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Tumor Discovery SRT with SIP planning for synovial sarcoma

for 6 months at 40 mg q24 h. Treatment was ended as 3 months, restaging CT scan described partial response
planned on July 20, and the full planned schedule was (RECIST 1.1 criteria), and she was found negative for
delivered. After 30 days from the end of RT, the patient disease relapse during clinical visit.
was visited for monitoring acute toxicity. She was in good The last patient follow-up was in January 2023.
clinical condition (ECOG PS1) and complained of only G1 She was in excellent performance status (PS0), clinical
dyspepsia, whereas her body weight remained stable. After
examination, and whole-body CT scan showed the
absence of disease (RECIST 1.1 criteria) 15 months after
Table 1. Dosimetric objectives (in black) and results (in blue)
concerning PTV treatment (Figure 6).

Target Dosimetric objectives 3. Discussion
PTV_FULL D80% > 40 Gy 3.1. Radiobiological and dosimetric considerations
36 Gy The intrinsic radioresistant phenotype, the site of tumor
PTV_SIP D70% > 32 Gy spread, and the possible consequences of a locoregional
27 Gy progression suggested us to attempt the maximization
PTV_SIB D95% > 42.75 Gy of tumor control probability through extreme
45 Gy hypofractionation. Another keypoint was represented by
PTV_FULL: Planning target volume obtained by adding a margin to the relatively paucity of other effective therapeutic options
internal target volume accounting for set-up errors and unpredictable in case of disease progression. Unfortunately, the upper
organ motion; PTV_SIP: PTV simultaneous integrated protection, abdomen represents a paradigm for planning complexities,
obtained by intersection between PTV and planning respect volumes given the presence of frequent tumor abutment near critical
of stomach, duodenum, and jejunum; PTV_SIB: The area inside the
PTV distant at least 7 mm from planning respect volumes of stomach, OARs, tumor motion, and OARs motion, and despite
duodenum, and jejunum cutting-edge SRT techniques, the intrinsic radiosensitivity
of most of the visceral OARs in the upper abdomen limits
Table 2. Dose constraints (in black) and dosimetric results the delivery of therapeutic doses.
(in blue) for organs at risk Taken these aspects together, we decided to perform a
OAR D 0,1cc D 2cc D 20cc feasibility study exploiting a relatively new concept of RT
(Gy) (Gy) (Gy) planning. SIP was defined by Brunner et al. as a deliberated
IM_DUODENUM ≤38 ≤32 ≤24 and calculated reduction in the dose prescription in area
34 31.8 15 of PTV overlapped with critical OARs . First published
[25]
IM_STOMACH ≤38 ≤32 ≤24 experiences seem to show a fair toxicity profile and a
38 32 26 promising local control result for radioresistant histological
IM_JEJUNUM ≤38 ≤32 ≤24 tumor types [26-30] .
38 28 18
PRV IM_DUODENUM/IM_ ≤40 ≤36 ≤28
STOMACH/IM_JEJUNUM/IM_COLON met met met
OAR Dmax D D 10cc
(Gy) 0.2cc (Gy)
(Gy)
Spinal chord <30 <22.5 -
met met
Great vessels <55 - <47
met met
OAR CONSTRAINT (Gy)
Vascular axis of kidney D66% <23
Met
Kidney at least 200cc <15 Gy (rV15): <15
Met
Liver at least 700cc <21 Gy (rV21): ≤21
Met Figure 6. The last follow-up computed tomography at 15 months from
OAR: Organ at risk; IM: Internal margin; PRV: Planning respect treatment showing complete regression of the mass and the free plane of
volume; met means that the dose constraint was respected the lesser gastric curvature.

Volume 2 Issue 2 (2023) 5 https://doi.org/10.36922/td.356