Local control rates with five-fraction stereotactic body radiotherapy for oligometastatic cancer to the lung.

Objective: To report our institutional experience with five fractions of daily 8-12 Gy stereotactic body radiotherapy (SBRT) for the treatment of oligometastatic cancer to the lung.

Methods: Thirty-four consecutive patients with oligometastatic cancers to the lung were treated with image-guided SBRT between 2008 and 2011. Patient age ranged from 38 to 81 years. There were 17 males and 17 females. Lung metastases were from the following primary cancer types: colon cancer (n=13 patients), head and neck cancer (n=6), breast cancer (n=4), melanoma (n=4), sarcoma (n=4) and renal cell carcinoma (n=3). The median prescription dose was 50 Gy in five fractions (range, 40-60 Gy) to the isocenter, with the 80% isodose line encompassing the planning target volume (PTV) [defined as gross tumor volume (GTV) + 7-11 mm volumetric expansion]. The follow-up interval ranged from 2.4-54 months, with a median of 16.7 months.

Results: The 1-, 2-, and 3-year patient local control (LC) rates for all patients were 93%, 88%, and 80% respectively. The 1-, 2-, and 3-year overall survival (OS) rates were 62%, 44%, and 23% respectively. The 1- and 2-year patient LC rates were 95% and 88% for tumor size 1-2 cm (n=25), and 86% for tumor size 2-3 cm (n=7). The majority (n=4) of local failures occurred within 12 months. No patient experienced local failure after 12 months except for one patient with colon cancer whose tumors progressed locally at 26 months. All five patients with local recurrences had colorectal cancer. Statistical analyses showed that age, gender, previous chemotherapy, previous surgery or radiation had no significant effect on LC rates. No patient was reported to have any symptomatic pneumonitis at any time point.

Conclusions: SBRT for oligometastatic disease to the lung using 8-12 Gy daily fractions over five treatments resulted in excellent 1- and 2-year LC rates. Most local failures occurred within the first 12 months, with five local failures associated with colorectal cancer. The treatment is safe using this radiation fractionation schedule with no therapy-related pneumonitis.