The ability to treat individual patients with cancer on the basis of specific disease characteristics is increasingly important in the era of personalized and precision medicine.¹ By definition, delivering personalized medicine requires that clinicians have solid knowledge of these clinical characteristics when having discussions with patients and making treatment recommendations. However, the role of patients’ understanding of their clinical features in determining treatment outcomes is less clear. One could argue that it is essential for patients to have accurate knowledge of their cancer characteristics, particularly when there is a best (ie, guideline recommended) treatment available or when patients are to engage in informed decision making. Surprisingly, little research has evaluated the role of patients’ understanding of their disease and subsequent treatment patterns. Some prior research suggests that patients with cancer overestimate their risk of local and distant recurrence and that this overestimation can drive overuse of certain treatments.^2-4 Yet there has been little focus specifically on the association between patients’ knowledge of their disease at the time of diagnosis and receipt of guideline-recommended therapies, such as systemic chemotherapy, radiation, and hormone replacement therapy (HRT).

The well-written article by Freedman et al⁵ that accompanies this editorial contributes to this topic through a population-based survey of women with stage 0 to III breast cancer identified using the Northern California region of the California Cancer Registry (a SEER registry). The authors interviewed women after their diagnosis and report the association between the patients’ knowledge of their disease (stage/estrogen receptor/progesterone receptor/human epidermal growth factor receptor 2/grade) and use of National Comprehensive Cancer Network guideline-recommended initial treatment. The results revealed overall high rates (81% to 91%) of use of appropriate treatment (chemotherapy, radiation, and HRT), defined as use by those eligible for treatment. The study further found that patients’ knowledge of their disease characteristics was significantly associated with appropriate use of treatment (eg, knowledge of stage associated with use of chemotherapy, knowledge of ER status associated with use of HRT).

Although this analysis provides support for a link between patients’ understanding of their disease characteristics and use of appropriate treatment, it also begs the question of how and when patients actually obtain their knowledge about their disease. The authors suggest their results support the hypothesis that understanding one’s disease is associated with appropriate treatment initiation; yet, as noted in the manuscript, they were not able to assess the direction of the association. It is equally as plausible that the patients’ knowledge of their disease characteristics improved after treatment initiation. Furthermore, the time period during which patients were surveyed—from 4 months to 3 years post diagnosis—provided substantial opportunity for patients to gain information about their disease.

Evidence that physicians fail to recognize when patients have misperceptions about their cancer⁶ suggests that not all patients are obtaining accurate information about their disease from their physicians or even before treatment. Because most of the patients in the Freedman et al⁵ study received the appropriate treatment and were more highly educated (with two-thirds having some college or more education), there was less ability to explore the rates of appropriate use in the those with lower education and lower literacy. Additional research in these vulnerable subgroups of patients is sorely needed, particularly if disease knowledge is in fact a precursor to use of guideline-concordant cancer care. The Freedman et al⁵ study highlights the need to untangle the direction of the association between communication of disease information and treatment decision making.

Because the Freedman et al⁵ analysis focused only on women eligible for treatment, they did not evaluate whether patients who understood that their disease characteristics did not warrant a treatment were less likely to receive it. This represents another aspect of personalized cancer care related to decreasing overtreatment among patients whose disease characteristics do not necessitate aggressive treatment.^7,8 A review by Carlson and Roth⁹ of the impact of Oncotype testing and results on use of chemotherapy provides some evidence to support this association, showing a trend toward less aggressive treatment use in patients with low recurrence scores. However, whether this trend was driven by clinicians’ interpretation and appropriate recommendations or by patients’ willingness to forego less beneficial treatment after understanding their clinical characteristics (in this case, recurrence score) cannot be determined. Thus, similar to the results of Freedman et al,⁵ these findings underscore the need to better clarify how disease information intended to improve the ability to personalize treatment, including test results like Oncotype, is communicated to patients.

Ensuring that all patients have accurate comprehension of their disease information should be considered a key component of personalized medicine. If correct knowledge of cancer clinical characteristics truly influences the use of appropriate treatment (and nonuse of inappropriate treatment), then it becomes particularly critical that patients have this information before making treatment decisions with their clinicians. The study by Freedman et al⁵ is an important contribution to this field, yet further research is needed to determine whether, and how, patients obtain their clinical disease information and the degree to which they understand its meaning. The development and deployment of tools that can effectively build patients’ knowledge about their disease, ensure comprehension, and tailor treatment information to disease characteristics is an important area for growth to promote personalized cancer care.