How can metabolic activity decrease on PET scan while swelling increases in refractory DLBCL during second-line chemotherapy?
This situation can happen during treatment and doesn't necessarily mean the treatment isn't working. Here's what might be occurring:
When chemotherapy starts working, cancer cells begin dying off Show Full Answer
How can metabolic activity decrease on PET scan while swelling increases in refractory DLBCL during second-line chemotherapy?
This situation can happen during treatment and doesn't necessarily mean the treatment isn't working. Here's what might be occurring:
When chemotherapy starts working, cancer cells begin dying off. PET scans detect metabolic activity - essentially how actively cells are taking up glucose. As lymphoma cells die, they become less metabolically active, which shows as decreased activity on the PET scan.
However, the physical swelling (lymph node enlargement) can temporarily persist or even increase because:
* Dead and dying cancer cells create inflammation and fluid buildup
* Your immune system responds to the dying cancer cells, causing additional swelling
* The body needs time to clear away the dead tissue and cellular debris
* Inflammation from the treatment itself can contribute to swelling
This is sometimes called "pseudoprogression" - when imaging appears to show worsening disease despite actual improvement. The decrease in metabolic activity is actually an encouraging sign that the chemotherapy may be killing cancer cells, even though the physical size hasn't caught up yet.
Your oncology team will monitor both the metabolic activity and physical changes over time to determine how well the treatment is working. Additional biopsies or imaging may help clarify what's happening.
November 11, 2025
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