ESTRO 36 Abstract Book

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S98 ESTRO 36
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Material and Methods
Between March 2007 and December 2014, 250 patients
with localized prostate cancer underwent PPB, of which
32 patients had MLH identified radiologically on the MRI
scan. These patients were divided into three MLH groups,
mild(<5mm), moderate(5-10mm), severe(>10mm), by
measuring the distance of MLH (dMLH); between the
posterior transitional zone and the prostatic tissue
protruding into the bladder. We retrospectively analyzed
seed migration, DVH, operation time, genitourinary (GU)
toxicity, and DFS.
Results
Median follow-up is 53.5 months (range; 9-104months) and
median age is 68.5 years old(range; 57-75yo). MLH group
were respectively classified mild in 12, moderate in 12,
severe in 8. D’Amico risk classification were low risk in 21,
intermediate risk in 11.Median prostate volume was such
as 34.4cc/32.8cc/28.6cc (severe/moderate/mild). The
median D90 was 145Gy. All patients still have achieved
relapse-free survival. Implant migration and low-dose
level of median lobe tended to increase in severe
MLH.There was no relapse and PSA failure. The IPSS
(International Prostate Symptom Score) for most patients
worsened during the immediate post-implant period, but
most of these patients were resolved by their second
follow-up at 6 months. The median IPSS one month or six
months after post-implant were respectively 21.5 or
observed Grade 2 acute toxicity. The late toxicity
such as Grade 2 was observed in 25%, such as erectile
dysfunction, urinary hemorrhage and urethralgia.
Hemorrhage in Grade 3 was observed in just one case, who
had taken an aspirin for cerebral infarction. There was no
Grade 4 complication and the all complication was
acceptable.
Conclusion
In our study, MLH does not appear to be a strong
contraindication to PPB because there were no significant
differences in DFS and GU toxicity. However, we
experienced that seed migration and cold spot degree
tended to increase in severe MLH cases, we have to pay
attention to treat severe MLH.
Award Lecture: Honorary Members’ Award Lectures
SP-0191 Optimizing the Treatment of HPV-related
Oropharyngeal Cancer: the difficult journey back
B. O'Sullivan1
1 Princess Margaret Cancer Centre University Health
Network, Toronto, Canada
Traditional approaches to head and neck cancer (HNC)
have used either surgery +/- adjuvant radiotherapy, or
radiotherapy +/- chemotherapy. Thus treatment was
practiced with a paradigm that head and neck cancer
(HNC) is one disease requiring the same treatment,
modulated according to anatomic constraints influencing
whether function might be preserved, largely governed by
psychosocial attitudes directed at avoidance of surgical
ablation with resulting loss of function and esthetic
appearance. In fact, while avoiding surgery, a philosophy
evolved that greater intensity of non-surgical
management is optimal. However, current evidence
suggests the contrary and strong evidence that treatment-
related death (e.g. pharyngeal disabilities or other
problems) is claiming 10-20% of contemporary HNC
survivors (Forastiere et al JCO 2013) For the recently
emerged HPV-related oropharyngeal cancer (OPC),
approaches are even more complex since the traditional
cause of death (local or regional recurrence) is now rare
and most patients who die of disease succumb to distant
metastases (DM). Stage-for-Stage HPV-related OPC has
extremely favorable outcomes in terms of locoregional
control, overall survival, and outcome of salvage
treatments compared to traditional HNCs and the
evolution to current treatment intensity did not consider
HPV-related disease. The profiles of patients with HPV-
related OPC at risk of DM are now being better
understood. There is opportunity to modify approaches so
that intensive local treatment can be minimized while
patients at risk of DM are still selected for systemic
treatments. These strategies are being carefully explored
in clinical trials using risk-stratified approaches directed
by relevant end-points intended to safely return to less
intensive treatments analogous to those used in a previous
era.
SP-0192 Potential of radiation therapy to convert the
tumor into an in situ vaccine
S. Formenti1
1Weill Cornell Medical Center of Cornell University, New
York- NY, USA
Radiation therapy contributes both immunogenic and
immunosuppressive signals to the tumor
microenvironment. Preclinical strategies to enhance the
formers and/or mitigate the latter have demonstrated the
concrete possibility to shift this balancing act toward a
therapeutic success (J Natl Cancer Inst. 2013;105(4):256-
265). Preclinical experiments in several syngeneic mouse
models that mimic the setting of advanced cancer have
demonstrated promise of combining radiation and
immunotherapy. The preclinical data has consistently
found clinical confirmation. Particularly when combined
with immune checkpoint blockade, radiotherapy has
demonstrated to be a powerful adjuvant to
immunotherapy (Clin Cancer Res. 2005;11:728-734).
Clinical examples of synergy between radiation and
immune checkpoint inhibitors have been reported (N Engl
J Med. 2012;366(10):925-931; Transl Oncol.
2012;5(6):404-407; Int J Radiat Oncol Biol Phys.
2013;85(2):293-295; Cancer Immunol Res 2013;1(6):365-
372) and and interim results in our prospective clinical
trial confirm this finding (presented in room 1, May 17
session 051). Currently, multiple clinical trials are
exploring optimal combinations and scheduling of
radiotherapy and immunotherapy. Early evidence from
these trials confirms the hypothesis that radiation can
enhances responses to immune checkpoint inhibitors but
in the majority of patients tumors remain unresponsive,
warranting research to identify markers that predict
response. A recent study testing radiation with ipilimumab
in melanoma suggested that tumor expression of PDL-1
may predict lack of response to radiation and ipilimumab.
However, in lung cancer patients treated with radiation
and ipilimumab we found high PDL-1 expression among
patients achieving durable complete and partial
responses, without addition of PD-1 pathway inhibitors
(ASTRO Proceedings 2015, abstract #149). In fact, higher
expression of immune checkpoints has been hypothesized
as a marker of more immunogenic tumors (Science,
2015,October 9: 207-211). In addition, pre-treatment
mutational load has been found to be associated with
responses to immune checkpoint inhibitors (Science, 2015
Apr 3: 124-8). It will be important to determine if
radiation can compensate tumors with a low mutational
load, by inducing induce de novo T cell priming to multiple
tumor antigens (12) and could, therefore, achieve
responses in the absence of pre-existing neoantigens
(Science 2015;348(6230):69-74). The overall degree of
immune impairment of the patients may also be a critical
predictor of response to radiation + immunotherapy. For
instance, we found the pretreatment neutrophil /
lymphocyte ratio might enable a priori selection of
individuals with a propensity to develop abscopal
responses to the combination of radiation and GM-CSF
(Lancet Oncol. 2015 Jul;16(7):795-803). Strategies at
reducing radiation-induced lymphopenia are warranted to
assure adequate availability of naïve T cells when