Stereotactic body ablative radiotherapy for reirradiation of small volume head and neck cancers is associated with prolonged survival: Large, single-institution, modern cohort study.

BACKGROUND: Recurrent head and neck cancer has poor prognosis. Stereotactic body radiotherapy (SBRT) may improve outcomes by delivering ablative radiation doses. METHODS: We reviewed patients who received definitive-intent SBRT reirradiation at our institution from 2013 to 2020. Patterns of failure, overall survival (OS), and toxicities were analyzed. RESULTS: One hundred and thirty-seven patients were evaluated. The median OS was 44.3 months. The median SBRT dose was 45 Gy and median target volume 16.9 cc. The 1-year local, regional, and distant control was 78%, 66%, and 83%, respectively. Systemic therapy improved regional (p = 0.004) and distant control (p = 0.04) in nonmetastatic patients. Grade 3+ toxicities were more common at mucosal sites (p = 0.001) and with concurrent systemic therapy (p = 0.02). CONCLUSIONS: In a large cohort of SBRT reirradiation for recurrent, small volume head and neck cancers, a median OS of 44.3 months was observed. Systemic therapy improved regional and distant control. Toxicities were modulated by anatomic site and systemic therapy.

SABR for Skull Base Malignancies: A Systematic Analysis of Set-Up and Positioning Accuracy.

PURPOSE: Here we provide an analysis of the set-up and positioning accuracy of SABR for skull base malignancies to evaluate the use of site- or axis-specific margins to reduce field size. METHODS AND MATERIALS: Data were prospectively collected on 63 patients who received 304 fractions of SABR for recurrent/previously irradiated skull base tumors. Using our custom cushion-mask-bite-block immobilization system combined with ExacTrac x-ray and cone beam computed tomography (CBCT), set-up, residual, CBCT-positioning agreement, and intrafractional errors were measured. The resulting planning target volume (PTV) margins were estimated across 4 skull base subsites: anterior (group 1), central (group 2), posterolateral (group 3), and skull base-associated sites (eg, nasopharynx/retropharyngeal, cervical vertebrae 1-2, occiput) (group 4). RESULTS: On initial set-up, 66% of treatment courses required shifts of >2 mm or >2°, necessitating 4.9 mm PTV margins without image guidance. After correction, only 6 of 304 treatment sessions had residual errors >1 mm. CBCT-ExacTrac agreement was ≤1 mm in 89.1% of treatments and ≤1.5 mm in all but 1 session. Group 4 showed a higher rate of >1 mm or >1° CBCT-positioning differences compared with other groups (24.5% vs 7.8%; P = .0001), and the greatest variations occurred in the craniocaudal translational and the pitch rotational axes. Overall calculated PTV margins (based on intrafractional error) were 1.5 mm across subsites except for group 4, which required 2.0 mm margins. CONCLUSIONS: The use of 2.0 mm PTV margins for skull base SABR appears feasible using ExacTrac x-ray as the sole imaging modality for most subsites. However, PTVs were not uniformly equal, and the use of a site-specific nonuniform margin reduction to optimize critical-organ dose sparing may be feasible for select cases. These findings warrant clinical investigation.

Estimating PTV Margins in Head and Neck Stereotactic Ablative Radiation Therapy (SABR) Through Target Site Analysis of Positioning and Intrafractional Accuracy.

PURPOSE: Recurrent or previously irradiated head and neck cancers (HNC) are therapeutically challenging and may benefit from high-dose, highly accurate radiation techniques, such as stereotactic ablative radiation therapy (SABR). Here, we compare set-up and positioning accuracy across HNC subsites to further optimize the treatment process and planning target volume (PTV) margin recommendations for head and neck SABR. METHODS AND MATERIALS: We prospectively collected data on 405 treatment fractions across 79 patients treated with SABR for recurrent/previously irradiated HNC. First, interfractional error was determined by comparing ExacTrac x-ray to the treatment plan. Patients were then shifted and residual error was measured with repeat x-ray. Next, cone beam computed tomography (CBCT) was compared with ExacTrac for positioning agreement, and final shifts were applied. Lastly, intrafractional error was measured with x-ray before each arc. Results were stratified by treatment site into skull base, neck/parotid, and mucosal. RESULTS: Most patients (66.7%) were treated to 45 Gy in 5 fractions (range, 21-47.5 Gy in 3-5 fractions). The initial mean ± standard deviation interfractional errors were -0.2 ± 1.4 mm (anteroposterior), 0.2 ± 1.8 mm (craniocaudal), and -0.1 ± 1.7 mm (left-right). Interfractional 3-dimensional vector error was 2.48 ± 1.44, with skull base significantly lower than other sites (2.22 vs 2.77; P = .0016). All interfractional errors were corrected to within 1.3 mm and 1.8°. CBCT agreed with ExacTrac to within 3.6 mm and 3.4°. CBCT disagreements and intrafractional errors of >1 mm or >1° occurred at significantly lower rates in skull base sites (CBCT: 16.4% vs 50.0% neck, 52.0% mucosal, P < .0001; intrafractional: 22.0% vs 48.7% all others, P < .0001). Final PTVs were 1.5 mm (skull base), 2.0 mm (neck/parotid), and 1.8 mm (mucosal). CONCLUSIONS: Head and neck SABR PTV margins should be optimized by target site. PTV margins of 1.5 to 2 mm may be sufficient in the skull base, whereas 2 to 2.5 mm may be necessary for neck and mucosal targets. When using ExacTrac, skull base sites show significantly fewer uncertainties throughout the treatment process, but neck/mucosal targets may require the addition of CBCT to account for positioning errors and internal organ motion.

Improved setup and positioning accuracy using a three-point customized cushion/mask/bite-block immobilization system for stereotactic reirradiation of head and neck cancer.

The purpose of this study was to investigate the setup and positioning uncertainty of a custom cushion/mask/bite-block (CMB) immobilization system and determine PTV margin for image-guided head and neck stereotactic ablative radiotherapy (HN-SABR). We analyzed 105 treatment sessions among 21 patients treated with HN-SABR for recurrent head and neck cancers using a custom CMB immobilization system. Initial patient setup was performed using the ExacTrac infrared (IR) tracking system and initial setup errors were based on comparison of ExacTrac IR tracking system to corrected online ExacTrac X-rays images registered to treatment plans. Residual setup errors were determined using repeat verification X-ray. The online ExacTrac corrections were compared to cone-beam CT (CBCT) before treatment to assess agreement. Intrafractional positioning errors were determined using prebeam X-rays. The systematic and random errors were analyzed. The initial translational setup errors were -0.8 ± 1.3 mm, -0.8 ± 1.6 mm, and 0.3 ± 1.9 mm in AP, CC, and LR directions, respectively, with a three-dimensional (3D) vector of 2.7 ± 1.4 mm. The initial rotational errors were up to 2.4° if 6D couch is not available. CBCT agreed with ExacTrac X-ray images to within 2 mm and 2.5°. The intrafractional uncertainties were 0.1 ± 0.6 mm, 0.1 ± 0.6 mm, and 0.2 ± 0.5 mm in AP, CC, and LR directions, respectively, and 0.0° ± 0.5°, 0.0° ± 0.6°, and -0.1° ± 0.4° in yaw, roll, and pitch direction, respectively. The translational vector was 0.9 ± 0.6 mm. The calculated PTV margins mPTV(90,95) were within 1.6 mm when using image guidance for online setup correction. The use of image guidance for online setup correction, in combination with our customized CMB device, highly restricted target motion during treatments and provided robust immobilization to ensure minimum dose of 95% to target volume with 2.0 mm PTV margin for HN-SABR.

Effect of interfractional shoulder motion on low neck nodal targets for patients treated using volumetric-modulated arc therapy (VMAT).

VMAT is an important tool in the treatment of head and neck cancers, many of which also require treatment to the supraclavicular lymph nodes. However, full VMAT arcs treating this nodal region necessarily cause entrance beam to pass through patients' shoulders. Thus, interfractional variations in shoulder position may cause unwanted dose perturbations. To assess this possibility, six patients undergoing treatment at our institution for head and neck cancers with associated supraclavicular lymph node treatment were imaged with in-room CT-on-rails during the course of their treatments. This allowed for the establishment of a true record of the actual shoulder position during selected treatment fractions. Then, a full VMAT plan and a plan with VMAT arcs superior to the shoulder and a static anteroposterior field inferiorly were copied onto the patients' weekly image sets. The average one-dimensional shoulder motion was generally within 10 mm of the simulated position, with some notable exceptions. The standard deviation in week-to-week shoulder position relative to simulation was 4.3 mm and 4.2 mm in the SI and AP dimensions, respectively. The average nodal target mean dose across all fractions sampled was within 5% of planned for all patients and both plans. Similarly, the average D95 for the nodal target was within 5% of planned across all fractions sampled, with the single exception of the full VMAT plan for one patient. In most cases, the standard deviation in both target mean dose and D95 was smaller with the VMAT+static AP field plan than it was with the full VMAT plan.

Acupuncture for radiation-induced xerostomia in patients with cancer: a pilot study.

BACKGROUND: This pilot study evaluated if acupuncture can alleviate radiation-induced xerostomia among patients with cancer. Secondary objectives were to assess the effects of acupuncture on salivary flow and quality of life (QOL). METHODS: Nineteen patients received acupuncture twice a week for 4 weeks. RESULTS: Xerostomia inventory (XI) and patient benefit questionnaire (PBQ) scores were significantly better after acupuncture on weeks 4 and 8 than at baseline (XI: p = .0004 and .0001; PBQ: p = .0004 and .0011, respectively). For QOL at weeks 4 and 8, there was a significant difference for questions related to head/neck cancer (p = .04 and .006, respectively). At week 8, there was a significant difference in physical well-being (p = .04). At weeks 5 and 8, there were significant differences in the total score (p = .04 and .03, respectively). CONCLUSIONS: Acupuncture was effective for radiation-induced xerostomia in this small pilot study. Further research is needed.