Split-field Intensity-modulated Radiation Therapy Research Articles

Defining the dose-volume criteria for laryngeal sparing in locally advanced oropharyngeal cancer utilizing split-field IMRT, whole-field IMRT and VMAT.

PurposeTo determine the optimal dose‐volume constraint for laryngeal sparing using three commonly employed intensity modulated radiation therapy (IMRT) approaches in patients with oropharyngeal cancer treated to the bilateral neck.Materials and methodsThirty patients with stage II‐IVA oropharynx cancers received definitive radiotherapy with split‐field IMRT (SF‐IMRT) to the bilateral neck between 2008 and 2013. Each case was re‐planned using whole‐field IMRT (WF‐IMRT) and volumetric modulated arc therapy (VMAT) and plan quality metrics and dose to laryngeal structures was evaluated. Two larynx volumes were defined and compared on the current study: the Radiation Therapy Oncology Group (RTOG) larynx as defined per the RTOG 1016 protocol and the MDACC larynx defined as the components of the larynx bounded by the superior and inferior extent of the thyroid cartilage.ResultsTarget coverage, conformity, and heterogeneity indices were similar in all techniques. The RTOG larynx mean dose was lower with WF‐IMRT than SF‐IMRT (22.1 vs 25.8 Gy; P < 0.01). The MDACC larynx mean dose was 17.5 Gy ± 5.4 Gy with no differences between the 3 techniques. WF‐IMRT and VMAT plans were associated with lower mean doses to the supraglottic larynx (42.1 vs 41.2 vs 54.8 Gy; P < 0.01) and esophagus (18.1 vs 18.2 vs 36 Gy; P < 0.01).ConclusionsModern whole field techniques can provide effective laryngeal sparing in patients receiving radiotherapy to the bilateral neck for advanced oropharyngeal cancers.SummaryWe evaluated laryngeal dose in patients with locally advanced oropharyngeal cancer treated to the bilateral neck using split‐field IMRT (SF‐IMRT), whole‐field IMRT (WF‐IMRT) and volumetric arc therapy (VMAT). All three techniques provided good sparing of laryngeal structures and were able to achieve a mean larynx dose < 33 Gy. There were no significant differences in dose to target structures or non‐laryngeal organs at risk among techniques.

Daily Localization Impact on Decision of Split-Field or Whole-Field IMRT for Head and Neck Cancer Radiation Treatment

Daily Localization Impact on Decision of Split-Field or Whole-Field IMRT for Head and Neck Cancer Radiation Treatment

Sparing dysphagia/aspiration related structures using novel hybrid volumetric modulated arc therapy

PurposeStudies using split field IMRT to spare dysphagia/aspiration related structures (DARS) have raised concern regarding dose uncertainty at matchline. This study explores the utility of hybrid VMAT in sparing the DARS and assesses matchline dose uncertainty in postoperative oral cavity cancer patients and compares it with VMAT. Methods & materialsTen postoperative oral cavity cancer patients were planned with h-VMAT and VMAT using the same planning CT dataset. PTV and DARS were contoured using standard delineation guidelines. In h-VMAT 80% of the neck dose was planned using AP/PA technique and then VMAT optimization was done for the total PTV by keeping the corresponding AP/PA plan as the base dose. Planning goal for PTV was V95%≥95% and for DARS, adequate sparing. Plans and dose volume histograms were analyzed using dosimetric indices. Absolute point and portal dose measurements were done for h-VMAT plans to verify dose at the matchline. ResultsCoverage in both the techniques was comparable. Significant differences were observed in mean doses to DARS (Larynx: 24.36±2.51 versus 16.88±2.41Gy; p<0.0006, Pharyngeal constrictors: 25.16±2.41 versus 21.2±2.1Gy; p<0.005, Esophageal inlet: 18.71±2 versus 12.06±0.79Gy; p<0.0002) favoring h-VMAT. Total MU in both the techniques was comparable. Average percentage variations in point dose measurements in h-VMAT done at +3.5 and −3.5 positions were (1.47±1.48 and 2.28±1.35%) respectively. Average gamma agreement for portal dose measured was 97.07%. Conclusionh-VMAT achieves better sparing of DARS with no matchline dose uncertainty. Since these patients have swallowing dysfunction post-operatively, attempts should be made to spare these critical structures as much as possible.

Long-Term, Prospective Performance of the MD Anderson Dysphagia Inventory in “Low-Intermediate Risk” Oropharyngeal Carcinoma After Intensity Modulated Radiation Therapy

To characterize long-term MD Anderson Dysphagia Inventory (MDADI) results after primary intensity modulated radiation therapy (IMRT) for oropharyngeal carcinoma (OPC) among patients with "low-intermediate risk" OPC who would be eligible for current trials (eg, ECOG 3311, NRG HN002, CRUK PATHOS). A retrospective pooled analysis combined data from 3 single-institution clinical trials for advanced-stage head and neck carcinoma. Inclusion criteria were clinical stage III/IV OPC (T1-2/N1-2b, T3/N0-2b) treated with definitive split-field IMRT and prospectively collected MDADI at baseline and at least 1 posttreatment interval available in trial databases. Patients were sampled to represent likely human papillomavirus (HPV)-associated disease (HPV+/p16+ or <10 pack-years if HPV/p16 unknown). The MDADI composite scores were collected at baseline and 6, 12, and 24months after treatment. Pairwise tests were Bonferroni corrected for multiple comparisons. Forty-six patients were included. All received bilateral neck irradiation with a median dose of 70Gy and systemic therapy (57% concurrent, 43% induction only). Overall the mean baseline MDADI composite score was 90.1, dropping to 74.6 at 6months (P<.0001) and rising to 78.5 (P<.0001) and 83.1 (P=.002) by 12 and 24months relative to baseline, respectively, representing a clinically meaningful drop in MDADI scores at 6months that partially recovers by 24months (6 vs 24months, P=.05). Poor MDADI scores (composite <60) were reported in 4%, 11%, 15%, and 9% of patients at baseline and 6, 12, and 24months, respectively. Fifteen percent of patients had a persistently depressed composite score by at least 20 points at the 24-month interval. "Low-intermediate risk" patients with OPC treated with laryngeal/esophageal inlet dose-optimized split-field IMRT are highly likely to report recovery of acceptable swallowing function in long-term follow-up. Only 15% report poor swallowing function and/or persistently depressed MDADI at 12months or more after IMRT. These data serve as a benchmark future trial design and endpoint interpretation.

Split-field vs extended-field intensity-modulated radiation therapy plans for oropharyngeal cancer: Which spares the larynx? Which spares the thyroid?

Radiation of the low neck can be accomplished using split-field intensity-modulated radiation therapy (sf-IMRT) or extended-field intensity-modulated radiation therapy (ef-IMRT). We evaluated the effect of these treatment choices on target coverage and thyroid and larynx doses. Using data from 14 patients with cancers of the oropharynx, we compared the following 3 strategies for radiating the low neck: (1) extended-field IMRT, (2) traditional split-field IMRT with an initial cord-junction block to 40Gy, followed by a full-cord block to 50Gy, and (3) split-field IMRT with a full-cord block to 50Gy. Patients were planned using each of these 3 techniques. To facilitate comparison, extended-field plans were normalized to deliver 50Gy to 95% of the neck volume. Target coverage was assessed using the dose to 95% of the neck volume (D95). Mean thyroid and larynx doses were computed. Extended-field IMRT was used as the reference arm; the mean larynx dose was 25.7 ± 7.4Gy, and the mean thyroid dose was 28.6 ± 2.4Gy. Split-field IMRT with 2-step blocking reduced laryngeal dose (mean larynx dose 15.2 ± 5.1Gy) at the cost of a moderate reduction in target coverage (D95 41.4 ± 14Gy) and much higher thyroid dose (mean thyroid dose 44.7 ± 3.7Gy). Split-field IMRT with initial full-cord block resulted in greater laryngeal sparing (mean larynx dose 14.2 ± 5.1Gy) and only a moderately higher thyroid dose (mean thyroid dose 31 ± 8Gy) but resulted in a significant reduction in target coverage (D95 34.4 ± 15Gy). Extended-field IMRT comprehensively covers the low neck and achieves acceptable thyroid and laryngeal sparing. Split-field IMRT with a full-cord block reduces laryngeal doses to less than 20Gy and spares the thyroid, at the cost of substantially reduced coverage of the low neck. Traditional 2-step split-field IMRT similarly reduces the laryngeal dose but also reduces low-neck coverage and delivers very high doses to the thyroid.

Three-dimensional dose accumulation in pseudo-split-field IMRT and brachytherapy for locally advanced cervical cancer.

Dose accumulation of split-field external beam radiotherapy (EBRT) and brachytherapy (BT) is challenging because of significant EBRT and BT dose gradients in the central pelvic region. We developed a method to determine biologically effective dose parameters for combined split-field intensity-modulated radiation therapy (IMRT) and image-guided BT in locally advanced cervical cancer. Thirty-three patients treated with split-field-IMRT to 45.0-51.2 Gy in 1.6-1.8 Gy per fraction to the elective pelvic lymph nodes and to 20 Gy to the central pelvis region were included in this study. Patients received six weekly fractions of high-dose rate BT to 6.5-7.3 Gy per fraction. A dose tracker software was developed to compute the equivalent dose in 2-Gy fractions (EQD2) to gross tumor volume (GTV), organs-at-risk and point A. Total dose-volume histogram parameters were computed on the 3D combined EQD2 dose based on rigid image registration. The dose accumulation uncertainty introduced by organ deformations between IMRT and BT was evaluated. According to International Commission on Radiation Unit and Measurement and GEC European Society for Therapeutic Radiology and Oncology recommendations, D98, D90, D50, and D2cm3 EQD2 dose-volume histogram parameters were computed. GTV D98 was 84.0 ± 26.5 Gy and D2cc was 99.6 ± 13.9 Gy, 67.4 ± 12.2 Gy, 75.0 ± 10.1 Gy, for bladder, rectum, and sigmoid, respectively. The uncertainties induced by organ deformation were estimated to be -1 ± 4 Gy, -3 ± 5 Gy, 2 ± 3 Gy, and -3 ± 5 Gy for bladder, rectum, sigmoid, and GTV, respectively. It is feasible to perform 3D EQD2 dose accumulation to assess high and intermediate dose regions for combined split-field IMRT and BT.

Comparison of the Effect of Full-Neck Volumetric Modulated Arc Therapy IMRT Versus Split-Field IMRT Techniques on Radiation Dose to Low Neck Structures

Comparison of the Effect of Full-Neck Volumetric Modulated Arc Therapy IMRT Versus Split-Field IMRT Techniques on Radiation Dose to Low Neck Structures

A treatment planning method to avoid the larynx and eliminate the match-line in the treatment of head and neck cancer with intensity-modulated radiation therapy

Purpose This study aims to investigate a new planning method that avoids the match-line while maintaining larynx protection as in split field intensity-modulated radiation therapy (IMRT) and to evaluate the potential match-line dose variations with split IMRT.

Feasibility and efficacy study of weekly cisplatin with concurrent intensity-modulated radiation therapy for nasopharyngeal carcinoma: Preliminary results

The aim of this study was to assess the feasibility and efficacy of a weekly cisplatin 40 mg/m(2) regimen in patients with nasopharyngeal carcinoma treated concurrently with definitive intensity-modulated radiation therapy (IMRT). The primary endpoints were treatment compliance and acute toxicities. Twenty-two patients with newly diagnosed NPC were recruited in this phase II trial. All patients received definitive IMRT concurrently with weekly cisplatin 40 mg/m(2) for six cycles. The treatment technique was split-field IMRT (SF-IMRT) before August 2009 and whole-field IMRT (WF-IMRT) thereafter. The median follow-up time was 15.1 months (range, 1.5-30 months). No patients experienced regional recurrence or distant metastasis. One patient developed local recurrence. One patient died of non-malignant disease. For all patients, the 1-year overall survival, local recurrence-free survival, regional recurrence-free survival, and distant metastasis-free survival were 95.5%, 95.5%, 100%, and 100%, respectively. All patients received the full dose of RT. Twenty-one patients (95.5%) completed all six cycles of chemotherapy (CHT). Three patients experienced treatment delay. Of them, one had CHT delay, and the other two had IMRT delay. No treatment-related death was found. Acute toxicities were generally mild or moderate. Grade 3 and 4 toxicities accounted for less than 10% of overall occurrence in each corresponding category except for a relatively higher rate in stomatitis (Grade 3, 27%). Renal function impairment was not found. Weekly cisplatin with concurrent IMRT appears to be feasible and effective in treating NPC patients and these findings warrant further investigation.

Choosing an Intensity-Modulated Radiation Therapy Technique in the Treatment of Head-and-Neck Cancer

With the emerging use of intensity-modulated radiation therapy (IMRT) in the treatment of head-and-neck cancer, selection of technique becomes a critical issue. The purpose of this article is to establish IMRT guidelines for head-and-neck cancer at a given institution. Six common head-and-neck cancer cases were chosen to illustrate the points that must be considered when choosing between split-field (SF) IMRT, in which the low anterior neck (LAN) is treated with an anterior field, and the extended whole-field (EWF) IMRT in which the LAN is included with the IMRT fields. For each case, the gross tumor, clinical target, and planning target volumes and the surrounding critical normal tissues were delineated. Subsequently, the SF and EWF IMRT plans were compared using dosimetric parameters from dose-volume histograms. Target coverage and doses delivered to the critical normal structures were similar between the two different techniques. Cancer involving the nasopharynx and oropharynx are best treated with the SF IMRT technique to minimize the glottic larynx dose. The EWF IMRT technique is preferred in situations in which the glottic larynx is considered as a target, i.e., cancer of the larynx, hypopharynx, and unknown head-and-neck primary. When the gross disease extends inferiorly and close to the glottic larynx, EWF IMRT technique is also preferred. Depending on the clinical scenario, different IMRT techniques and guidelines are suggested to determine a preferred IMRT technique. We found that having this treatment guideline when treating these tumors ensures a smoother flow for the busy clinic.