Outcomes of carotid sparing intensity-modulated radiotherapy for early stage glottic cancer in 201 patients: Multicenter study of Turkish Radiation Oncology Society/TROD-01-007.

BACKGROUND: To assess and report clinical outcomes after carotid sparing intensity-modulated radiotherapy for early stage laryngeal cancer. METHODS: We retrospectively analyzed 201 patients with early stage glottic laryngeal cancer treated with carotid sparing intensity-modulated radiotherapy (IMRT)/volumetric modulated arc therapy (VMAT) techniques in six TROD centers. RESULTS: After a median follow-up of 31 months the actuarial 1- and 3-year local and locoregional control rates were 99.4% and 94.7%, 98.4% and 93%, respectively. T classification, anterior commissure involvement, IMRT technique, and type of fractionation were not found to be prognostic for local control. Overall, eight patients had lost their organ function due to recurrence or toxicity. Grade 3 and 4 acute laryngeal edema was seen in eight (4%) and one (0.5%) of patients, respectively. Grade 3 and 4 late laryngeal edema developed in two (1%) and one patient (0.5%), respectively. CONCLUSION: Oncologic outcomes of patients treated with carotid sparing IMRT were excellent; comparable with historical series, with acceptable side effects. Longer follow-up is needed to estimate long term effect on stroke.

Dosimetric comparison of intensity-modulated radiation therapy for early-stage glottic cancers with and without the air cavity in the planning target volume.

For early-stage glottic cancers, intensity-modulated radiation therapy (IMRT) has been shown to have comparable local control to 3D-conformal radiotherapy with the advantage of decreased dose to the carotid arteries. The planning target volume (PTV) for early glottic cancers typically includes the entire larynx, plus a 3 to 5 mm uniform margin. The air cavity within the larynx creates a challenge for the inverse optimization process as the software attempts to "build up" dose within the air. This unnecessary attempt at dose build-up in air can lead to hot spots within the rest of the PTV and surrounding soft tissue. We hypothesized that removal of the air from the PTV would decrease hot spots and allow for a more homogeneous plan while still maintaining adequate coverage of the PTV. We analyzed 20 consecutive patients with early-stage glottic cancer, T1-2N0, who received IMRT at our institution from April 2015 to December 2016. Each patient received 63 to 65.25 Gy in 2.25 Gy per fraction. Two plans were created for each case: one in which the PTV included the laryngeal air cavity and one in which the air cavity was subtracted from the PTV to create a new PTV-air structure. Dosimetric variables were collected for PTV-air structure from both IMRT plans, including V100%, D98% D2%, and D0.2%. Dosimetric variables for spinal cord and the carotid arteries were also recorded. Homogeneity index (HI) defined as D98/D2 was calculated. Two-sided t-tests were used to compare dosimetric variables. The median PTV volume was 69.9 cc (standard deviation [SD] ± 28.7 cc) and the median air cavity volume removed was 11.0 cc (SD ± 3.4 cc). A 2-sided t-test revealed a statistically significant decrease in max dose (112.7% vs 108.8%, p value = 0.0002) and improvement of HI (0.93 vs 0.91, p value = 0.0023) for the PTV air in the IMRT plan optimized for PTV air, which had air excluded, compared to the IMRT plan optimized for PTV with air included. There was no significant worsening of PTV-air coverage or significant increase in doses to the organs at risk (OARs). The removal of the air cavity from the PTV for early-stage glottic cancers does not compromise PTV coverage or sparing of OARs and can result in a more homogeneous IMRT plan. A more homogeneous plan has the potential to reduce treatment morbidity, although further study is warranted to investigate the clinical impact of air cavity removal from the PTV.

Standardisation of Target Volume Delineation for Carotid-sparing Intensity-modulated Radiotherapy in Early Glottis Cancer.

AIMS: Recently, carotid-sparing intensity-modulated radiotherapy (IMRT) for early laryngeal glottis (T1/T2N0M0) cancer has generated interest in the hope of avoiding long-term carotid toxicity, as well as concerns relating to geographical misses and long-term normal tissue toxicity. The aim of this review was to summarise the current literature on carotid-sparing IMRT for early glottis cancer, with particular focus on definitions of target volumes and the carotid arteries as organs at risk. In addition, we make suggestions for standardisation of these structures, dose constraints and dose reporting. MATERIALS AND METHODS: From 73 references, 16 articles met the criteria for inclusion in this systematic review. These papers described two case reports, 11 planning studies and three prospective studies. RESULTS: There was variation in all target volume definitions with no clear consensus. The greatest variability was in clinical target volume definition. Carotid artery and spinal cord delineation were not always defined and most studies did not use a carotid artery constraint. Of the eight studies that reported carotid artery delineation, no two studies delineated the same length of carotid artery, yet most studies reported mean doses. Most studies used IMRT with three to seven fields. Five studies used arc therapy and two studies used tomotherapy. CONCLUSION: This review highlights a lack of consensus in target volume definitions in carotid-sparing IMRT. Ultimately, long-term prospective data are required to show the benefit of carotid-sparing IMRT. Pooled data will prove useful as most studies will report on small numbers of patients. Therefore, adopting a consensus now on target volume definition, dose constraints and dose reporting will be crucial.

Clinical and dosimetric implications of intensity-modulated radiotherapy for early-stage glottic carcinoma.

Conventional parallel-opposed radiotherapy (PORT) is the established standard technique for early-stage glottic carcinoma. However, case reports have reported the utility of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) with or without image guidance (image-guided radiotherapy, IGRT) in select patients. The proposed advantages of IMRT/VMAT include sparing of the carotid artery, thyroid gland, and the remaining functional larynx, although these benefits remain unclear. The following case study presents a patient with multiple vascular comorbidities treated with VMAT for early-stage glottic carcinoma. A detailed explanation of the corresponding treatment details, dose-volume histogram (DVH) analysis, and a review of the relevant literature are provided. Conventional PORT remains the standard of care for early-stage glottic carcinoma. IMRT or VMAT may be beneficial for select patients, although great care is necessary to avoid a geographical miss. Clinical data supporting the benefit of CRT are lacking. Therefore, these techniques should be used with caution and only in selected patients.

Carotid-Sparing TomoHelical 3-Dimensional Conformal Radiotherapy for Early Glottic Cancer.

PURPOSE: The purpose of this study was to investigate the dosimetric benefits and treatment efficiency of carotid-sparing TomoHelical 3-dimensional conformal radiotherapy (TH-3DCRT) for early glottic cancer. MATERIALS AND METHODS: Ten early-stage (T1N0M0) glottic squamous cell carcinoma patients were simulated, based on computed tomography scans. Two-field 3DCRT (2F-3DCRT), 3-field intensity-modulated radiation therapy (3F-IMRT), TomoHelical-IMRT (TH-IMRT), and TH-3DCRT plans were generated with a 67.5-Gy total prescription dose to the planning target volume (PTV) for each patient. In order to evaluate the plan quality, dosimetric characteristics were compared in terms of conformity index (CI) and homogeneity index (HI) for PTV, dose to the carotid arteries, and maximum dose to the spinal cord. Treatment planning and delivery times were compared to evaluate treatment efficiency. RESULTS: The median CI was substantially better for the 3F-IMRT (0.65), TH-IMRT (0.64), and TH-3DCRT (0.63) plans, compared to the 2F-3DCRT plan (0.32). PTV HI was slightly better for TH-3DCRT and TH-IMRT (1.05) compared to 2F-3DCRT (1.06) and 3F-IMRT (1.09). TH-3DCRT, 3F-IMRT, and TH-IMRT showed an excellent carotid sparing capability compared to 2F-3DCRT (p < 0.05). For all plans, the maximum dose to the spinal cord was < 45 Gy. The median treatment planning times for 2F-3DCRT (5.85 minutes) and TH-3DCRT (7.10 minutes) were much lower than those for 3F-IMRT (45.48 minutes) and TH-IMRT (35.30 minutes). The delivery times for 2F-3DCRT (2.06 minutes) and 3F-IMRT (2.48 minutes) were slightly lower than those for TH-IMRT (2.90 minutes) and TH-3DCRT (2.86 minutes). CONCLUSION: TH-3DCRT showed excellent carotid-sparing capability, while offering high efficiency and maintaining good PTV coverage.

Carotid-Sparing TomoHelical 3-Dimensional Conformal Radiotherapy for Early Glottic Cancer / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The purpose of this study was to investigate the dosimetric benefits and treatment efficiency of carotid-sparing TomoHelical 3-dimensional conformal radiotherapy (TH-3DCRT) for early glottic cancer. MATERIALS AND METHODS: Ten early-stage (T1N0M0) glottic squamous cell carcinoma patients were simulated, based on computed tomography scans. Two-field 3DCRT (2F-3DCRT), 3-field intensity-modulated radiation therapy (3F-IMRT), TomoHelical-IMRT (TH-IMRT), and TH-3DCRT plans were generated with a 67.5-Gy total prescription dose to the planning target volume (PTV) for each patient. In order to evaluate the plan quality, dosimetric characteristics were compared in terms of conformity index (CI) and homogeneity index (HI) for PTV, dose to the carotid arteries, and maximum dose to the spinal cord. Treatment planning and delivery times were compared to evaluate treatment efficiency. RESULTS: The median CI was substantially better for the 3F-IMRT (0.65), TH-IMRT (0.64), and TH-3DCRT (0.63) plans, compared to the 2F-3DCRT plan (0.32). PTV HI was slightly better for TH-3DCRT and TH-IMRT (1.05) compared to 2F-3DCRT (1.06) and 3F-IMRT (1.09). TH-3DCRT, 3F-IMRT, and TH-IMRT showed an excellent carotid sparing capability compared to 2F-3DCRT (p < 0.05). For all plans, the maximum dose to the spinal cord was < 45 Gy. The median treatment planning times for 2F-3DCRT (5.85 minutes) and TH-3DCRT (7.10 minutes) were much lower than those for 3F-IMRT (45.48 minutes) and TH-IMRT (35.30 minutes). The delivery times for 2F-3DCRT (2.06 minutes) and 3F-IMRT (2.48 minutes) were slightly lower than those for TH-IMRT (2.90 minutes) and TH-3DCRT (2.86 minutes). CONCLUSION: TH-3DCRT showed excellent carotid-sparing capability, while offering high efficiency and maintaining good PTV coverage.

Carotid sparing intensity-modulated radiation therapy achieves comparable locoregional control to conventional radiotherapy in T1-2N0 laryngeal carcinoma.

BACKGROUND: Although intensity-modulated radiotherapy (IMRT) is a standard of care for many head and neck cancers, its use for carotid-sparing (CS) therapy in early-stage laryngeal carcinoma is controversial. METHODS: 330 consecutive patients with early-stage laryngeal carcinoma were treated from 1/1989 to 5/2011, including 282 conventional radiotherapy (CRT) and 48 CS-IMRT patients. The median follow-up was 43 (CS-IMRT) and 66 (CRT) months. RESULTS: There was no difference in local failure rates comparing patients undergoing CS-IMRT with CRT, with 3-year local control rates of 88% vs. 89%, respectively (p=0.938). Using a 1cm circumferential margin, the average dose to the left and right carotid arteries was 48.3 and 47.9 Gy, respectively. 88% of locoregional recurrences involved the ipsilateral true vocal cord, including all local recurrences in the IMRT group. CONCLUSIONS: These results warrant further prospective evaluation of CS-IMRT for early-stage glottic larynx cancer.