The National Cancer Institute has identified salient guiding principles that define state-of-the-science biospecimen resource practices and promote biospecimen and data quality (NCI Best Practices for Biospecimen Resources). The current NCI Best Practices do not comprise detailed laboratory procedures; rather, they consist of principles by which such procedures should be developed by biospecimen resources. The recommendations are intended to be adapted, as appropriate, based on the mission and scientific needs of individual biospecimen resources. While adoption of the NCI Best Practices is voluntary, the Institute believes that the principles outlined in this document support the goal of optimizing biospecimens for cancer research. Link to full doc
Biospecimen Collection, Processing, Storage, Retrieval, and Dissemination
The aim of every biospecimen resource should be to collect, maintain, and disseminate the highest quality biospecimens, based on the intended research use. High-quality biospecimens are defined as those that most closely resemble the biospecimen prior to its removal from the human research participant. Once the biospecimen is collected (and sometimes prior to its removal), the biospecimen may begin to take on new characteristics based on changes to its environment; e.g., changes in exposure to certain nutritional, chemical, or other environmental factors that may occur during a surgical or collection procedure.
Such changes may result in inaccurate determinations of the molecular and physical characteristics of those components during subsequent analysis. Every attempt should be made to minimize the effects of biospecimen handling on biospecimen integrity. Note that guidance provided is intended to be applied when planning biospecimen collection, prior to the initiation of the collection efforts. In addition, study design will dictate whether certain variables can be controlled and data collected as described below.
Pre-Analytic and Analytic Variables
A variety of factors may affect biospecimen quality and research results; these may be divided into two general categories designated “pre-analytic variables” and “analytic variables.” Pre-analytic variables refer to factors that influence biospecimen integrity prior to its removal from the human research participant and carry through to the point at which a biological specimen is ready for testing. Analytic variables refer to those factors that affect performance of a particular testing procedure.
Pre-analytic variables may be divided into three general areas:
- The physiology of the human research participant prior to biospecimen collection;
- Uniformity of biospecimen collection practices; and,
- Biospecimen handling practices prior to their inclusion in downstream testing.
Uniformity in Biospecimen Collection Practices
The methods used to remove and collect biospecimens from human research participants may influence the quality of the biospecimens collected. Significant research has indicated that during surgical removal of biospecimens, the amount of time following the cessation of blood flow to an organ can affect both levels and molecular profiles of target analytes (Spruessel et al. 2004; Lin et al. 2006). The biospecimen should be preserved as quickly as possible after removal from the patient; e.g., appropriately-sized tissue sections snap-frozen and/or placed into 10 percent phosphate-buffered formalin, as appropriate. When biospecimens are collected from participants, the site at which the biospecimen is removed (tumor or nontumor, as well as the location within the tumor), any anesthetic being used, the length of time blood flow is blocked from the tissue, any stabilizing agents used to preserve the biospecimen following its removal, the type of fixatives used, the length of time the tissues are exposed to fixatives, and the temperature at which biospecimens are maintained following collection may all affect molecular stability and degradation.
Prior to the collection or removal of biospecimens, a plan should be in place to allow for the appropriate annotation of the biospecimens. This annotation should include information about the human research participant, and timing of collection and processing activities; e.g., the type of clearing agent, the type and temperature of paraffin used to process the biospecimen, etc. (ISBER 2008). These data should be maintained in a database that can be linked to the biospecimen at all times.
Biospecimen Handling Procedures
Every attempt should be made to optimize the handling of biospecimens to minimize resulting molecular changes that may result from the processing activities. This includes not only the temperature and timing of biospecimen processing but also such considerations as the size and volume of the biospecimen that will be stored for future use. Smaller samples allow for minimal cycles of freezing and thawing. When samples are stored in a frozen state, the rate at which they are cooled to the storage temperature can influence the rate at which molecular degradation is allowed to proceed.
Biospecimen Acquisition, Fixation, and Shipment
Core Prognostex, Inc. (CPX) provides products and services to enable the uniform collection of high-quality human biospecimens consistent with NCI/OBBR best practice guidelines. The protocols, kits, and devices were originally developed by CPX to support breast cancer research trials in order to secure solid tumor samples for biomarker studies without compromising pathologic evaluation of the tumor. However, the products and methodologies developed for breast cancer are valid for many other types of cancers as well. This means that that the products and services offered by CPX can be applied to other types of cancers, including cancers of the prostate, lung, pancreas, ovary, and soft tissues.