SARS CoV-2 has deeply affected life all over the world with its rapid transmission and fatal ARDS. It is stated that the biggest factor in the transmission of the disease is carriers who have the disease asymptomatically. Asymptomatic infection has been reported in the COVID-19 pandemic [7,8]. Although the frequency of asymptomatic infections in society is not fully known, an estimate was made based on the screening during quarantine in the Japanese cruise ship in Yokohama. The cruise ship hosting 3,711 people underwent a 2-week quarantine after a former passenger was found with COVID-19 post-disembarking. 634 people on board tested positive for the causative virus. The researchers conducted statistical modeling to derive the delay-adjusted asymptomatic proportion of infections, along with the infections' timeline. The estimated asymptomatic proportion was 17.9% [9]. And also, experts from the Infectious Diseases Society of America (IDSA) explain that some of the asymptomatic patients were pre-symptomatic and started to spread the virus 24-48 hours before developing symptoms.
Oncology patients have to go to the hospital due to the necessity of continuing their oncological treatment. Although the patients stated that they complied with the rules of isolation in their living spaces, we found that 15 (53.5%) of 28 patients with whom they live together at home go out to work and 12 (42.8%) patients came to the hospital by using public transport. So they did not fully comply with social isolation due to compulsory reasons. As asymptomatic patients are not tested, the possibility that these patients may be asymptomatic carriers or in presymptomatic period, increases the risk of infection spread to both other patients and healthcare professionals. Therefore, PCR test was performed on every patient who would receive anti-cancer treatment even if they did not have symptoms suggesting COVID-19 infection. In our study, PCR test was positive in 28 of 312 patients that we tested, and the positivity rate was 8.9%. Only three (10.7%) of the oncology patients had mild symptoms, 25 patients (89.3%) had no symptoms.
Because of the changes on computed tomography (CT) of the chest can be positive earlier than other clinical symptoms and laboratory findings, it is very useful for early diagnosis. Common abnormal radiography findings were consolidation and ground glass opacities, with bilateral, peripheral, and lower lung zone distributions [10]. All positive patients underwent a low-dose lung CT, and approximately half of them have COVID-19 involvement. When the limited number of literature is reviewed, a correlation is reported between the level of lung parenchymal involvement in CT and the severity of the clinical course [11]. It is noteworthy that in almost half of our cases there are no CT findings and the involvement in patients with CT findings is relatively limited (approximately 10%). This finding may explain the low frequency of symptoms in the patient group. With the treatment given in the early period, only one of our patients required hospitalization, and the same patient died 1 week after the diagnosis.
It is not clear that, whether 89.3% of the patients had asymptomatic infection was coincidental or due to the effect of their immunosuppressive disease and treatments. Since the excessive response of the immune system is considered as one of the causes of lung damage [12], impaired immune response in cancer patients may be the reason that the patients were asymptomatic [13]. No patient developed symptoms in 14 days of follow-up, except for three. So these patients are in the position of a carrier for the spread of the infection. We believe that screening tests should be performed at regular intervals and the isolation rules should be applied more strictly in these patients, even if they are asymptomatic before treatment, in order to continue their treatment without any problems and to prevent the risk of transmission. Also, giving chemotherapy to an asymptomatic but infected patient may increase the severity of the course of infection.
In summary, in oncology patients who are receiving active anti-cancer treatment without symptoms and findings suggestive of COVID-19 infection, we have to recognize the asymptomatic group of patients. For this reason, we recommend testing for COVID-19 in oncology patients actively receiving therapy, periodically or before each anti-cancer treatment. If we are unable to test before each treatment, it would be correct for healthcare professionals and their families to take precautions as if the patient was COVID-19 positive, in terms of the risk of contamination of the people they are in contact with.