Residual cancer may be undetected post-radiotherapy treatment

A new study warns that even if scans show no signs of cancer, some small cancer cells might still be present. This is known as residual cancer. Researchers from the University of Chicago Medical Center found that this hidden cancer can lead to worse health outcomes. Residual cancer can be hard to detect. It often remains invisible on scan images after treatments like radiotherapy. This treatment is effective for many cancer types, but it might leave behind tiny cancer cells that can cause problems later. The study notes that residual disease is more common than previously thought. For example, about 40% of lung cancer cases and up to 69% of kidney cancer cases show some remaining cancer cells after treatment. Dr. Muzamil Arshad emphasized the need to rethink how treatment success is evaluated. Relying solely on imaging can mislead doctors and patients into believing that treatment was fully effective. One specific treatment, known as stereotactic ablative radiotherapy (SABR), is famous for its precision and success on scans. However, follow-up biopsies often reveal those hidden cancer cells long after treatment. Patients with residual cancer are more likely to face cancer recurrence and shorter survival rates. This issue has been observed across various cancer types, including rectal, cervical, and prostate cancers. The editorial advises that doctors should use biopsy tests more regularly to get a clearer picture of a patient’s condition and improve treatment effectiveness.