SBRT of Recurrent HNC Should be Most Effective in Patients With Nasopharyngeal or Small Volume Lesions

Abstract

Precise beam-delivery techniques like SRT/SBRT have allowed reirradiation as a potentially curative salvage therapy. It is generally agreed that SBRT remains a reasonable choice of salvage for inoperable recurrence of head and neck cancer, because its GTV-limited dose delivery prevents acute radiation toxicity and offers acceptable treatment tolerance. This is a retrospective analysis of reirradiation of 65 patients with recurrent HNC using microbeam SBRT over 2010-2017. The median age of the patients was 58 years (range, 28–91 years), with 38 males and 27 females. All recurrences occurred in the previously radiated with the dose ≥40 Gy. Patients who received SBRT as a planned boost after primary radiation therapy and those who had second primary tumor outside the reirradiation area were excluded from the analysis. Recurrent HNC characteristics were as follows: according to primary site—24 NPC, 17OPC, 15 OCC, 4 HPC, 3 with nasal cavity, and 2 with LXC; according to T stage—9 T0, 10rT1, 26rT2, 13rT3, and 7rT4; according to N stage—52 rN0, 9rN1, and 4 N2. Patients had received median dose in PTV of 24 Gy (minimum 5 Gy, maximum 52 Gy, mean: 22, 7 Gy ± 8.65 Gy SD in 1-13 fractions). The median BED (for alpha/beta = 3 Gy) from first radiation was 60.48 Gy (range 46.8-72 Gy), from secondary radiation was 66.7 Gy (range 13.3-121 Gy) and sum of both treatments was 127 Gy (range 62-156 Gy). The median follow-up time for all reradiated patients was 16 months, and the 2-year overall survival rate was 27%. Estimated prognostic factors for overall survival were: primary site (nasopharynx versus other sites), PTV maximal diameter, and PTV volume. Detailed analysis of PTV maximal diameter and PTV volume showed a lower response rate in patients with tumor diameter greater than 4cm (65%) and volume greater than 21cm3 (34%), compare to <4cm (80%; P=.045) and <21cm3 group (53%; P=.008). The 2-year overall survival rates were 16.4% in the >4cm PTV maximal diameter group and 34% (P=.003) in the <4cm PTV maximal diameter group and 22% in the >21cm3 PTV volume group and 32.5% (P=.002) in the <21cm3 PTV volume group. We recorded 2 incidents of haemorrhage during reirradiation in the >4cm PTV maximal diameter group. For recurrent HNC patients, the “r” tumor site, the amount of PTV volume, and PTV maximal diameter are significant prognostic factors for patient survival after reirradiation using SBRT.