Interim analysis of a prospective phase I/II trial of SBRT for liver metastases

Stereotactic Body Radiation Therapy (SBRT) is a potent means of systemic cytoreductive therapy for selected patients with metastatic cancer. We here report an interim analysis of a prospective Phase I/II study of SBRT for liver metastases. Eligible patients with liver metastases met these criteria: (1) maximum tumor diameter < 6 cm; (2) < 3 discrete lesions; (3) treatment planning confirmed >= 700 cm(3) of normal liver receives < 15Gy. The gross tumor volume (GTV) was expanded 5 - 10 mm to yield the planning target volume, which received 60 Gy in 3 fractions of SBRT over 3 - 14 days in the Phase II component of the trial. As of July, 2006, 36 patients have been enrolled: 18 in Phase I, 18 in Phase II. The median age was 58 years ( range 27 - 91); the M: F ratio was 20:16. The most common primary sites were lung (n = 10), colorectal (n = 9), and breast (n = 4). Among 21 pts with >= 6 months post-SBRT follow-up (median 19 months, range 6 - 29), one instance of SBRT-related grade 3 toxicity occurred in subcutaneous tissue superficial to the liver. No grade IV toxicity occurred. For 28 discrete lesions treated (median GTV 14 cm 3, range 1 - 98) the 18 month actuarial local control estimate is 93%. This interim analysis indicates that a very high rate of durable in-field tumor control can be safely achieved with SBRT to 1 - 3 liver lesions as administered in this protocol, to a prescription dose of 60 Gy in 3 fractions.