A new study reinforces the expectation that cancer patients who postpone radiation therapy treatments will have poorer outcomes than those who fully comply with the program as scheduled. No surprise there, but the researchers also found that the differences are sharp, consistent across disease sites and observable despite eventual program completion by the stragglers.

Armed with these findings, clinicians can view noncompliance with radiation therapy—a particular problem in low-income populations—as a “behavioral biomarker to identify high-risk patients who require additional interventions,” according to the authors of the study, which is posted online ahead of print in the International Journal of Radiation Oncology • Biology • Physics.

Led by by Nitin Ohri, MD, Albert Einstein College of Medicine, New York City, the researchers reviewed the cases of 1,227 patients who completed curative-intent, external-beam radiation therapy at Einstein’s Montefiore Medical Center from 2007 to 2012 for cancers of the head and neck, breast, lung, cervix, uterus and rectum.

They deemed as noncompliant any patient who missed two or more appointments en route to completing the regimen.

Overall, 266 of the 1,227 (21.7 percent) were noncompliant.

In univariate analyses, the noncompliance correlated with

• Increased recurrence risk (5-year cumulative incidence, 16 percent in noncompliant patients vs. 7 percent in compliant patients);
• Inferior recurrence-free survival (5-year actuarial rate, 63 percent vs. 79 percent); and
• Inferior overall survival (5-year actuarial rate, 72 percent v. 83 percent).

Moreover, inferior outcomes as gauged by these measures held in multivariable analyses adjusted for disease site and stage, comorbidity score, gender, ethnicity, race and socioeconomic status.

Plus, after adjusting to account for doses eventually delivered, the team found that noncompliant patients’ courses were prolonged by an average of only one week compared to compliant patients—and a large majority of noncompliant patients (78 percent) had five or fewer no-shows.  

The researchers further observed that low socioeconomic status correlated with noncompliance. This factor linked with poor outcomes in univariate analyses but not with those in multivariable models.

In their discussion, Ohri et al. note that the latter finding “suggests to us that patient behavior patterns, which are difficult to account for in most registry-based analyses, may mediate observed associations between socioeconomic status and cancer outcomes.”

Interventions that improve patients’ overall adherence with recommended diagnostic, therapeutic and follow-up procedures “may help to address disparities in cancer outcomes,” the authors add. “These might include patient navigation programs, management of mood disorders and assistance with transportation.”