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Highlights • This feasibility study showed thyroid sparing in head and neck cancer patients. • Thyroid sparing with acceptable target volume coverage was possible with IMRT. • Average mean dose to thyroid was significantly reduced with thyroid optimization. • Thyroid optimized plans had relatively unchanged doses to surrounding OARs., Background Radiation-induced hypothyroidism is a common toxicity of head and neck radiation. Our re-planning study aimed to reduce thyroid dose while maintaining target coverage with IMRT. Methods We retrospectively identified patients with oral-cavity (n = 5) and oropharyngeal cancer (n = 5). Treatment plans were re-optimized with 45 Gy thyroid mean dose constraint, then we cropped the thyroid out of PTVs and further reduced thyroid dose. Target coverage was delivering 100% dose to ≥ 93% of PTV and 95% of dose to > 99% of PTV. Results Originally, average mean dose to thyroid was 5580 cGy. In model I, this dropped to 4325 cGy (p

Adequate dose homogeneity and full prescription dose delivery to the scalp still remains a dosimetric problem during scalp irradiation due to the anatomical shape of the cranium. Confounding variables such as gravity, the irregular and convex shape of the cranium, air gaps between scalp surface and commercial bolus, and potential inconsistencies in a 3D printed bolus can negatively impact the dose delivered to the scalp surface during scalp irradiation. The purpose of this retrospective case study was to implement the use of a 3D milled rigid bolus technique combined with volumetric modulated arc therapy (VMAT) treatment planning and evaluate the dosimetric efficacy in delivering dose to the surface of the scalp. The 8-patient retrospective case study consisted of patients with a scalp lesion treated using a 3D milled bolus, VMAT, 6 megavoltage (MV) photon beams, and aligned for treatment using daily conebeam computed tomography (CT) and 6° of freedom couch positioning. Dose volume histograms (DVHs) were used to evaluate maximum dose delivered to the planning target volumes (PTVs) while the dose homogeneity index (DHI) was calculated and compared to that of an ideal value of 1. The researchers evaluated the minimum dose delivered to the individual PTVs after plan normalization. The researchers found that the 3D milled bolus coupled with volumetric modulated arc therapy increased surface dose homogeneity, while also increasing the percentage of planning target volumes receiving full prescription dose. With statistically significant results, patient specific 3D milled rigid bolus offers a viable bolus option for treatment of superficial scalp lesions when combined with volumetric modulated arc therapy treatment planning. However, a larger sample size used in a scientific research study across multiple institutions would be desirable to validate these case study findings.

The purpose of this study was to investigate the dosimetric impact of weight loss in head and neck (H&N) patients and examine the effectiveness of adaptive planning. Data was collected from 22 H&N cancer patients who experienced weight loss during their course of radiotherapy. The robustness of Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) treatment plans were compared including the potential need for replanning. The dosimetric impact of weight loss was evaluated by calculating a verification plan for each patient on an assessment CT scan taken during the course of treatment. Using a regression analysis, significance was tested for the dosimetric change in target volumes and 10 specific organs at risk (OAR) using an anatomical separation difference in the H&N at corresponding levels. For both the IMRT and VMAT plans, a significant correlation was found for the dose to 5% of the high risk Planning Target Volume (PTV) (D5), dose to 95% of the intermediate risk PTV and Clinical Target Volume (CTV) (D95), and the percentage of the pharynx receiving 65 Gy. An independent t-test was also performed for each metric in the VMAT and IMRT plans showing the dose to 95% of the intermediate risk PTV as significant. No quantitative method for finding the threshold of anatomical separation difference requiring a replan was established. Based on the increase in dose to organs at risk and increased target coverage due to separation loss, it was concluded that adaptive radiotherapy may not always be necessary when alignment of bony anatomy and remaining soft tissue is within tolerance. Physician judgment and preference is needed in such situations.

Background Nearly all meningiomas express somatostatin receptor 1/2 (SSTR1/SSTR2); therefore, SSTR ligands such as 68Ga-DOTATATE can be utilized for meningioma radiotherapy treatment planning. Incorporation of 68Ga-DOTATATE PET assists with target delineation and may reduce the dose to organs-at-risk (OARs). We hypothesize that 68Ga-DOTATATE PET-based treatment plans will reduce dose to OARs when compared to MRI-based plans. METHODS All treatment plans were rendered on computed tomography (CT) planning datasets, using RapidArc and 6MV photon energy. Two arcs were positioned on the coplanar axis with alternated collimator settings of 0 and 90 degrees to promote MLC sparing with a third unique vertex arc chosen independently to spare normal brain tissue and associated organs at risk (OAR). For MRI structures, a 1 cm expansion from the gross tumor volume (GTV) created a clinical treatment volume (CTV)60. A 2 cm expansion created a CTV54. For PET structures, a 1 cm expansion from the GTV created a CTV60. A 3 mm isotropic expansion created planning treatment volumes (PTVs). Plans were optimized such that Dmax to brainstem remained limited to 60Gy or less and Dmax to optic structures was limited to 54Gy or less. RESULTS 18 meningioma patients were included (9 post-operative, 9 intact). The mean PTV volume using MRI was 258 ccs (306 ccs for post-operative, 210 ccs for intact), and the mean PTV volume using PET was 60 ccs (97 ccs for post-operative, 91 ccs for intact). The mean radiation dose to both optic nerves, the optic chiasm, both hippocampi, and the brainstem was reduced favoring PET-based treatment plans for both post-operative and intact patients. CONCLUSION Our study shows that incorporation of 68Ga-DOTATATE PET can reduce dose to OARs for post-operative and intact patients, and this difference may translate to reduced toxicity. 68Ga-DOTATATE PET guided radiation treatments are worthy of future prospective investigation.

Purpose Multiple studies have reported favorable outcomes for stereotactic radiosurgery (SRS) in the treatment of limited brain metastases. An obstacle of SRS in the management of numerous metastases is the longer treatment time using traditional radiosurgery. Single-isocenter multitarget (SIMT) SRS is a novel technique that permits rapid therapy delivery to multiple metastases. There is a lack of clinical evidence regarding its efficacy and safety. We report the outcomes of patients treated with this technique. Methods and Materials We reviewed the records of patients with intact or resected brain metastases treated with SRS in 1 to 5 fractions using SIMT technique at our institution, with at least 1 available follow-up brain magnetic resonance imaging. Survival, disease control, and toxicity were evaluated using Cox regression, logistic regression, and Kaplan-Meier analysis. Results We identified 173 patients with 1014 brain metastases. Median follow up was 12.7 months. Median beam-on time was 4.1 minutes. The median dose to the brain was 219.4 cGy. Median overall survival and freedom from intracranial progression were 13.2 and 6.3 months, respectively. Overall survival did not differ between patients treated with greater than or less than 4 lesions (hazard ratio, 1.03; 95% confidence interval 0.66-1.61; P = .91). Actuarial 1- and 2-year local control were 99.0% and 95.1%, respectively. Rates of grade 2 and grade 3 or higher radionecrosis were 1.4% and 0.9%, respectively. Conclusions SIMT radiosurgery delivered in 1 to 5 fractions offers excellent local control and acceptable toxicity in the treatment of multiple intact and postoperative brain metastases. This technique should be evaluated prospectively.

Purpose/Objective(s) Radiation treatment planning for meningioma conventionally involves MRI contrast enhanced images to define residual tumor. However, the gross tumor volume may be difficult to delineate for patients with a meningioma in the skull base, sagittal sinus, or post resection. Advanced PET imaging using 68(GA)DOTATATE PET, which has been shown to be more sensitive and specific than MRI imaging, can be used for target volume delineation in these circumstances. We hypothesize that 68(GA)DOTATATE PET scan-based treatment planning will lead to differences in radiation treatment volumes and will be more precise compared to standard MRI alone. Materials/Methods Our study evaluated retrospective, deidentified, and blinded gross tumor volume (GTV) contour delineation of 5 CNS specialists (3 neuroradiologists, 2 CNS radiation oncologists) for 26 patients diagnosed with a meningioma who received both a 68(GA)DOTATATE PET and an MRI for radiation treatment planning. Both the MRI and the PET-based GTV were non-sequentially contoured by each physician for each patient. We defined a significant difference in volume delineation if there was > 100% difference in contoured volume found for 80% of physicians or more when comparing MRI and PET. A PET only lesion was defined as any lesion not seen on MRI but delineated on PET imaging by at least 80% of physicians. This lesion would need to be non-adjacent to the MRI based contours for the same patient. Results The mean volume of MRI based contours was 12.5 ccs (range 0.55-62 ccs). The mean volume for PET directed contours was 13.7 ccs (range 0.24-94 ccs). We found 15/26 (58%) patients had at least a 100% difference in volume between PET and MRI for 80% of physician contours. 8/26 (31%) patients had new non-adjacent areas contoured on PET that were not contoured by these physicians on the corresponding MRI. These new areas would not have been in the traditional MRI based volumes. Conclusion We found a significant difference in PET based volumes with 58% showing major differences in volume and 31% showing new areas not seen on MRI. This has major implications on tumor control. Our study supports that 68(GA)DOTATATE PET imaging can help radiation oncologist be more precise with radiation treatment volumes. Utilization of 68(GA)DOTATATE PET may find undetected areas of disease which in turn can improve local control and progression free survival. 68(GA)DOTATATE PET guided treatment planning should be studied prospectively.

PURPOSE Radiation treatment planning for meningiomas conventionally involves MRI contrast enhanced images to define residual tumor. However, the gross tumor volume may be difficult to delineate for patients with a meningioma in the skull base, sagittal sinus, or post resection. Advanced PET imaging using 68(GA)DOTATATE PET, which has been shown to be more sensitive and specific than MRI imaging, can be used for target volume delineation in these circumstances. We hypothesize that 68(GA)DOTATATE PET scan-based treatment planning will lead to smaller radiation volumes and will detect additional areas of disease compared to standard MRI alone. METHODS Our data evaluated retrospective, deidentified, and blinded gross tumor volume (GTV) contour delineation with 7 CNS specialists (3 neuroradiologists, 4 CNS radiation oncologists) for 26 patients diagnosed with a meningioma who received both a 68(GA)DOTATATE PET and an MRI for radiation treatment planning. Both the MRI and the PET were non-sequentially contoured by each physician for each patient. RESULTS The mean MRI volume for each physician ranged from 24.14-35.52 ccs. The mean PET volume for each physician ranged from 10.59-20.54 ccs. The PET volumes were significantly smaller for 6 out of the 7 physicians. In addition, 7/26 (27%) patients had new non-adjacent areas contoured on PET by at least 6 of the 7 physicians that were not contoured by these physicians on the corresponding MRI. These new areas would not have been in the traditional MRI based volumes. CONCLUSION Our study supports that 68(GA)DOTATATE PET imaging can help radiation oncologist create smaller and more precise radiation treatment volumes. Utilization of 68(GA)DOTATATE PET may find undetected areas of disease which in turn can improve local control and progression free survival. 68(GA)DOTATATE PET guided treatment planning should be studied prospectively.

Purpose/Objective(s) Sinonasal tumors are a rare and aggressive type of head and neck tumor. Radiation therapy is one of the primary treatment modalities for sinonasal malignancies, yet previous studies have shown that radiation to the head and neck region can damage the pituitary gland leading to endocrine dysfunction. The purpose of this study is to determine the relationship between radiation dose and endocrine dysfunction in the hypothalamic-pituitary axis in patients undergoing radiation therapy for treatment of sinonasal and skull-based malignancies. Materials/Methods A retrospective chart review examined data from 89 adult patients receiving radiation therapy for sinonasal and skull-based malignancies at an academic institution between 2007 – 2019. Mean and max radiation doses to the hypothalamus and pituitary gland were determined from computed tomography scans. Patients were evaluated for endocrine levels before and after completion of radiotherapy. All patients were evaluated for thyroid stimulating hormone (TSH) and thyroxine (T4) levels, while a subset of patients (n = 27) were also assessed for adrenocorticotropic hormone (ACTH), cortisol, prolactin, insulin-like growth factor 1 (IGF1), and testosterone levels. Endocrine dysfunction was defined as a new onset of abnormal endocrine levels following radiation therapy. Results The percentage of patients demonstrating post-radiation endocrine dysfunction in each hypothalamic-pituitary axis was as follows: TSH: 50%, T4: 43%, ACTH: 40%, Cortisol: 52%, Prolactin: 31%, IGF1: 11%, Testosterone: 38%. Logistic regression analysis indicated a significant relationship between mean radiation dose to pituitary gland and TSH dysfunction (P = 0.0090), with increased dose correlated with higher rates of TSH dysfunction (Odds ratio: 1.05; 95% confidence interval: 1.01 – 1.09). Similarly, there was a significant relationship between max radiation dose to pituitary gland and TSH dysfunction (P = 0.0053) with increased dose correlated with higher rates of TSH dysfunction (Odds ratio: 1.05; 95% confidence interval: 1.02 – 1.09). Conclusion Cranial radiotherapy for the treatment of sinonasal and skull-based malignancies was accompanied by endocrine dysfunction in 64% of patients studied. Mean and max radiation dose to the pituitary gland were statistically significant parameters predicting TSH dysfunction. We recommend that clinicians regularly monitor endocrine levels in patients following radiation therapy, particularly in cases where high radiation doses are used.

Laryngeal squamous cell carcinoma is the second most common head and neck cancer. Its pathogenesis is strongly associated with smoking. The management of this disease is challenging and mandates multidisciplinary care. Currently, accepted treatment modalities include surgery, radiation therapy, and chemotherapy—all focused on improving survival while preserving organ function. Despite changes in smoking patterns resulting in a declining incidence of laryngeal cancer, the overall outcomes for this disease have not improved in the recent past, likely due to changes in treatment patterns and treatment-related toxicities. Here, we review emerging concepts and novel strategies in the use of radiation therapy in the management of laryngeal squamous cell carcinoma that could improve the relationship between tumor control and normal tissue damage (therapeutic ratio).