Response, Remission, and Cure: What the Terms Mean in Cancer Care

Oncology has a specific vocabulary for describing how a tumour responds to treatment - and these terms carry precise meanings that are different from how they are used in everyday language. Understanding them helps you interpret what your oncologist tells you about your progress.

Objective response and RECIST criteria

Response to treatment is measured using standardised criteria called RECIST (Response Evaluation Criteria in Solid Tumours). RECIST provides definitions that allow consistent assessment across patients and clinical trials. Tumour size is measured on imaging (usually CT) at baseline and at each assessment point, and changes are categorised according to defined thresholds.

Complete response (CR)

A complete response means that there is no detectable tumour on imaging or other assessment. All known lesions have disappeared. This is the best possible imaging outcome. Importantly, complete response does not mean the cancer has been eliminated entirely at a microscopic level - very small numbers of tumour cells may remain below the detection threshold of current imaging. This is why monitoring continues even after a complete response is documented.

In pembrolizumab clinical trials, complete response rates vary considerably by tumour type - from under 5% in some settings to 15-20% in others. Patients who achieve a complete response are among those most likely to have durable, long-lasting benefit.

Partial response (PR)

A partial response means the total tumour burden has decreased by 30% or more from baseline. The cancer has responded but has not disappeared. Many patients who benefit meaningfully from pembrolizumab achieve a partial rather than complete response - their disease is smaller and more controlled, but not absent.

Stable disease (SD) and progressive disease (PD)

Stable disease means the tumour has neither grown enough to qualify as progression nor shrunk enough to qualify as a partial response. For some patients, stable disease for an extended period represents meaningful benefit from treatment. Progressive disease means the tumour has grown by 20% or more, or new lesions have appeared - indicating that the current treatment is not adequately controlling the cancer.

Remission and cure

Remission is a clinical term meaning that the signs and symptoms of cancer have significantly reduced or disappeared. It does not necessarily mean the cancer is gone. In the context of advanced cancer, remission that persists for many years after stopping treatment - as seen in some pembrolizumab responders - is sometimes described informally as cure, though oncologists are cautious with this word given the possibility of very late recurrence in some cancer types.