Since the SARS-CoV-2 epidemic began, interest in thromboprophylaxis has grown. It was subsequently recognized that COVID-19 patients in hospitals should, unless contraindicated, receive pharmaceutical thromboprophylaxis with Low-Molecular-Weight Heparin (LMWH) (in line with long-established clinical practises on antithrombotic prophylaxis in patients hospitalised for an acute medical process). Although conventional preventive doses of LMWH were used in some cohorts of COVID-19 hospitalised patients, early reports of a high risk of thrombotic events encouraged some scientific societies and expert bodies to recommend using greater doses of LMWH in particular patient subgroups. At the time, the evidence supporting these recommendations was scant, and, as might be expected, more intense thromboprophylaxis was associated with an increase in haemorrhagic complications.

There was little evidence at the time to back up these suggestions, and as might be predicted, more extensive thromboprophylaxis was related to an increase in haemorrhagic symptoms. Some, but not all, concerns have been resolved by the results of randomised clinical trials comparing various intensities of antithrombotic prophylaxis (standard, intermediate, or therapeutic dosages of LMWH) in hospitalised patients with COVID-19. The use of higher than usual LMWH preventive doses does not seem to have any therapeutic effect in COVID-19 patients in critical care units, although the outcomes are more variable in patients admitted to traditional hospital wards.

In a meta-analysis of aggregated data, therapeutic doses of LMWH compared to standard prophylactic doses were associated with a decrease in thromboembolic events, as well as an increase in major bleeding (although this increase was smaller in absolute terms than the decrease in thrombosis) and no significant differences in mortality. The use of therapeutic dosages of LMWH as opposed to routine prophylaxis in a subset of COVID-19 patients in conventional hospital wards without extra haemorrhagic risk factors was suggested in numerous guidelines that were amended as a result of these data. Soon, meta-analyses of patient data will be accessible, and these studies will presumably aid in determining which patient subgroups may profit from this approach the most.

The International Thrombosis and Cancer Initiative (ITAC) has sponsored the most recent edition of the international clinical practise guidelines for the treatment and prevention of venous thromboembolism (VTE) in cancer patients9, which for the first time contains a section on the treatment and prevention of VTE in patients with cancer and COVID-19. The panellists advise using the same strategy in these situations as in cancer patients without COVID-19. This suggestion is supported by two points. First off, there is no proof that hospitalised cancer patients with COVID-19 have a higher risk of VTE than patients with COVID-19 who are not suffering from cancer (although it may have been more appropriate to compare the incidence of VTE in hospitalised cancer patients with and without COVID-19).

The issue arises from the question of whether to offer regular preventative doses as prescribed by the ITAC guidelines for cancer patients or therapeutic levels as proposed by the more general guidelines. The basic but less useful response is that patients should be evaluated on an individual basis, taking into account the balance of thrombotic/haemorrhagic risk in each situation. However, despite the lack of published data, it's possible that the COVID-19-related thrombotic risk is no longer as significant as it was during the pandemic's early stages due to widespread vaccination, changing virus features, and advancements in illness management.

If this is the scenario, it raises concerns about the credibility of clinical trial findings that were primarily made at the beginning of the pandemic because, technically accurate; the utilization of therapeutic levels of LMWH would have less of an effect on preventing thrombotic events. It does not seem unreasonable to be cautious and advise that, generally, patients with cancer and COVID-19 admitted to a conventional hospital ward should receive standard prophylaxis with LMWH given this ambiguity and the greater haemorrhagic risk of cancer patients.

For specific recommendations on thromboprophylaxis in cancer patients and COVID-19 in people who do not need hospitalisation, even less information is available. In clinical cases, many patients undergoing cancer therapy do not get a thrombotic risk assessment, which may result in the underutilization of outpatient thromboprophylaxis. If it hasn't already been done, thromboembolic risk should be assessed in cancer patients with COVID-19 (there are several validated scales for this purpose). Regardless of a COVID-19 diagnosis, pharmacological thromboprophylaxis is likely necessary in a significant portion of patients.

Personalized medicine and precision medicine are two recent concepts that have applications in the field of thromboembolic illness. Evidence-based recommendations are tremendously helpful, but they invariably miss out on a number of situations that happen frequently in clinical practise. Despite the fact that these knowledge gaps are constantly diminishing as a result of advanced technologies, there is still a lot of room for clinical practice.