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this case, the clinical condition and functional status of the patient allowed the continuation of his cancer
treatment despite the diagnosis of COVID-19.

In the case of radiotherapy, we have not found consistent evidence regarding its effect on the evolution
[39]
and prognosis of COVID-19. However, the latest ASCO recommendations advise suspending treatment
during active infection. On the other hand, the NICE guidelines on the administration of radiotherapy
[45]
and COVID-19 state that an active SARS-CoV-2 infection should not be considered as the only factor
when evaluating the administration of radiotherapy and that each individualized patient situation should
be taken into account. We encourage readers to frequently consult society clinical practice guidelines for
advice, given the rapidly changing scientific evidence.

DIAGNOSIS AND IMAGE FOLLOW-UP WITH IMAGING IN COVID-19 AND LUNG CANCER
PATIENTS: KEY ASPECTS
In patients with lung cancer, chest computed tomography (CT) is the imaging technique of choice for the
[46]
diagnosis, staging, and follow-up, as well as for planning treatment with radiotherapy . CT has a very
relevant role in COVID-19, both in the diagnosis and in the screening of serious complications such as
[47]
pulmonary thromboembolism, bacterial or fungal infection .
CT has been reported to have a sensitivity of up to 97%, which is significantly higher than RT-PCR in
the diagnosis of COVID-19. In a study with 1014 patients from Wuhan in which both techniques were
compared, positive confirmations were found in 88% with CT and 59% with RT-PCR and up to 93% of the
patients were considered positive on CT before confirmation by RT-PCR test . However, the specificity of
[48]
[49]
CT was only 25% to 33% .
Therefore, CT is a useful imaging technique, especially in the initial phases of infection when the RT-PCR
is negative, but there is a high clinical and epidemiological suspicion when the follow-up CT of cancer
patients not suspected of having an infection incidentally shows the typical radiological alterations of
COVID-19.

The most frequent findings of COVID-19 infection on chest CT include the presence of ground glass
opacities or patchy consolidations, which are associated or not with linear images due to thickening of the
septa, peripherally located, bilaterally or multi-lobular; the presence of a diffuse alveolar pattern; or areas
[50]
of organizing pneumonia . When these findings are observed in a situation with a high prevalence of
the disease, the diagnosis of COVID-19 infection is highly probable, and a clinical and epidemiological
investigation must be carried out to rule it out.

In patients who have received radiotherapy weeks or months before the SARS-CoV-2 infection,
a differential diagnosis must be made with radiotherapy pneumonitis (RP) given that it´s clinical
manifestations are similar to those of COVID: progressive dyspnoea and cough, with or without fever.

It is important to know the field of radiation therapy and the time elapsed since the end of treatment.
Ground glass lesions and patchy consolidations appear on CT in the early stages of RP and are
indistinguishable from COVID-19 infection. COVID-19 should be suspected when the lesions are bilateral
[51]
and appear outside the radiation field . 2 to 24 months after the last radiation therapy dose, signs of
fibrosis appear including traction bronchiectasis and loss of volume, and the presence of new-onset lesions
gives rise to complex radiological patterns in which it is difficult to identify typical signs of COVID-19
infection.