Are end-of-treatment PET scans necessary?

This study investigated whether end-of-treatment PET scans could be left out if the mid-treatment scans were negative (no cancer activity). The authors concluded that the end-of-treatment scans were essential, even in patients with negative interim results.

Positron emission tomograpy (PET) scans are used to assess cancer severity. Patients with Hodgkin lymphoma generally undero PET scans at the start, middle and end of treatment. Studies have shown that interim (middle) scans can predict patient outcome. This questions whether end-of-treatment scans are needed. Lowering the number of scans needed may reduce a patient's radiation exposure.

This study aimed to determine whether end-of-treatment scans were necessary.

This study examined the interim and end-of-treatment scans of 76 patients. All were treated with 3-8 cycles of ABVD (doxorubicin, bleomycin, vinblastine, and dacarbazine) chemotherapy. No patient had their treatment changed based on their interim-scan score. Patients were followed for an average of 58.9 months.

Treatment failure occurred in 20% of patients. End-of-treatment scans predicted 80% of treatment failures. Interim scans predicted 47% of treatment failures. 

Results varied depending on whether the results from both types of scans were negative (no cancer activity) or positive (a small amount of cancer activity). After 5 years, 87% of patients with negative interim scans were disease progression free compared to 56% of those with positive scans. 96% of patients with negative end-of-treatment scans were progression free compared to 23% of those with positive scans. The cancer was 24.02-fold more likely to relapse if end-of-treatment scans were positive. This is compared to a 3.79-fold increased likelihood for positive interim scans.

The authors concluded that end-of-treatment PET scans were important, even in patients with negative interim scans.

This study used different methods for interpreting interim and end-of-treatment scans. Larger prospective studies are needed to confirm these findings.

Discuss the timing and importance of PET scans with your doctor.