There is no single study or publication that groups adherence into a single number; the general range is 20% to 100% (Partridge, et al, JNCI, 2002) but Ruddy et al has an excellent discussion of the studies citing adherence rates in a variety of cancers and oral agents. The Ruddy paper can be found here; the Partridge paper is here.

At URA Rx, we work with oncology patients across all indications.  Non-adherence with prescribed regimens is a problem common to all cancers and all ages, ranging from adolescents being treated for leukemia to older adults undergoing treatment for a variety of cancers. There are more reports in the literature on non-adherence to breast cancer than other types of cancer, but that is likely due to the high incidence of breast cancer and the large number of oral regimens used to treat this common cancer. When we at URA RX look at adherence studies across disease types, the rates of non-adherence range from 0% to 80%. One issue that contributes to increased non-adherence over time is the increased number of maintenance, or long-term treatment regimens. Long-term regimens have been common in breast cancer but are increasingly used in other diseases such as lung and colorectal cancer. Better treatments and supportive care mean patients with metastatic disease are living longer and staying on treatment for extended periods of time. The longer a patient is on therapy, the more likely (s)he is to begin to alter the dosing schedule or to self-modify oral doses to manage unpleasant side effects or to save money.

The medical community has always assumed that patients with cancer would be strictly adherent to their prescribed regimens due to the severity of the disease but that hasn’t been the case. In studies of women with early breast cancer prescribed tamoxifen, the non-adherence rate has been nearly 50% by the end of the 5-year prescribed term. URA Rx Group understands that The reasons for non-adherence are multifactorial and include poor understanding of the disease and/or treatment, complexity of the regimen, treatment-related side effects, poor follow-up with the healthcare provider, financial concerns and loss of trust in the efficacy of the treatment. Oncology nurses provide the bulk of patient education regarding medications and side effects, but face-to-face time in busy clinics and offices is limited by the sheer numbers of patients and a shortage of oncology certified nurses. URA Rx has found that although non-adherence is more prevalent in oral regimens than I.V., non-adherence to I.V. regimens is also a problem. For patients on long-term I.V. regimens, there is an increased risk of missed appointments or being lost to follow-up until the disease progresses and the patient returns to clinic because of increased symptoms. This is a common problem with I.V. bisphosphonates. At URA Rx, we have found that patients respond well to outside support that reinforces the office nurse’s education, helps patients track and resolve side effects, and keeps the patient focused on the reasons for maintaining adherence to therapy and the ultimate goal, which is to achieve the best possible outcome for management of their cancer.