874 / 1082
S858
ESTRO 36 2017
_______________________________________________________________________________________________
1
Agency for Healthcare research and quality, US
department
of
Health
in
Human
services;
https://effectivehealthcare.ahrq.gov/ehc/products/322/998/MethodsGuideforCERs_Viswanathan_IndividualStudie
s.pdf
Results
The search strategy resulted in 1095 abstracts (
Figure 1
)
of which 44 studies fulfilled the inclusion criteria and were
available in full text (one study was excluded based on
study quality criteria). The review is expected to include
syntheses of dose-response relationships for seven gastro-
intestinal
symptoms
(bleeding/diarrhea/frequency/incontinence/pain/proctit
is/urgency: n=18/3/4/10/3/4/4), three genitourinary
symptoms
(hematuria/incontinence/obstruction:
n=4/4/3), and one sexual dysfunction symptom (erectile
dysfunction: n=3) following EBRT. The corresponding
figures for BT±EBRT will be two (bleeding/urgency:
n=6/2), four (incontinence/obstruction/pain/stricture:
n=4/2/3/2), and one symptom (erectile dysfunction: n=2).
Results for diarrhea, stool frequency, and defecation
urgency following EBRT are presented in
Figure 2
. Dose
cut points for the rectum and anal canal/sphincter region
generally followed the same linear slope for
diarrhea/defecation urgency across studies; for stool
frequency they were less consistent.
Conclusion
Our review demonstrates continuous and innovative
activity in the field of late toxicity after prostate cancer
RT since the QUANTEC publications. There is an increased
recognition of intra- and inter-structure specific doses,
and even though rectal bleeding remains the most studied
symptom, there is also a trend towards other non-
aggregated symptoms.
EP-1610 Predictors for morbidity from planned vs.
delivered rectal dose maps in RT of prostate cancer
J. Trane
1
, O. Casares Magaz
1
, L. Bentzen
2
, K. Busch
1
, M.
Thor
3
, L.P. Muren
1
1
Aarhus University Hospital - Aarhus University, Medical
Physics, Aarhus, Denmark
2
Aarhus University Hospital, Oncology, Aarhus, Denmark
3
Memorial Sloan-Kettering Cancer Center, Medical
Physics, New York, USA
Purpose or Objective
Patient-reported gastro-intestinal (GI) symptoms
following radiotherapy (RT) for prostate cancer have
recently been associated with metrics derived from rectal
dose surface maps. In a recent study we developed rectum
dose map based normal tissue complication probability
(NCTP) models for three common late GI symptoms (at
least 20% prevalence in the cohort used for modelling). In
the present study we used such dose maps and connected
NTCP models to compare the planned, daily and summed
rectal dose distributions for patients with repeat
volumetric imaging acquired during the course of RT.
Material and Methods
The patients included in this study were treated according
to a national clinical trial for patients with locally
advanced prostate cancer, irradiating concomitantly the
pelvic lymph nodes and seminal vesicles to 55 Gy and the
prostate to 78 Gy using volumetric modulated arc therapy.
The treatment plans were recalculated on weekly repeat
cone-beam (CB) CTs (6-8 CBCTs per patient) following
Hounsfield Unit override to bone and water. Rectal dose
maps were created for the planned dose distribution as
well as for the dose distributions re-calculated on weekly
CBCTs using a method recently developed by our group.
The weekly CBCTs were averaged to provide a measure for
the summed/accumulated dose across the course of RT.
NTCPs were calculated for the planned, weekly and
averaged rectal dose maps using three spatially based
response models (based on areas and extents from the
rectal dose maps) for three patient-reported GI symptoms:
faecal leakage, obstruction and defecation urgency. The
study included four prostate cancer patients, one with and
three free from late Grade 2+ GI symptoms after RT.
Results
Dose differences exceeding +/- 10 Gy (scaled to the full
treatment course) were seen in the dose maps for all
patients and in all scans (Fig. 1). The largest systematic
dose increase in the maps during the course of therapy was
seen in the patient that experienced Grade 2+ GI
symptoms after treatment. This patient also had higher
NTCPs for all three spatial dose metric based models for
the average map across treatment compared to the
planned dose distribution (e.g. 10% vs 6% for faecal
leakage), while smaller differences were seen for the
three other patients (Table 1).