For this review, the term metastatic cancer
is defined as “the spread of cancer from one part of the body to another.”3
This definition includes Stage IV cancer, the stage at which “the cancer has spread to another organ.”20
Staging is determined by “location of the primary tumor; tumor size and number of tumors; lymph node involvement, cell type and tumor grade; and presence or absence of metastasis.”20
Other equivalent terms used in the research literature are “advanced”6
cancer. Advanced cancer
is defined as cancer that has spread to other places in the body and usually cannot be cured or controlled with treatment.21
It is important to note, however, that not all persons with metastatic or advanced cancer are in the palliative or end-of-life phase. These distinctions will be made when the reviewed studies are described in detail.
Data Sources and Search Strategy
The search strategy included searching electronic databases, hand-searching reference lists, and communicating with experts in the field. Electronic databases selected were those cited previously in previous systematic reviews9,10–14
on persons with local or regional cancer and exercise: MEDLINE, EMBASE, CINAHL, PsycINFO, the Cochrane Central Register of Controlled Trials, the Cochrane Databases of Systematic Reviews (EBM Reviews—Ovid), and PEDro.
The search was conducted up to and including May 8, 2008, using the following keywords: metastatic or palliative or advanced AND cancer or neoplasm AND exercise or physical activity or exercise therapy or physical fitness. The search strategy was modified for each database and exploded, when possible, in order to maximize sensitivity and produce a comprehensive search. These search terms were chosen from an examination of search terms used in similar reviews and modified after consultation with a health sciences reference librarian. Terms were searched for title, abstract, and subject heading.
Study Selection: Inclusion and Exclusion Criteria
Articles were included at the title stage based on (1) population: persons with metastatic, advanced, or palliative cancer; and (2) intervention: exercise as the intervention or a component of the intervention. Titles that were unclear were also included at this stage. Abstracts of the selected studies were included based on population, intervention, and (3) publication in a peer-reviewed journal. Following these steps, full texts were reviewed using these inclusion criteria. Because of the lack of studies involving persons with metastatic cancer, articles were not screened based on comparisons, control groups, or outcome measures, in order to include as many relevant studies as possible.
Throughout the search process, exclusion criteria were (1) population
: studies of persons with lymphoma, melanoma, or myeloma (these are not considered to be metastatic cancers)3
and studies in which results of those with metastatic cancer could not be separated from those with non-metastatic cancer; and (2) type
: studies in languages other than English or French, newspaper editorials, critical reviews of individual articles, and qualitative research studies. In addition, studies were excluded if less than one-third of the sample had metastatic or advanced cancer.
Two independent reviewers (WPF, RB) screened all titles, abstracts, and full texts. Disagreements between the reviewers were resolved by consensus. Arbitration by a third reviewer (CR) was used for unresolved disagreements.
Levels of Evidence
Levels of evidence from the Oxford Centre for Evidence-Based Medicine (CEBM)22
were assigned to each study by one reviewer (HW) and then checked by a second reviewer (CR; see ).
Table 1 Oxford Centre for Evidence-Based Medicine Levels of Evidence for Therapy/Prevention, Aetiology/Harm (May 2001)22
Study Quality Assessment
Two quality-assessment tools were used, depending on study design. Randomized controlled trials (RCTs) were assessed using criteria from van Tulder et al.23
(see ); case series were assessed using the case-series criteria24
Table 2 Methodological Quality Assessment Tool for Randomized Controlled Trials23
Table 3 Methodological Quality Assessment Tool for Case Series24
Quality assessment for the included studies was performed by four reviewers (WPF, CR, RB, CV); each reviewer assessed quality for two or three of the studies, and the results were then checked by a second reviewer. Each reviewer evaluated the full text of the articles, answering the appropriate list of questions with a “yes,” “no,” or “not reported.” A point was granted only for a “yes.” Disagreements were resolved via discussion and consensus.
Grades of recommendation (see ) from the Oxford CEBM22
were summarized for the studies by one reviewer (HW) and then checked by a second (CR).
Table 4 Oxford Centre for Evidence-based Medicine—Grades of Recommendation (May 2001)22
A data-extraction tool was developed and pilot-tested on three studies. Pilot testing was completed by two independent reviewers (RB, CR), and amendments were made where necessary. Once no new additions or modifications were forthcoming, pilot testing was deemed complete.
Data extraction for the 10 included articles5,8,18,25–31
was performed by four reviewers (RB, WPF, CR, CV); each reviewer extracted data for two or three of the articles, and the results were then checked by a second reviewer. Disagreements were resolved via discussion and consensus.
A summary of findings for each study was compiled to depict study quality, level of evidence, design type, sample characteristics, intervention type, outcomes, and results (see ).
Characteristics of Included Studies