Cancer diagnosis and suicide outcomes: Umbrella review and methodological considerations.
BACKGROUND
Suicide outcomes in cancer patients represent a major public health concern. We performed an umbrella review (UR) including all meta-analyses (MAs) and systematic reviews (SRs) published on the association between cancer and suicide outcomes.


METHODS
Eligible studies were searched in the main scientific databases up to January 23rd, 2021. Eligible MAs/SRs focused on all suicide phenotypes among cancer patients. Evidence of the association was extracted; the credibility and quality of the included studies were evaluated using ad-hoc tools, including "A MeaSurement Tool to Assess systematic Reviews-2-Revised" (AMSTAR-2-R).


RESULTS
Six MAs and 6 SRs were included. The standardized mortality ratio of suicide in cancer patients was 1.5 to 1.7-fold higher than in the general population. Risk factors for suicide outcomes among cancer patients were male sex and older age, a cancer diagnosis within the prior year, and some specific cancer sites. Among 107 associations, 90 (84.1%) were supported by high credibility of evidence (class II). However, all studies reported a large heterogeneity (I2> 50%) and the majority of them reported considerable heterogeneity (I2> 75%). All MAs used random-effects measures. All MAs but one assessed publication bias and only one disclosed it. The majority of MAs/SRs showed critically low quality based on AMSTAR-2-R.


LIMITATIONS
We could not perform additional analyses due to the limited number of MAs.


CONCLUSIONS
This UR underlines the inflated risk for suicide among cancer patients. Upcoming, well-designed studies are needed to account for a broader set of variables. Several methodological issues likewise warrant attention.