ESTRO 36 Abstract Book

S207

ESTRO 36 2017

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healing ulcer. Another alternative is to extend the

observation interval for an additional 1-2 months.

Follow up – detection and treatment of regrowth

Regrowths are inherently a part of the organ preservation

approach, and follow-up should be aimed at early

detection of local regrowth. The vast majority of local

regrowths after W&W are located intraluminal and occur

within 12-18 months. The backbone of local follow up is

frequent examination by DRE and endoscopy during the

first two years, supplemented by MRI to detect the less

frequently occurring regrowths deeper in the bowel wall

or lymph nodes. Our current schedule has a 3-4 monthly

flexible sigmoidoscopy and MRI in the first year and 6

monthly thereafter until year 5.

A TME is the best oncological option when a patient

presents with a regrowth. Alternatives can be considered

in various situations, such as a local excision of an isolated

luminal regrowth in a patient with a high operative risk or

patient preference to avoid major surgery and/or a

definitive colostomy. Organ preservation series show that

with adequate follow and early detection local regrowths

occur in 15-25% and are mostly amenable to salvage

treatment with good outcome.

Conclusion

Organ preservation constitutes a paradigm change with

different treatment concepts: willingness to adapt the

surgical plan according to the response, prolonging the

observation time in good responders, the role of TME as

salvage surgery, and expanding the role of patients in

treatment choices. Although the risk seems low, there is

no high-level evidence that organ preservation is as safe

as standard TME surgery. This should be balanced against

the possible benefits: avoidance of operative morbidity

and mortality of a TME procedure, and an improved quality

of life through. Because of a high interest of patients, the

surgical community should cautiously move ahead and

offer the option of organ preservation to patients in a

controlled setting and combine this with providing further

evidence. This can be achieved by setting up a prospective

organ preservation protocol with standardized assessment

and follow up in centers that add their data to a large

multicenter database. At least initially it seems wise to

concentrate organ preservation in a limited number of

centers in order to gain sufficient expertise more quickly.

SP-0389 Imaging and molecular profiles to predict

response to chemoradiotherapy: where do we stand?

K. Haustermans

UZ KUL, Department of Radiation Oncology, Leuven,

Belgium

The tumor response to preoperative chemoradiotherapy

(CRT) is heterogeneous. About 20% of the patients achieve

a pathological complete response (pCR). Patients with a

pCR have a favorable long term outcome with excellent

local control and disease-free survival. Adopting a watch

and wait strategy in these patients is appealing since

rectal cancer surgery entails complications, morbidity and

even mortality. Strategies should be explored to precisely

select patients who are candidates for a less invasive

strategy. Conventional imaging lacks accuracy for

restaging after CRT and is therefore not useful to select

candidates for organ preservation. In recent years, there

has been growing interest in molecular markers and

functional imaging to improve clinical response

assessment. Since immunity and inflammation play a

critical role in tumorigenesis, inflammatory parameters

might give useful information on the patient’s tumor

response. Another promising strategy for the prediction of

the response to CRT is the use of functional imaging.

Diffusion-weighted imaging (DWI) and 18F-fluorodeoxy

glucose positron emission tomography (FDG PET-CT) have

emerged as promising tools in the prediction of tumor

response before, during and after CRT. Besides the

common parameters determined on these images such as

the Apparent Diffusion Coefficient (ADC) and the

Standardized Uptake Value (SUV), tumor phenotypes can

also be characterized by extracting a large number of

quantitative image features (radiomics). A uniform

prospective registration of patients with rectal cancer

managed with a non-surgical approach will result in a

detailed understanding of patient selection and will

enable us to assess long-term outcome.

Symposium: Radiotherapy of brain tumours

SP-0390 Radiotherapy for low grade glioma in adults

in 2017. What’s crazy!

S. Villà Freixa

Catalan Institute of Oncology. Universitat Autònoma de

Barcelona, Radiation Oncology, Badalona. Catalonia,

Spain

Diffuse low grade glioma (LGG) is a heterogeneous group

of tumors in terms of survival. Maximal surgical resection

is the initial optimal treatment but no clear evidences

have been published. Adjuvant treatment using

radiotherapy (RT) and chemotherapy has been used in high

risk patients and a significant improvement of survival has

been shown. RT plays a key role in the RTOG series but

timing, volumes and dose are still undefined. After the

final results of EORTC 22033 and RTOG 98-02 trials it has

been suggested that chemotherapy is active for LGG.

Indeed, chemotherapy did not imply a decline in MME

score in the American trial. Nowadays however the main

argument for delaying RT in patients with LGG is to avoid

neurocognitive and quality of life deteriorations.

Nevertheless, no significant differences in quality of life

were reported between RT and temozolomide groups in

the EORTC 20033 trial when analysis of the questionnaires

were done, with acceptable level of compliance. Notably,

median progression free survival for patients in the RT

group was superior to chemotherapy group (not

significant). In the new era of molecular biology for

gliomas with its prognostic potential role, it is important

to underlay that the major strength of EORTC 22033 trial

was that molecular data (

IDH 1/2

, 1p/19q co-deletion)

were available in more than 80% of patients (45% of

patients in the RTOG 98-02 trial). RT seemed to be as

effective as temozolomide in patients with

IDH1

IDH2

mutations and 1p/19q co-deletion. For Radiation Oncology

community, it is pending to solve several questions: 1-

Defining volumes (GTV, CTV, PTV), and protecting

hippocampus using co-registrations with CT, different

sequences of MRI and PET scan. 2- Using new modifications

of IMRT (as VMAT) or protontherapy as standard. 3-

Determining dose fractionation and total dose, taking into

account that the standard EORTC dose of 50.4 Gy has not

been compared with lower total dose. In conclusion, it

seems that in high risk LGG patients the combination of RT

with chemotherapy improves survival and progression free

survival and that RT is comparable to temozolomide.

However, Radiation Oncology community has to step

forward in defining techniques and total dose and

fractionation.

SP-0391 What is the role of combined chemo-

radiotherapy for grade III glioma in adults?

A. Chalmers

Inst. of Cancer Sciences-Univ. Glasgow The Beatson

West of Scotland Cancer Center, Department of Clinical

Oncology, Glasgow, United Kingdom

Classification, prognosis and treatment of grade III glioma

is now determined predominantly by molecular

biomarkers, with 1p19q chromosomal co-deletion

conferring a clear prognostic benefit and also being

associated with better response to chemotherapy. The