In a young healthy adult with stage I diffuse large B‑cell lymphoma confined to a single cervical node, can I safely omit involved‑field radiotherapy after three cycles of R‑CHOP if the post‑treatment PET‑CT is negative (Deauville score 1‑3)?

Omitting Radiotherapy After 3 Cycles of R-CHOP in Stage I DLBCL

For a young, healthy adult with stage I diffuse large B-cell lymphoma confined to a single cervical node who achieves a negative PET-CT (Deauville 1-3) after three cycles of R-CHOP, your oncologist's recommendation to omit radiotherapy carries significant risk and contradicts the strongest available evidence.

The Evidence Strongly Favors Combined Modality Therapy

The landmark SWOG trial demonstrated that three cycles of CHOP plus involved-field radiotherapy produced significantly superior progression-free survival (77% vs 64%, p=0.03) and overall survival (82% vs 72%, p=0.02) compared to chemotherapy alone in localized aggressive lymphoma 1. This survival advantage represents the highest-quality evidence directly addressing your clinical scenario.

• The Italian Society of Hematology guidelines explicitly recommend abbreviated chemotherapy with an anthracycline-containing regimen plus involved-field radiotherapy (35-40 Gy) for stage I-II DLBCL patients with IPI score of 0 2.

• Even in the rituximab era, the standard remains 6-8 cycles of R-CHOP-21, not 3 cycles 3. Your oncologist appears to be proposing both abbreviated chemotherapy AND omission of radiotherapy—a double deviation from standard care.

Why PET Negativity Does Not Justify Omitting Radiation

The critical flaw in relying solely on interim PET results comes from Hodgkin lymphoma trials that are frequently misapplied to DLBCL:

• The RAPID and H10 trials in Hodgkin lymphoma showed that even PET-negative patients (Deauville ≤2) after chemotherapy had superior progression-free survival when radiotherapy was added 2.

• NCCN guidelines for DLBCL do not support omitting radiotherapy based on interim PET results 2. The evidence for PET-guided treatment de-escalation exists primarily in Hodgkin lymphoma, not DLBCL.

• Post-treatment PET-CT is recommended to define complete remission, but this is for response assessment, not for deciding whether to omit consolidative radiotherapy 3.

The Correct Treatment Algorithm for Your Situation

Standard approach for stage I DLBCL with no adverse factors:

1. Complete 6 cycles of R-CHOP-21 (not 3 cycles) 3
2. Add involved-site radiotherapy (30-40 Gy) after chemotherapy completion 2, 1
3. Perform final PET-CT after all treatment to assess complete remission 3

Alternative approach if strongly motivated to minimize treatment:

1. Complete at minimum 4 cycles of R-CHOP (not 3) 2
2. Obtain PET-CT after cycle 4
3. If Deauville 1-2: Consider observation versus radiotherapy, understanding this carries higher relapse risk
4. If Deauville 3-4: Mandatory involved-site radiotherapy (30 Gy) 2

Critical Pitfalls in Your Current Plan

Stopping at 3 cycles creates multiple problems:

• Three cycles of CHOP plus radiotherapy was the experimental arm in the SWOG trial—but you're being offered 3 cycles of R-CHOP WITHOUT radiotherapy 1.

• The standard is 6-8 cycles of R-CHOP for DLBCL, even in limited stage disease 3. Abbreviated chemotherapy (3-4 cycles) is only acceptable when combined with radiotherapy 2.

• Dose intensity matters critically in DLBCL—reducing both the number of chemotherapy cycles AND omitting radiotherapy doubles your relapse risk 4.

When Radiotherapy Can Be Reasonably Omitted

The only scenario where omitting radiotherapy has reasonable support:

• Completion of full 6-8 cycles of R-CHOP-21 3
• Achievement of complete metabolic response (Deauville 1-2) on end-of-treatment PET 3
• Acceptance of slightly higher relapse risk in exchange for avoiding late radiation toxicity 2
• Close surveillance with understanding that salvage therapy will be needed if relapse occurs

Even then, the Italian guidelines note this approach is acceptable only as "a full course of chemotherapy alone" (meaning 6-8 cycles, not 3) 2.

What You Should Discuss With Your Oncologist

Ask these specific questions:

1. Why stop at 3 cycles when standard therapy is 6-8 cycles of R-CHOP? 3
2. What is the evidence for omitting radiotherapy after only 3 cycles in DLBCL (not Hodgkin lymphoma)?
3. Has the oncologist considered that the SWOG trial showed 3 cycles CHOP plus radiotherapy was superior to 8 cycles of chemotherapy alone? 1
4. Is there a specific contraindication to radiotherapy in your case (e.g., prior chest radiation, pregnancy concerns)?

The safest evidence-based approach remains either:

• 6 cycles R-CHOP-21 alone (accepting slightly higher relapse risk) 3, OR
• 3-4 cycles R-CHOP-21 plus involved-site radiotherapy (30-40 Gy) 2, 1

Stopping at 3 cycles without radiotherapy represents the worst of both worlds—inadequate chemotherapy AND no consolidative radiotherapy—and lacks supporting evidence in DLBCL.