Thromboembolism during neoadjuvant therapy for rectal cancer: a systematic review

Thromboembolism (TE) is a common, costly and morbid complication that is also associated with decreased survival in cancer patients. However, the risk of cancer-associated TE varies because of the multitude of patient-, cancer- and treatment-related influences. Thromboprophylaxis (TP) is currently not widely adopted in the ambulant population. A review of the literature was undertaken to determine the rate of TE and the benefit of TP in patients with rectal cancer during neoadjuvant therapy (nT).

A systematic literature search of electronic databases, including PubMed and Embase, was performed (1995-2012) for all studies assessing nT in rectal cancer. Data were extracted and used to assess study design, patient demographic and clinical characteristics, treatment protocols and TE incidence. A systematic review was conducted to identify the rates of TE. The search strategy included text terms and MeSH headings for TP, rectal cancer and nT.

Twelve of 86 studies met quality criteria for reporting TE complications and described 10 pulmonary emboli and three deep-vein thromboses in 3375 patients (overall TE rate = 0.38%). Ninety per cent of pulmonary emboli reported were fatal, suggesting significant under-reporting of TE events, even in high-quality studies.

The risk of fatal pulmonary embolism in studies examining nT in rectal cancer that reported complications systematically was one in 375 (0.27%; 95% CI: 0.09-0.44%). The overall TE rate, as well as the effectiveness of TP during nT, remains unknown. TE events should be systematically reported using common terminology frameworks in cancer studies.