Any drug treatment may be accompanied by adverse events or toxicity. This is especially true for anticancer therapies, generally named chemotherapies, administered to kill cancer cells [1].

The extent of side effects or toxicity depends on the dose and can vary from subject to subject and from treatment to treatment. It is important to note that many of the side effects are temporary, decreasing and/or gradually disappearing in the days following administration or discontinuation of treatment.

Patients generally accept the chemotherapy side effects considering the benefits that treatment produces, even if most of these interfere with a good quality of life. The most common side effects of classic chemotherapy include hair loss, anemia, fatigue, nausea, vomiting, diarrhea, infections, bruising or small bleeding; and also, cognitive problems (“chemo brain”) [2,3]. The main organs that may be affected by chemotherapy are those in which normal cells proliferate rapidly, this is why chemotherapy drugs, which act on the ability of cells to multiply themselves, can also destroy some healthy cells that reproduce quickly. Among these are the blood cells, those of the hair follicles, the cells that line the mouth, stomach and intestine, and those of the reproductive organs. Such drugs cause DNA damage or stop cells in mitosis, targeting both dividing cancer and dividing healthy cells. Clearly, DNA damaging chemotherapy treatments may cause damage to both cancer and healthy cells to generate toxic side-effects [4].

If many side effects recover, some anticancer medicines however may cause irreversible toxicity like second tumours (i.e. myelodysplastic syndrome, acute myeloid leukaemia or acute lymphocytic leukaemia). These substances include cisplatin, anthracyclines, topoisomerase II inhibitors and certain alkylating agents. Following prolonged treatment with these medicinal products, the risk of developing a second tumour, compared to an untreated person, increases in two years after the end of treatment, reaches the apex between 5 and 10 years and then decreases until it cancels [5].

The appearance of side effects, mild and treatable, or severe with serious complications, may limit the amount of chemotherapy treatment, reducing anti-cancer efficacy. For this reason, researchers continue to study and propose new treatments, new combinations of drugs and new administration schemes to make chemotherapy more effective against cancer and less harmful to the rest of the organism.

In this perspective, monoclonal antibody drugs are cancer treatments that enlist natural immune system functions to fight cancer, carrying fewer side effects than traditional chemotherapies. They act flagging cancer cells, triggering cell-membrane destruction, blocking cell growth, preventing blood vessel growth, blocking immune system inhibitors, directly attacking cancer cells, delivering radiation treatment or chemotherapy, binding cancer and immune cells. Common side effects are allergic reactions, nausea, vomiting, diarrhea, skin rashes and low blood pressure. Serious, but rare, side effects may include severe allergy-like reactions leading to death; monoclonal antibodies that deliver radioactive particles or chemotherapy drugs may be associated with low blood cell counts that can be severe and persistent; certain monoclonal antibodies increase the risk of high blood pressure, congestive heart failure and heart attacks; and others are associated with a higher risk of inflammatory lung disease. Sores and rashes on the skin can lead to serious infections and monoclonal antibody drugs designed to stop cancer from forming new blood vessels have an increased risk of severe internal bleeding [6].

A new safer treatment is the chimeric antigen receptor (CAR)-T-cell therapy, which is a promising approach for the treatment of refractory malignancies. The cytokine-release syndrome (CRS) [7] and CAR-T-cell-related encephalopathy syndrome (CRES) are the most-common toxicities observed after CAR-T-cell therapy and, rarely, CRS can evolve into fulminant hemophagocytic lymphohistiocytosis (HLH). Intensive monitoring, accurate grading, and prompt management of toxicities with aggressive supportive care, anti-IL-6 therapy, and/ or corticosteroids for severe cases could reduce the morbidity and mortality associated with CAR-T-cell therapy [8].