Initial report of the genitourinary and gastrointestinal toxicity of post-prostatectomy proton therapy for prostate cancer patients undergoing adjuvant or salvage radiotherapy

Figures & data

Figure 1. Representative dose color-wash distribution for post-prostatectomy PT using opposed lateral beams—contours: CTV (pink), PTV (navy), bladder (yellow), rectum (brown), right femoral head (orange), left femoral head (green), and ERB (purple). Daily imaging and alignment technique using the ERB with diluted contrast for visualization and alignment of the ARW with the PB CTV on daily kV-kV imaging.

Table 1. Post-prostatectomy PT cohort baseline demographic, clinical, and treatment characteristics.

N		100
Age (yrs)	Median (Range)	64	(42–77)
Race/ethnicity	White	70	70%
	Black	21	21%
	Unknown	5	5%
	Asian	3	3%
	Hispanic	1	1%
Preoperative PSA (ng/mL)	Mean (Range)	8.46 ± 8.70	(0.46–57.60)
Surgery type	Radical retropubic prostatectomy	23	23%
	Radical perineal prostatectomy	1	1%
	Radical robotic assisted prostatectomy	68	68%
	Unknown	8	8%
Pathologic tumor stage	T2	51	51%
	T3	46	46%
	T4	1	1%
	Unknown	2	2%
Pathologic nodal stage	N0	88	88%
	N1	9	9%
	Unknown	3	3%
Pathologic gleason score	5	1	1%
	6	12	12%
	7	65	65%
	8	12	12%
	9	10	10%
Margin status	Positive	59	59%
	Negative	34	34%
	Unknown	7	7%
Pre-RT PSA (ng/mL)	Mean (range)	0.76 ± 1.57	(0–8.50)
Months Post-operative	Median (range)	25	(5–216)
Comorbid Conditions	HTN	40	40%
	Hypercholesterolemia	17	17%
	Hemorrhoids	11	11%
	DM	10	10%
	GU PMH	70	70%
Patient reported outcomes	IPSS	6.6 ± 6.1
	IPSS bother	2.1 ± 1.7
	IIEF	10.4 ± 7.3
	EPIC bowel function	90.8 ± 10.8
	EPIC bowel bother	93.3 ± 11.2
Field	WP and PB	20	20%
	PB only	80	80%
Modality	Proton only	69	69%
	Proton and IMRT	31	31%
Proton technique	Passive scattering	13	13%
	Pencil beam scanning	86	86%
	Passive scattering and pencil beam scanning	1	1%
Prescribed dose (Gy RBE)	66.6	3	3%
	70.2	89	89%
	75.6	8	8%
Concurrent ADT	Yes	34	34%
	No	66	66%

PSA: prostate specific antigen; RT: radiotherapy; GU PMH: genitourinary past medical history defined as an antecedent history of significant urinary sign or symptoms, including benign prostatic hyperplasia, prior transurethral resection of the prostate, bladder outlet obstruction, and/or lower urinary tract symptoms; IPSS: International prostate symptom score; IIEF: International index of erectile function; EPIC: expanded prostate cancer index composite.

Table 2. Acute and late maximum GU and GI CTCAE v 4.0 toxicities for post-prostatectomy PT.

Toxicity	GU		GI
Grade	Acute^a	Late^b	Acute^a	Late^b
0	14 (14.0)	14 (17.7)	66 (66.0)	58 (73.4)
1	71 (71.0)	49 (62.0)	34 (34.0)	21 (26.6)
2	15 (15.0)	16 (20.3)	–	–

N = 100 during PT and up 3 months after completion.

N = 79 patients with minimum 3 months follow up. There were no grade ≥3 toxicities.

GU: genitourinary; GI: gastrointestinal; CTCAE: common terminology criteria for adverse events.

Table 3. Frequency of specific maximum GU grade 2 toxicities with post-prostatectomy PT.

GU toxicity	Acute (N = 100)	Late (N = 79)
Frequency	3 (3)	9 (11.4)
Retention	3 (3)	1 (1.3)
Incontinence	11 (11)	5 (6.3)
Hematuria	0 (0)	4 (5.1)
Tract pain	1 (1)	1 (1.3)
Urgency	2 (2)	4 (5.1)
Total	15 (15)	16 (20.3)

Figure 2. Kaplan-Meier survival estimates for late (A) GU grade 2 and (B) GI grade 1 toxicity–free survival for post-prostatectomy PT.

Figure 3. Patient reported outcomes (mean ± standard deviation) at baseline and after post-prostatectomy PT.

Figure 4. Comparative mean dose volume histograms for bladder-related parameters and GU and rectal-related parameters and GI acute toxicities. The shaded regions (gray and pink) represent the standard deviations for each curve with the red shaded region representing the area of overlap between the 2 curves.