BACKGROUND Covid-19 pandemic has opened several new disease scenarios yielding novel syndromes which have never been seen before or resurrecting old inflammatory phenomenon no longer recorded, like radiation recall (RR) syndromes. Radiation recall syndrome is a limited field inflammatory reaction occurring in a previous irradiated volume several months or year before induced by a triggering factor. The most reported phenomena are skin reactions, although other organs could be involved, like the lung as in radiation recall pneumonitis (RRP). It is a well described inflammatory reaction, occurring within a previous irradiated pulmonary volume several months or years later radiotherapy (RT), triggered by factors like drugs, chemotherapy agents, immunotherapy or vaccination. Indeed in the Covid -19 pandemic, RRP following anti-Covid 19 vaccination administration or SARS-CoV2 virus have been just recorded. Herein, we describe a RRP triggered by COVID-19 pulmonary infection, in a woman previously treated with adjuvant breast cancer radiotherapy. CASE PRESENTATION A 65-year-old woman was diagnosed with invasive stage III A (pT2 pN2 M0) G2, Luminal B ductal carcinoma of the right breast, in 2016. After breast conserving surgery and adjuvant chemotherapy, postoperative radiotherapy was applied on the supraclavicular area and the remaining breast.In March 2020, she complained of fever, mild dyspnoea and cough. The real-time polymerase chain reaction on nasopharyngeal swab was positive for SARS-CoV2. The chest computed tomography (CT) scan showed radiologic features in the right lung, miming the previous radiation treatment fields. She was admitted to a Covid Unit and treated per protocol. Chest CT scan 3 months later showed a complete resolution, with a consolidated pulmonary fibrosis.CONCLUSIONRadiation recall pneumonitis is an inflammatory reaction occurring within a previous irradiation of lung volume induced by triggering factors (drugs, ultraviolet light, viruses). The precise underlying mechanism has not been defined yet. A fascinating hypothesis could be that a previous radiation due to a lung repaired damage, might induce an inflammatory response that can leave a kind of “damage cell memory” and can be triggered after many years by a strong immune activation, such as occurs in COVID19 pneumonia.

The COVID-19 pandemic has opened several new disease scenarios, yielding novel syndromes that have never been seen before and resurrecting old inflammatory phenomena that are no longer recorded, such as radiation recall (RR) syndromes. Radiation recall syndrome is a limited field inflammatory reaction that occurs in a volume that was irradiated several months or years previously before being induced by a triggering factor. The most frequently reported phenomena are skin reactions; however, other organs could be involved, such as the lungs in radiation recall pneumonitis (RRP). It is a well-described inflammatory reaction that occurs within a pulmonary volume that was irradiated several months or years previously via radiotherapy (RT), triggered by factors such as drugs, including chemotherapy agents, immunotherapy, or vaccination. Indeed, during the COVID-19 pandemic, RRP following anti-COVID-19 vaccination or SARS-CoV2 infection was recently reported. ACE receptor-rich tissues such as lung or skin tissues were mainly involved. Herein, we present a case of RRP triggered by COVID-19 pulmonary infection in a woman who previously underwent adjuvant breast cancer radiotherapy. Although symptoms were typical, pulmonary CT findings depicted a unique distribution of ground-glass opacities (GGOs) throughout the previous radiation portals and mirror-like the radiation fields. Anamnesis and radiation plan evaluation were crucial in the diagnosis of RRP.

Coronavirus disease 2019 (COVID-19), is a novel infectious disease responsible for a severe acute respiratory syndrome due to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, which was firstly reported in January 2020 in Wuhan, Hubei Province, China, and then rapidly spread to other countries beyond China with a pandemic proportion in these last two years. In its severe lung expression, disease onset may result in death due to massive alveolar damage and progressive respiratory failure due to acute lung injury (ALI) which predisposes to fatal acute respiratory distress syndrome (ARDS). Autopsies reports describe a diffuse alveolar damage with vascular congestion, inflammatory cell population entrapped, thrombosis with hyaline membrane formation in the alveolar walls allowing to an irreversible lung destruction. Altogether these findings remind the radiation oncologists many similarities with radiation induced lung injury which is a well-known side effect of radiotherapy for lung cancer. A fascinating hypothesis is that a common inflammatory paradoxical response of lung could be underlying the injury whatever the causes may be, virus, drugs or ionizing radiation. In this paper we will review the similarities between these two illnesses just going through the mechanisms of ALI-ARDS and the role of the most important immune cells and cytokines involved.

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