How can PET scans be used to predict treatment results for older patients with Hodgkin lymphoma?

This study compared ways to interpret PET scans to see which best predicted treatment results for older patients with Hodgkin lymphoma (HL). The authors identified several methods of PET scan analysis that were able to predict how effective treatment was for these patients.

PET scans are often used to diagnose patients with HL and to examine how effective treatment was. For PET scans to work, a dye is injected into patients. This dye spreads to areas in the body consuming the most energy (such as growing cancer cells). The scan then highlights these areas.

It is sometimes difficult to compare two scan images, such as before and after treatment. This can make it hard to analyze if patients responded to treatment. It is unclear how reliable PET scan results are for patients with HL aged 65 and older and what type of analysis is best for these patients.

Data from 123 patients with HL aged 65 and older that received chemotherapy were analyzed. Patients had PET scans before and after treatment. 73 patients were classified as having no signs of cancer (complete response). 23 patients had a reduction in the amount of cancer or no response to treatment (not-complete response)

The intensity of the dye in the tumor was compared to the liver (tumor-liver ratio). The tumor-liver ratio was higher in patients with a not-complete response (9.7) compared to patients with a complete response (7.7). The dye intensity in the tumor was also compared to the blood (tumor-blood ratio). The tumor-blood ratio was higher in patients with a not-complete response (7.3) compared to patients with a complete response (5.9).

Cancer cells use the dye for energy. This can be measured and is called metabolic tumor volume (MTV). MTV was higher in patients with a not-complete response (132) than in patients with a complete response (106.5). Another way to measure how much dye cancer cells are using is called tumor lesion glycolysis (TLG). The TLG was higher in patients with a not-complete response (1671) than in patients with a complete response (1327).

Patients survived for 37 months on average. Lower tumor-liver ratio and tumor-blood ratio scores predicted patients who survived longer. Patients survived for 29 months without cancer worsening on average. Tumor-liver ratio, tumor-blood ratio, MTV, and TLG scores predicted patients who survived longer without cancer worsening.

The authors concluded that PET scans can predict treatment results for older patients with HL.

This study used medical records data which means that some information was not available for all patients. Patients received different types of chemotherapy in this study and some received radiotherapy which may limit analysis. This study would benefit from confirming the results in a larger patient group.