The emergence of COVID-19 presented a global health challenge, intersecting with existing health concerns like cancer. Understanding the relationship between SARS-CoV-2 and cancer is important for patients, healthcare providers, and the public. This involves recognizing how cancer impacts vulnerability to the virus, how the pandemic altered cancer care, and whether the virus itself might influence cancer development.
Increased Vulnerability of Cancer Patients to COVID-19
Individuals with cancer or undergoing treatment face heightened susceptibility to severe COVID-19 outcomes. This increased risk stems from compromised immune systems, weakened by the cancer itself, especially hematologic malignancies, metastatic cancer, or lung cancer. Cancer treatments like chemotherapy, radiation, and some immunotherapies further suppress the body’s defenses, leaving patients more vulnerable to infections.
Cancer patients contracting COVID-19 have experienced more challenging outcomes than the general population. Studies indicate higher rates of hospitalization, ICU admission, and mechanical ventilation. Data also suggest cancer patients faced approximately five times greater risk of dying from COVID-19 than individuals without pre-existing conditions. Those who received chemotherapy within 28 days of diagnosis showed an increased mortality risk [2.2].
Cancer type and stage also influence vulnerability. Patients with hematologic, lung, or metastatic cancers consistently show higher frequencies of severe COVID-19 events and worse outcomes. While immunotherapy’s impact on COVID-19 severity can be complex, patients with underlying immunosuppression receiving these treatments have sometimes experienced worse outcomes [3.2].
COVID-19’s Impact on Cancer Diagnosis and Treatment
The COVID-19 pandemic caused widespread disruptions in cancer care, from early detection to ongoing treatment. Fear of contagion, lockdown measures, and healthcare resource reallocation led to significant delays in routine cancer screenings and diagnostic procedures [1.3, 3.3, 4.3, 5.3]. For instance, in April 2020, screenings for breast, colon, prostate, and lung cancers saw reductions of 85%, 75%, 74%, and 56% respectively [1.3, 4.3].
These delays extended to diagnostic testing, with a decrease in cancer tests ordered for various types, including breast, lung, and colon cancer [2.3]. Consequently, fewer new cancer cases were diagnosed, with estimates showing decreases from 19% to 78% in some periods due to reduced screenings [5.3]. This reduction means many cancers may have progressed undetected to more advanced stages, potentially leading to poorer long-term outcomes and increased mortality [1.3, 2.3].
Beyond diagnosis, scheduled cancer treatments, including surgeries, chemotherapy, and radiation therapy, experienced significant interruptions and postponements [1.3, 3.3]. In Ontario, Canada, a 60% drop in cancer surgeries was observed at the pandemic’s outset in 2020 [2.2]. Such delays, even as short as four weeks, have been associated with reduced survival across various cancer types. Modeling suggests pandemic-related disruptions could lead to approximately 20,000 additional cancer deaths in Canada between 2020 and 2030 [2.2]. Healthcare systems adapted by shifting to telemedicine, but the overall impact on care delivery was substantial [2.2].
Investigating a Link Between COVID-19 and Cancer Development
A common concern is whether SARS-CoV-2 infection can directly cause new cancers. Current scientific understanding indicates no definitive evidence of a direct causal link between the virus and new malignancies [3.4, 4.4]. While some viruses are known oncogenic agents, such as human papillomavirus (HPV) or hepatitis B and C viruses (HBV, HCV), SARS-CoV-2 has not been established in this category [1.4, 2.4, 5.4].
However, ongoing research explores potential indirect effects of COVID-19 that might influence cancer risk. One focus is chronic inflammation, particularly associated with Long COVID, where symptoms persist for months or years after initial infection [1.6, 2.6]. Chronic inflammation can lead to DNA damage and create an environment conducive to cancer development by increasing mutations and activating oncogenic pathways like JAK-STAT, MAPK, and NF-κB [1.6, 2.6, 3.6].
Another theoretical mechanism involves the virus’s potential to modulate the immune system and reactivate other latent viruses known to cause cancer, such as Epstein-Barr virus [4.6]. While anecdotal reports of unusual cancers emerging post-COVID have surfaced, these observations remain subjects of active study and are not yet established facts [3.4, 4.4].
Strategies for Cancer Patients During the Pandemic
For individuals with cancer, navigating the pandemic required strategies to minimize risks and maintain care continuity. COVID-19 vaccination is recommended for cancer patients and survivors, as studies show vaccines are safe and effective in this population [3.7, 5.7]. Although the immune response might be less robust in immunocompromised cancer patients, vaccination significantly reduces the risk of severe COVID-19, hospitalization, and death [1.7, 4.7]. Booster doses further demonstrate effectiveness in preventing severe outcomes and hospitalizations for cancer patients [2.7, 5.7].
Beyond vaccination, maintaining protective measures is important. This includes consistent masking, especially indoors and in healthcare settings, to protect immunocompromised individuals. Practicing social distancing and frequent hand hygiene also reduces exposure risk. Additionally, avoid close contact with individuals who are sick [3.7, 4.7, 5.7].
Open communication with the oncology care team is important. Patients should discuss treatment plans, symptom changes, and telemedicine options to ensure care continuity while minimizing exposure risks [2.8, 3.7]. Addressing mental health concerns is also important for overall well-being. Support groups, psychological services, and healthy behaviors like physical activity, balanced diet, and adequate sleep can help manage anxiety, depression, and isolation [1.9, 2.9, 3.9].