Hypofractionated Radiation Therapy (66 Gy in 22 Fractions at 3 Gy per Fraction) for Favorable-Risk Prostate Cancer: Long-term Outcomes

Long-Term Outcomes of Dose-Escalated Hypofractionated Radiotherapy in Localized Prostate Cancer

This retrospective study aimed to provide some clinical outcomes regarding effectiveness, toxicity, and quality of life in PCa patients treated with dose-escalated moderately hypofractionated radiation therapy (HFRT). Patients received HFRT to a total dose of 66 Gy in 22 fractions (3 Gy/fraction) delivered via volume modulated arc therapy (VMAT) in 2011-2016. Treatment effectiveness was measured by the biochemical failure-free survival rate. Toxicity was assessed according to the criteria of the Radiation Therapy Oncology Group (RTOG) and quality of life according to the criteria of the European Organization for Research and Treatment of Cancer (EORTC). In this regard, quality of life (QoL) was measured longitudinally, at a median of 2 and 5 years after RT. Enrolled patients had low-risk (40.2%), intermediate-risk (47.5%), and high-risk (12.3%) PCa. Median follow-up was 75 months. The biochemical failure-free survival rate was 94.2%. The incidence of acute grade 2 or higher gastrointestinal (GI) and genitourinary (GU) toxicity was 9.84% and 28.69%, respectively. The incidence rate of late grade 2 or higher GI and GU toxicity was 1.64% and 4.10%, respectively. Expanded Prostate Cancer Index Composite (EPIC) scores showed that the majority of patients maintained their QoL. HFRT to 66 Gy with VMAT was associated with adequate biochemical control, low toxicity and good reported GU and GI quality of life.

Retrospective comparison of rectal toxicity between carbon-ion radiotherapy and intensity-modulated radiation therapy based on treatment plan, normal tissue complication probability model, and clinical outcomes in prostate cancer

This retrospective study assessed the treatment planning data and clinical outcomes for 152 prostate cancer patients: 76 consecutive patients treated by carbon-ion radiation therapy and 76 consequtive patients treated by moderate hypo-fractionated intensity-modulated photon radiation therapy. These two modalities were compared using linear quadratic model equivalent doses in 2 Gy per fraction for rectal or rectal wall dose-volume histogram, 3.6 Gy per fraction-converted rectal dose-volume histogram, normal tissue complication probability model, and actual clinical outcomes. Carbon-ion radiation therapy was predicted to have a lower probability of rectal adverse events than intensity-modulated photon radiation therapy based on dose-volume histograms and normal tissue complication probability model. There was no difference in the clinical outcome of rectal adverse events between the two modalities compared in this study.

Plasmonic gel nanocomposites for detection of high energy electrons

Radiation therapy is a common treatment modality employed in the treatment of cancer. High energy photons are the primary source of radiation but when administered, they leave an exit dose resulting in radiation damage to the adjacent healthy tissues. To overcome this, high energy electrons are employed in cases of skin cancer to minimize radiation induced toxicity. Despite these advances, measurement of delivered radiation remains a challenge due to limitations with existing dosimeters including labor intensive fabrication, complex read-out techniques and post-irradiation instability. To overcome these limitations, we have developed a novel colorimetric plasmonic gel nanocomposite for the detection of therapeutic levels of radiation delivered in electron beam therapy. The plasmonic nanocomposite consists of an agarose gel matrix encapsulating precursor gold ions, which are reduced to gold nanoparticles as a result of exposure to high energy electrons. The formation of gold nanoparticles renders a change in color to the agarose matrix, resulting in the formation of plasmonic gel nanocomposites. The intensity of the color formed exhibits a linear relation with the delivered electron dose, which can be quantified using absorbance spectroscopy. The plasmonic gel nanocomposites were able to detect doses employed in fractionated electron therapy, including in an anthropomorphic phantom used for planning radiation treatments in the clinic. Furthermore, the use of glutathione as a quenching agent facilitated qualitative and quantitative spatial mapping of the delivered dose. Our results indicate that the ease of fabrication, simplicity of detection and quantification using absorbance spectroscopy, determination of spatial dose profiles, and relatively low cost make the plasmonic gel nanocomposite technology attractive for detecting electron doses in the clinic.

Urinary quality of life outcomes in men who were treated with image-guided intensity-modulated radiation therapy for prostate cancer

PURPOSE

Quality of life (QoL) outcomes play a major role in the treatment selection for prostate cancer (CaP). We evaluated the urinary QoL outcomes in men who were treated with image-guided intensity-modulated radiation therapy (IG-IMRT) for CaP.

METHODS AND MATERIALS

We enrolled men who were diagnosed with CaP and underwent IG-IMRT in a large urological group practice into a prospectively maintained database. The typical radiation treatment dosage to prostates and seminal vesicles was 8100 cGy in 45 fractions. Urinary QoL was self-assessed using the standardized incontinence grade and International Prostate Symptom Score (IPSS) at baseline and at each follow-up visit. We evaluated the cumulative incidence of urinary incontinence and changes in both continence and IPSS over time.

RESULTS

Of the 3602 men who were eligible for analysis, 3086 (85.7%) had no urinary incontinence; 479 (13.3 %) had minimal incontinence (no requirement for pads), and 37 (1.0 %) had significant urinary incontinence that required the use of pads or interfered with activities of daily living, at baseline. After a median follow-up of 24 months (range: 12.0-41.0 months), these numbers were 80.6%, 17.4%, and 2.0%, respectively. Radiation therapy appeared to have a beneficial effect on some men: 54.1% of men with minimal incontinence became completely continent of urine during follow-up. Of those with significant urinary incontinence, 29.7% reported resolution and 27.0% reported improved symptoms with no requirement for pads. Of the 1276 men with moderate IPSS, the mean IPSS decreased from 12 to 9.8 at the time of the last follow-up (P < .001). Similarly, of the 233 men with severe IPSS, the mean IPSS decreased from 24 to 13 at the time of the last follow-up (P < .001).

CONCLUSION

IG-IMRT for clinically localized CaP is associated with a relatively low incidence of urinary incontinence. Although unexplained, IG-IMRT seems to improve symptoms in some men with baseline urinary incontinence and moderate-to-severe IPSS.

Treatment outcomes with hypofractionated high-dose radiation therapy for prostate cancer

AIM

To report the treatment results of a retrospective cohort of prostate cancer patients treated with Hypo-RT with a high equivalent biological effective dose (BED).

BACKGROUND

Hypofractionated radiotherapy (Hypo-RT) has gained popularity and interest in the treatment of prostate cancer. However, there are few experiences with adequate follow-up reporting treatment results using high equivalent dose with Hypo-RT.

MATERIALS AND METHODS

We assigned 149 men with low-, intermediate- and high-risk prostate cancer to receive Hypo-RT with a total dose of 69 Gy/23 fractions. Late gastrointestinal (GI) and genitourinary (GU) toxicity were prospectively evaluated according to modified RTOG criteria. Biochemical no evidence of disease (bNED) was defined as the nadir prostate-specific antigen level plus 2 ng/mL.

RESULTS

The median follow-up was 53 months. For the entire cohort, the 5-year bNED rate was 94.6%, and for low-, intermediate- and high-risk patients the 5-year bNED was 100%, 96.4%, and 86% (p = 0.007), respectively. The 5-year overall survival rate was 92%. Only 1 patient died from the disease at 48 months after treatment, giving a 5-year cancer-specific survival of 98%. The worst grade ≥2 rate GI and GU toxicity was 13.4% and 14%, respectively. No grade >3 toxicity was observed. The presence of grade ≥2 GI and GU toxicity at the last follow-up was only 1.3% and 3%, respectively.

CONCLUSIONS

Hypo-RT (69 Gy/23 fractions) with a high equivalent BED produces excellent rates of biochemical control for low, intermediate and high-risk prostate cancer. The long term GU and GI toxicity rates were considered low and acceptable.

Target margins in radiotherapy of prostate cancer

We reviewed the literature on the use of margins in radiotherapy of patients with prostate cancer, focusing on different options for image guidance (IG) and technical issues. The search in PubMed database was limited to include studies that involved external beam radiotherapy of the intact prostate. Post-prostatectomy studies, brachytherapy and particle therapy were excluded. Each article was characterized according to the IG strategy used: positioning on external marks using room lasers, bone anatomy and soft tissue match, usage of fiducial markers, electromagnetic tracking and adapted delivery. A lack of uniformity in margin selection among institutions was evident from the review. In general, introduction of pre- and in-treatment IG was associated with smaller planning target volume (PTV) margins, but there was a lack of definitive experimental/clinical studies providing robust information on selection of exact PTV values. In addition, there is a lack of comparative research regarding the cost-benefit ratio of the different strategies: insertion of fiducial markers or electromagnetic transponders facilitates prostate gland localization but at a price of invasive procedure; frequent pre-treatment imaging increases patient in-room time, dose and labour; online plan adaptation should improve radiation delivery accuracy but requires fast and precise computation. Finally, optimal protocols for quality assurance procedures need to be established.

Predicting toxicity in radiotherapy for prostate cancer

This comprehensive review addresses most organs at risk involved in planning optimization for prostate cancer. It can be considered an update of a previous educational review that was published in 2009 (Fiorino et al., 2009). The literature was reviewed based on PubMed and MEDLINE database searches (from January 2009 up to September 2015), including papers in press; for each section/subsection, key title words were used and possibly combined with other more general key-words (such as radiotherapy, dose-volume effects, NTCP, DVH, and predictive model). Publications generally dealing with toxicity without any association with dose-volume effects or correlations with clinical risk factors were disregarded, being outside the aim of the review. A focus was on external beam radiotherapy, including post-prostatectomy, with conventional fractionation or moderate hypofractionation (<4Gy/fraction); extreme hypofractionation is the topic of another paper in this special issue. Gastrointestinal and urinary toxicity are the most investigated endpoints, with quantitative data published in the last 5years suggesting both a dose-response relationship and the existence of a number of clinical/patient related risk factors acting as dose-response modifiers. Some results on erectile dysfunction, bowel toxicity and hematological toxicity are also presented.

Strategy for stochastic dose-rate induced enhanced elimination of malignant tumour without dose escalation

The efficacy of radiation therapy, a primary modality of cancer treatment, depends in general upon the total radiation dose administered to the tumour during the course of therapy. Nevertheless, the delivered radiation also irradiates normal tissues and dose escalation procedure often increases the elimination of normal tissue as well. In this article, we have developed theoretical frameworks under the premise of linear-quadratic-linear (LQL) model using stochastic differential equation and Jensen's inequality for exploring the possibility of attending to the two therapeutic performance objectives in contraposition-increasing the elimination of prostate tumour cells and enhancing the relative sparing of normal tissue in fractionated radiation therapy, within a prescribed limit of total radiation dose. Our study predicts that stochastic temporal modulation in radiation dose-rate appreciably enhances prostate tumour cell elimination, without needing dose escalation in radiation therapy. However, constant higher dose-rate can also enhance the elimination of tumour cells. In this context, we have shown that the sparing of normal tissue with stochastic dose-rate is considerably more than the sparing of normal tissue with the equivalent constant higher dose-rate. Further, by contrasting the stochastic dose-rate effects under LQL and linear-quadratic (LQ) models, we have also shown that the LQ model over-estimates stochastic dose-rate effect in tumour and under-estimates the stochastic dose-rate effect in normal tissue. Our study indicates the possibility of utilizing stochastic modulation of radiation dose-rate for designing enhanced radiation therapy protocol for cancer.

Practical aspects and uncertainty analysis of biological effective dose (BED) regarding its three-dimensional calculation in multiphase radiotherapy treatment plans

PURPOSE

There is a growing interest in the radiation oncology community to use the biological effective dose (BED) rather than the physical dose (PD) in treatment plan evaluation and optimization due to its stronger correlation with radiobiological effects. Radiotherapy patients may receive treatments involving a single only phase or multiple phases (e.g., primary and boost). Since most treatment planning systems cannot calculate the analytical BED distribution in multiphase treatments, an approximate multiphase BED expression, which is based on the total physical dose distribution, has been used. The purpose of this paper is to reveal the mathematical properties of the approximate BED formulation, relative to the true BED.

METHODS

The mathematical properties of the approximate multiphase BED equation are analyzed and evaluated. In order to better understand the accuracy of the approximate multiphase BED equation, the true multiphase BED equation was derived and the mathematical differences between the true and approximate multiphase BED equations were determined. The magnitude of its inaccuracies under common clinical circumstances was also studied. All calculations were performed on a voxel-by-voxel basis using the three-dimensional dose matrices.

RESULTS

Results showed that the approximate multiphase BED equation is accurate only when the dose-per-fractions (DPFs) in both the first and second phases are equal, which occur when the dose distribution does not significantly change between the phases. In the case of heterogeneous dose distributions, which significantly vary between the phases, there are fewer occurrences of equal DPFs and hence the inaccuracy of the approximate multiphase BED is greater. These characteristics are usually seen in the dose distributions being delivered to organs at risk rather than to targets.

CONCLUSIONS

The finding of this study indicates that the true multiphase BED equation should be implemented in the treatment planning systems due to the inconsistent accuracy of the approximate multiphase BED equation in most of the clinical situations.

Treatment outcome of localized prostate cancer by 70 Gy hypofractionated intensity-modulated radiotherapy with a customized rectal balloon

Purpose

We aimed to analyze the treatment outcome and long-term toxicity of 70 Gy hypofractionated intensity-modulated radiotherapy (IMRT) for localized prostate cancer using a customized rectal balloon.

Materials and Methods

We reviewed medical records of 86 prostate cancer patients who received curative radiotherapy between January 2004 and December 2011 at our institution. Patients were designated as low (12.8%), intermediate (20.9%), or high risk (66.3%). Thirty patients received a total dose of 70 Gy in 28 fractions over 5 weeks via IMRT (the Hypo-IMRT group); 56 received 70.2 Gy in 39 fractions over 7 weeks via 3-dimensional conformal radiotherapy (the CF-3DRT group, which served as a reference for comparison). A customized rectal balloon was placed in Hypo-IMRT group throughout the entire radiotherapy course. Androgen deprivation therapy was administered to 47 patients (Hypo-IMRT group, 17; CF-3DRT group, 30). Late genitourinary (GU) and gastrointestinal (GI) toxicity were evaluated according to the Radiation Therapy Oncology Group criteria.

Results

The median follow-up period was 74.4 months (range, 18.8 to 125.9 months). The 5-year actuarial biochemical relapse-free survival rates for low-, intermediate-, and high-risk patients were 100%, 100%, and 88.5%, respectively, for the Hypo-IMRT group and 80%, 77.8%, and 63.6%, respectively, for the CF-3DRT group (p < 0.046). No patient presented with acute or late GU toxicity ≥grade 3. Late grade 3 GI toxicity occurred in 2 patients (3.6%) in the CF-3DRT group and 1 patient (3.3%) in the Hypo-IMRT group.

Conclusion

Hypo-IMRT with a customized rectal balloon resulted in excellent biochemical control rates with minimal toxicity in localized prostate cancer patients.

Different rectal toxicity tolerance with and without simultaneous conventionally-fractionated pelvic lymph node treatment in patients receiving hypofractionated prostate radiotherapy

PURPOSE

To investigate added morbidity associated with the addition of pelvic elective nodal irradiation (ENI) to hypofractionated radiotherapy to the prostate.

METHODS AND MATERIALS

Two-hundred twelve patients, treated with hypofractionated radiotherapy to the prostate between 2004 and 2011, met the inclusion criteria for the analysis. All patients received 70 Gy to the prostate delivered over 28 fractions and 103 (49%) received ENI consisting of 50.4 Gy to the pelvic lymphatics delivered simultaneously in 1.8 Gy fractions. The mean dose-volume histograms were compared between the two subgroups defined by use of ENI, and various dose-volume parameters were analyzed for effect on late lower gastrointestinal (GI) and genitourinary (GU) toxicity.

RESULTS

Acute grade 2 lower GI toxicity occurred in 38 (37%) patients receiving ENI versus 19 (17%) in those who did not (p = 0.001). The Kaplan-Meier estimate of grade ≥ 2 lower GI toxicity at 3 years was 15.3% for patients receiving ENI versus 5.3% for those who did not (p = 0.026). Each rectal isodose volume was increased for patients receiving ENI up to 50 Gy (p ≤ 0.021 for each 5 Gy increment). Across all patients, the absolute V70 of the rectum was the only predictor of late GI toxicity. When subgroups, defined by the use of ENI, were analyzed separately, rectal V70 was only predictive of late GI toxicity for patients who received ENI. For patients receiving ENI, V70 > 3 cc was associated with an increased risk of late GI events.

CONCLUSIONS

Elective nodal irradiation increases the rates of acute and late GI toxicity when delivered simultaneously with hypofractioanted prostate radiotherapy. The use of ENI appears to sensitize the rectum to hot spots, therefore we recommend added caution to minimize the volume of rectum receiving 100% of the prescription dose in these patients.

Image-guided hypofractionated radiotherapy in low-risk prostate cancer patients

Aim. To evaluate efficacy and toxicity of image-guided hypofractionated radiotherapy (HFRT) in the treatment of low-risk prostate cancer. Outcomes and toxicities of this series of patients were compared to another group of 32 low-risk patients treated with conventional fractionation (CFRT). Methods. Fifty-nine patients with low-risk prostate cancer were analysed. Total dose for the prostate and proximal seminal vesicles was 60 Gy delivered in 20 fractions. Results. The median follow-up was 30 months. The actuarial 4-year overall survival, biochemical free survival, and disease specific survival were 100%, 97.4%, and 97.4%, respectively. Acute grade 1-2 gastrointestinal (GI) and genitourinary (GU) toxicity rates were 11.9% and 40.7%, respectively. Grade 1 GI and GU late toxicity rates were 8.5% and 13.6%, respectively. No grade ≥2 late toxicities were recorded. Acute grade 2-3 GU toxicity resulted significantly lower (P = 0.04) in HFRT group compared to the CFRT group. The cumulative 4-year incidence of grade 1-2 GU toxicity was significantly higher (P < 0.001) for HFRT patients. Conclusions. Our study demonstrated that hypofractionated regimen provided excellent biochemical control in favorable risk prostate cancer patients. The incidence of GI and GU toxicity was low. However, HFRT presented higher cumulative incidence of low-grade late GU toxicity than CFRT.