How is chemosensitivity measured in a 45-year-old patient with Diffuse Large B-Cell Lymphoma (DLBCL) after salvage chemotherapy following a partial response to R-CHP (Rituximab (rituximab), Cyclophosphamide (cyclophosphamide), Hydroxydaunorubicin (doxorubicin), and Prednisone (prednisone))?

Measuring Chemosensitivity After Salvage Chemotherapy in DLBCL

Primary Assessment Method

Chemosensitivity after salvage chemotherapy is measured by radiographic response assessment using PET-CT imaging, with patients classified as chemosensitive if they achieve either a complete metabolic response (CMR) or partial response (PR), which determines eligibility for consolidation with high-dose chemotherapy and autologous stem cell transplantation. 1, 2

Response Assessment Protocol

Imaging Modalities

• PET-CT scan is the gold standard for response assessment after salvage chemotherapy, evaluating metabolic activity and anatomic changes 1, 2
• CT imaging of chest, abdomen, and pelvis provides anatomic correlation and measures reduction in tumor burden 2
• Response should be assessed after completion of the salvage regimen (typically 2-3 cycles of R-DHAP, R-ICE, R-GDP, or R-ESHAP) 1

Response Categories Defining Chemosensitivity

Chemosensitive disease includes:

• Complete metabolic response (CMR): Complete resolution of FDG-avid disease on PET-CT 1, 2
• Partial response (PR): ≥50% reduction in tumor burden with residual metabolic activity 1, 2

Chemoresistant disease includes:

• Stable disease (SD): <50% reduction or <25% increase in tumor burden 1
• Progressive disease (PD): ≥25% increase in tumor burden or new lesions 1

Clinical Implications of Response Assessment

For Chemosensitive Patients (CMR or PR)

• Patients achieving CMR or PR should proceed immediately to high-dose chemotherapy with autologous stem cell transplantation (ASCT) as consolidation therapy 1, 2
• The 3-year overall survival for chemosensitive patients proceeding to ASCT is approximately 65%, with progression-free survival of 60% 3
• Patients achieving PR to initial R-CHP who then respond to salvage have approximately 45% long-term remission rates 3

For Chemoresistant Patients (SD or PD)

• Patients with stable or progressive disease after salvage chemotherapy have poor outcomes with <20% achieving long-term remission 3
• These patients should be considered for alternative salvage regimens, allogeneic stem cell transplantation, or enrollment in clinical trials with novel agents rather than proceeding directly to ASCT 1, 2
• Allogeneic transplantation should be considered for patients with refractory disease to salvage therapy 2

Important Prognostic Distinctions

Response to Initial Therapy Matters

• Patients who achieved partial response to initial R-CHP have better salvage outcomes (45% long-term survival) compared to those with stable/progressive disease on initial therapy (<20% long-term survival) 3
• This distinction helps stratify which patients are most likely to benefit from standard salvage approaches versus requiring experimental therapies 3

Salvage Regimen Response Rates

• Overall response rates to first salvage chemotherapy in primary refractory DLBCL range from 15-45% depending on regimen 4
• R-DHAP achieves approximately 15% response rate, R-ESHAP 36%, and R-GDP 45% in primary refractory disease 4
• The response rate to salvage determines whether patients can proceed to potentially curative ASCT 1, 2

Common Pitfalls to Avoid

• Do not delay response assessment: Imaging should be performed promptly after completing salvage cycles to avoid disease progression during evaluation 2
• Do not proceed to ASCT without documented chemosensitivity: Transplanting chemoresistant patients yields extremely poor outcomes and exposes them to unnecessary toxicity 3, 4
• Do not rely solely on CT imaging: PET-CT provides superior assessment of metabolic response and should be used when available 1, 2
• Do not assume all partial responses are equivalent: Patients with minimal residual disease on PET may still benefit from ASCT, whereas those with extensive residual disease may require additional salvage therapy first 2