Sparing the contralateral submandibular gland without compromising PTV coverage by using volumetric modulated arc therapy

Clinical and dosimetric risk stratification for patients at high-risk of feeding tube use during definitive IMRT for head and neck cancer

•

Understanding feeding tube risk is critical to optimal weight maintenance during radiotherapy.

•

T-stage, Level II lymphadenopathy risk stratify feeding tube use into 4 groups.

•

The addition of cervical oesophagus dose can further refine these risk stratified groups.

Introduction

To identify organs to which dose limitation using intensity modulated radiotherapy (IMRT) can potentially modify the incidence and duration of feeding tube use, during and immediately following therapy for head and neck cancer.

Materials and methods

One hundred and fourteen patients treated with definitive IMRT (± concurrent chemotherapy) head and neck mucosal cancers were included. Patients received a prophylactic feeding tube and followed up by a dietician for at least eight weeks post-radiotherapy. Salivary and swallowing organs were delineated for each patient. Tumour and dosimetric variables were recorded for all patients and analysed for incidence and duration of feeding tube use for at least 25% of dietary requirements.

Results

Multivariate analysis showed T-classification ≥3 and level II lymphadenopathy as independent significant predictors of incidence and duration of feeding tube use in oral cavity, pharyngeal and supraglottic primaries. Mean dose deposited in the cervical oesophagus over 36Gy further increased the incidence and duration of feeding tube use. Mean dose deposited in the base of tongue and superior pharyngeal constrictor muscles affected incidence and duration of feeding tube use, respectively.

Discussion

In patients treated with definitive IMRT, T-classification and Level II lymphadenopathy, combined with a mean cervical oesophagus dose over 36Gy can a stratify patients into eight distinct risk groups for using feeding tubes for at least 25% of their dietary requirements.

Risk factors and distribution features of level IB lymph nodes metastasis in nasopharyngeal carcinoma

OBJECTIVE

The objective of this study is to investigate the risk factors and distribution features for level IB metastasis in nasopharyngeal carcinoma (NPC) and provide clinical evidence for defining the indications and clinical target volume (CTV) of prophylactic level IB irradiation.

METHODS

We retrospectively analyzed 798 patients with newly-diagnosed, non-metastatic and histologically confirmed NPC underwent intensity-modulated radiation therapy (IMRT). Two sides of neck in each patient have been analyzed separately. The correlations of level IB metastasis and the clinical risk factors were analyzed with Chi-square test and logistic regression model. The risk score model (RSM) of level IB metastasis was calculated by totaling up the scores of each independent variable. We divided level IB into three areas, including anterolateral space of submandibular glands, medial space of the submandibular glands and submandibular glands.

RESULTS

Maximal axial diameter (MAD) of level IIA nodes >20mm or extra capsular spread (ES) of level IIA nodes, anterior half of nasal cavity involvement and submandibular gland involvement/compression were independently significantly risk factors for level IB lymph nodes (LNs) metastasis at diagnosis. Two groups based on RSM were obtained: low risk (total score=0-2.5); high risk (4-8.5). The incidence of IB LNs metastasis at diagnosis of the two groups were 0.9% and 6.3%, respectively (P<0.001). The cervical lymph nodes of level IB were distributed in the anterolateral space of submandibular glands. There was no positive/negative LNs inside or medial space of the submandibular glands.

CONCLUSION

Level IB LNs metastasis is associated with MAD of level IIA nodes >20mm or ES of level IIA nodes, anterior half of nasal cavity involvement and submandibular gland involvement/compression in NPC patients. Omission of level IB irradiation may be feasible for patients with low-risk IB LNs metastasis at diagnosis. The submandibular gland should not be included in level IB.

Comparison of treatment techniques for reduction in the submandibular gland dose: A retrospective study

Introduction

Recent studies have suggested reducing the dose submandibular glands receive when patients undergo head and neck radiotherapy can play a crucial role in preventing xerostomia. However, they are traditionally not spared due to concern that target coverage may be compromised. We investigated the possibility of sparing the contralateral submandibular gland (cSM) by utilising modern planning techniques.

Methods

10 head and neck patients previously treated with conformal therapy at our centre were retrospectively planned using intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT). Each patient was prescribed 70 Gy in 35 fractions to the primary volume, with 56 Gy delivered to the elective nodal areas. The primary objective was to spare the cSM gland using appropriate dose constraints.

Results

Mean dose to the cSM gland was reduced to an acceptable dose level (39 Gy) for all patients replanned using an IMRT or VMAT technique, without compromising planned target volume (PTV) coverage or other critical structures. VMAT was able to reduce the mean dose to 31.5 ± 5.5 Gy compared to 34.5 ± 4.8 Gy of IMRT and offered improved plan conformity.

Conclusion

Sparing the cSM gland is possible using IMRT and VMAT planning, whilst preserving coverage on the elective PTV. This has produced a change in protocol in our department, more focus placed on sparing the SM glands. VMAT is a viable alternative method of delivering treatment and will be utilised when required.

Prophylactic exercises among head and neck cancer patients during and after swallowing sparing intensity modulated radiation: adherence and exercise performance levels of a 12-week guided home-based program

The background and purpose of this paper is to investigate adherence, exercise performance levels and associated factors in head and neck cancer (HNC) patients participating in a guided home-based prophylactic exercise program during and after treatment [swallowing sparing intensity modulated radiation therapy (SW-IMRT)]. Fifty patients were included in the study. Adherence was defined as the percentage of patients who kept up exercising; exercise performance level was categorized as low: ≤1, moderate: 1–2, and high: ≥2 time(s) per day, on average. Associations between 6- and 12-week exercise performance levels and age, gender, tumour site and stage, treatment, intervention format (online or booklet), number of coaching sessions, and baseline HNC symptoms (EORTC-QLQ-H&N35) were investigated. Adherence rate at 6 weeks was 70% and decreased to 38% at 12 weeks. In addition, exercise performance levels decreased over time (during 6 weeks: 34% moderate and 26% high; during 12 weeks: 28% moderate and 18% high). The addition of chemotherapy to SW-IMRT [(C)SW-IMRT] significantly deteriorated exercise performance level. Adherence to a guided home-based prophylactic exercise program was high during (C)SW-IMRT, but dropped afterwards. Exercise performance level was negatively affected by chemotherapy in combination with SW-IMRT.

A longitudinal evaluation of improvements in radiotherapy treatment plan quality for head and neck cancer patients

PURPOSE

To investigate changes in head-and-neck cancer (HNC) plan quality following the introduction of new technologies and planning techniques in the last decade.

METHODS AND MATERIALS

Thirty plans were selected from each of four successive periods (P). P1: 7-field static intensity-modulated radiotherapy (IMRT) with parotid gland sparing; P2: dual-arc volumetric-modulated arc therapy (VMAT, similar to P3-P4), including submandibular gland sparing; P3: inclusion of individual swallowing muscles and attempts to further reduce parotid and oral cavity doses through manual interactive optimization; P4: containing the same organs-at-risk (OARs) as P3, but automatically interactively optimized. Plan benchmarking included mean salivary gland/swallowing muscle/oral cavity (Dsal/Dswal/Doc) doses. Differences in mean doses between the periods were analyzed by an ANCOVA, taking geometric differences across periods into account.

RESULTS

Compared to P1, P2 plans improved Dsal by 3.4Gy on average. P3 improved Dsal/Dswal/Doc by 6.9/11.5/7.2Gy over P2, showing that Dswal and Dsal could be improved simultaneously. In P4, Doc/Dswal slightly improved over P3 by 1.7/3.8Gy. Improved OAR sparing in P3/P4 did not come at the cost of increased dose deposition elsewhere and planning target volume (PTV) dose homogeneity was similar.

CONCLUSIONS

New technologies and planning techniques were successfully implemented into routine clinical care and resulting in improved HNC plan quality.

Can knowledge-based DVH predictions be used for automated, individualized quality assurance of radiotherapy treatment plans?

Background

Treatment plan quality assurance (QA) is important for clinical studies and for institutions aiming to generate near-optimal individualized treatment plans. However, determining how good a given plan is for that particular patient (individualized patient/plan QA, in contrast to running through a checklist of generic QA parameters applied to all patients) is difficult, time consuming and operator-dependent. We therefore evaluated the potential of RapidPlan, a commercial knowledge-based planning solution, to automate this process, by predicting achievable OAR doses for individual patients based on a model library consisting of historical plans with a range of organ-at-risk (OAR) to planning target volume (PTV) geometries and dosimetries.

Methods

A 90-plan RapidPlan model, generated using previously created automatic interactively optimized (AIO) plans, was used to predict achievable OAR dose-volume histograms (DVHs) for the parotid glands, submandibular glands, individual swallowing muscles and oral cavities of 20 head and neck cancer (HNC) patients using a volumetric modulated (RapidArc) simultaneous integrated boost technique. Predicted mean OAR doses were compared with mean doses achieved when RapidPlan was used to make a new plan. Differences between the achieved and predicted DVH-lines were analyzed. Finally, RapidPlan predictions were used to evaluate achieved OAR sparing of AIO and manual interactively optimized plans.

Results

For all OARs, strong linear correlations (R² = 0.94–0.99) were found between predicted and achieved mean doses. RapidPlan generally overestimated the amount of achievable sparing for OARs with a large degree of OAR-PTV overlap. RapidPlan QA using predicted doses alone identified that for 50 % (10/20) of the manually optimized plans, sparing of the composite salivary glands, oral cavity or composite swallowing muscles could be improved by at least 3 Gy, 5 Gy or 7 Gy, respectively, while this was the case for 20 % (4/20) AIO plans. These predicted gains were validated by replanning the identified patients using RapidPlan.

Conclusions

Strong correlations between predicted and achieved mean doses indicate that RapidPlan could accurately predict achievable mean doses. This shows the feasibility of using RapidPlan DVH prediction alone for automated individualized head and neck plan QA. This has applications in individual centers and clinical trials.

Investigation of the feasibility of elective irradiation to neck level Ib using intensity-modulated radiotherapy for patients with nasopharyngeal carcinoma: a retrospective analysis

BACKGROUND

To assess the feasibility of elective neck irradiation to level Ib in nasopharyngeal carcinoma (NPC) using intensity-modulated radiation therapy (IMRT).

METHODS

We retrospectively analyzed 1438 patients with newly-diagnosed, non-metastatic and biopsy-proven NPC treated with IMRT.

RESULTS

Greatest dimension of level IIa LNs (DLN-IIa) ≥ 20 mm and/or level IIa LNs with extracapsular spread (ES), oropharynx involvement and positive bilateral cervical lymph nodes (CLNs) were independently significantly associated with metastasis to level Ib LN at diagnosis. No recurrence at level Ib was observed in the 904 patients without these characteristics (median follow-up, 38.7 months; range, 1.3-57.8 months), these patients were classified as low risk. Level Ib irradiation was not an independent risk factor for locoregional failure-free survival, distant failure-free survival, failure-free survival or overall survival in low risk patients. The frequency of grade ≥ 2 subjective xerostomia at 12 months after radiotherapy was not significantly different between low risk patients who received level Ib-sparing, unilateral level Ib-covering or bilateral level Ib-covering IMRT.

CONCLUSION

Level Ib-sparing IMRT should be safe and feasible for patients without a DLN-IIa ≥ 20 mm and/or level IIa LNs with ES, positive bilateral CLNs or oropharynx involvement at diagnosis. Further investigations based on specific criteria for dose constraints for the submandibular glands are warranted to confirm the benefit of elective level Ib irradiation.

Regional recurrence of oropharyngeal cancer after definitive radiotherapy: a case control study

Background

Elective treatment of lymph nodes in oropharyngeal cancer (OPC) has impact on both regional recurrences (RR) and risk of late side effects. This study was performed to quantify the dose-dependent impact on RR and overall survival (OS) in a prospectively collected cohort of OPC from the ARTSCAN study with emphasis on elective treatment.

Methods

ARTSCAN is a previously published prospective, randomized, multicentre study of altered radiotherapy (RT) fractionation in head and neck cancer. In ARTSCAN the elective treatment volume for node positive OPC varied significantly between centres due to local treatment principles. All patients with OPC in complete response after primary treatment were eligible for the present case–control study. Cases were patients with RR during five years follow-up. Patients with no recurrence were eligible as controls. Four controls per case were matched according to T- and N-stage. Mean (D_mean) and median (D_50%) dose for the lymph node level (LNL) of RR in the cases and the corresponding LNL in the controls were analysed with conditional logistic regression. OS was estimated with the Kaplan-Meier method and evaluated by multivariate Cox regression analysis.

Results

There was a dose-dependent risk reduction for D_50% in the interval that represented elective treatment (40–50 Gy) (OR = 0.18, p < 0.05) and a trend in the same dose interval for D_mean (OR = 0.19, p = 0.07). OS rates at five years were 0.39 (0.24-0.65) for cases and 0.70 (0.62–0.81) for controls (p < 0.001). The Kaplan-Meier and the Cox regression analysis for cases categorised by delivered dose showed an inverse relationship between dose and survival. The cases with RR in a LNL outside planning target volume (PTV) (D_mean < 40 Gy) had an OS rate comparable to that of all patients, and those with RR in a LNL in PTV_elective (D_mean 40–60 Gy) or PTV_tumour (D_mean >60 Gy) did significantly worse (p < 0.05). The same inverse relationship was also shown for a small subset of patient with known HPV-status, defined by over expression of p16 (p < 0.05).

Conclusions

There was a significant risk reduction for RR of elective treatment. However the OS for patients with RR outside target volumes was not affected, with similar results for patients with HPV-positive OPC. This could be an argument for a prospective randomized study on limited elective target volumes in OPC.

Automatic interactive optimization for volumetric modulated arc therapy planning

BACKGROUND

Intensity modulated radiotherapy treatment planning for sites with many different organs-at-risk (OAR) is complex and labor-intensive, making it hard to obtain consistent plan quality. With the aim of addressing this, we developed a program (automatic interactive optimizer, AIO) designed to automate the manual interactive process for the Eclipse treatment planning system. We describe AIO and present initial evaluation data.

METHODS

Our current institutional volumetric modulated arc therapy (RapidArc) planning approach for head and neck tumors places 3-4 adjustable OAR optimization objectives along the dose-volume histogram (DVH) curve that is displayed in the optimization window. AIO scans this window and uses color-coding to differentiate between the DVH-lines, allowing it to automatically adjust the location of the optimization objectives frequently and in a more consistent fashion. We compared RapidArc AIO plans (using 9 optimization objectives per OAR) with the clinical plans of 10 patients, and evaluated optimal AIO settings. AIO consistency was tested by replanning a single patient 5 times.

RESULTS

Average V95&V107 of the boost planning target volume (PTV) and V95 of the elective PTV differed by ≤0.5%, while average elective PTV V107 improved by 1.5%. Averaged over all patients, AIO reduced mean doses to individual salivary structures by 0.9-1.6Gy and provided mean dose reductions of 5.6Gy and 3.9Gy to the composite swallowing structures and oral cavity, respectively. Re-running AIO five times, resulted in the aforementioned parameters differing by less than 3%.

CONCLUSIONS

Using the same planning strategy as manually optimized head and neck plans, AIO can automate the interactive Eclipse treatment planning process and deliver dosimetric improvements over existing clinical plans.

Evaluation of a knowledge-based planning solution for head and neck cancer

PURPOSE

Automated and knowledge-based planning techniques aim to reduce variations in plan quality. RapidPlan uses a library consisting of different patient plans to make a model that can predict achievable dose-volume histograms (DVHs) for new patients and uses those models for setting optimization objectives. We benchmarked RapidPlan versus clinical plans for 2 patient groups, using 3 different libraries.

METHODS AND MATERIALS

Volumetric modulated arc therapy plans of 60 recent head and neck cancer patients that included sparing of the salivary glands, swallowing muscles, and oral cavity were evenly divided between 2 models, Model(30A) and Model(30B), and were combined in a third model, Model60. Knowledge-based plans were created for 2 evaluation groups: evaluation group 1 (EG1), consisting of 15 recent patients, and evaluation group 2 (EG2), consisting of 15 older patients in whom only the salivary glands were spared. RapidPlan results were compared with clinical plans (CP) for boost and/or elective planning target volume homogeneity index, using HI(B)/HI(E) = 100 × (D2% - D98%)/D50%, and mean dose to composite salivary glands, swallowing muscles, and oral cavity (D(sal), D(swal), and D(oc), respectively).

RESULTS

For EG1, RapidPlan improved HI(B) and HI(E) values compared with CP by 1.0% to 1.3% and 1.0% to 0.6%, respectively. Comparable D(sal) and D(swal) values were seen in Model(30A), Model(30B), and Model60, decreasing by an average of 0.1, 1.0, and 0.8 Gy and 4.8, 3.7, and 4.4 Gy, respectively. However, differences were noted between individual organs at risk (OARs), with Model(30B) increasing D(oc) by 0.1, 3.2, and 2.8 Gy compared with CP, Model(30A), and Model60. Plan quality was less consistent when the patient was flagged as an outlier. For EG2, RapidPlan decreased D(sal) by 4.1 to 4.9 Gy on average, whereas HI(B) and HI(E) decreased by 1.1% to 1.5% and 2.3% to 1.9%, respectively.

CONCLUSIONS

RapidPlan knowledge-based treatment plans were comparable to CP if the patient's OAR-planning target volume geometry was within the range of those included in the models. EG2 results showed that a model including swallowing-muscle and oral-cavity sparing can be applied to patients with only salivary gland sparing. This may allow model library sharing between institutes. Optimal detection of inadequate plans and population of model libraries requires further investigation.

Submandibular gland-sparing radiation therapy for locally advanced oropharyngeal squamous cell carcinoma: patterns of failure and xerostomia outcomes

Background

Saliva from submandibular glands (SMG) is necessary to minimize xerostomia. It is unclear whether SMG can be safely spared in patients undergoing bilateral neck radiotherapy for locally advanced oropharyngeal cancer without increasing the risk of marginal recurrence. We evaluated the outcomes of contralateral submandibular gland (cSMG) sparing intensity-modulated radiation therapy (IMRT).

Methods

All patients with stage III/IV oropharyngeal squamous cell carcinoma treated with bilateral neck IMRT from 2006–2012 at our institution were included. Appropriately selected patients with favorable primary tumor characteristics and no definite contralateral neck disease were treated with cSMG-sparing IMRT. Patterns of failure and xerostomia outcomes were retrospectively analyzed.

Results

114 patients were treated. 89% had stage IV disease and 89% received definitive radiation therapy. 76 patients (67%) received cSMG sparing IMRT. With a median follow-up of 30 months, there were 10 local, 9 regional, and 10 distant recurrences. 2-year overall survival was 86% and 2-year loco-regional control was 87%. In cSMG spared patients, the mean cSMG dose was 30.7 Gy. Late grade 2+ xerostomia was significantly reduced in the cSMG spared group compared to those without SMG sparing (6 months: 23% vs. 72%, 12 months: 6% vs. 41%, 24 months: 3% vs. 36%, all p < 0.0007). There were no peri-SMG marginal recurrences in the cSMG-spared cohort.

Conclusions

cSMG sparing IMRT did not increase marginal failures in this series of locally advanced oropharyngeal SCC patients. Xerostomia was significantly reduced in cSMG spared patients.

Different treatment planning protocols can lead to large differences in organ at risk sparing

BACKGROUND AND PURPOSE

Different planning protocols may define varying planning target volume (PTV) dose criteria. We investigated the hypothesis that this could result in differences in organ-at-risk (OAR) sparing.

MATERIAL AND METHODS

Volumetric modulated arc therapy plans were created for ten locally advanced head and neck cancer patients following PTV criteria specified by the RTOG, EORTC and institutional (VUmc) protocols. Resulting plans were evaluated on the basis of the homogeneity index, calculated for the boost/elective PTVs as HIB/HIE=100%*(D2%-D98%)/D50% and mean dose to individual and composite salivary (compsal) and swallowing (compswal) OARs.

RESULTS

RTOG plans were the most homogeneous, with mean HIB of 8.2±0.9%, compared to 9.5±1.0%/11.6±1.5% for the VUmc/EORTC plans. EORTC plans provided most OAR sparing, with compsal/compswal doses of 24.6±7.7/22.9±4.2Gy, compared to 32.2±9.7/29.9±4.2Gy and 28.4±8.1/24.7±5.3Gy for RTOG and VUmc, respectively. EORTC provided 7.2/7.7Gy mean dose reductions to the contra/ipsilateral parotid glands compared to RTOG.

CONCLUSIONS

Different planning protocols resulted in different levels of PTV dose homogeneity. We observed differences of up to ⩾7Gy in composite and individual mean OAR doses. This could influence rates of toxicity and should be taken into account when comparing clinical studies. A consensus should be reached between major trial groups on appropriate PTV parameters.

Toward optimal organ at risk sparing in complex volumetric modulated arc therapy: an exponential trade-off with target volume dose homogeneity

PURPOSE

Conventional radiotherapy typically aims for homogenous dose in the planning target volume (PTV) while sparing organs at risk (OAR). The authors quantified and characterized the trade-off between PTV dose inhomogeneity (IH) and OAR sparing in complex head and neck volumetric modulated arc therapy plans.

METHODS

Thirteen simultaneous integrated boost plans were created per patient, for ten patients. PTV boost(B)/elective(E) optimization priorities were systematically increased. IHB and IHE, defined as (100% - V95%) + V107%, were evaluated against the average of the mean dose to the combined composite swallowing and combined salivary organs (D-OAR(comp)). To investigate the influence of OAR size and position with respect to PTVB/E, OAR dose was evaluated against a modified Euclidean distance (DMB/DME) between OAR and PTV.

RESULTS

Although the achievable D-OAR(comp) for a given level of PTV IH differed between patients, excellent logarithmic fits described the D-OAR(comp)/IHB and IHE relationship in all patients (mean R(2) of 0.98 and 0.97, respectively). Allowing an increase in average IHB and IHE over a clinically acceptable range, e.g., from 0.4% ± 0.5% to 2.0% ± 2.0% and 6.9% ± 2.8% to 14.8% ± 2.7%, respectively, corresponded to a decrease in average dose to the composite salivary and swallowing structures from 30.3 ± 6.5 to 23.6 ± 4.7 Gy and 32.5 ± 8.3 to 26.8 ± 9.3 Gy. The increase in PTVE IH was mainly accounted for by an increase in V107, by on average 5.9%, rather than a reduction in V95, which was on average only 2%. A linear correlation was found between the OAR dose to composite swallowing structures and contralateral parotid and submandibular gland, with DME (R(2) = 0.83, 0.88, 0.95). Only mean ipsilateral parotid dose correlated with DMB (R(2) = 0.87).

CONCLUSIONS

OAR sparing is highly dependent on the permitted PTVB/E IH. PTVE IH substantially influences OAR doses. These results are relevant for clinical practice and for future automated treatment-planning strategies.

Sparing level Ib lymph nodes by intensity-modulated radiotherapy in the treatment of nasopharyngeal carcinoma

BACKGROUND

We retrospectively investigated the patterns of locoregional relapse and survival of patients to evaluate whether sparing level Ib lymph nodes by intensity-modulated radiotherapy (IMRT) in the treatment of nasopharyngeal carcinoma was feasible.

METHODS

One hundred and twenty nasopharyngeal carcinoma patients received treatment with level Ib lymph nodes spared by IMRT between January 2005 and August 2008 in our center. Before treatment, each patient underwent enhanced magnetic resonance imaging of the nasopharynx and neck. Patients with negative cervical lymph nodes received radiotherapy to the nasopharynx, skull base and upper neck drainage areas, while patients with cervical lymph node involvement received treatment to the whole neck. The prescription doses were 66-70.4 Gy/30-32 fractions to the gross tumor volume of nasopharynx, 66 Gy to the positive neck nodes, 60 Gy to the high-risk clinical target volume and 54 Gy to the low-risk clinical target volume. Patients staged III, IV A/B or II also received chemotherapy.

RESULTS

The median follow-up of these 120 patients was 54 months. The 5-year local control, regional control, distant metastasis-free and overall survival rates were 90.7, 96.5, 84.8 and 81.4 %, respectively. Four patients suffered regional recurrence: 2, 1 and 1 experienced regional recurrence in level II, retropharyngeal and parotid lymph nodes, respectively.

CONCLUSION

In nasopharyngeal carcinoma patients with negative level Ib lymph nodes who are treated with level Ib-sparing IMRT, regional lymph node recurrence alone is rare. Therefore, sparing level Ib lymph nodes by IMRT is feasible in selected patients.