ESTRO 36 Abstract Book

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S166 ESTRO 36
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V30, and V40) were obtained. Receiver operating
characteristic (ROC) curve identified DVH thresholds that
predicted for grade≥ II HT toxicity with highest specificity.
All data was dichotomized across these cut-offs.
Univariate and multivariate analysis was performed with
SPSS, version 20.
Results
Of the 94 patients randomized to IMRT arm, 74 received
concurrent cisplatin (median cycles=4). Grades I-V HT was
seen in 55.5%, 32.5%, 5%, 0% and 0% patients, respectively
demonstrating low incidence of HT during bowel sparing
IMRT. Leukopenia, neutropenia, anemia, and
thrombocytopenia ≥ grade II was observed in 24.3%, 5.3%,
17.6%, and 0%, respectively. None of the HT resulted in
treatment break. On comparing BM delineation techniques
the FH sub volumes were 25%-47% of WB sub-volumes. The
mean V5, V10, V20, V30, and V40 for WP FH and WB were
99%, 93%, 77%, 60%, and 36%; and 99%, 94%, 80%, 60%, and
36%, respectively suggesting unintended desirable BM
sparing. On univariate analysis WPL FH V30 > 55% (p=0.04)
predicted for overall grade ≥ II HT, WP V10 >95% (p= 0.04)
for grade ≥ II leucopenia and ilium V20 > 90% (p=0.04) for
hemoglobin toxicity. On multivariate analysis, only WP FH
V10 >95% (p value 0.04, OR 3.3 (1-11.5) was statistically
significant for grade ≥ II leucopenia.
Conclusion
The IMRT arm of NCT01279135 (PARCER study) that
employed strict bowel constraints also had unintentional
dosimetrically desirable BM sparing. This was associated
with low absolute rates of HT. Within the setting of bowel
sparing IMRT WP FH V10 should be restricted to ≤95% for
simultaneous bowel and BM sparing. However as none of
the other dosimetric variables predicted for HT, WB
marrow contours could serve as a resource sparing
strategy while planning pelvic IMRT.
OC-0319 Cervix cancer: dose-volume effects in
pathologic lymph nodes
W. Bacorro1, R. Mazeron2, I. Dumas3, A. Escande 2, A.
Huertas2, R. Sun2, P. Castelnau-Marchand2, C. Haie-
Meder 2, C. Chargari2
1 Benavides Cancer Institute- UST Hospital, Radiation
Oncology, Manila, Philippines
2 Gustave Roussy, Radiation Oncology, Villejuif, France
3 Gustave Roussy, Medical Physics, Villejuif, France
Purpose or Objective
Whereas clear dose-volume relationships have been
demonstrated for the tumor and organs at risk in locally
advanced cervix cancer, the optimal threshold to reach
for pathologic lymph nodes remains uncertain. The
objective was to identify planning aim for pathologic
nodes.
Material and Methods
Patients treated with curative intent for a cervical cancer
with nodal involvement were identified. Their treatment
combined external beam radiotherapy (EBRT) and image-
guided brachytherapy (IGABT). Nodal boosts were
performed sequentially or using the simultaneous
integrated boost (SIB) technique depending on the EBRT
technique used. The contributions of EBRT, IGABT (D 98)
and nodal boosts were converted in 2-Gy equivalent
(α/β=10 Gy) and summed. Each node was considered
individually, and followed from diagnosis to relapse.
Resected nodes during para-aortic node surgical staging
were not considered. Statistical analyses comprised log-
rank tests (univariate analyses), Cox proportional model
(factors with p ≤0.1 in univariate) and probit analyses.
Results
One hundred and fifteen patients were included, with a
total number of nodes of 288 (2.5 per patient). PET-CT
was performed in 90.6% of the patients; para-aortic
dissection in 53.8%. Histologic subtypes comprised
squamous cell carcinomas (SCC) in 88.9%,
adenocarcinomas in 8.5% and adenosquamous in 2.6%. The
mean pathologic node volume at diagnosis was 3.4±5.8
cm3. The mean EBRT and nodal boost doses were 44.3±0.9
Gy and 10.0±2.9 Gy respectively. The mean IGABT
contribution to pelvic nodes was 4.2±2.6 Gy. Finally the
mean total dose to lymphadenopathies was 55.3±5.6 Gy.
Concomitant chemotherapy was administrated in 96.5% of
the patients. After a median follow-up of 33.5 months, 20
patients (17.4%) experienced relapses in nodes initially
considered pathologic at diagnosis (local relapse). Among
them recurrences were observed in a total of 44 nodes
(15.3%). The mean time from treatment completion to
relapse was 9.0±11.8 months.
There was no significant relationship between the dose
delivered to pathologic nodes and local control probability
(p=0.38). Univariate analyses tested various factors:
subtypes (SCC versus others, p=0.35), concomitant
chemotherapy (p=0.39), use of SIB (p=0.07), volume at
diagnosis (threshold: 3 cm3, p<0.0001) and dose (≥ 57.5
Gy, p=0.039). The last three factors were entered in a
multivariate analysis. Volume (HR=8.2, 4.0-16.6,
p<0.0001) and dose (HR=2, 1.05-3.9, P=0.034) remained
independent, whereas SIB was not (p=0.99). Subsequent
Probit analysis combining dose and volume showed
significant relationships with the probability of local
control (Figure).
Conclusion
The initial volume was the main prognostic factor of
control in pathologic lymph nodes. A dose superior to 57.5
Gy was also associated with a better local control
probability. Further studies are required to refine these
findings.
Poster Viewing : Session 7: Upper and lower GI
PV-0320 Stereotactic body radiotherapy for liver
metastases based on functional treatment planning
M.M. Fode 1, J. Petersen 2, E. Worm 2, M. Sørensen3, K.
Bak-Fredslund3, S. Keiding 3, M. Høyer4
1Aarhus University Hospital, Department of Oncology,
Aarhus C, Denmark
2Aarhus University Hospital, Department of Medical
Physics, Aarhus C, Denmark