Can you develop allergy to chemotherapy?

Chemotherapy is one of the treatment alternatives used in cancer patients (along with radiotherapy, immunotherapy or surgery) during which a drug made up of chemical molecules that eliminate cancer-causing cells is introduced intravenously. Although this treatment is recommended when the benefits outweigh the risks, they often come with numerous side effects. Among patients who receive some types of chemotherapy, there is a small percentage of patients who develop hypersensitivity reactions or allergies to it. Due to the frequent and varied side effects of chemotherapy, it is very difficult to identify this small group of patients. Hypersensitivity or allergy reactions are similar to classic allergies, such as pollen allergies. But why does allergy to chemotherapy appear?

A dangerous but rare allergy

Almost all types of chemotherapy can cause hypersensitivity or allergy reactions, but only 5% of them are reported. This is due, in large part, to the fact that the oncology specialists who treat these patients are not usually trained to identify the typical symptoms of an allergic reaction, so it is likely that the number of this type of patient is higher. If we analyze the data according to the type of chemotherapy, although the prevalence varies, we see that among those who receive platinum (a specific type of chemical compound), the percentage can reach up to 46% of patients . Although it is important to emphasize that these types of reactions are not usually serious, the worst consequence is that the patient must stop treatment . In most cases, chemotherapy treatment with platinum is the best option for the patient, and the fact of developing an allergy is a major complication in controlling the disease. However, allergy specialists have found a possible solution.

The most important thing for these patients is a quick and accurate diagnosis, which must come from an allergy specialist . Here we find the first problem, since, as a general rule, these patients are treated by oncology specialists. The personnel in charge of supervising and administering intravenous doses containing chemotherapy are trained to react quickly in case of adverse reactions. However, it is not usually trained to be able to identify if it is an allergic reaction or another type of adverse effect.

Although sometimes it may be impossible to distinguish the symptoms, there are a series of tests that can be performed to rule out or confirm the allergy . The diagnostic tests are very similar to those used to diagnose any classic pollen or food allergy. These include blood antibody tests, skin tests, or even a treatment challenge if other tests are inconclusive. Currently, there are many studies that try to optimize and standardize the performance of these tests to reduce the margin of error. The implementation of multidisciplinary teams for this type of patient has many advantages, and in this context, having allergy specialists can be key.

Diagnosis is just the beginning

Once the patient has received a diagnosis of allergy against chemotherapy, there is the option of performing a desensitization treatment . This protocol, developed and promoted by researchers such as Mariana Castells in Boston, has been adapted and implemented in numerous centers and hospitals. The protocol consists of reintroducing chemotherapy little by little, starting with a very low amount that is increased as long as the patient does not present symptoms. At the end of several sessions of this desensitization protocol, the patient is able to tolerate a dose of chemotherapy comparable to standard treatment .

The advantages of using this protocol are obvious, since it allows the patient to continue with their treatment to control the cancer, ensuring that the development of the allergy has as little impact as possible on their prognosis. Although there are still many unanswered questions about the mechanism of action of this protocol, the results are successful in more than 90% of patients . However, it should be performed by an allergist or immunologist who is familiar with diagnosing and treating allergic reactions. Collaboration between departments here is essential to ensure that the patient receives the best treatment available.

To date, the reason why some patients receiving chemotherapy develop allergy to the treatment is unknown. During the development of the disease and the start of treatments such as radiotherapy or chemotherapy, the immune system of these patients undergoes many changes in order to eliminate cancer cells. Although desensitization protocols are very useful in these cases, studies are still required to understand the process and be able to optimize them based on the characteristics of each patient . Oncology treatment is a field in constant change and the possibility of carrying out desensitization protocols is not only an advantage for patients, but for oncology in general, since it allows chemotherapy to be continued and its efficacy to be evaluated.

References:

Moñino-Romero et al. 2021. Soluble FcεRI, IgE, and tryptase as potential biomarkers of rapid desensitizations for platin IgE sensitized cancer patients. J Allergy Clin Immunol Pract. doi: 10.1016/j.jaip.2020.01.047

Pagani et al. 2022. Hypersensitivity reactions to chemotherapy: an EAACI Position Paper. Allergy. doi: 10.1111/all.15113