Correlation of Biochemical and FDG PET/CT Responses Following Induction Therapy In Newly Diagnosed Multiple Myeloma: A Prospective Observational Study

Homdutt  Sharma; Pradeep  Kumar; Neelabh  Nayan; Rakesh  Kumar; Tulika  Seth; Rishi  Dhawan; Jasmita  Dass; Mukul  Aggarwal; Ganesh Kumar  Viswanathan; Richa  Chauhan; Manoranjan  Mahapatra

doi:10.18502/ijhoscr.v20i2.21781

Homdutt Sharma Department of Hematology, All India Institute of Medical Sciences, Delhi, India
Pradeep Kumar Department of Hematology, All India Institute of Medical Sciences, Delhi, India
Neelabh Nayan Department of Hematology, All India Institute of Medical Sciences, Delhi, India
Rakesh Kumar Department of Nuclear Medicine, All India Institute of Medical Sciences, Delhi, India
Tulika Seth Department of Hematology, All India Institute of Medical Sciences, Delhi, India
Rishi Dhawan Department of Hematology, All India Institute of Medical Sciences, Delhi, India
Jasmita Dass Department of Hematology, All India Institute of Medical Sciences, Delhi, India
Mukul Aggarwal Department of Hematology, All India Institute of Medical Sciences, Delhi, India
Ganesh Kumar Viswanathan Department of Hematology, All India Institute of Medical Sciences, Delhi, India
Richa Chauhan Department of Hematology, All India Institute of Medical Sciences, Delhi, India
Manoranjan Mahapatra Department of Hematology, All India Institute of Medical Sciences, Delhi, India

DOI: https://doi.org/10.18502/ijhoscr.v20i2.21781

Keywords: Multiple myeloma; Biochemical response; FDG PET/CT scan; Focal lesion; Extramedullary

Abstract

Background: Multiple myeloma is a heterogeneous malignancy with patchy bone marrow involvement, often leading to discrepancies between biochemical and imaging-based response assessments. Site-specific bone marrow biopsies may miss focal disease, while FDG PET/CT detects metabolically active lesions, offering complementary prognostic value.

Materials and Methods: This prospective study included 44 newly diagnosed multiple myeloma patients. The primary aim was to assess the correlation between biochemical and PET/CT responses at six months post-induction. A secondary objective was to evaluate the impact of PET/CT response on 12-month EFS.

Results: The median age was 55.5 years. At baseline, >3 focal lesions and EMD were observed in 61.4% and 34.1% of patients, respectively. After six months of induction therapy, 86.3% achieved ≥VGPR biochemically, but 52.3% remained PET/CT-positive. Baseline >3 focal lesions and extramedullary disease (EMD) significantly predicted persistent PET/CT positivity (p = 0.004). Notably, 50% of patients with ≥VGPR (very good partial response) still showed PET/CT-positive findings. At 12 months, 75% of patients with clinical events had positive PET/CT at six months versus 47.2% without events (p = 0.245). Event-free survival was lower in the PET/CT-positive group (73.9% vs. 90.4%, p = 0.182), though not statistically significant.

Conclusion: 18-FDG PET/CT can detect residual disease not captured by biochemical markers, highlighting the value of combined assessment in multiple myeloma. Baseline >3 focal lesions and EMD predicted persistent PET/CT positivity. Although PET/CT positivity at six months showed a trend toward worse 12-month EFS, larger studies are needed to confirm its prognostic significance.