6th ICHNO Abstract Book

6th ICHNO

page 11

ICHNO Conference

International Conference on innovative approaches in Head and Neck Oncology

16 – 18 March 2017

Barcelona, Spain

__________________________________________________________________________________________

A significant gain in regional control rate was observed in

favor of ARCON. Both AR and ARCON are excellent

strategies for larynx preservation in (moderately)

advanced larynx carcinoma with good functional

outcome.

Symposium: Reductions of radiation induced toxicities

SP-014 Target volume reduction

W. De Neve

De Neve Wilfried, Belgium

Abstract text

Radio(chemo)therapy (RCT) with curative intent for head

and neck cancer (HNC) results in significant toxicity which

is related to dose-volume parameters of target and

surrounding normal tissues. Data on target-volume

reduction as a strategy to reduce toxicity are scarce.

Volumes for elective nodal irradiation are often manifold

larger than volumes for gross tumour irradiation. A

multicentre prospective randomised phase II trial

investigated whether a 3-phase adaptive IMRT-scheme

using reduced volumes of elective neck could reduce

toxicity without compromising disease control compared

to standard non-adaptive IMRT. In the experimental arm,

elective sub-volumes were omitted if the population-

based probability of subclinical disease was lower than

~7%. There were no significant differences in disease

control, survival, acute or late toxicity and QOL between

the experimental and the control arms. One patient in the

experimental arm had regional recurrence in a region of

the elective neck that would have been irradiated in the

control arm. Volume de-escalation based on population-

statistics are small, probably too small to yield relevant

benefit regarding toxicity. Patient-individual volume de-

escalation using sentinel lymph node mapping seems more

promising. This could lead to a large volume de-

escalation, as shown by Daisne et al. [1]. In this study, a

significant reduction by factor of 2 of elective neck

volume was achieved. Initial results of the ongoing phase

II study of the same research group are promising, with

the absence of any regional relapse in 22 patients at

median follow-up of 14 months [2]. The utility of PTV-

margins > 0 mm around elective neck volumes is

debatable.

Clinical target volumes around GTV or tumour bed are

based on educated guess rather than on scientific

evidence. Surveys demonstrate large variations in GTV-

delineation with no reports that smaller delineations

change the rates or locations of recurrences. Reducing the

high-dose CTV in nasopharyngeal cancer did not negatively

affect survival rates but did reduce the late xerostomia

events [3]. The use of reduced (5 mm ->3 mm) CTV-to-PTV

margins in HNSCC was associated with reduced late

toxicity while maintaining loco-regional control [4]. In

oropharyngeal cancer, a planning study showed significant

NTCP-reduction for ipsilateral parotid and contralateral

submandibular glands by omitting the PTV-margin [5].

GTV is the union of volumes of malignancy demonstrable

by imaging and clinical examination. 18FDG-PET

translated to smaller GTV sub-volumes for the primary

tumour than CT. PET-based planning demonstrated an

improvement on dosimetry by lowering dose to organs at

risk [6]. This information has been clinically investigated

to dose-escalate volumes smaller than the multimodality

GTV but not yet to reduce dose to low-avidity parts of the

multimodality GTV aiming at reducing toxicity. Clinical

data exist on the use of tumour regression in adaptive

radiotherapy (ART) to treat smaller GTVs, CTVs and PTVs.

ART increased minimum and decreased maximum doses in

target volumes and improved dose/volume metrics of

organs-at-risk [7]. The results revealed considerable

heterogeneity in patient-specific benefit from ART which

was underestimated by reporting population-average. ART

has been explored to investigate the limits of dose-

escalation [8]. Quantitative clinical data of ART regarding

toxicity reduction are scarce, if not inexistent.

Conclusions: ICRU recommends generous inclusion of

(presumably) diseased and normal tissue volumes in GTV,

CTV and PTV. Evidence exists that more restricted PTV,

CTV and GTV volume definition may translate to less

toxicity without increasing recurrence rates.

References

1. Daisne JF et al. Radiat Oncol 2014,9:121.

2. Longton E et al. Int J Radiat Oncol Biol Phys

2015,93:S71-S72.

3. Lin YW et al. PLoS One. 2015 Apr 28;10(4):e0125283.

doi:

10.1371/journal.pone.0125283

4. Chen AM et al. Head Neck. 2014 Dec;36(12):1766-72

5. Samuels SE et al. Int J Radiat Oncol Biol Phys. 2016 Nov

1;96(3):645-52

6. Leclerc M et al. Radiother Oncol. 2015 Jul;116(1):87-

93.

7. Olteanu LA et al. Radiother Oncol. 2014 Jun;111(3):348-

SP-015 Prophylactic swallowing exercises in head and

neck radiotherapy

H.R. Mortensen

Mortensen Hanna Rahbek, Department of Oncology,

Aarhus C, Denmark

Abstract text

While treatment of head and neck cancer has improved

the survival rates over the past years, long-term morbidity

plays an increasing role. One of the significant morbidities

is long term radiotherapy-related dysphagia. Dysphagia is

a symptom that covers many different problems often

leading to serious consequences and greatly affecting

patient’s quality of life. Different approaches have been

taken towards reducing radiotherapy-related dysphagia

including swallowing exercises implemented either as

prophylactic exercises or reactive exercises.

Publications on prophylactic swallowing exercises have

emerged during the past few years but evidence is still

scarce. Studies are heterogeneous according to study

design, interventions, evaluation times, outcomes and

how they are measured making a comparison complicated.

A review of the literature shows, that the current studies

mostly include few participants, only a few small

randomized controlled trials, high risk of bias and not all

exercises used have sufficient evidence for long-term

improvement in swallowing. Endpoints include objective

endpoints, observed-rated endpoints, patient-reported

endpoints and clinical endpoints like tube feeding.

Evaluation times ranged from a few weeks to several

months.

In general, most studies reports some positive results of

swallowing therapy but the benefit is not consistent and

not related to specific measures. Work is ongoing to

elaborate on these differences. High rates of dropouts are

a major concern when interpreting the studies and

compliance to the exercises is generally poor.

In conclusion, the evidence for prophylactic swallowing

exercises for all patients being superior to therapeutic

intervention in symptomatic patients is still scarce. To

address the question properly larger studies are needed

with minimal risk of bias, strong methodologies and an

agreement on primary outcome, evaluation method and

time.