Abstract
ObjectivesTo report on overall survival (OS), local control (LC), dose-outcome relationships, and related toxicities following stereotactic body radiation therapy (SBRT) for locally recurrent, previously irradiated squamous cell carcinoma of the head and neck (rSCCHN).MethodsWe queried the prospectively-maintained RSSearch® Registry for patients with rSCCHN treated with five-fraction SBRT from January 2008 to November 2016. Patients with non-squamous cell histology, missing registry data regarding prior irradiation, those treated with less than five fractions of SBRT, and those treated with SBRT in primary or boost settings were excluded. LC and OS were estimated using the Kaplan-Meier method with comparisons between groups completed using log-rank t-tests and multivariable Cox regression. Logistic regression analyses were used to examine factors predictive of toxicity.ResultsForty-five rSCCHN patients treated with SBRT delivered in five fractions at 12 radiotherapy centers were identified. Prescription doses ≥ 40 Gy were associated with higher one-year rates of OS, LC, and a higher likelihood of experiencing toxicities. Acute and late toxicity rates were low (22.2% and 15.6%, respectively) and were all Grade 1-2 with only one late Grade 3 esophagitis.ConclusionSalvage SBRT for rSCCHN resulted in outcomes comparable to prior single-institutional reports in a multi-institutional cohort across clinical settings with low toxicity, thus supporting more widespread adoption of SBRT with recommended doses ≥ 40 Gy.
Highlights
Stereotactic body radiation therapy (SBRT) has emerged as a viable re-irradiation strategy for unresectable locally recurrent previously irradiated squamous cell carcinomas of the head and neck, with recent multi-institutional comparative effectiveness analyses suggesting less acute toxicity and comparable outcomes when contrasting SBRT to intensity-modulated radiation therapy (IMRT) [1,2]
Our results support tumor control probability data recently presented by the American Association of Physics in Medicine Working Group on Stereotactic Body Radiation Therapy (WGSBRT), which described a significant increase in local control (LC) and overall survival (OS) with dose escalation from 25 Gy to 40 Gy and recommended a minimum prescription dose of 40 Gy for all recurrent head and neck cancer (rHNC) tumors treated with SBRT [21]
We provide a unique method to analyze outcomes of rHNC patients treated with SBRT across numerous institutions
Summary
Stereotactic body radiation therapy (SBRT) has emerged as a viable re-irradiation strategy for unresectable locally recurrent previously irradiated squamous cell carcinomas of the head and neck (rSCCHN), with recent multi-institutional comparative effectiveness analyses suggesting less acute toxicity and comparable outcomes when contrasting SBRT to intensity-modulated radiation therapy (IMRT) [1,2]. The first Phase I dose-escalation trial using SBRT for rSCCHN reported a median overall survival (OS) of six months with no Grade 3/4 toxicities from dose tiers ranging from 25 Gy to 44 Gy [4]. This data was followed by reports which demonstrated that dose escalation to 50 Gy in five fractions was feasible with SBRT for rSCCHN [5].
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