International Journal of Radiation Oncology*Biology*Physics
Clinical InvestigationRectal Dose–Volume Differences Using Proton Radiotherapy and a Rectal Balloon or Water Alone for the Treatment of Prostate Cancer
Introduction
Chronic rectal toxicity remains one of the most important dose-limiting factors for the treatment of prostate cancer. Rectal toxicity has been related to the volume of the rectum and rectal wall radiated 1, 2, 3, 4, 5, 6, 7, 8, 9. Furthermore, limiting rectal dose on the basis of normal tissue constraints has been found to decrease this toxicity. As such, chronic rectal toxicity will be determined by the rectum dose–volume curve and not the dose prescribed to the target 3, 4.
A rectal balloon (RB) has the theoretical advantage of distending the rectal wall and moving it away from the high-dose area anteriorly 7, 10, 11, 12, 13. Thus it decreases the relative volume of rectum or rectal wall radiated to intermediate and high doses. For photon therapy, it also has the relative advantage of increasing rectal air volume, thereby decreasing the dose at the inner rectal wall (13).
Although an RB may likewise decrease the relative volume of the rectum or rectal wall radiated in proton therapy, it may provide only a small absolute advantage because of the low rectal doses being delivered. Furthermore, for proton therapy water is used in the RB to better control the proton dose distribution and decrease inhomogeneities due to the air–tissue interface. Thus proton therapy will not necessarily have the potential advantage of decreasing the inner rectal wall dose seen with photons. Water alone, however, may distend the rectum adequately during the course of proton therapy, obviating the need for an RB.
We analyzed 30 proton plans for 15 patients who underwent CT and MRI scans with RB or water alone. We analyzed the volumes of the rectum, rectal wall, and rectal wall at the level of the planning target volume (PTV) for this analysis.
Section snippets
Methods and Materials
Thirty plans on 15 consecutive patients treated between August 2006 and October 2006 on one of our three institutional review board–approved prostate proton protocols (UFPTI 0001, UFPTI 0002, and UFPTI 0003) were selected for the present analysis. All patients had American Joint Committee on Cancer Stage II (T1–T2N0M0) clinically confined disease to the prostate.
Results
Characteristics of the variables included for this analysis can be seen in Table 1. Rectum volumes were larger with the RB for all cases, resulting in a 35% relative difference. Absolute and relative differences were also seen for the rectal wall and modified rectal wall 7-cm volumes when using an RB. The rectal wall volume defined by a 3-mm-thick rim represents a volume–surface area approximation of the rectal contents excluding nonrectal tissue in the cavity. Thus, the rectal wall defines the
Discussion
Multiple randomized and prospective trials have shown an advantage for high-dose radiation 15, 16, 17, 18, 19, 20, 21. Chronic rectal toxicity, however, continues to be one of the dose-limitating factors in prostate cancer therapy 2, 3, 4, 5, 6, 8, 22, 23, 24 A clear dose–volume relationship has been demonstrated for rectal toxicity in radiotherapy for prostate cancer, which calls for new ways to decrease the rectal dose using proton therapy and rectal distention, either with an RB or with
Conclusions
We observed good compliance and low rectal doses regardless of whether water alone or an RB was used. An RB provides selected patients with a small but significant dosimetric advantage in proton prostate radiotherapy. However, most patients will derive no benefit, and some may actually be at risk for increased toxicity with an RB. Water alone was well tolerated and will benefit most patients. Careful selection has the potential to improve the therapeutic ratio of proton treatment for either an
References (29)
- et al.
Endoscopic scoring of late rectal mucosal damage after conformal radiotherapy for prostatic carcinoma
Radiother Oncol
(2000) - et al.
Rectal sequelae after conformal radiotherapy of prostate cancer: Dose-volume histograms as predictive factors
Radiother Oncol
(2001) - et al.
Phase II dose escalation study of image-guided adaptive radiotherapy for prostate cancer: Use of dose-volume constraints to achieve rectal isotoxicity
Int J Radiat Oncol Biol Phys
(2005) - et al.
Dose-volume analysis of predictors for chronic rectal toxicity after treatment of prostate cancer with adaptive image-guided radiotherapy
Int J Radiat Oncol Biol Phys
(2005) - et al.
Late rectal bleeding after conformal radiotherapy of prostate cancer. II. Volume effects and dose-volume histograms
Int J Radiat Oncol Biol Phys
(2001) - et al.
Risk factors of late rectal bleeding after carbon ion therapy for prostate cancer
Int J Radiat Oncol Biol Phys
(2006) - et al.
Proctitis after external-beam radiotherapy for prostate cancer classified by Vienna Rectoscopy Score and correlated with EORTC/RTOG score for late rectal toxicity: Results of a prospective multicenter study of 166 patients
Int J Radiat Oncol Biol Phys
(2007) - et al.
Dose-volume histograms associated to long-term colorectal functions in patients receiving pelvic radiotherapy
Radiother Oncol
(2005) - et al.
Estimation of the incidence of late bladder and rectum complications after high-dose (70-78 GY) conformal radiotherapy for prostate cancer, using dose-volume histograms
Int J Radiat Oncol Biol Phys
(1998) - et al.
3-D conformal radiotherapy of localized prostate cancer: A subgroup analysis of rectoscopic findings prior to radiotherapy and acute/late rectal side effects
Radiother Oncol
(2006)
Rectal dose sparing with a balloon catheter and ultrasound localization in conformal radiation therapy for prostate cancer
Radiother Oncol
Rectal wall sparing by dosimetric effect of rectal balloon used during intensity-modulated radiation therapy (IMRT) for prostate cancer
Med Dosim
Treatment of prostate cancer with radiotherapy: Should the entire seminal vesicles be included in the clinical target volume?
Int J Radiat Oncol Biol Phys
Prostate cancer radiation dose response: Results of the M. D. Anderson phase III randomized trial
Int J Radiat Oncol Biol Phys
Cited by (25)
Preliminary Analysis of a Phase II Trial of Stereotactic Body Radiation Therapy for Prostate Cancer With High-Risk Features After Radical Prostatectomy
2023, Advances in Radiation OncologyCitation Excerpt :One of the theoretical advantages of using SBRT in this scenario is based on the proposed α/β of 1.5 for prostate cancer, for which 30 Gy in 6 Gy fractions and 32 Gy in 6.4 Gy fractions (5 treatments) would be a dose equivalent in 2 Gy fractions of 64 and 72 Gy, respectively. Considering an estimated α/β of 3.5 for normal tissue, a dose equivalent in 2 Gy fractions of only 52 and 58 Gy would be delivered to the portions of the rectum or bladder receiving total prescription doses.15-17,27-34 Beyond radiobiologic advantages, a much shorter treatment schedule offers patients convenience beyond being more cost-effective compared with other RT modalities.35
The technological basis for adaptive ion beam therapy at MedAustron: Status and outlook
2018, Zeitschrift fur Medizinische PhysikCitation Excerpt :Prostate patients treated at MedAustron receive four very thin markers (GoldAnchor, Stockholm, Sweden) that are implanted under ultrasound guidance. Furthermore, the rectum is filled with 100 ml of saline solution [18]. In addition, patients have to follow a specific drinking protocol, i.e. the bladder is emptied half an hour before treatment and then the patients have to drink 500 ml of water to establish a comfortably filled bladder during treatment.
Patient-reported Quality of Life After Proton Beam Therapy for Prostate Cancer: The Effect of Prostate Size
2017, Clinical Genitourinary CancerA significant decrease in rectal volume and diameter during prostate IMRT
2011, Radiotherapy and OncologyCitation Excerpt :Prostate motion as well as its relationship with RV variability during the course of radiotherapy is not a new concern. Many institutions have implemented various rectal fixation strategies to improve reproducibility, including rectal balloon [38,41–45], ultrasound [32,46], radio-opaque markers [27,28,47], and on board imaging [26,39,48–53]. The feasibility of some of these modalities is limited by the fact that they can be invasive and some require additional costs.
Is there a role for endorectal balloons in prostate radiotherapy? A systematic review
2010, Radiotherapy and OncologyCitation Excerpt :It was originally designed as an endorectal coil in magnetic resonance imaging (MRI) and the balloon has a concave shape for optimal conformation to the prostatic-rectal interface. In prostate RT 60, 80, and 100 cc of inflated air have been reported [24,30,31], resulting in balloon diameters of 4.0–4.5 cm. The second ERB (ERB2) is a 5-cm-long silkolatex balloon, fixed on a 30-cm-long two-way rectal tube, made of soft rubber with a silkolatex coating, used for barium enema procedures (Nordmann, Rüsch AG, Kernen, Germany).
Dosimetric Changes Resulting From Patient Rotational Setup Errors in Proton Therapy Prostate Plans
2009, International Journal of Radiation Oncology Biology Physics
Conflict of interest: none.