Extending hypofractionated stereotactic body radiotherapy to tumours larger than 70cc – effects and side effects

Stereotactic body radiotherapy (SBRT) for tumours ≥5 cm is poorly studied and its utility and feasibility is uncertain. We here report the Karolinska experience of SBRT in this setting. All patients had a gross tumour volume (GTV) ≥70 cc, a prescribed physical dose of at least 40 Gy and received treatment between 1995–2012. We included 164 patients with 175 tumours located in the thorax (<i>n</i> = 86), the liver (<i>n</i> = 27) and the abdomen (<i>n</i> = 62) and treated with a median prescribed dose (BED_{α/β 10Gy}) of 80 Gy (71.4–113). One- and 2- year local control rates were 82% and 61%. In multivariate analyses, minimum dose to the GTV and histological subtype were associated with local control. Renal cell carcinoma (RCC) histology showed the most favourable local control − 94% at 2 years for all histologies. Thirty-seven patients experienced grade 3–5 toxicity most likely related to SBRT. Seven of the ten patients with grade 5 toxicity, had a centrally located tumour in the thorax. SBRT of tumours &gt;5 cm in diameter may be an option for peripherally located lung and abdominal tumours. Histological origin and tumour location should be considered before treatment.