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S227
ESTRO 36
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3
Besançon University Hospital J Minjoz, Department of
Radiation Oncology, Besançon, France
4
Unicancer Centre Antoine Lacassagne, Radiotherapy,
Nice, France
5
Peter MacCallum Cancer Centre, Division of Radiation
Oncology, Melbourne, Australia
6
Goethe University Frankfurt, Department of
Radiotherapy and Oncology, Frankfurt am Main,
Germany
Purpose or Objective
Optimal timing of surgery after neoadjuvant chemo-
radiotherapy (NAD-CRT) is still controversial. Literature
data suggest an improvement in pathological complete
response (pCR) after prolongation of surgical interval (SI)
after NAD-CRT. The aim of this study was to evaluate the
effects of SI on pCR in a pooled dataset of locally advancer
rectal cancer (LARC) patients (pts) coming from 7
randomized trials.
Material and Methods
Pts data were extracted from the following LARC trials:
Accord 12/0405, EORTC 22921, FFCD 9203, CAO/ARO/AIO-
94, CAO-ARO-AIO-04, INTERACT and TROG 01.04. Inclusion
criteria for pts selection were: LARC (clinical tumor stage
(cT) 3-4, clinical nodal stage (cN) 0-1-2 and no distant
metastases) and NAD-CRT followed by surgery. The SI was
calculated from the end of NAD-CRT. Pts were divided into
two groups according to median of the surgery time (MST):
shorter interval group (SIG) (pts who had surgery before
MST) and longer interval group (LIG) (pts who had surgery
after MST). The primary outcome was to determine the
rate of pCR related to SI. The secondary outcome was to
compare post-surgical complications in two groups and the
impact of pCR rates on local recurrence (LR), metastases-
free survival (MFS) and overall survival (OS). Pearson's Chi-
squared test, Kaplan-Meier curves and univariate logistic
regression model (uLRM) were used for data analysis. A p-
value<=0.05 was considered significant.
Results
This pooled dataset included 5247 pts; 3078 pts satisfied
the inclusion criteria and were analyzed in this study.
Recruitment in the period investigated by the study took
place as follows: 453 pts from 1993 to 1998, 613 from 1999
to 2003, 1023 from 2004 to 2008 and 996 from 2009 to
2014. 440 (14%) pts had pCR. The cumulative pCR rate rose
significantly when time between NAD-CRT and surgery was
increased, until reaching a plateau at 16 weeks (Figure 1).
MST was 6 weeks (range 1-31, range interquartile 5-7). The
SIG and the LIG had 1953 and 1132 pts, respectively. pCR
rates were significantly higher in the LIG as compared to
the SIG (19% vs 11.6%, p<0.01). cT, cN, surgery procedure
and post surgical complications were distributed equally
between the two groups. The results of uLRM are
summarized in table 1. Finally, considering only the pCR
events there was no statistically significant difference in
term of LR, MFS and OS between the two groups.
Comparing the two groups, considering pCR and no pCR
pts, there was no statistically significant difference in
term of LR, MFS and OS between them.
Conclusion
The results of these pooled analyses confirm that the
prolongation of SI after the end of NAD-CRT increased the
rate of pCR in LARC pts. The cumulative pCR rate reached
a plateau at 16 weeks; moreover longer SI has no impact
on post surgical complication rates. No statistically
significant difference was observed in term of survival
outcomes between the SIG and the LIG in pCR pts.
OC-0429 Neoadjuvant chemoradiotherapy or 5x5 Gy
followed by chemotherapy in rectal cancer: the
RAPIDO trial
C. Marijnen
1
, For the cooperative group of the RAPIDO
trial
2
1
Leiden University Medical Center LUMC, Department of
Radiotherapy, Leiden, The Netherlands
Purpose or Objective
Current standard for the most locally advanced rectal
cancers is preoperative chemoradiotherapy (CRT), and,
variably per institution, postoperative adjuvant
chemotherapy. Short-course preoperative radiation with
delayed surgery induces tumour downstaging in both
randomized and observational studies. In the RAPIDO trial,
the value of short-term preoperative radiotherapy with
5x5 Gy followed by neoadjuvant chemotherapy is
investigated in a randomized fashion.
Material and Methods
Patients with rectal cancer with high risk features for
systemic or local failure on magnetic resonance imaging
were eligible. Randomization took place between a
standard arm A
:
long course chemoradiotherapy followed