A review of plan library approaches in adaptive radiotherapy of bladder cancer

Figures & data

Table 1. Summary of included studies.

Author, year, study type	Patient no.	ART method	Library size	Additional time (min)	Technique used	Partial/whole bladder	Full/empty bladder
® Burridge 2006 [19]	20	Different CTV-PTV margins applied	3	Recognised as necessary but not specified	3DCRT	–	Empty
℗ Foroudi 2009 [27]	5	Boolean, mean and smallest CTV	3	7	3DCRT	Whole bladder	Empty
℗ Lalondrelle 2009 [14]	15	Three successive CT scans	3	15-20 overall	3DCRT	Whole bladder	Emptied before first scan
℗ Foroudi 2010 [16]	27	Composite	3	5-8	3DCRT	Whole bladder	Empty
® Wright 2010 [44]	2	Based on planning and four CBCT	5	–	IMRT	Whole bladder + integrated boost	–
℗ Vestergaard 2010 [26]	10	3 methods	3	–	IMRT	Whole bladder	Empty
℗ Kron 2010 [20]	27	Composite	3	–	3DCRT	Whole bladder	Empty
℗ Tuomikoski 2011 [28]	5	Four successive CT scans	3–4	5–10	VMAT	Whole bladder + partial boost	Emptied and drank water
® Murthy 2011 [33]	10	Isotropic PTVs	6	21 overall	Helical tomotherapy	–	Both
® Hutton, 2012 [23]	10	Composite volume	3	7	–	Both	Empty
℗ Kuyumcian 2012 [46]	26	Composite method	3	Recognised but not specified	3DCRT	–	Empty
℗ Meijer 2012 [35]	20	Two planning CT and interpolation	6	12	IMRT	Whole bladder + SIB	Full
℗ Tuomikoski 2013 [30]	5	Four successive CT scans	3–4	–	VMAT	Both	Emptied and drank water
℗ McDonald 2013 [13]	25	Composite	3	<14 min	3DCRT	–	Empty
® Vestergaard 2013 [24]	7	Composite	3	–	IMRT	–	Empty
® Webster 2013 [39]	20	Comparison of plan library and composite	4	Recognised as necessary but not specified	3DCRT	Whole bladder	Empty
℗ Foroudi 2014 [29]	50	Composite	3	–	3DCRT	Whole bladder	Empty
® Vestergaard 2014 [38]	13	DVF vs. composite	3	–	–	–	Empty
℗ Vestergaard 2014 [25]	20	Composite	3	8	VMAT	–	Empty
℗ Gronberg 2015 [32]	9	Composite CTV (planning and CBCT)	3	Recognised as necessary but not specified	VMAT	–	Empty
℗ Lutkenhaus 2015 [37]	10	Two planning CT and interpolation	5	Recognised as necessary but not specified	VMAT	Whole bladder + lymph nodes	Full
℗ Murthy 2015 [34]	44	Anisotropic PTV margins	3 or 6	Recognised as necessary but not specified	Tomotherapy based IMRT	Whole bladder ± SIB	Both
® Tuomikoski 2015 [28]	10	Comparison (multiple CT vs. CBCT scans)	CT = 4CBCT = 3	–		Whole bladder	CT = full CBCT = empty
® Canlas 2016 [31]	8	CTV based on CT with five anisotropic margins.	5	Recognised as necessary but not specified	–	Whole bladder	Empty

®: retrospective study; ℗: prospective study.

Table 2. Summary of review endpoints.

Endpoint	Studies that support endpoint	Studies that refute endpoint
1. Plan libraries improve accuracy for bladder cancer.	The plan library approach overcame intra-fractional bladder filling [27,30–32,37].Allowed for geometric verification [11,13,14,16,19,23–34].The conventional plan was used in small number of patients only [14,16,29].A plan library of three plans is uncomplicated, safe and efficient [19,34,46].Plan library reduces the incidence of a geometric miss [14].No significant intra-fraction movements or changes in bladder filling [35].Better and/or improved PTV coverage [19,23,25,31,32,35,38].Improved CTV coverage [14,16,31,39].Minimises dose to organs at risk [13,14,16,19,23–25,27,32–35,38,44].Minimises dose to small bowel at high dose levels [27,30,31,37].Imaging dose can be adjusted [19,20,26,28].Potentially improves the therapeutic ratio [13,19,25,34,35].	Risk of geographical miss due to intra-fractional bladder filling [33].Risk of geometric miss [47].Inaccuracies in matching to skeletal surrogates [27].The conventional plan was deemed most appropriate in the majority of  patients [27].No plan in the plan library was deemed suitable [14,16,28,29,32,35].Geographical misses caused by confusion [28,35].In appropriate plan choice [29,35].Bladder CTV after treatment had expanded outside the chosen plan [29,33].Fails to account for rectal and bowel filling [26,37,47].No significant difference between adaptive and non-adaptive strategies in terms of  target coverage [37,39].Poor CTV coverage (offline protocol) and insufficient coverage in 9% of patients  (online protocol) [29].Dose constraints could not be met [25].Higher integral dose due to increased frequency of imaging (if 5 cGy) [20].Higher integral dose due to numerous CT imaging [28,30].Any gain from the individualised approach is offset by the less conformal  conventional plan used at the start [46].Not suitable for all patients [14,24,25].
2. Plan libraries are feasible in the clinical setting for bladder cancer.	High concordance of plan selection among therapists [13,14,19,23,31].Technology is available to allow plan libraries to be used in the clinical setting [11].Concluded plan library to treat bladder cancer is feasible [13,14,23,25,28].	A large inter-observer variability for plan choice after training [46].Difficulties with choosing a plan for partial bladder irradiation [27].Availability of technology may hinder its implementation [27,33,39,47].Additional training was given, which costs time and money [11,12,32,37,39].Increased treatment time [16,21,22,25–27,29,37].Resource implications, daily workflow is affected due to longer treatment slots and  treatment planning [19,27,34,39,47].Failure of pilot to multi-centre study [29].

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