2. Defining recurrent cancer

This is the detection of the cancer following a period of time after completion of primary treatment. The NCI Dictionary of Cancer terms [2], defines recurrent cancer as "Cancer that has recurred (come back) after a period of time during which the cancer could not be detected". This is vague and open to interpretation and in clinical practice requires more careful scrutiny:


For example, a unit that regularly scans patients after primary treatment may detect evidence of recurrent disease sooner than a unit which relies on serial tumour markers. Indeed, 2 units may use imaging as part of surveillance but one unit may scan more often that another, or measure tumour markers more frequently than another. Complicating this further is that not all recurrences are associated with rising tumour markers and different modalities of imaging have differing sensitivities and specificities in detecting early or small volume recurrent disease. Compounding the understanding of the role of, and efficacy of, different managements for recurrent disease is tumour and patient heterogeneity [3]. As a consequence, caution needs to be given to the interpretation of data on the efficacy of different managements of recurrent cancer —including the role of surgery in recurrent ovarian cancer (ROC). Trial design and the endpoints of trials have important implications [3–5]. It is generally accepted though that overall survival (OS) is the most clinically relevant and the most clearly definable endpoint [3]. Modern imaging and tumour makers have replaced what was the common practice of second look laparotomy (SLL) in OC, which is no longer recommended. Unlike most other recurrent gynaecological cancers where typically histologic confirmation of recurrence is required before treatment, this is the exception in cases of ROC.

Essentially all OC patients receive platinum-based chemotherapy as part of primary treatment and some concepts are used to help stratify and compare managements of recurrent cancer. These include (1) platinum-sensitive and platinum-resistant disease [6] and (2) platinum-free interval (the interval between date of last platinum dose and date of relapse, PFI) and (3) progression-free survival (PFS). The definition of platinum sensitive and platinum resistant is somewhat arbitrary, but clinically useful. There is an argument that surgical trials might instead focus on date of last treatment (treatment-free interval (TFI)), and date of last operation rather than response to platinum or PFI [7]. Platinum-sensitive OC is defined as disease that is undetected at completion of primary treatment with platinum and which is undetectable for at least 6 months after completion of platinum-based chemotherapy; platinum-resistant disease is ovarian cancer that is detected within 6 months of completion of platinum-based chemotherapy. Other terms used in reports on recurrent cancer are time to first subsequent treatment and intervention-free interval. It is not clear what impact the use of maintenance therapy as an extension of primary treatment will have on these definitions.
