An investigation of intensity-modulated radiation therapy versus conventional two-dimensional and 3D-conformal radiation therapy for early stage larynx cancer

Dosimetric comparison between carotid-sparing IMRT and 3DCRT in early glottic cancer patients treated with definitive radiation therapy

BACKGROUND

The purpose of this study was to evaluate the dosimetric benefits of carotid-sparing IMRT (intensity-modulated radiation therapy) over 3DCRT (three-dimensional conformal radiation therapy) in early glottic cancer patients.

MATERIAL AND METHODS

Ten patients with histologically proven early-stage squamous cell cancer of glottis (T1N0), treated with definitive radiotherapy, were selected retrospectively for the dosimetric analysis. Patients were originally treated with 3DCRT technique. For comparison purpose, IMRT plans were generated for each patient. Dosimetric comparison was done between two techniques (IMRT and 3DCRT) in terms of PTV (planning target volume) coverage, HI (homogeneity index), CI (conformity index), and doses to right carotid artery, left carotid artery, and spinal cord.

RESULTS

V95% for the PTV was higher in IMRT plans (98.26%) as compared to 3DCRT plans (95.12%) (P-value <0.001), whereas V105% for PTV was significantly higher in 3DCRT plans (16.77%) as compared to IMRT plans (0.32%) (P-value 0.11). In terms of both HI and CI, IMRT plans showed better conformity as compared to 3DCRT plans, with statistically significant difference. Both right and left carotid arteries' average mean and maximum doses were significantly lower in IMRT plans as compared to 3DCRT plans (P-value <0.001). IMRT plans resulted in significant carotid-sparing as compared to 3DCRT plans in terms of V35 and V50 (P-value <0.001).

CONCLUSION

Carotid-sparing IMRT resulted in better PTV coverage and lower carotid artery dose as compared to 3DCRT in early glottic cancer patients.

Comparison of Survival Outcomes of Different Treatment Options for cT1-2, N0 Glottic Carcinoma: A Propensity Score–Weighted Analysis

Background

Treatments for cT1-2, N0 glottic squamous cell carcinoma (GLSCC) include endoscopic resection, open surgery, and radiotherapy. The purpose of this study was to compare the outcomes of three treatment modalities and provide reference data for treatment selection.

Methods

In all, 4274 patients with cT1-2, N0 GLSCC underwent these three treatment modalities from 2004 to 2015 were identified from the Surveillance, Epidemiology, and End Results-18 database. Overall survival (OS) and disease-specific survival (DSS) of patients treated with the three modalities were compared.

Results

In the entire cohort, there were no significant differences in 5-year OS and 5-year DSS among the three treatment groups. In subgroup analyses based on stage and age, endoscopic resection provided significantly better 5-year survival than radiotherapy for cT1, N0 patients aged &lt;65 years, with an OS rate of 89.0% vs. 82.3% (p = 0.009) and a DSS rate of 95.6% vs. 88.2% (p = 0.021). For 5-year DSS, open surgery also had better outcomes than patients who received radiotherapy (5-year DSS: 98.5% vs. 88.2%, respectively; p = 0.046).

Conclusions

To summarize, for cT1, N0 GLSCC patients younger than 65 years, surgical treatment (either endoscopic or open) appears to be superior to the radiotherapy, and endoscopic resection should probably be the first consideration.

Early-Stage Glottic Squamous Cell Carcinoma in the Era of Image-Guided Radiotherapy

Early-stage squamous cell cancer (SCC) of the glottis has a good prognosis. Therefore, patients have long survival outcomes and may potentially suffer from late toxicities of radiotherapy. Radiotherapy with a conventional parallel-opposed-pair or anterior-oblique beam arrangements for stage 1 and 2 glottic SCC have field borders that traditionally cover the entire larynx, exposing organs-at-risk (e.g. carotid arteries, contralateral vocal cord, contralateral arytenoid and inferior pharyngeal constrictor muscles) to high radiation doses. The potential long-term risk of cerebrovascular events has attracted much attention to the dose that carotid arteries receive. Swallow and respiratory motion of laryngeal structures has been an important factor that previously limited reduction of the radiation treatment volume. Motion has been evaluated using multiple imaging modalities and this information has been used to calculate PTV margins for generation of more limited target volumes. This review discusses the current literature surrounding dose-effect relationships for various organs-at-risk and the late toxicities that are associated with them. This article also reviews the currently available data and effects of laryngeal motions on dosimetry to the primary target. We also review the current limitations and benefits of a more targeted approach of radiotherapy for early-stage glottic SCCs and the evolution of CT-based IGRT and MR-guided radiotherapy techniques that may facilitate a shift away from a conventional 3D-conformal radiotherapy approach.

Outcomes between intensity-modulated radiation therapy versus 3D-conformal in early stage glottic cancer

BACKGROUND

The purpose of this study is to evaluate practice patterns and outcomes between intensity-modulated radiation therapy (IMRT) and 3D-conformal radiation (3D-CRT) in early stage glottic cancer.

METHODS

The linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database was used to identify and compare patient and disease profiles, mortality, and toxicity in patients with T1-2 larynx cancer undergoing definitive radiation (RT).

RESULTS

A total of 1520 patients underwent definitive radiation with 3D-CRT (n = 1309) or IMRT (n = 211). Non-white race, those with a Charlson Comorbidity Index ≥2, T2 disease, and those treated at community practices were more likely to undergo IMRT. Rates of IMRT increased from 2006 to 2015, while relative rates of 3D-CRT decreased. Two-year CSS was superior with 3D-CRT (hazard ratio [HR], 0.38; 95% confidence interval [CI], 0.22-0.65; p < 0.001). There was no difference in OS between 3D-CRT and IMRT (p = 0.119).

CONCLUSIONS

Patients receiving 3D-CRT had improved CSS compared to IMRT with no difference in OS.

3D conformal, IMRT and VMAT for the treatment of head and neck cancer: a brief literature review

Aim:

The objective of this study has been to identify monitor unit (MU) and treatment time variations, volume coverage dissimilarity among 3D conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) treatment plans for head and neck cancer (HNC) based on literature review.

Methods:

A number of HNC cases were studied with the investigation of conformity and homogeneity index.

Results:

When high-dose modulation was required around small organs at risk (OARs), a clinically acceptable IMRT plan was achieved as VMAT usually required longer dose optimisation time. The greatest benefit of VMAT has been rapid treatment delivery allowing improved patient comfort, reduced intra-fraction motion and increased patient throughput. In some papers, 3D-CRT was shown not to meet well the requirements on parotid glands. One paper showed that cerebellum dose was lower for 3D-CRT than IMRT. However, it was found in other papers that OAR sparing with 3D-CRT was reasonable but in complex cases not enough.

Conclusions:

IMRT usually consists of several treatment fields with different directions, hundreds of beam lets with modulated intensity, an advantage over 3D-CRT, whereas VMAT has advantage over IMRT due to rotating beam utilisation. VMAT has lower total MU and treatment times than IMRT and 3D-CRT, while maintaining similar dosimetric endpoints.

Evaluating different radiotherapy treatment plans, in terms of critical organ scoring index, conformity index, tumor control probability, and normal tissue complication probability calculations in early glottic larynx carcinoma

Purpose

In this study, it is aimed to compare three different radiotherapy treatment planning techniques in terms of critical organ scoring index (COSI), two different conformity index (CI), tumor control probability (TCP), and normal tissue complication probability (NTCP) calculations in early (T1) glottic larynx carcinoma (T1GL). Furthermore, it is aimed to investigate these parameters compliance with dose-volume histograms (DVH) parameters.

Materials and Methods

Ten T1GL patients were immobilized in a supine position with a head and neck thermoplastic mask. Treatment plans were created with opposed lateral fields (OLAFs) and intensity-modulated radiation therapy (IMRT) techniques with a total dose of 66 Gy in 33 fraction with 2 Gy/day. IMRT fields were selected as five fields (5IMRT) and seven fields (7IMRT). Dosimetric evaluation of three different treatment plans for T1GL carcinoma was performed in two consequential steps. First step was the assessment of planning target volume (PTV), all organs at risks (OARs), and normal tissue (NT) dose calculations according to given dose constraint directions and comparing the plans via DVH. In the second step, for PTV, the compatibility of DVH data with CIs-TCP was investigated where COSI-NTCP was compared with DVH for OARs. The DVH data were considered as reference in all evaluations.

Results

The CI_RTOG mean values were significantly closer to 1 with IMRT plans when compared to OLAF plans (P = 0.005). The CI_PADDICK mean values revealed that OLAF plans were significantly worse than IMRT plans (P = 0.005). No statistically significant difference was found between all three plans in terms of homogeneity index mean values (P = 0.076). The calculated mean TCP values were significantly better for 7IMRT plans when compared to OLAF and 5IMRT plans (P = 0.007 and P = 0.017, respectively). Both NTCP and COSI evaluations, which is compatible with DVH, significantly favored OLAF plan for spinal cord and 7IMRT for thyroid gland. The COSI evaluations, which are compatible with DVH, significantly favored 7IMRT plan for carotid arteries and 5IMRT plan for NT.

Conclusion

Our results demonstrated that CI_PADDICK-TCP calculations for PTV and COSI-NTCP calculations for OARs were compatible with DVH in T1 GL plans. Therefore, we suggest such parameters as valuable tools for choosing the feasible one among multiple plans and even with different treatment machines.

Outcomes after radiation therapy for T2N0/stage II glottic squamous cell carcinoma

BACKGROUND

We report outcomes for patients with T2N0M0 glottic squamous cell carcinoma (SCC) treated with radiation therapy (RT).

METHODS

Patients who received definitive RT for T2 glottic SCC from 2000 through 2013 were retrospectively reviewed.

RESULTS

One hundred and thirteen patients were analyzed (median follow-up time 91 months; 85 patients received three-dimensional conformal radiotherapy [3D-CRT] and 28 received intensity-modulated radiation therapy [IMRT]). Fractionation was conventional (58%) or altered (42%); 20 patients (18%) received concurrent chemotherapy. Five-year local control was 83% for the 3D-CRT vs 81% for the IMRT group (P = .76). The ultimate locoregional control at 5 years was 100% for IMRT vs 91% for 3D-CRT (P = .1). The 5-year overall survival (OS) was 78% for 3D-CRT vs 81% for IMRT (P = .83). On multivariate analysis, younger age was the only independent predictor of improved OS (P = .0002).

CONCLUSIONS

Oncologic and survival outcomes were excellent for patients with T2N0 glottic cancer. Patients treated with IMRT and 3D-CRT had no statistically significant differences in all investigated endpoints.

Emerging Concepts and Novel Strategies in Radiation Therapy for Laryngeal Cancer Management

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).

Predictors of chemotherapy and its effects in early stage squamous cell carcinoma of the larynx

BACKGROUND

Squamous cell carcinoma (SCC) of larynx is a common head and neck cancer. For cases that are node negative, the role of definitive concurrent chemoradiation is unclear and not supported by guidelines but used at provider discretion. To address this knowledge gap, we examined the oncological outcomes with additional chemotherapy and factors correlated with the chemotherapy administration.

METHODS

We queried the National Cancer Database for patients with early stage (T2N0M0) laryngeal SCC treated nonsurgically. Multivariable logistic regression identified predictors of chemotherapy. Multivariable Cox regression evaluated predictors of survival. Propensity matching accounted for indication biases.

RESULTS

We identified 7181 patients meeting the eligibility criteria, of which 1568 (22%) patients received chemotherapy in addition to radiation. Predictors of chemotherapy use included younger age, Caucasian race, more remote year of treatment, higher grade, sites other than glottis, treatment at a community cancer center, and use of intensity-modulated radiation therapy. Median overall survival was not significantly different in the two arms analyzed-65 months (95% confidence interval [CI] 60, 72months) with chemotherapy compared to 70 months without chemotherapy (95% CI 66, 75 months, P<.37). Predictors for survival on propensity-matched multivariable analysis were increased age, male sex, less education, lower income, higher comorbidity score, receipt of treatment at a community center, and nonglottic sites.

CONCLUSIONS

This study shows no clear survival benefit with chemotherapy in early stage disease. Although this implies that chemotherapy should not be routinely delivered, individualized judgment and prospective studies are recommended as the biology behind this interesting finding is undefined.

LEVEL OF EVIDENCE

2C (Outcomes Research).

Preliminary Simulation Study of Carotid Artery and Pharyngeal Constrictor Muscle Sparing-Radiotherapy in Glottic Carcinoma

Background:

This preliminary simulation study aimed to compare the dosimetric outcomes of carotid arteries (CAs) and pharyngeal constrictor muscle (PCM) in patients with T1N0M0 glottic carcinoma undergoing helical tomotherapy-intensity modulated radiotherapy (HT-IMRT) and 3-dimensional conformal radiotherapy (3D-CRT) plans.

Methods:

In addition to the clinical target volume (CTV) which was defined as the entire larynx, the CAs and PCM of 11 glottic carcinoma patients were delineated. The CTV was uniformly expanded 5 mm to create a planning target volume (PTV) relative to the PCM and at a distance of 2 mm from the CA. The dosimetric characteristics in HT-IMRT and lateral opposed fields-based 3D-CRT plans were analyzed.

Results:

Median D_95%and V_100% of PTV were significantly higher in HT-IMRT (p < 0.001) compared to 3D-CRT. The right/left CA dosimetric outcomes, including the mean doses (20.7/21.5 Gy versus 48.7/50.5 Gy), D_max (53.6/52.0 Gy versus 67.4/67.7 Gy), V₃₀ (25.0/27.1% versus 77.6/80.3%), V₄₀ (8.0/7.9% versus 74.6/71.9%), and V₅₀ (2.0/1.2% versus 70.0/71.6%) were also significantly lower in HT-IMRT (p < 0.05), similar to the mean PCM doses (49.6 Gy versus 62.6 Gy for 3D-CRT;p < 0.001), respectively.

Conclusions:

Our present results demonstrated the feasibility of simultaneous sparing of the CAs and PCM in HT-IMRT- compared to 3D-CRT plans in glottic carcinoma patients undergoing definitive radiotherapy.

Outcomes of carotid-sparing IMRT for T1 glottic cancer: Comparison with conventional radiation

OBJECTIVES

We aim to report oncologic outcomes after conventional radiotherapy (ConRT) using opposed lateral beams and intensity-modulated radiation therapy (IMRT) for tumor (T)1 nodal (N)0 T1 N0 glottic squamous cell carcinoma.

STUDY DESIGN

Retrospective case-control study.

METHODS

We retrospectively reviewed demographic, disease, and treatment characteristics for patients treated at our institution during 2000 to 2013.

RESULTS

One hundred fifty-three patients (71%) were treated using ConRT and 62 (29%) using IMRT. The median follow-up for all patients was 68 months. There was no statistically significant difference in 5-year local control between patients with T1a versus T1b disease (94% vs. 89%, respectively, P = 0.5). Three-year locoregional control for patients treated with ConRT was 94% compared to 97% with IMRT (P = 0.4). Three-year overall survival (OS) for patients treated with ConRT was 92.5% compared with 100% with IMRT (P = 0.1). Twelve of 14 patients with local recurrence underwent salvage surgery with 5-year ultimate locoregional control of 98.5% and 97.1% in the ConRT and IMRT cohorts, respectively (P = 0.7). Multivariate analysis showed age < 60 years (P < 0.0001) and pretreatment Eastern Cooperative Oncology Group performance status <2 (P = 0.0022) to be independent correlates of improved OS. Postradiation cerebrovascular events were in four patients in the ConRT cohort (3%), whereas no patients in the IMRT cohort suffered any events.

CONCLUSION

Because the oncologic outcomes for patients treated with IMRT were excellent and IMRT allows for carotid sparing, we have transitioned to IMRT as our standard for most patients with T1 glottic cancer.

LEVEL OF EVIDENCE

3b Laryngoscope, 130:146-153, 2020.

Patterns of Care and Outcomes of Intensity-Modulated Radiotherapy and 3D Conformal Radiotherapy for Early Stage Glottic Cancer: A National Cancer Database Analysis

Early stage glottic cancer has traditionally been treated with 3D conformal radiotherapy (3DCRT). However, intensity-modulated radiotherapy (IMRT) has been recently adopted as an alternative to decrease toxicity. Here, we compared the usage and outcomes of IMRT and 3DCRT for patients with early stage squamous cell carcinoma (SCC) of the glottic larynx. Using the National Cancer Database, we identified patients with Stage I–II SCC of the glottis who received 55–75 Gy using IMRT (n = 1623) or 3DCRT (n = 2696). Median follow up was 42 months with a 5-year overall survival (OS) of 72%. Using a nominal logistic regression, race, ethnicity, year of diagnosis and fraction size were associated with the receipt of IMRT (p < 0.05). Using Kaplan–Meier methods and Cox proportional hazards models as well as a propensity matched cohort, there was no difference in OS for patients who received IMRT versus 3DCRT (hazard ratio (HR), 1.08; 95% confidence interval (95% CI), 0.93–1.26; p = 0.302). However, there was a survival benefit for patients receiving slight hypofractionation as compared to conventional fractionation (HR, 0.78; 95% CI, 0.69–0.92; p = 0.003). IMRT was associated with similar survival as 3DCRT, supporting the implementation of this potentially less toxic modality without compromising survival.

Outcome of Early-Stage Glottic Laryngeal Carcinoma Patients Treated with Radical Radiotherapy Using Different Techniques

Purpose

The aim was to evaluate the treatment outcomes and prognostic characteristics of patients with early-stage glottic laryngeal carcinoma who underwent radical radiotherapy (RT) with different techniques.

Patients and Methods

Radiotherapy was applied using the 2D conventional technique between 1991 and 2004 (130 patients), 3DCRT until 2014 (125 patients), and by VMAT until January 2017 (44 patients). Clinical T stages were 38 (12.7%) for Tis, 209 (69.9%) for T1, and 52 (17.4%) for T2. Radiotherapy technique and energy, anterior commissure involvement, and stage were analyzed as prognostic factors.

Results

The median total dose was 66 (50–70) Gy, and median follow-up time was 72 (3–288) months; 5-year disease-specific survival (DSS) rates were 95.8%, 95.5%, and 88.6%, respectively, in Tis, T1, and T2 stages. In multivariate analyses, anterior commissure involvement was found significant for all survival and local control rates. The patients treated with VMAT technique had better local control and DSS rates. However, these results were not statistically significant.

Conclusion

In early-stage laryngeal carcinomas, radical RT is a function sparing and effective treatment modality, regardless of treatment techniques.

Study Protocol: Prospective Study of Concurrent Chemoradiotherapy with S-1 and Hypofractionated Radiotherapy for Outpatients with Early Glottic Squamous Cell Carcinomas

Background:

The recommended treatment strategies for early glottic carcinoma with intent of larynx preservation are primarily radiotherapy. However, the outcomes of radiotherapy for bulky T1 or T2 glottic carcinoma are unsatisfactory. We designed a protocol consisting of concurrent chemoradiotherapy using S-1 as the radiosensitizer. We have performed this protocol in patients with favorable T2 lesions and demonstrated its efficacy and safety. In contrast, we have treated non-bulky T1 glottic carcinomas with 2.25 Gy per fraction, for a total of 25-28 fractions, starting in 2011 to improve efficacy and shorten the treatment period. Since this treatment strategy was implemented for T1 disease, no local failure has occurred to date, and it appears to be almost as safe as radiotherapy using 2.0 Gy per fraction. With the aim of improving the local control rate and shortening the treatment period primarily for favorable T2 disease, we changed the dose of radiation in our protocol from 2.0 Gy to 2.25 Gy per fraction, for a total of 25 fractions (from 30 fractions). The present study aims to evaluate the efficacy and safety of this new protocol.

Methods:

This study will be conducted as a clinical, prospective, single-armed, non-randomized trial. Patients are to receive S-1 (55.3 mg /m² /day, once daily) and radiotherapy (2.25 Gy per fraction, for a total of 25 fractions). S-1 and radiotherapy are started on the same day that radiotherapy is performed, 3-6 hours after oral administration of S-1. The primary study aim is the 3-year local control rate. The secondary study aims are overall survival, voice-preservation survival, disease-free survival, complete response rate, completion rate, and toxicity.

Result and conclusion:

This is the first single-center, non-randomized, prospective study of concurrent chemoradiotherapy with S-1 and hypofractionated radiotherapy to be conducted. The trial will evaluate the efficacy and safety of our protocol.

Comparison of three and four-field radiotherapy technique and the effect of laryngeal shield on vocal and spinal cord radiation dose in radiotherapy of non-laryngeal head and neck tumors

Introduction: Due to the effect of radiation on both the tumor and the surrounding normal tissues, the side effects of radiation in normal tissues are expected. One of the important complications in the head and neck radiotherapy is the doses reached to the larynx and spinal cord of patients with non-laryngeal head and neck tumors.

Materials and Methods: In this study, CT scan images of 25 patients with non-laryngeal tumors including; lymph nodes, tongue, oropharynx and nasopharynx were used. A three-field and a four-field treatment planning with and without laryngeal shield in 3D CRT technique were planned for each patient. Subsequently, the values of Dmin, Dmean, Dmax and Dose Volume Histogram from the treatment planning system and NTCP values of spinal cord and larynx were calculated with BIOPLAN and MATLAB software for all patients.

Results: Statistical results showed that mean values of doses of larynx in both three and four-field methods were significantly different between with and without shield groups. Comparison of absorbed dose didn’t show any difference between the three and four field methods (P>0.05). Using Shield, just the mean and minimum doses of spinal cord decreased in both three and four fields. The NTCP of the spinal cord and larynx by three and four-field methods with shield in the LKB and EUD models significantly are less than that of the three and four fields without shields, and in the four-field method NTCP of larynx is less than three radiation field.

Conclusion: The results of this study indicate that there is no significant difference in doses reached to larynx and spinal cord between the treatments techniques, but laryngeal shield reduce dose and NTCP values in larynx considerably.

Use of Volumetric Modulated arc Radiotherapy in Patients with Early Stage Glottic Cancer

Aims and background

We compared conformal, intensity-modulated radiotherapy (IMRT) and intensity-modulated arc therapy (IMAT) in early stage glottic cancer in terms of dosimetric features as target coverage, dose to the organs at risk and total treatment time.

Methods and materials

Five consecutive T1 glottic squamous cell carcinoma patients were selected for the study. Three-dimensional conformal radiotherapy (3D-CRT), 3-field or 5-field intensity-modulated radiotherapy (3F-IMRT and 5F-IMRT), or IMAT, which was in 2 different forms – a regular IMAT (R-IMAT) and an alternative IMAT (A-IMAT) with an unirradiated section, was planned for each patient. The prescribed dose was 63 Gy in 28 fractions. The minimum dose for 95% of the clinical target volume (D95), maximum dose point at clinical target volume (Dmax), total monitor units, left and right carotid artery doses (V35 and V50 – percentage of volume receiving 35 Gy and 50 Gy), and total treatment time were calculated for each plan.

Results

Median D95 values in the 5 plans studied with each technique ranged between 63 and 63.3 Gy (P = NS). Median Dmax values for each technique ranged between 65.4 and 70.8 Gy. The number of hot spots with IMRT and IMAT was significantly higher than with 3D-CRT plans. Conformal radiotherapy plans median V35 (93.6%) and V50 (76.6–83.3%) values for carotid arteries were significantly higher than with IMRT and IMAT (2.9%-11.4% and 0.0%). Average treatment times for 3D-CRT, 3F-IMRT, 5F-IMRT, R-IMAT and A-IMAT techniques were calculated as 64, 119, 147, 39 and 32 seconds, respectively.

Conclusions

IMAT has significantly decreased the treatment time compared to IMRT and 3D-CRT with acceptable homogeneous clinical target volume coverage and low carotid dose.

Dose de-escalation to the normal larynx using conformal radiotherapy reduces toxicity while maintaining oncologic outcome for T1/T2 glottic cancer

We evaluated the efficacy of dose de-escalation to the normal larynx using conformal radiotherapy (CRT) for T1/T2 glottic cancer. For conventional RT (2DRT, n = 38), the laryngeal box received a median equivalent dose in 2 Gy fractions (EQD2) of 66 Gy. For CRT (n = 42; 3D-CRT, 20; intensity-modulated RT, 22), clinical target volume (CTV)1 (gross tumor with a 3-mm margin) and CTV2 (laryngeal box) received median EQD2s of 66.6 Gy and 52.2 Gy, respectively. With a 71-month median follow-up, five-year local control and overall survival rates for 2DRT vs. CRT were 88.1% vs. 95.1% (p = 0.405) and 94.7% vs. 90.7% (p = 0.102), respectively. Grade 2 and 3 pharyngitis rates were 52.6% and 5.3% for 2DRT vs. 35.7% and 2.4% for CRT (p = 0.121). Grade 2 and 3 dermatitis rates were 42.1% and 2.6% for 2DRT vs. 35.7% and 0% for CRT (p = 0.013). The maximum phonation time increased from 12.1 ± 7.1 to 14.0 ± 6.6 seconds after 2DRT (p = 0.375) and from 12.0 ± 5.5 to 13.8 ± 10.1 seconds after CRT (p = 0.313). Fundamental frequency decreased from 150.6 ± 40.3 to 121.9 ± 30.2 Hz after 2DRT (p = 0.039) and from 138.5 ± 31.9 to 126.1 ± 23.7 Hz after CRT (p = 0.058). CRT can effectively de-escalate the normal larynx dose while maintaining oncologic outcome and voice quality.

Supracricoid partial laryngectomy with crico-hyoido-epiglottopexy for glottic carcinoma with anterior commissure involvement

Glottic cancers discovered at an early stage (T1-T2) can be treated with either radiotherapy or surgery. The aim of our study is to analyse survival and functional results of supra-cricoid partial laryngectomy (SCPL) with crico-hyoido-epiglottopexy (CHEP) as surgical treatment for glottic carcinoma with anterior commissure involvement. We performed a retrospective study (1996-2013) which included patients who underwent SCPL-CHEP for glottic squamous cell carcinoma with involvement of the anterior commissure. Before surgery, all patients underwent staging including head, neck and chest CT-scan with contrast injection as well as suspension laryngoscopy under general anaesthesia. A total of 53 patients were included. The median follow-up period was 124 months. Tumour resection was complete in 96.2% of cases. The overall, specific and recurrence-free survival rates at 5 years were, respectively, 93.7%, 95.6% and 87.7%. The average period of hospitalisation was 18 days. The average time elapsed before decannulation and before restoration of oral feeding were 15 and 18 days, respectively. SCPL-CHEP is an important option for laryngeal surgical preservation. It allows adequate disease control as well as good functional results as long as the indications are well respected and the surgical techniques are mastered.

Phantom-to-clinic development of hypofractionated stereotactic body radiotherapy for early-stage glottic laryngeal cancer

The purpose of this study was to commission and clinically test a robotic stereotactic delivery system (CyberKnife, Sunnyvale, CA) to treat early-stage glottic laryngeal cancer. We enrolled 15 patients with cTis-T2N0M0 carcinoma of the glottic larynx onto an institutional review board (IRB)-approved clinical trial. Stereotactic body radiotherapy (SBRT) plans prescribed 45 Gy/10 fractions to the involved hemilarynx. SBRT dosimetry was compared with (1) standard carotid-sparing laryngeal intensity-modulated radiation therapy (IMRT) and (2) selective hemilaryngeal IMRT. Our results demonstrate that SBRT plans improved sparing of the contralateral arytenoid (mean 20.0 Gy reduction, p <0.001), ipsilateral carotid D_max (mean 20.6 Gy reduction, p <0.001), contralateral carotid D_max (mean 28.1 Gy reduction, p <0.001), and thyroid D_mean (mean 15.0 Gy reduction, p <0.001) relative to carotid-sparing IMRT. SBRT also modestly improved dose sparing to the contralateral arytenoid (mean 4.8 Gy reduction, p = 0.13) and spinal cord D_max (mean 4.9 Gy reduction, p = 0.015) relative to selective hemilaryngeal IMRT plans. This "phantom-to-clinic" feasibility study confirmed that hypofractionated SBRT treatment for early-stage laryngeal cancer can potentially spare dose to adjacent normal tissues relative to current IMRT standards. Clinical efficacy and toxicity correlates continue to be collected through an ongoing prospective trial.

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.

Volumetric modulated arc therapy for carotid sparing in the management of early glottic cancer

Purpose

Radiotherapy of the neck is known to cause carotid artery stenosis. We compared the carotid artery dose received between volumetric modulated arc therapy (VMAT) and conventional fixed-field intensity-modulated radiotherapy (IMRT) plans in patients with early glottic cancer.

Materials and Methods

Twenty-one early glottic cancer patients who previously underwent definitive radiotherapy were selected for this study. For each patient, double arc VMAT, 8-field IMRT, 3-dimensional conformal radiotherapy (3DCRT), and lateral parallel-opposed photon field radiotherapy (LPRT) plans were created. The 3DCRT plan was generated using lateral parallel-opposed photon fields plus an anterior photon field. VMAT and IMRT treatment plan optimization was performed under standardized conditions to obtain adequate target volume coverage and spare the carotid artery. Dose-volume specifications for the VMAT, IMRT, 3DCRT, and LPRT plans were calculated with radiotherapy planning system. Monitor units (MUs) and delivery time were measured to evaluate treatment efficiency.

Results

Target volume coverage and homogeneity results were comparable between VMAT and IMRT; however, VMAT was superior to IMRT for carotid artery dose sparing. The mean dose to the carotid arteries in double arc VMAT was reduced by 6.8% compared to fixed-field IMRT (p < 0.001). The MUs for VMAT and IMRT were not significantly different (p = 0.089). VMAT allowed an approximately two-fold reduction in treatment delivery time in comparison to IMRT (3 to 5 minutes vs. 5 to 10 minutes).

Conclusion

VMAT resulted in a lower carotid artery dose compared to conventional fixed-field IMRT, and maintained good target coverage in patients with early glottic cancer.

Volumetric modulated arc radiotherapy of the whole larynx, followed by a single affected vocal cord, for T1a glottic cancer: Dosimetric analysis of a case

Radiation therapy (RT) and endolaryngeal surgery are standard treatments for early-stage glottic cancer. They have closely matched oncological outcomes; however, it is debatable which method is superior in terms of functional outcomes. Several dosimetric studies have demonstrated that, compared with conventional RT, intensity-modulated RT (IMRT) reduces unnecessary radiation of the adjacent normal tissues, including the carotid artery and thyroid gland. However, RT targets the whole larynx, whereas endolaryngeal surgery is a highly focused treatment involving the en bloc resection of a tumor with safety margins. For T1a glottic cancer, in which the tumor is limited to one vocal cord, the technical feasibility of targeting IMRT on the single vocal cord affected has been investigated; however, the clinical feasibility and the possibility of inferior local control remain to be elucidated. In the present case study, IMRT was used to treat the whole larynx first, and then to treat a single vocal cord. The patient in the present study had T1a glottic cancer, and received volumetric modulated arc therapy with a total dose of 63 Gy/28 fractions. The first treatment phase (40.5 Gy/18 fractions) targeted the whole larynx to eliminate subclinical disease. The second treatment phase (22.5 Gy/10 fractions) targeted only the involved vocal cord. During this treatment phase, the exposure of the non-involved right vocal cord, the right carotid artery and the thyroid gland to the radiation was lower compared with the continuation of the initial treatment approach. These findings suggested that changing the target volume from the whole larynx to the affected vocal cord during the course of IMRT is feasible for T1a glottic cancer, and that it may reduce functional side effects while maintaining oncological outcomes.

Simulation study of high-dose-rate brachytherapy for early glottic cancer

PURPOSE

External beam radiation therapy (EBRT) is effective for early glottic cancers, with cure rates of ∼90% for T1 tumors. EBRT has strengths but also disadvantages including radiation to healthy tissues and duration of 5-7 weeks. With advances in laryngeal framework surgery, new devices can provide reliable, minimally invasive access to the larynx. Such devices could be modified to insert brachytherapy catheters. Brachytherapy could provide focused radiation while limiting dose to normal structures in the larynx and neck. As a preliminary step, we performed simulations comparing EBRT to high-dose-rate brachytherapy to assess if this approach could provide dosimetric advantage.

METHODS AND MATERIALS

One- and 2-catheter brachytherapy simulations were performed for 3 patients with T1 glottic carcinoma. Percentage of dose delivered to the target and adjacent structures was compared with conventional EBRT using 3D and intensity-modulated radiation therapy approaches.

RESULTS

Percentage of structures exposed to 50% of the dose was lower for brachytherapy compared with 3D EBRT and intensity-modulated radiation therapy, particularly for the cricoid and contralateral arytenoid. Dose was also lower for the carotid-internal jugular vein complexes compared with 3D EBRT. Dose profiles did not differ significantly between 1- and 2-catheter simulations.

CONCLUSION

Brachytherapy can decrease radiation to normal tissues including laryngeal cartilages and carotid-internal jugular vein complexes. Recent advancements allowing catheter placement may afford the potential to decrease radiation to healthy tissues with decreased treatment time. However, careful, stepwise evaluation of feasibility and outcomes in model systems is required before recommending this approach for such high cure rate cancers in humans.

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 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.

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.

Consequences of tumor planning target volume reduction in treatment of T2-T4 laryngeal cancer

Background and purpose

Since lymph nodes volumes are generally four times the volume of the primary PTV, the advantage of using tight margins around the primary PTV is not clear. Therefore treatment margins of T2-T4 laryngeal carcinoma for IMRT are generally chosen in such a way that the PTV is comparable to that in conventional radiotherapy. The aim of this study is to quantify the effect of volume reduction of the primary PTV of T2-T4 laryngeal carcinoma with regard to late toxicity despite elective irradiation of lymph node levels II to IV.

Methods

Two treatment plans based on conservative (GTV-PTV = 15 mm and 20 mm cranial), and on evidence-based tight margins (GTV-PTV = 8 mm) were calculated for 16 patients. Toxicity effects were estimated based on the dose distributions.

Results

Compared to conservative margins, using tight margins resulted in: 1) significant reduction of the normal tissue complication probability (NTCP) for swallowing muscles and submandibular glands, 2) significant reduction of the mean dose in all organs at risk (OAR), 3) a mean dose smaller than 60 Gy for all OARs except for the laryngeal cartilages. When the lymph node levels II to IV were prescribed with an elective dose, an NTCP reduction of 53% for the swallowing muscles and of 23% for the submandibular glands was found by using tight instead of conservative margins. When positive nodes were present, NTCP reduction amounted to 29% and 15%, respectively.

Conclusions

There is a potential benefit in realizing evidence-based tight margins for laryngeal cancer patients despite elective irradiation of lymph node levels II to IV.

Dosimetric and radiobiologic comparison of 3D conformal, IMRT, VMAT and proton therapy for the treatment of early-stage glottic cancer

BACKGROUND

This study aims to compare dosimetrically and radiobiologically 3D conformal, intensity modulated radiation therapy (IMRT), RapidArc (RA) volumetric modulated arc therapy and proton therapy techniques for early-stage glottic cancer.

METHODS

Ten patients were retrospectively selected. Photon treatment planning was performed using Eclipse External Beam Planning, and proton planning was performed using CMS Xio. The minimum, mean and maximum dose values for planning target volume (PTV), mean and maximum dose values for organ at risk, % of volume of PTV receiving at least 95% of the prescription dose, and D20, D50 and D90 of carotid arteries were compared. Biological response models of tumour control probabilities and normal tissue complication probabilities were calculated.

RESULTS

IMRT, RA and proton plans versus three-dimensional conformal radiotherapy (3D-CRT) plans consistently provided superior PTV coverage and decreased mean dose to the thyroid and carotid arteries.

CONCLUSION

All these three modalities showed superiority with less variation among themselves compared with 3D-CRT plans. Clinical investigation is warranted to determine if these treatment approaches will translate into a reduction in radiation therapy-induced toxicities.

A nomogram to predict loco-regional control after re-irradiation for head and neck cancer

BACKGROUND AND PURPOSE

Loco-regionally recurrent head and neck cancer (HNC) in the setting of prior radiotherapy carries significant morbidity and mortality. The role of re-irradiation (re-RT) remains unclear due to toxicity. We determined prognostic factors for loco-regional control (LRC) and formulated a nomogram to help clinicians select re-RT candidates.

MATERIAL AND METHODS

From July 1996 to April 2011, 257 patients with recurrent HNC underwent fractionated re-RT. Median prior dose was 65 Gy and median time between RT was 32.4 months. One hundred fifteen patients (44%) had salvage surgery and 172 (67%) received concurrent chemotherapy. Median re-RT dose was 59.4 Gy and 201 (78%) patients received IMRT. Multivariate Cox proportional hazards were used to identify independent predictors of LRC and a nomogram for 2-year LRC was constructed.

RESULTS

Median follow-up was 32.6 months. Two-year LRC and overall survival (OS) were 47% and 43%, respectively. Recurrent stage (P=0.005), non-oral cavity subsite (P<0.001), absent organ dysfunction (P<0.001), salvage surgery (P<0.001), and dose >50 Gy (P=0.006) were independently associated with improved LRC. We generated a nomogram with concordance index of 0.68.

CONCLUSION

Re-RT can be curative, and our nomogram can help determine a priori which patients may benefit.

Volumetric modulated arc radiotherapy sparing the thyroid gland for early-stage glottic cancer: A dosimetrical analysis

Previous studies on advanced radiotherapy (RT) techniques for early stage glottic cancer have focused on sparing the carotid artery. However, the aim of the present study was to evaluate the dosimetric advantages of volumetric modulated arc therapy (VMAT) in terms of sparing the thyroid gland in early-stage glottic cancer patients. In total, 15 cT1N0M0 glottic cancer patients treated with definitive RT using VMAT were selected, and for dosimetric comparison, a conventional RT plan comprising opposed-lateral wedged fields was generated for each patient. The carotid artery, thyroid gland and spinal cord were considered organs at risk. The prescription dose was 63 Gy at 2.25 Gy per fraction. For the thyroid gland and carotid artery, all compared parameters were significantly lower with VMAT compared with conventional RT. For the thyroid gland, the median reduction rates of the mean dose (D_mean), the volume receiving ≥30% of the prescription dose (V₃₀) and the V₅₀ were 32.6, 40.9 and 46.0%, respectively. The D_mean was 14.7±2.6 Gy when using VMAT compared with 22.2±3.9 Gy when using conventional RT. The differences between the techniques in terms of planning target volume coverage and dose homogeneity were not significant. When considering a recent normal tissue complication probability model, which indicated the mean thyroid gland dose as the most significant predictor of radiation-induced hypothyroidism, the dosimetric advantage shown in this study may be valuable in reducing hypothyroidism following RT for early stage glottic cancer patients.

Risk of fatal cerebrovascular accidents after external beam radiation therapy for early-stage glottic laryngeal cancer

BACKGROUND

This study compared the risk of fatal cerebrovascular accidents (CVAs) in patients with early-stage glottic laryngeal cancer receiving surgery or external beam radiation therapy (EBRT).

METHODS

Using a competing risks survival analysis, we compared the risk of death because of CVA among patients with early-stage glottic laryngeal cancer receiving surgery or EBRT in the Surveillance, Epidemiology, and End Results (SEER) database.

RESULTS

The cumulative incidence of fatal CVA at 15 years was higher in patients receiving EBRT (2.8%; 95% confidence interval [CI], 2.3% to 3.4%) compared to surgery (1.5%; 95% CI, 0.8% to 2.3%; p = .024). In multivariable competing risks regression models, EBRT remained associated with an increased risk of fatal CVA compared to surgery (adjusted hazard ratio [HR], 1.75; 95% CI, 1.04-2.96; p = .037).

CONCLUSION

Treatment for early-stage glottic laryngeal cancer with EBRT was associated with a small increase in the risk of late fatal CVA events relative to surgery.

Estimation of daily interfractional larynx residual setup error after isocentric alignment for head and neck radiotherapy: quality assurance implications for target volume and organs-at-risk margination using daily CT on- rails imaging

Larynx may alternatively serve as a target or organs at risk (OAR) in head and neck cancer (HNC) image-guided radiotherapy (IGRT). The objective of this study was to estimate IGRT parameters required for larynx positional error independent of isocentric alignment and suggest population-based compensatory margins. Ten HNC patients receiving radiotherapy (RT) with daily CT on-rails imaging were assessed. Seven landmark points were placed on each daily scan. Taking the most superior-anterior point of the C5 vertebra as a reference isocenter for each scan, residual displacement vectors to the other six points were calculated postisocentric alignment. Subsequently, using the first scan as a reference, the magnitude of vector differences for all six points for all scans over the course of treatment was calculated. Residual systematic and random error and the necessary compensatory CTV-to-PTV and OAR-to-PRV margins were calculated, using both observational cohort data and a bootstrap-resampled population estimator. The grand mean displacements for all anatomical points was 5.07 mm, with mean systematic error of 1.1 mm and mean random setup error of 2.63 mm, while bootstrapped POIs grand mean displacement was 5.09 mm, with mean systematic error of 1.23 mm and mean random setup error of 2.61 mm. Required margin for CTV-PTV expansion was 4.6 mm for all cohort points, while the bootstrap estimator of the equivalent margin was 4.9 mm. The calculated OAR-to-PRV expansion for the observed residual setup error was 2.7 mm and bootstrap estimated expansion of 2.9 mm. We conclude that the interfractional larynx setup error is a significant source of RT setup/delivery error in HNC, both when the larynx is considered as a CTV or OAR. We estimate the need for a uniform expansion of 5 mm to compensate for setup error if the larynx is a target, or 3 mm if the larynx is an OAR, when using a nonlaryngeal bony isocenter.

Risk of cerebrovascular events in elderly patients after radiation therapy versus surgery for early-stage glottic cancer

PURPOSE

Comprehensive neck radiation therapy (RT) has been shown to increase cerebrovascular disease (CVD) risk in advanced-stage head-and-neck cancer. We assessed whether more limited neck RT used for early-stage (T1-T2 N0) glottic cancer is associated with increased CVD risk, using the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database.

METHODS AND MATERIALS

We identified patients ≥66 years of age with early-stage glottic laryngeal cancer from SEER diagnosed from 1992 to 2007. Patients treated with combined surgery and RT were excluded. Medicare CPT codes for carotid interventions, Medicare ICD-9 codes for cerebrovascular events, and SEER data for stroke as the cause of death were collected. Similarly, Medicare CPT and ICD-9 codes for peripheral vascular disease (PVD) were assessed to serve as an internal control between treatment groups.

RESULTS

A total of 1413 assessable patients (RT, n=1055; surgery, n=358) were analyzed. The actuarial 10-year risk of CVD was 56.5% (95% confidence interval 51.5%-61.5%) for the RT cohort versus 48.7% (41.1%-56.3%) in the surgery cohort (P=.27). The actuarial 10-year risk of PVD did not differ between the RT (52.7% [48.1%-57.3%]) and surgery cohorts (52.6% [45.2%-60.0%]) (P=.89). Univariate analysis showed an increased association of CVD with more recent diagnosis (P=.001) and increasing age (P=.001). On multivariate Cox analysis, increasing age (P<.001) and recent diagnosis (P=.002) remained significantly associated with a higher CVD risk, whereas the association of RT and CVD remained not statistically significant (HR=1.11 [0.91-1.37,] P=.31).

CONCLUSIONS

Elderly patients with early-stage laryngeal cancer have a high burden of cerebrovascular events after surgical management or RT. RT and surgery are associated with comparable risk for subsequent CVD development after treatment in elderly patients.

Comparative dosimetry of volumetric modulated arc therapy and limited-angle static intensity-modulated radiation therapy for early-stage larynx cancer

To compare relative carotid and normal tissue sparing using volumetric-modulated arc therapy (VMAT) or intensity-modulated radiation therapy (IMRT) for early-stage larynx cancer. Seven treatment plans were retrospectively created on 2 commercial treatment planning systems for 11 consecutive patients with T1-2N0 larynx cancer. Conventional plans consisted of opposed-wedged fields. IMRT planning used an anterior 3-field beam arrangement. Two VMAT plans were created, a full 360° arc and an anterior 180° arc. Given planning target volume (PTV) coverage of 95% total volume at 95% of 6300 cGy and maximum spinal cord dose below 2500 cGy, mean carotid artery dose was pushed as low as possible for each plan. Deliverability was assessed by comparing measured and planned planar dose with the gamma (γ) index. Full-arc planning provided the most effective carotid sparing but yielded the highest mean normal tissue dose (where normal tissue was defined as all soft tissue minus PTV). Static IMRT produced next-best carotid sparing with lower normal tissue dose. The anterior half-arc produced the highest carotid artery dose, in some cases comparable with conventional opposed fields. On the whole, carotid sparing was inversely related to normal tissue dose sparing. Mean γ indexes were much less than 1, consistent with accurate delivery of planned treatment. Full-arc VMAT yields greater carotid sparing than half-arc VMAT. Limited-angle IMRT remains a reasonable alternative to full-arc VMAT, given its ability to mediate the competing demands of carotid and normal tissue dose constraints. The respective clinical significance of carotid and normal tissue sparing will require prospective evaluation.

Definitive radiotherapy for early stage glottic cancer by 6 MV photons

Purpose

To evaluate the clinical outcome of early glottic cancer (GC) treated by primary radiotherapy (RT) with 6 MV photons.

Methods and materials

We retrospectively reviewed the medical records of 695 consecutive patients with T1N0 and T2N0 GC treated between 1983 and 2005 by RT in our institution. Clinical outcome in terms of local control (LC), overall survival (OS) and cause- specific survival (CSS) rate were evaluated.

Results

The median follow-up time was 10.5 years. The 10-year actuarial LC rates were as follows: T1A, 91%; T1B, 87%; T2, 77%. The 10-year OS were as follows: T1, 74.2%; T2, 70.7%. The 10-year CSS were as follows: T1, 97.7%; T2, 97.1%.

Poorly differentiated histology and tumor biologically effective dose < 65 Gy₁₅ were adverse factors in both LC of T1 and T2 disease. Involvement of anterior commissure was an adverse factor in both LC and CSS of T1 disease. Subglottic extension was associated with poor LC in T2 disease whereas hemoglobin <13.0 was associated with poor LC and CSS of T2 disease.

Conclusion

Primary RT remains an option among the various standard treatments for early GC. Clinical treatment outcome by 6MV photons is similar and comparable to historic data of Cobalt-60 and 2 MV photons.

Comparison of external beam treatment techniques for T1-2, N0, M0 glottic cancers

The purpose of this study was to compare 4 different external beam radiation therapy treatment techniques for the treatment of T1-2, N0, M0 glottic cancers: traditional lateral beams with wedges (3D), 5-field intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and proton therapy. Treatment plans in each technique were created for 10 patients using consistent planning parameters. The photon treatment plans were optimized using Philips Pinnacle(3) v.9 and the IMRT and VMAT plans used the Direct Machine Parameter Optimization algorithm. The proton treatment plans were optimized using Varian Eclipse Proton v.8.9. The prescription used for each plan was 63 Gy in 28 fractions. The contours for spinal cord, right carotid artery, left carotid artery, and normal tissue were created with respect to the patient's bony anatomy so that proper comparisons of doses could be made with respect to volume. An example of the different isodose distributions will be shown. The data collection for comparison purposes includes: clinical treatment volume coverage, dose to spinal cord, dose to carotid arteries, and dose to normal tissue. Data comparisons will be displayed graphically showing the maximum, mean, median, and ranges of doses.

Increased risk of ischemic stroke in young nasopharyngeal carcinoma patients

PURPOSE

Radiation/chemoradiotherapy-induced carotid stenosis and cerebrovascular events in patients with nasopharyngeal carcinoma (NPC) can cause severe disability and even death. This study aimed to estimate the risk of ischemic stroke in this patient population over more than 10 years of follow-up.

METHODS AND MATERIALS

The study cohorts consisted of all patients hospitalized with a principal diagnosis of NPC (n=1094), whereas patients hospitalized for an appendectomy during 1997 and 1998 (n=4376) acted as the control group and surrogate for the general population. Cox proportional hazard model was performed as a means of comparing the stroke-free survival rate between the two cohorts after adjusting for possible confounding and risk factors.

RESULTS

Of the 292 patients with ischemic strokes, 62 (5.7%) were from the NPC cohort and 230 (5.3%) were from the control group. NPC patients ages 35-54 had a 1.66 times (95% CI, 1.16-2.86; p=0.009) higher risk of ischemic stroke after adjusting for patient characteristics, comorbidities, geographic region, urbanization level of residence, and socioeconomic status. There was no statistical difference in ischemic stroke risk between the NPC patients and appendectomy patients ages 55-64 years (hazard ratio=0.87; 95% CI, 0.56-1.33; p=0.524) after adjusting for other factors.

CONCLUSIONS

Young NPC patients carry a higher risk for ischemic stroke than the general population. Besides regular examinations of carotid duplex, different irradiation strategies or using new technique of radiotherapy, such as intensity modulated radiation therapy or volumetric modulated arc therapy, should be considered in young NPC patients.