• Palliative care

    Care given to improve the quality of life of patients who have a serious or life-threatening disease. The goal of palliative care is to prevent or treat as early as possible the symptoms of a disease, side effects caused by treatment of a disease, and psychological, social, and spiritual problems related to a disease or its treatment. Also called comfort care, supportive care, and symptom management. [NCI]

  • Pathognomonic

    Having to do with a sign or symptom that is specific to a certain disease. [NCI]

  • Patient-oriented research

    Refers to a continuum of research that engages patients as partners, focusses on patient-identified priorities and improves patient outcomes. This research, conducted by multidisciplinary teams in partnership with relevant stakeholders, aims to apply the knowledge generated to improve healthcare systems and practices. [CIHR]

  • PD-1 (programmed cell death-1)

    The receptor in the PD-1 checkpoint pathway that sends negative signals to the T-cell when it connects to a PD-1 or PD-2 ligand (PD-L1 or PD-L2). These negative signals normally slow down or stop the immune response when it’s no longer necessary. Certain cancer cells can influence the engagement of this checkpoint, which puts the brakes on the immune response. [Patient Resource LLC]

  • PDX

    Short form for “patient derived xenografts,” are models of cancer where the tissue or cells from a person’s tumour are implanted into an immunodeficient or “humanized” mouse (a mouse with functioning human genes, cells, tissues, and/or organs). PDX models simulate the person’s cancer and can be used to identify and test different treatment options before using them in the person. [Adapted from Lai Y et al. (2017). Current status and perspectives of patient-derived xenograft models in cancer research. Journal of Hematology & Oncology, 10(1):106.]

  • Pharmacodynamics

    The study of actions of drugs on the body—what effects a drug has on the patient, including mechanisms of action, beneficial and adverse effects of the drug, and the drug’s clinical applications. [From]

  • Pharmacogenomics

    The study of how genetic makeup affects pharmacodynamics and pharmacokinetics and thus affects drug selection and application to individual patients. [From]

  • Pharmacokinetics

    The study of actions of the body on drugs—the absorption, distribution, storage, and elimination of a drug. [From]

  • Placebo

    In clinical trials, a placebo is usually a tablet or capsule with no active ingredients, or a sham treatment that is meant to make the patient believe that a medical procedure has occurred. Placebos are used so that the subjects in the control group (and often researchers involved in administering or evaluating the trial as well) are unable to tell who is receiving the active drug or treatment. Using placebos prevents bias in judging the effects of the medical intervention being tested. [CIHR]

  • Polymorphism

    A common change in the genetic code in DNA. Polymorphisms can have a harmful effect, a good effect, or no effect. Some polymorphisms have been shown to increase the risk of certain types of cancer. [NCI]

  • Power

    The power of a statistical test is a measure of a study’s ability to detect a statistically significant difference between the results of the intervention group and the control group in a randomized controlled trial. A difference is considered statistically significant when it is highly unlikely to have occurred by chance. A study’s power is partly determined by the size of the difference in scores between the groups, but it is also affected by how many people are included in the study and how much variation there is within each of the groups. For example, if there are too few people in the study, even a large difference may not produce a statistically significant result. [CIHR]

  • Precision medicine

    A form of medicine that uses information about a person’s genes, proteins, and environment to prevent, diagnose, and treat disease. In cancer, precision medicine uses specific information about a person’s tumour to help diagnose, plan treatment, find out how well treatment is working, or make a prognosis. Examples of precision medicine include using targeted therapies to treat specific types of cancer cells, such as HER2-positive breast cancer cells, or using tumour marker testing to help diagnose cancer. Also called personalized medicine. [NCI]

  • Precursor lesion

    A definable pathologic state that frequently progresses directly to disease. Well-studied precancers, or precursors of cancer, have illuminated several complex aspects of the natural history for cervical and colorectal cancer, and have helped to suggest and evaluate successful intervention programs in prevention and patient management. [From Wacholder, S. (2013). Precursors in cancer epidemiology: aligning definition and function. Cancer Epidemiology, Biomarkers & Prevention, 22(4): 521–7. PMC3738010.]

  • Predatory journal

    An alleged academic publication, where publishers actively solicit manuscripts and charge publications fees without providing robust peer review and editorial services. Non-existent peer review, misleading journal names (often similar to legitimate journals), and false information about editors and journal impact factors are among the strategies deployed by these publishers. [Adapted from Shamseer L et al. (2017). Potential predatory and legitimate biomedical journals: can you tell the difference? A cross-sectional comparison. BMC Medicine, 15(28).]

  • Prevention

    Primary – preventing a disease before it occurs. For example, reducing the chances that young people will take up smoking by providing school-based tobacco prevention programs. Secondary – preventing a worsening or future occurrence of a disease after evidence of the disease has already been found. An example would be a doctor removing a pre-cancerous skin lesion before it becomes cancerous and spreads. Tertiary – means treatment for an ongoing disease. An example would be treatment designed to reduce the spread of cancer metastases. [Adapted from CIHR]

  • Prognosis

    A medical prognosis is a prediction of the course of a disease and likelihood of recovery, disability, or death, based on medical expertise. It includes factors such as the patient’s medical history, the course of treatment being followed, and the statistical likelihood of the outcome of the disease in other people. [CIHR]

  • Proliferation

    Cell division and development (growth). [Patient Resource LLC]

  • Prophylactic

    In medicine, something that prevents or protects. For example, prophylactic oophorectomy is surgery intended to reduce the risk of ovarian cancer by removing the ovaries before cancer develops. [Adapted from NCI]

  • Proteomics

    The study of the structure and function of proteins, including the way they work and interact with each other inside cells. [NCI]

  • Proto-oncogene

    A gene involved in normal cell growth. Mutations (changes) in a proto-oncogene may cause it to become an oncogene, which can cause the growth of cancer cells. [NCI]