Radiotherapy in Good-Prognosis DLBCL


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I was disturbed by the article on “Radiotherapy in Good-Prognosis ­DLBCL” published recently in The ASCO Post.1

As a practicing radiation oncologist for 30 years, I have seen the evolution of radiation techniques (and philosophy) for non-Hodgkin lymphoma progress from regional—or even systemic—dosing to just localized. Radiotherapy is now utilized for either primary or consolidation regimens for a patient with localized, good-prognosis diffuse large B-cell lymphoma (DLBCL).

Modern localized radiotherapy for non-Hodgkin lymphoma consists of a very modest and almost asymptomatic dose administered to the original presentation site(s) after chemotherapy produces either a complete or partial response, or even as primary treatment alone. The combination technique (R-CHOP [rituximab (Rituxan), cyclophosphamide, doxorubicin, vincristine, and prednisone] plus radiotherapy), as used in the study by the Lysa/Goelams Group reported in The ASCO Post, also produced excellent localized control.2 Similarly, excellent localized control is reported in study after study in American, European, and Asian reports.3

Misleading Report?

It is well recognized that the local-regional radiation treatment intent is not to increase systemic control or overall survival but to diminish local failures. The report published in The ASCO Post seems to misrepresent these accepted findings by indicating consolidative radiotherapy is (completely?) unnecessary for DLBCL patients achieving complete response after chemotherapy.

In contrast, the reported local relapse rate in this study differs significantly in the two arms when “local control” is analyzed (100% with radiotherapy vs 42% without) rather than systemic relapses (5% with radiotherapy vs 8% without). The latter actually reflects the failure of systemic chemotherapy and not localized consolidation radiotherapy (or salvage radiotherapy for patients achieving a partial response). This is not clearly reported and can mislead the casual reader.

‘Survival Bias’

Furthermore, failures occurred in only 20 (7%) of 301 enrolled patients. This confirms an excellent prognosis overall in the analyzed population but can distract from any radiotherapy advantage by “survival bias.” A better analysis for such a small number of systemic failures is to actually compare the raw numbers. Systemic failure occurred in 8 patients with radiotherapy vs 12 patients without radiotherapy. This equals a 35% absolute reduction in systemic failures with radiotherapy—with 100% local control—which is statistically significant.

Finally, seven patients achieved a partial response without radiotherapy and only one with radiotherapy. This is an absolute 85% difference at the “end of treatment.”

Achieving complete response (with or without radiotherapy) matured into a 90% overall 5-year survival rate. Therefore the goal is to achieve a “complete” response. Inducing maximum local control with consolidation radiotherapy is an additional tool to facilitate that worthwhile outcome, as the study confirms. ■

—Theodore E. Yaeger, MD,
FACR, FACRO, FRSM
Professor of Radiation Oncology
University of North Carolina at Chapel Hill
Distinguished Alumnus of Drexel University, Philadelphia
Medical Director, McCreary Cancer Center
Lenoir, North Carolina

Disclosure: Dr. Yaeger reported no potential conflicts of interest.

References

1. Helwick C: Radiotherapy in good-prognosis DLBCL. The ASCO Post 6(3):17, 2015.

2. Lamy T, Damaj G, Gyan E, et al: R-CHOP with or without radiotherapy in non-bulky limited-stage diffuse large B-cell lymphoma (DLBCL): Preliminary results of the prospective randomized phase III 02-03 trial from the Lysa/Goelams Group. 2014 ASH Annual Meeting. Abstract 393. Presented December 8, 2014.

3. Brady LW, Yaeger TE (eds): Encyclopedia of Radiation Oncology. New York, Springer, 2012.



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