Final Results of a Phase II Danish Trial Testing Low Dose Total Body Irradiation Following Six Bi-Weekly RCHOP-14 Plus 2 Extra Rituximab in Elderly High risk Patients with Aggressive CD20+ Diffuse Large B-Cell Lymphoma (DLBCL)

Background: To further improve the results achieved by adding Rituximab (R) and shortening chemotherapy interval in elderly patients, an effective but relatively non-toxic treatment modality is needed. We tested therefore the addition of low dose total body irradiation (LTBI) of 1,6 Gy given after chemo-immunotherapy.
Methods: A multicenter, phase II trial including patients >60 yrs with stage II-IV, CD20-positive DLBCL was performed between 2003 and 2007. Patients received 6x R-CHOP-14 + 2x R alone followed by LTBI given as 2 courses of 4 daily fractions of 0,2 Gy separated by 2 weeks of rest. Radiotherapy to sites of bulky (>7.5 cm) disease was given according to the local guidelines of the participating centres.
Results: Forty two patients were included. Observation time ranged from 3 to 47 months with median follow up of 24 months. The median age was 67 years; 62% had stage III or IV; 48% had B symptoms and 36% had bulky (> 7.5 cm) disease; 50% had ECOG score ≥ 1; 76% had elevated LDH and 57% had IPI of >2. Twenty four patients (57%) achieved a CR or CRu at the end of chemotherapy, while 12 (28.5%) were in PR. One of the 12 PR patients refused LTBI. Of the remaining 11 PR patients who received LTBI, 8 (82%) achieved CR in the first follow up after LTBI while the remaining 3 patients had initially stable disease but progressed shortly after. One patient (2%) progressed under chemotherapy while seven patients (17%) relapsed after achieving CR. Six of these refractory/relapsed cases presented with IPI ≥ 3. 
The 3-yr event-free and progression-free survival values were 64.8% (SE: 8.7%) and 73.5% (SE: 8.9%), respectively, while the 3-yr overall survival was 85.4% (SE: 5.5%).
There were 3 toxic deaths (7.1%) due to sepsis occurring during chemotherapy. Ninteen of 235 cycles of CHOP (8%) were given at reduced dose levels in 3 patients (7%), while 3 cycles (1.3%) were delayed but given at 100% dose level. None of the 305 injections of Rituximab were dose reduced. Only one of 31 patients (3%) got his second LTBI cycle at 75% of the planned dose because of thrombocytopenia. CTC Gr 3-4 neutropenia occurred following 50 of 250 R-CHOP-14 cycles (20%). CTC Gr. 3-4 thrombocytopenia was seen in 8 pts (22%) following LTBI.
Conclusions: Despite the high risk profile of the patient cohort enrolled in this trial, the 3-yr outcome values match the results of the best performing recent phase III clinical trials designed for elderly patients with DLBCL. Adding LTBI to 6 cycles of R-CHOP-14 was well tolerated and effective in converting the majority of PRs into CRs. Therefore, it may provide survival benefit and should be tested in a randomised setting.