Update on my dad’s NHL journey – blood results after chemo and PET concerns

Hi everyone, I wanted to give an update and ask for some perspective.
My dad has non-Hodgkin lymphoma and finished his last chemotherapy about one month ago. His last PET/CT showed a very good response overall — the original mass became very small (less than 1 cm), but there was still some slight activity mentioned. This has been the biggest source of anxiety for me because his doctor told us that if there is still active lymphoma, the situation could be very serious.
His recent blood work came back:
LDH: 265 (previously 193 one month after finishing chemo)
CRP: 0.61
Hemoglobin: 14.4
White blood cells: 8.97
Neutrophils: 6.47
Platelets: 301
Creatinine: 0.96, eGFR 93.9
Bilirubin: 0.3
ALT/GPT: 221
GGT: 93
The blood counts look good — no anemia, no low platelets, and no obvious bone marrow problems. The main abnormal findings are the elevated liver enzymes and the mildly elevated LDH.
I’m trying to understand how much the LDH increase could mean. Could the liver enzymes or other issues (medications, chemo recovery, heart issues) contribute to LDH being higher? Or does this pattern raise concern that the lymphoma is growing?
My dad also had a significant drop in heart function after treatment (low EF), which has complicated decisions about further therapy if needed.
I know nobody can diagnose from blood work alone, but I’m struggling with the uncertainty. Does anyone have experience with residual PET activity after treatment that turned out to be inflammation or healing rather than active lymphoma?
Thank you to anyone who reads this and shares their experience.