Adjuvant
A substance added to a drug to aid its action, specifically in increasing immune response.

Agent studies
In cancer prevention trials, studies that look at whether taking certain medications, vitamins, minerals, or food supplements can prevent cancer.

Cancer
The general term covering more than 100 diseases characterized by abnormal and uncontrolled growth of cells.

Chemotherapy
Treatment with anticancer drugs.

Control Group
In a clinical trial, the participants who receive, depending on the study, either standard treatment or a placebo.

Double-blind
A process used to prevent bias in a clinical study. Neither participants nor physicians know who is taking the study agent and who is not.

Intervention Group
The participants in a trial who receive the medication or study agent being tested.

Investigator
The experienced clinical researcher who prepares a treatment plan and implements it with a patient.

Lymphedema
Arm swelling, a complication that can occur with breast cancer treatment.

Phase I, II, or III Trials
In cancer prevention clinical trials, each step, or phase, is designed to answer different questions about the study agent. The first two phases include only a small number of participants, but the third can involve hundreds of sites and thousands of participants.

Phase I: researchers seek to find the best way to give a new treatment and how much can be given safely. These studies are offered only to patients whose cancer has spread and who can't be helped by other known treatments.

Phase II: the study focus is on learning whether the agent has a biologic effect in preventing cancer. If a treatment shows activity against cancer in Phase II, it moves to Phase III.

Phase III: these trials compare a promising new agent to the standard one or to no agent. Trials involve two groups: the intervention group and the control group.

Placebo
A tablet or capsule that looks like the medication being tested but doesn't contain any active ingredient.

Protocol
An action plan for a clinical trial. It states what a study will do, how, and why. It explains the number of people to be studied, who is eligible, what they will take, what tests they will receive and how often, and what information is gathered.

Randomization
Participants are assigned by chance, often by a computer, either to receive the study agent (intervention group) or not (control group).

Sentinel Node
The lymph node to which breast cancer or melanoma cells are likely to travel first.

Single-blind
Patients do not know which of the trial treatments they are receiving, to prevent personal bias from influencing their reactions and study results.

Sponsor
The agency or firm responsible for financing a clinical study.

Study Arm
In clinical trials, patients assigned to one part or segment of a study receiving a specific treatment.