Practical Considerations for Identifying and Managing ILD in Breast Cancer

Mark D. Pegram, MD: In the case of trastuzumab deruxtecan, which is the drug most likely to be associated with ILD [interstitial lung disease] among the drugs that we use for HER2-positive metastatic breast cancer, the all-grade incidence is around 15% in the DESTINY-Breast01 registrational trial that won FDA approval. That’s the latest data sweep from mid-2020. Of those, however, there were 2.7% of patients who had grade 5 events. That’s the situation we really want to avoid. That’s why there’s so much focus and attention on history-taking, physical examination findings with a stethoscope. It’s really important now to hone your physical diagnosis skills so that you can hear crackles in the lung field with a stethoscope that might give you clinical suspicion of ILD. So that’s also critical in addition to the imaging that I mentioned previously. It’s really important to discover it early so that you can intervene, withhold the drug, use steroids if clinically indicated, and hopefully, avoid the really serious cases that wind up with the mechanical ventilation and ICU [intensive care unit].

Charles A. Powell, MD, MBA: COVID-19 is ubiquitous in certain communities, and whenever a patient or anybody has new respiratory symptoms, COVID-19 is top of mind. That will require testing for COVID-19, and that testing is a routine part of the diagnostic evaluation that is done in oncology clinics, multidisciplinary clinics, pulmonary clinics, and internal medical clinics. It is incredibly important to rule out COVID-19 as a cause of the new symptoms or the new imaging findings. That applies of course to individuals who are vaccinated and to individuals who may still not be vaccinated.

Mark D. Pegram, MD: A lot of doctors are nervous about using trastuzumab deruxtecan because they don’t want to be in a situation where they contemplate, trying to decide does a patient have COVID-19 or do they have drug-induced interstitial lung disease? I find that perhaps it is not such a great argument to withhold trastuzumab deruxtecan because they’re 2 very different syndromes. For example, the COVID-19 infection is sometimes associated with peculiar other signs or symptoms such as like anosmia and COVID-19 toes. There are lots of clues that can tell you that this is clearly an infectious insult with a virus and not a drug-induced phenomenon. Fever is another one; fever is ubiquitous with COVID-19. It can be seen with drug-induced ILD to be sure, but it’s usually less frequent compared to viral infection in terms of fever. The other thing about COVID-19 is you can make the diagnosis. There are tests for COVID-19, and they’re pretty definitive tests, especially if you do multiple tests on a patient. You can usually reach the diagnosis with relative ease. That would exclude the possibility of ILD if somebody has a positive COVID-19 test and let’s say, consolidation on a chest radiograph. It is pretty easy to tell those 2 apart in most cases.

Now, could there be subtle situations, or could somebody have both COVID-19 infection and drug-induced ILD? Sure, that’s possible, but it’s just unlikely, especially now that we’re finally in an era of vaccination, and most of our patients are being vaccinated. That said, there’s still a lot of work to be done to find out how robust the responses are to vaccines in our patients with breast cancer, and that work is still ongoing, unfortunately. We don’t have good data to show how protective the vaccines are in patients who have had recent chemotherapy, and so forth. We need a lot more information there. So it is possible to have both COVID-19 and interstitial lung disease, and that’s a very complex situation. Obviously, you would treat the COVID-19 infection in a supportive fashion like you would for any other patient without cancer. Then as that’s resolving, if the resolution of the viral infection doesn’t result in improvement in the pulmonary signs or symptoms, then you may need to consider an ILD diagnosis, which in that case, might require a biopsy, for example, a lung biopsy.

Transcript Edited for Clarity