Excess adiposity and survival in patients with colorectal cancer: a systematic review

Abstract

Excess adiposity is an established risk factor for incident colorectal cancer (CRC) but whether this association extrapolates to poorer survival is unclear. We undertook a systematic review to examine relationships between measures of adiposity and survival in patients with CRC. For distinction, we included pre-diagnosis exposure and CRC-related mortality. We performed dose-response meta-analyses and assessed study quality using eight domains of bias. Six study categories were identified based on (i) timing of adiposity measurement relative to survival analysis time zero and (ii) clinical setting. Several types of adiposity measurements were reported; body mass index (BMI) was the commonest. For pre-diagnosis cohorts, baseline BMI negatively impacted on CRC-related mortality in men only (risk estimate per 5 kg m(-2) = 1.19, 95% confidence intervals: 1.14-1.25). The other groups were pre-diagnosis BMI but diagnosis as time zero; population-based cohorts; treatment cohorts; observational analyses within adjuvant chemotherapy trials; patients with metastatic CRC - each had several biases (e.g. treatment selection, reverse causality) and sources of confounding (e.g. chemotherapy 'capping'). Overall, there was insufficient evidence for a strong link between adiposity and survival. These findings demonstrate an important principle: an established link between an exposure (here, adiposity) and increased cancer incidence does not necessarily extrapolate into an inferior post-treatment outcome.

Influence of BMI on short-term surgical outcome after colorectal cancer surgery: a study based on the Swedish national quality registry

“…Similar results have been shown for other major surgical cancer procedures [11]. However, in a recent review, Parkin et al draw the conclusion that there is little evidence supporting a strong link between adiposity and survival in patients with CRC [12].…”

“…It has been used for that purpose since the early 1980s [25], and in a recent study using CT, it was shown that obese stage II CRC patients were at higher risk for poor outcome, with significantly worse disease-free survival than patients with less visceral fat [24]. A possible explanation for such findings may be that excess visceral adiposity seems to induce a pro-tumorigenic environment through metabolic, immunologic, and endocrine processes involving chronic inflammation, insulin resistance, and increased levels of insulin-like growth factor [12,26,27].…”

Temporal changes in loss of life expectancy due to cancer in Australia: a flexible parametric approach

“…Year of diagnosis However, the evidence for the role of most risk factors (such as obesity [23][24][25][26]) and cancer prognosis is mixed and depends on the cancer type.…”

Influence of Visceral Fat in the Outcomes of Colorectal Cancer

“…Other papers suggested that increased VF was a significant predictor of worst disease-free survival in patients with resectable CRC [10] and reduced overall survival in CRC patients receiving adjuvant chemotherapy [16]. In contrast, other works demonstrated that patients with higher VF tended to have better overall-survival that non-visceral obesity patients [12] and a meta-analyses concluded that there was insufficient evidence to prove the presence of a strong link between adiposity and survival [26]. Emerging literature reports the “obesity paradox” in cancer, which suggests that cancer survival is U-shaped and that extremes of weight may have better survival [27, 28].…”