Changing drug therapy can help breast cancer patients get full benefit of tamoxifen treatment
December 19, 2015
Using drug data from his hospital's Breast Cancer Disease Site Group clinical database, the researchers logged any patient on tamoxifen or AI therapy as well as those on CYP2D6 inhibitors. A total of 531 patients were found to be eligible for the study; 463 received one of the prescribed hormonal therapies, while 68 were on a CYP2D6 inhibitor but not receiving hormonal treatment. Seven patients receiving tamoxifen and 16 taking an AI were also on a strong CYP2D6 inhibitor - five percent of all the patients studied. One patient on tamoxifen and six on an AI were also receiving a moderate enzyme inhibitor, and 24 on tamoxifen and 40 on an AI were taking weak CYP2D6 inhibitors.
Tamoxifen must be metabolised in the liver before it can become active. "We have known for a while that patients with a deficiency in CYP2D6 activity did not derive the full benefit from tamoxifen because they cannot metabolise it to endoxifen, its active metabolite," says Mr. Hopkins. "CYP2D6 medications can mimic this pharmacogenomic phenotype by inhibiting the metabolism of tamoxifen and hence reducing its therapeutic effect."
The team now intends to follow up the work by expanding quality assurance on therapies to every breast cancer patient currently under treatment at the centre - over 6000 a year - and by exploring CYP2D6 testing for some of those patients. Such tests before treatment begins can help doctors identify those patients with a CYP2D6 deficiency and allow the possibility of offering AI rather than tamoxifen therapy from the outset.
"The work we have done demonstrates why good communication and seamless data transfer is so important in health care," says Mr. Hopkins. "Patients can receive care from many different health care professionals - oncologists, other specialists, family doctors etc - and they can receive medications from multiple pharmacies. If there is insufficient information transfer between the individuals who care for a patient, the risks of drug interactions increase, and this can affect the quality and efficacy of care being given.
"I believe that we need to have policies in place to require health care providers and their agencies, including private insurance companies, to provide better access to information for health care professionals involved in patient care. If these organisations try to protect their information in an unreasonable manner it can seriously impact care and outcomes for patients."
SOURCE Ottawa Hospital Regional Cancer Centre