A phase II trial of low-dose total body irradiation and subcutaneous interleukin-2 in metastatic melanoma.

BACKGROUND AND PURPOSE: Our own experimental data suggests a therapeutic synergism between low-dose total body irradiation (LTBI) and interleukin-2 (IL-2). PATIENTS AND METHODS: Forty-five patients received a maximum of 2 cycles of high dose subcutaneous (s.c.) IL-2 and LTBI. One treatment cycle included 5 weeks treatment followed by 2 weeks break and composed of a single radiation fraction 0.1 Gy on days 1, 8, 22 and 30 and IL-2: 18 MU x 2 daily s.c. on days 2 to 5 and days 16-19 as well as 9 MU x 2 daily s.c. on days 9-12 and 31-34. In 17 patients, flow cytometric analyses of the various subpopulations of immune cells were done on blood samples before the first LTBI fraction and 24h after LTBI as well as after the first week of treatment. RESULTS: Two patients (4.4%) had a partial response (PR) and 13 patients (29%) had stable disease (SD). The duration of the partial remission and stable disease did not exceed 3 months. The median overall survival was 5.8 months (95% CI, 4-8 months). Thirty-four of the 58 treatment cycles (74%) were given in 100% of the intended dose without modification or delay. The dose was modified in 15 cycles (26%) because of progression (6), liver toxicity (3), CNS toxicity (2), thrombocytopenia (1), lung morbidity (1) and itching (1). There were no treatment-related deaths. Flowcytometry data showed a significant increase in the percentage of cells carrying the beta chain of IL-2 receptor (CD122+), a significant increase in the percentage of NK cells (CD56+ cells) as well as a significant reduction in the percentage of B cells (CD20+) and monocytes (CD14+). CONCLUSIONS: This LTBI and IL-2 regimen was well tolerated, however it cannot be recommended because of its low clinical efficacy. No indication of increased efficacy or altered toxicity was seen using LTBI.

Tumour burden and interleukin-2 dose affect the interaction between low-dose total body irradiation and interleukin 2.

Low-dose total body irradiation (LTBI) has a synergistic immune-mediated antitumour effect when used in combination with interleukin 2 (IL-2) in a murine metastatic malignant melanoma model. To optimise the use of this combination treatment this study was performed to test the effect of tumour burden and dose of both LTBI and IL-2 on the therapeutic potential of this treatment strategy. Ten-week-old female C57BL/6 mice were inoculated intravenously (day 0) with 1 million B16F1 malignant melanoma cells. Groups of mice received no treatment, a single fraction of LTBI alone, IL-2 treatment alone, or a combination of LTBI and IL-2. Two doses of LTBI and IL-2 were tested. LTBI was given on day +10 and IL-2 treatment started on day +11. On day +18 the mice were killed. The lungs were removed and analysed for tumour burden. Lung sections were also tested for infiltrating leucocytes using immunohistochemical staining. In one experiment, mice were treated at day +7 with low-dose IL-2 with and without LTBI. LTBI (in the two tested doses) showed no independent therapeutic effects. An IL-2 dose of 300,000 Cetus units (CU) that was effective and showed synergism with LTBI when mice were treated on day +7 failed to show a therapeutic effect when mice were treated on day +10, at which time the initial tumour burden had doubled. High-dose IL-2 (600,000 CU), in contrast, led to a significant reduction in metastatic burden compared to the control group. Combining high-dose IL-2 with LTBI led to a further significant reduction in tumour burden. Moreover, this combination was associated with a less severe vascular leakage syndrome compared to IL-2 alone. IL-2 and combination treatment was associated with an increase in the number of tumour-infiltrating immune cells, but only the number of tumour-infiltrating natural killer cells reflected therapeutic efficacy. It was concluded that tumour burden at the time of treatment and IL-2 dose are two crucial factors affecting the synergism between LTBI and IL-2. The combination may not only be more effective than IL-2 alone but also less toxic.

Low-dose total body irradiation augments the therapeutic effect of interleukin-2 in a mouse model for metastatic malignant melanoma.

BACKGROUND: Low-dose total body irradiation (LTBI) is known for its antitumor immune modulatory effects. Moreover, there is theoretical ground suggesting that combining LTBI with interleukin-2 (IL-2) will have a synergistic immune-mediated antitumor effect. However, the use of LTBI in combination with IL-2 or other forms of immunotherapy has not been tested before. AIM OF THE WORK: To test the efficacy of combining LTBI and IL-2 in controlling lung metastases in a murine model for malignant melanoma compared to IL-2 alone. MATERIAL AND METHODS: Ten-week-old female C57BL/6 mice were inoculated intravenously (on day 0) with 1 million B16F1 malignant melanoma cells. The mice received either no treatment (control group), LTBI alone (single fraction of 0.75 Gy), IL-2 treatment alone (30,000 CU x 2 daily for 5 consecutive days), or a combination of LTBI and IL-2. LTBI was given on day +7 and IL-2 treatment started day +8. On day +14, the mice were sacrificed and the lungs were removed and analyzed for tumor burden. Lung sections were also tested for tumor-infiltrating cells using immunohistochemical staining. Peripheral blood and splenic cells were collected and tested for the percentage of the various lymphocytic subsets using immunostaining and flow cytometry. RESULTS: Tumor burden expressed as the percentage of lung area occupied with metastases (+/- 1 SD), was the same in the control group (8.1 +/- 4.9%), and in the group receiving LTBI alone (8.3 +/- 4.5%). Tumor burden was reduced to 6.4% (+/- 3.4%) in the IL-2 alone group (P = 0.3) and further reduced to 3% (+/- 1%) in the combined treatment group (P = 0.004). The difference in tumor burden between the IL-2 alone group and the combined treatment group was statistically significant (P = 0.006). The combined treatment caused a significant increase in the number of natural killer (NK) cells and macrophages infiltrating the metastatic sites. This was associated with a significant increase in the percentage of CD122+ (IL-2R beta) cells and NK cells in both peripheral blood and spleens. CONCLUSION: We conclude that combining LTBI and IL-2 treatment is synergistic and therapeutically more effective than IL-2 alone. The data points to NK cells and macrophages as likely major effectors of the synergistic outcome of the combined treatment. This observation may have important clinical implications in the treatment of patients with metastatic malignant melanoma.