Which scanning method is more accurate for patients with relapsed or refractory Hodgkin lymphoma who received biological therapy?

This study compared CT and PET scans to understand which was more accurate at predicting biological treatment results in patients with relapsed or refractory Hodgkin lymphoma (HL). The results showed that PET scans were more sensitive than CT scans in these patients.

Biological therapy has improved treatment results for patients with HL. This includes patients who did not respond to previous treatment (refractory) and those who saw a return of the cancer (relapsed).  Nivolumab (Opdivo) is such a biological therapy. 

Scans are needed after treatment to understand how well a patient responded. This can indicate if a patient needs more treatment if some cancer still remains. A CT scan can be done to show how internal organs and tissues look like. PET scan uses a specialized dye to show how organs function. For other therapies, PET scans are more accurate than CT scans at indicating patients’ responses to treatment.  It is unclear which type of scan is more accurate following biological therapy such as nivolumab.

Data from 45 patients with relapsed or refractory HL who received nivolumab was analyzed. Patients received CT and PET scans approximately 2 months and 6.7 months after treatment began. 

At the 2-month assessment, 44% of patients were classified as having responded to treatment using CT scans. 4% of patients had no signs of HL (complete response) and 40% had a significant decrease in the tumor (partial response). By PET scanning, 56% of patients were classified as having responded to treatment. 29% of patients had a complete response and 27% had a partial response.

PET scans were 6.5 times more likely to detect a complete response. After PET scanning, the treatment results of 44% of patients were changed from what was observed on CT scans. Of the 20 patients whose results were changed, 55% were reclassified as having a complete response.

After 6.7 months, PET scans reclassified 31% of patients. While CT scans showed 6 patients had a complete response to treatment, PET scans showed that 12 patients had a complete response.

Between 2 and 6.7 months, 64% of patients remained in the same response classification by CT scans and 72% by PET scans. 22% of patients were reclassified in a worse classification by CT scan and 25% by PET scan.

The authors concluded that PET scans were more sensitive than CT scans for patients who received biological therapy. Results 6 months after treatment were more accurate than those at two months.

This study had a small number of patients and should be repeated in larger numbers for confirmation. This study used medical records data which means that some patient information was not available.