The Medco Research Institute (MRI) has claimed that medications taken by as many as 75% of cancer patients interfere with the effects of oral kinase inhibitors, a major class of adjunctive cancer therapy.
The effect of the medication interference is to weaken the effectiveness of the anti-cancer treatment and/or increase its toxicity, the study found.
Oral kinase inhibitors, which suppress tumour cell metabolism, are widely prescribed for their ability to increase the effectiveness (and reduce effective dosage levels) of chemotherapy.
The MRI study, which looked at 4,617 cancer patients, found that 23–74% of them were being prescribed a medication that interfered with their oral cancer drug. Of these, 43% showed a reduction in the efficacy of the cancer drug and 68% showed an increase in its toxicity.
Oral kinase inhibitors include (UK trade names): Glivec (imatinib), Tarceva (erlotinib), Sprycel (dasatinib), Afinitor (everolimus), Tyverb (lapatinib), Tasigna (nilotinib), Votrient (pazopanib), Nexavar (sorafenib) and Sutent (sunitinib).
The medications that interfere with them, according to the study, are calcium channel blockers, antifungal agents, steroids, proton pump inhibitors and some antibiotics.
Dr Steve Bowlin, Senior Director at the MRI and co-author of the study, said: “Since these are drugs launched in the past decade for fairly small patient populations, we are learning more about how they are used in real-world settings as compared to traditional clinical trials that test safety and efficacy in a tightly-controlled environment.
“Oncologists are not always aware of other medications prescribed by other doctors and vice-versa, which can pose a real hazard for their patients on oral cancer therapies.”