tumor length x tumor width x tumor width)/2 = weight in mg
Maximum Tumor Size/Weight:
Mice: 20 mm in diameter or 4000 mg
Rats: 40 mm in diameter or 8000 mg
Please note that maximum size/weight applies to the total tumor mass burden (whether one or multiple tumors). Requests to exceed these maximums must be scientifically justified and approved by the IACUC.
The following clinical signs should be incorporated into the humane endpoints in tumor-bearing animals.
- Tumor(s) interfere with ambulation, eating, drinking, or elimination
- Weight loss >20% of pre-procedure body weight
- Persistent anorexia or dehydration
- Unable to maintain an upright posture or to ambulate
- Muscle atrophy or emaciation
- Lethargy or failure to respond to gentle stimuli
- Labored respiration – particularly if accompanied by cyanosis
- Enlarged lymph nodes or spleen due to tumor infiltration
- Significant abdominal distension, incontinence, or prolonged diarrhea
- Ulcerated tumors (Note: Tumor necrosis with ulceration of overlying skin is generally considered a humane endpoint. However, an exception may be submitted to the IACUC for consideration on a case by case basis for studies that involve the administration of tumor therapy in which tumor necrosis/ulceration may be a feature of regression. To request an exception, the features of tumor regression must be described in an animal use protocol and be approved by the IACUC.)
The following Body Condition Score (BCS) system should also be used, especially in rodents with tumors within the body cavity. The general physical condition of the animal is an important factor in effectively following the progression of tumors in rodents. A scoring system of “1” (emaciated/wasted) to “5” (obese) assists with assessment of overall health of the animal. It is important to note that treatments designed to affect tumor growth (such as chemotherapeutics) which are often part of tumor load studies, can lead to weight loss and poor body condition. Thus, the BCS becomes an important assessment tool in the tumor load experiments.
Rodents must be euthanized if:
- the animal's BCS is 1/5 or
- the BCS is 2/5 and the animal shows decreased activity/responsiveness.
Implantable & Inducible Tumors
It is required that cell lines and biologicals derived from human or other mammalian tissues be free of common rodent pathogens. Please review the IACUC policy on Cell Lines and Biologicals Used in Rodents to determine whether testing will be required prior to use in an MUSC animal facility. Final determination of the need for testing is made by the Biosafety Officer in consultation with the Attending Veterinarian and documented on the required Biological Materials Appendix..
Tumor implantation sites should be chosen to minimize damage to adjacent normal structures and must be specified in the VARA. The IACUC recommends implanting tumors on the dorsum or flank of an animal, as these areas will likely have the least amount of site-related morbidity. If other sites are to be used, site selection must be justified in the protocol.
- Sites involving the face, limbs or perineum should be avoided as there is little to no space for tumor growth and expansion, and they may interfere with eating, drinking or elimination.
- Intramuscular implantation is considered to be painful due to distension of the muscle by the tumor(s) and must be monitored closely.
- Paster, Eden V; Villines, Kimberly A; Hickman, Debra L. Endpoints for Mouse Abdominal Tumor Models: Refinement of Current Criteria. Comp Med, Volume 59, Number 3, June 2009 , pp. 234-241(8).
- Akiko Sato, VMD, Brenda Klaunberg, VMD, and Ravi Tolwani, DVM, PhD. Overview In Vivo Bioluminescence Imaging. Comparative Medicine. Vol 54, No 6. December 2004
- The Guide for the Care and Use of Animals 2011
- NCI neoplasia guidelines http://ncifrederick.cancer.gov/Lasp/Acuc/Frederick/GuidelinesFnl.aspx