Patients who miss two or more regularly scheduled radiation therapy sessions may be at increased risk of recurrence even if they eventually complete their course of treatment, researchers reported after a recent study. The findings were published in the International Journal of Radiation Oncology, Biology, Physics

Researchers analyzed data from more than 1,200 patients who had received external-beam radiation therapy for head and neck, breast, lung, cervical, uterine, or rectal cancer between 2007 and 2012. Of the patients, 22% were considered noncompliant (missed two or more scheduled radiation therapy treatments), and although they eventually completed all of their planned treatments, their course of radiation therapy was extended by 7.2 days.  

After adjusting for demographic and clinical variables, the researchers found that noncompliant patients had increased risk of disease recurrence and lower rates of survival without disease recurrence. Although the researchers recognized that tumor repopulation—cancer cells dividing at an accelerated rate after a halt in treatment—may be to blame for the recurrence, they also hypothesized that radiation noncompliance may be a warning sign for broader risk factors that can negatively affect outcomes, such as unmet mental health needs, lack of social support, and noncompliance with other treatments like chemotherapy. 

The authors suggested that practitioners use these circumstances as an opportunity to ask patients in real time why they missed their treatments and provide immediate referrals to supportive care, mental health services, transportation assistance, or other resources. They also noted that future research is needed to identify factors that can reliably predict noncompliance before treatment even begins.