Clinical results from first use of prostate stent as fiducial for radiotherapy of prostate cancer

Figures & data

Figure 1. Patient flow diagram. A total of 150 eligible patients, fulfilling the inclusion criteria, were screened. One hundred accepted participation and gave informed consent. Seven patients went off study. Reasons for patients to go off-study were a) two patients refused to accept further waiting time for a second stent after failed insertion of the first stent, b) in three patients previously unknown stricture in the urethra was discovered during insertion, c) one patient had the stent removed as urine outlet was obstructed (unrecognized TURP patient), d) one patient experienced an iatrogenic displacement during an unplanned cystoscopy. In the remaining 93 patients a Memocore™ were inserted in 61 patients and a Memokath™ in 32. The stent migrated in three patients.

Figure 2. The memory shape Nickel-Titanium (Ni-Ti) prostate stents used as fiducial in the study. Both stents are shown in their expanded form. Both stents are made from 0.65 mm diameter Ni-Ti wire. The length of the stent is adapted to the individual length of the prostate part of urethra prior to insertion. a) The Memocore™ stent used in case the prostate part of urethra less than or equal to 40 mm. b) The Memokath™ stent used in case the prostate part of urethra of more than 40 mm.

Table I. Demographics for patients treated with the stent (n = 90).

Age
Median	68 years
Range	55–78 years
TNM
T1	22
T2	23
T3	45
Gleason Score
6	11
7	60
8	7
9	12
PSA
Median	14.0 ng/ml
Range	3–93 ng/ml
Risk Group
Low (PSA < 10 ng/ml Gleason <7 T1-T2a)	3
Intermediate (PSA 10–20 ng/ml Gleason = 7 T2b-T2c)	20
High (PSA > 20 ng/ml and Gleason > 7 T3-T4)	67

Figure 3. Plot of prostate volumes outlined on pre-radiotherapy and mid-radiotherapy MR scans. Black dots represent the three patients in whom a potential partial migration was estimated comparing sagittal MR images from the two MR scans. Other patients are represented by a white dot. a) Mid-treatment MR prostate volume (MRmid) plotted against the prostate pre-treatment volume outlined on MR (MRpre). Data are from the 90 patients in whom volumes were available in both MR scans. Error bars represents change in volume if the radius of the prostate is changed plus or minus one millimetre. b) Mismatch in MR volumes in co-registered MR volumes were defined as MRpre-MRmid and MRmid - MRpre. A corresponding theoretical difference (CAP_2mm) was calculated assuming that the prostate is a sphere and the stent has partial migrated 2 mm between MR scans. Difference between the CAP_2mm volume and the two mismatch volumes are plotted in Any true migration of equal to or more than 2 mm should give a dot in the grey area.

Table II. Acute toxicities related to insertion and removal of fiducials in the prostate, i.e. gold markers or prostate stent.

Ref.	Procedure	N	Urinary Tract Infection	Urinary Retention	Incontinence	Dysuria	Haematuria	Rectal bleeding	Pain severe
[8]	Biopsy	1051	11%	2%		7%	16%	3%
[9]	GM	177					15%	4%	9%
[10]	GM	209	2%			2%	4%	9%	15%
[11]	GM	12				12%	25%	8%
[12]	Stent	211	6%	10%	7%		3%		3%
This study	Stent insertion	97	1%	6%	6%	7%	7%		10%
This study	Stent removal	87	1%	16%			3%		5%

N = number of patients; GM = gold marker. Blank cells means that no data was available.

Table III. Acute urinary toxicities estimated using the International Prostate Symptom Score (IPSS) patient questionnaire.

				IPSS Change from Baseline
Ref.		N	IPSS Baseline	Stent	RTmid	RTend	Stent Removed
[13]	Seed	166	3			13
[14]	Seed	172	7.5			12
[15]	GM	55	12			10
This study	GM	60	9		5	8
This study	Stent	56	11	2	7	9	−1

Seed = patients treated with iodine seeds; GM = gold marker. N = number of patients; Baseline = median IPSS value before seed, GM or stent insertion; Stent = median IPSS change from baseline 1–2 weeks after insertion of stent; RTmid = median value of IPSS change from baseline IPSS half way trough radiotherapy; RTend = median IPSS change from baseline IPSS at the end of radiotherapy; Stent removed = median value of IPSS change from baseline one month after stent removal; Blank cells mean no data was available.

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