1. Introduction
Cancer is one of the major leading causes of death worldwide (1). According to World Health Organization (WHO) reports, breast, colorectal, lung, and liver cancers had the highest incidence and mortality rate in the Eastern Mediterranean Region (EMR) in 2020 (2). These types of cancers with similar incidence and mortality are also observed in Iran and there is an increment trend in incidence and mortality rate for most cancers (3). Surgery, radiation therapy, and systemic treatment are the main cancer treatment protocols that are applied separately or in combination for cancer patients (4). Chemotherapy, as a systemic treatment of cancer, has many side effects (5) such as nausea and vomiting, diarrhea, mucositis, fatigue, and hair loss (6, 7).
For reducing the short-term and long-lasting side effects of chemotherapy, a great proportion of cancer patients used the Complementary and Alternative Medicines (CAM) (8-10); this usage is commonly without the consultation provided by physicians and health care workers (11). Among CAM therapies, herbal medicines are more popular among patients. Current reports show a remarkable and variable prevalence of using herbal medicine by cancer patients from 14% to 66.7% (12-15), especially during conventional treatments or palliative care and chemotherapy (37% -38%) (16, 17). In fact, the concurrent usage of herbal medicines with conventional therapies is one of the most important concerns in cancer treatment which can lead to unexpected consequences (18, 19).
In the pharmacokinetic interactions, herbal medicines due to their pharmacokinetic properties interact with chemical agents and affect the absorption, distribution, metabolism, and excretion of chemotherapeutic agents when orally used. The pharmacodynamics interactions often are lower clinically significant than pharmacokinetic interactions (20-22). The herb-drug interactions in cancer patients are more important, however, the prevalence of this event among cancer patients is not known and limited studies reported only a proportion of patients who were at risk for herb-drug interactions (19, 23, 24). Along with the unclear prevalence of herb-drug interactions in cancer patients, the epidemiological predictors of it are also unknown and several studies have only reported the mechanisms of some herb-drug interactions (19, 25, 26). As regards a great proportion of Iranian cancer patients use herbal medicine in combination with a chemotherapeutic agent (27), and according to the lack of updated studies on this issue, the aim of this study was to determine the prevalence of potential herb-drug interactions among these patients and also identify the epidemiological predicting factors of herb-drug interactions for Iranian cancer patients.