Background
Retrospective single-institution analysis (MD Anderson Cancer Center) of primary cutaneous B-cell lymphoma — non-leg type (PCBCL-NLT) — treated with radiation therapy, 2002–2014. 39 patients, 42 lesions. Predominantly PCFCL and PCMZL. RT was the sole treatment in most cases. Key question: is low-dose RT (≤12 Gy) as effective as standard-dose RT (>12 Gy)?
Interventions and follow up
Arm A: Low-dose RT ≤12 Gy (including as low as 4 Gy)
Arm B: Higher-dose RT >12 Gy; retrospective comparison, no randomizatio
Primary endpoint: Local control, overall survival, progression-free survival
mFollow up: Not specified
Arm B: Higher-dose RT >12 Gy; retrospective comparison, no randomizatio
Primary endpoint: Local control, overall survival, progression-free survival
mFollow up: Not specified
Results
Local Control: 100% — all 42 lesions achieved complete response; zero in-field failures
Out-of-field relapses: 7 patients (18%); 3 successfully salvaged with further RT
Low-dose vs. high-dose RT: No significant difference in PFS or OS (P=NS)
Minimum effective dose: 4 Gy demonstrated complete responses
Out-of-field relapses: 7 patients (18%); 3 successfully salvaged with further RT
Low-dose vs. high-dose RT: No significant difference in PFS or OS (P=NS)
Minimum effective dose: 4 Gy demonstrated complete responses
Adverse events
Main adverse events: Low-dose RT (≤12 Gy) extremely well tolerated; minimal skin reactions; no grade ≥3 toxicity reported. Standard-dose RT (24–30 Gy) associated with greater skin toxicity at treatment site.
Conclusions
Low-dose RT (as low as 4 Gy) achieves 100% complete response for PCBCL non-leg type with no in-field failures. No dose-response advantage was identified for doses above 12 Gy. Given the indolent natural history of PCBCL-NLT and high rate of out-of-field relapse, low-dose RT minimizes toxicity while maximizing local control.
Key Limitations
Key Limitations: Retrospective, small sample (n=39); no randomization; heterogeneous doses (4–40 Gy) with selection bias (sicker/bulkier disease likely received higher doses); short follow-up; cannot exclude late relapses at low-dose sites.
Clinical Context
Supports the trend toward very-low-dose RT for indolent PCBCL. The ISRT 4 Gy × 2 fractions (8 Gy) approach (from the UK multicenter experience) and the MDACC experience together support low-dose RT as standard for PCFCL/PCMZL. Current NCCN guidelines now list 24–30 Gy but acknowledge emerging evidence for lower doses in highly selected patients.
References