To Bleed or Not to Bleed. A Prediction Based on Individual Gene Profiling Combined With Dose–Volume Histogram Shapes in Prostate Cancer Patients Undergoing Three-Dimensional Conformal Radiation Therapy

Worsening of 2-year patient-reported intestinal functionality after radiotherapy for prostate cancer including pelvic node irradiation

BACKGROUND AND PURPOSE

To quantify patient-reported 2-year intestinal toxicity (IT) from pelvic nodal irradiation (PNI) for prostate cancer. The association between baseline/acute symptoms and 2-year worsening was investigated.

MATERIALS AND METHODS

Patient-reported IT was prospectively assessed through the Inflammatory Bowel Disease Questionnaire (IBDQ), filled in at baseline, radiotherapy mid-point and end, at 3 and 6 months and every 6 months until 5 years. Two-year deterioration of IBDQ scores relative to the Bowel Domain was investigated for 400 patients with no severe baseline symptoms and with questionnaires available at baseline, 2 years, RT mid-point and/or end and at least three follow-ups between 3 and 18 months. The significance of the 2-year differences from baseline was tested. The association between baseline values and ΔAcute (the worst decline between baseline and RT mid-point/end) was investigated.

RESULTS

In the IBDQ lower scores indicate worse symptoms. A significant (p < 0.0001) 2-year mean worsening, mostly in the range of -0.2/-0.4 points on a 1-7 scale, emerged excepting one question (IBDQ29, "nausea/feeling sick"). This decline was independent of treatment intent while baseline values were associated with 2-year absolute scores. The ΔAcute largely modulated 2-year worsening: patients with ΔAcute greater than the first quartile (Q1) and ΔAcute less or equal than Q1 showed no/minimal and highly significant (p < 0.0001) deterioration, respectively. Rectal incontinence, urgency, frequency and abdominal pain showed the largest mean changes (-0.5/-1): risk of severe worsening (deemed to be of clinical significance if ≤ 2) was 3-5 fold higher in the ΔAcute ≤ Q1 vs ΔAcute > Q1 group (p < 0.0001).

CONCLUSION

A modest but significant deterioration of two-year patient-reported intestinal symptoms from PNI compared to baseline was found. Patients experiencing more severe acute symptoms are at higher risk of symptom persistence at 2 years, with a much larger prevalence of clinically significant symptoms.

Genetic predictors of radiation-induced morbidity in prostate cancer patients

Cancer survivors often face adverse effects of treatment, which have a significant impact on morbidity and mortality. Normal-tissue side effects following radiotherapy (RT), as one of therapeutic modalities, are common and may seriously affect quality of life which is especially important in long-term prostate cancer (PC) survivors. Upgrading in our knowledge in radiation biology have led to the better understanding that genetics plays a significant role in determining a patient's predisposition to developing late RT toxicity, leading to the new field of research called "radiogenomics". With the evolution of DNA sequencing technologies and genomic analysis, radiogenomics made an appearance as a state-of-the-art science in the field of personalized medicine with the goal of detection the genetic determinants RT adverse reactions. A single-nucleotide polymorphism (SNPs) - based assay could be used to predict the risk of RT side effects along with clinical features and treatment factors. Several SNPs have been identified that are associated with late radiation-induced morbidity in PC patients. Most importantly, these SNPs make up genes expressed in the tissues that are likely at the root of these symptoms, including the bladder, rectum, and small intestine, which are most exposed in PC RT. Furthermore, genome-wide association studies are likely to lead to an increasing number of genetic polymorphisms that can predict long-term RT complications. Finally, radiogenomics attempts to predict which PC patients will show radiosensitivity, so that radiation oncologists, as well as surgeons, can change treatment accordingly in order to reduce side effects or increase the RT effectiveness.

Gamma-H2AX Foci Decay Ratio as a Stronger Predictive Factor of Late Radiation Toxicity Than Dose-Volume Parameters in a Prospective Cohort of Prostate Cancer Patients

PURPOSE

Late radiation toxicity is a major dose-limiting factor in curative cancer radiation therapy. Previous studies identified several risk factors for late radiation toxicity, including both dose-volume factors and genetic predisposition. Herein, we investigated the contribution of genetic predisposition, particularly compared with dose-volume factors, to the risk of late radiation toxicity in patients treated with highly conformal radiation therapy.

METHODS AND MATERIALS

We included 179 patients with prostate cancer who underwent treatment with curative external beam radiation therapy between 2009 and 2013. Toxicity was graded according to the Common Terminology Criteria for Adverse Events version 4.0. Transcriptional responsiveness of homologous recombination repair genes and γ-H2AX foci decay ratios (FDRs) were determined in ex vivo irradiated lymphocytes in a previous analysis. Dose-volume parameters were retrieved by delineating the organs at risk (OARs) on CT planning images. Associations between risk factors and grade ≥2 urinary and bowel late radiation toxicities were assessed using univariable and multivariable logistic regression analyses. The analyses were performed using the highest toxicity grade recorded during the follow-up per patient.

RESULTS

The median follow-up period was 31 months. One hundred and one patients (56%) developed grade ≥2 late radiation toxicity. Cumulative rates for urinary and bowel grade ≥2 late toxicities were 46% and 17%, respectively. In the multivariable analysis, factors significantly associated with grade ≥2 late toxicity were transurethral resection of the prostate (P = .013), γ-H2AX FDR <3.41 (P = .008), and rectum V70 >11.52% (P = .017).

CONCLUSIONS

Our results suggest that impaired DNA double-strand break repair in lymphocytes, as quantified by γ-H2AX FDR, is the most critical determining factor of late radiation toxicity. The limited influence of dose-volume parameters could be due to the use of increasingly conformal techniques, leading to improved dose-volume parameters of the organs at risk.

Late Gastrointestinal Tolerance After Prostate Radiotherapy: Is the Anal Canal the Culprit? A Narrative Critical Review

INTRODUCTION

Late gastro-intestinal toxicities (LGIT) secondary to pelvic radiotherapy (RT) are well described in the literature. LGIT are mainly related to rectal or ano-rectal irradiation; however, involvement of the anal canal (AC) in the occurrence of LGIT remains poorly described and understood.

MATERIALS AND METHODS

The aim of this work was to explore the potential role of the AC in the development of LGIT after prostate irradiation and identify predictive factors that could be optimized in order to limit these toxicities. This narrative literature review was realized using the Pubmed database. We identified original articles published between June 1997 and July 2019, relating to LGIT after RT for localized prostate cancer and for which AC was identified independently. Articles defining the AC as part of an anorectal or rectal volume only were excluded.

RESULTS

A history of abdominal surgery or cardio-vascular risk, anticoagulant or tobacco use, and the occurrence of acute GIT during RT increases the risk of LGIT. A dose-effect relationship was identified between dose to the AC and development of LGIT. Identification and contouring of the AC and adjacent anatomical structures (muscles or nerves) are justified to apply specific dose constraints. As a limitation, our review mainly considered on 3DCRT which is no longer the standard of care nowadays; we did not identify any reports in the literature using moderately hypofractionated RT for the prostate and AC specific dosimetry.

CONCLUSION

These results suggest that the AC may have an important role in the development of LGIT after pelvic RT for prostate cancer. The individualization of the AC during planning should be recommended in prospective studies.

Radiation-induced damage in the lower gastrointestinal tract: Clinical presentation, diagnostic tests and treatment options

Radiation therapy is an important ally when treating malignant lesions in the pelvic area, but it is not exempt of adverse events. There are some measures that can be taken to reduce the possibility of these effects, but some are non-modifiable factors related to previous treatments, location of the lesions or comorbidities. There is a wide variety of clinical presentations that can be of an acute or chronic onset that go from mild to severe forms or that can have a great impact in the quality of life. Medical available therapies as metronidazole, sucralfate, mesalizine or probiotics, can be of aid although some lack of solid evidence of efficacy. Endoscopic treatment can be performed with argon plasma coagulation, bipolar cautery, radiofrequency, laser therapy or dilation. Hyperbaric therapy can be applied in refractory cases and surgery must be reserved to selected patients due to its high morbidity and mortality.

Identification of diagnostic and prognostic biomarkers, and candidate targeted agents for hepatitis B virus-associated early stage hepatocellular carcinoma based on RNA-sequencing data

Primary liver cancer is a rapidly progressing neoplasm with high morbidity and mortality rates. The present study aimed to identify potential diagnostic and prognostic biomarkers, and candidate targeted agents for hepatitis B virus (HBV)-associated early stage hepatocellular carcinoma (HCC). The gene expression profiles were extracted from the Gene Expression Omnibus database. Differentially expressed genes (DEGs), hub genes and the enrichment of signaling pathways were filtered out via a high-throughput sequencing method. The association between hub genes and the effects of the abnormal expression of hub genes on the rate of genetic variation, overall survival (OS), relapse-free survival (RFS), progression-free survival (PFS) and disease-free survival (DSS) of patients with HCC, as well as pathological stage and grade, were analyzed using different databases. A total of 1,582 DEGs were identified. Gene Ontology analysis revealed that the DEGs were mainly involved in the ‘oxidation-reduction process’, ‘steroid metabolic process’, ‘metabolic process’ and ‘fatty acid beta-oxidation’. Enrichment analysis of Kyoto Encyclopedia of Genes and Genomes pathways revealed that the DEGs were mainly associated with ‘metabolic pathways’, ‘PPAR signaling pathway’, ‘fatty acid degradation’ and the ‘cell cycle’. A total of 8 hub genes were extracted. Additionally, the abnormal expression levels of hub genes were closely associated with the OS, RFS, PFS and DSS of patients, the pathological stage and the grade. Furthermore, abnormal expression levels of the 8 hub genes were found in >30% of all samples. Several small molecular compounds that may reverse the altered DEGs were identified based on Connectivity Map analysis, including phenoxybenzamine, GW-8510, resveratrol, 0175029-0000 and daunorubicin. In conclusion, the dysfunction of fat metabolic pathways, the cell cycle, oxidation-reduction processes and viral carcinogenesis may serve critical roles in the occurrence of HBV-associated early stage HCC. The identified 8 hub genes may act as robust biomarkers for diagnosis and prognosis. Some small molecular compounds may be promising targeted agents against HBV-associated early stage HCC.

Refinement & validation of rectal wall dose volume objectives for prostate hypofractionation in 20 fractions

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LRB was correlated to irradiation technique and several % rectal wall cut points.

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The predictive role of dosimetric variables relates to the irradiation technique.

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Dose volume objectives for patients treated with IMRT/VMAT are reported.

Background and purpose

Dose-volume objectives for the rectum have been proposed to limit long term toxicity after moderately hypofractionated radiotherapy (MHRT) for localized prostate cancer. The purpose of the present study is to validate and possibly refine dose volume objective for the rectal wall after 20-fraction MHRT.

Materials and methods

All patients treated by 20-fraction MHRT at a single Institution were identified and relative rectal wall (%RW) DVH retrieved. The endpoint of the study is the development of grade 2+ late rectal bleeding (LRB) according to a modified RTOG scale. Clinical and dosimetric predictors of LRB were investigated at both uni- and multi-variable analysis.

Results

293 patients were identified and analyzed. Of them, 35 (12%) developed the endpoint. At univariable analysis, antithrombotic drug usage (yes vs no), technique (3DCRT vs IMRT/VMAT) and several %RW DVH cut-points were significantly correlated with LRB. However, within patients treated by 3DCRT (N = 106), a bi-variable model including anti-thrombotic drug usage and selected %RW dose/volume metrics failed to identify independent dosimetric predictors of LRB. Conversely, within patients treated with intensity modulation (N = 187), the same model showed a progressively higher impact of the percent of RW receiving doses above 40 Gy. Based on this model, we were able to confirm (V32), refine (V60) and identify a novel (V50) cut-point for the %RW.

Conclusion

We recommend the following dose volume objectives for the %RW in order to minimize the risk of LRB after 20-fraction MHRT: V32 ≤ 50%; V50 ≤ 25.8% and V60 ≤ 10%.

Evaluating the predictive value of quantec rectum tolerance dose suggestions on acute rectal toxicity in prostate carcinoma patients treated with IMRT

Aim

To investigate the predictive value of convenience of rectum dosimetry with Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) dose limits, maximum rectum dose (Dmax), total rectal volume (TVrectum), rectal volume included in PTV (VrectumPTV) on Grade 2-3 acute rectal toxicity for utilization in clinical practice.

Background

Numerous previous data have reported frequent acute proctitis after external-beam RT of prostate cancer. Predicting toxicity limited with dose information is inadequate in clinical practice due to comorbidities and medications used.

Materials and Method

Sixty-four non-metastatic prostate cancer patients treated with IMRT were enrolled. Patients were treated to a total dose of 70-76 Gy. Rectal dose volume histograms (DVH) of all patients were evaluated retrospectively, and a QUANTEC Score between 0 and 5 was calculated for each patient. The correlation between the rectal DVH data, QUANTEC score, TVrectum, VrectumPTV, rectum Dmax and Grade 2-3 rectal toxicity was investigated.

Results

In the whole group grade 1, 2 and 3 acute rectal toxicities were 25%, 18.8% and 3.1%, respectively. In the DVH data, rectum doses of all patients were under RTOG dose limits. Statistically significant correlation was found between grade 2-3 rectal toxicity and TVrectum (p = 0,043); however. It was not correlated with QUANTEC score, VrectumPTV and Dmax.

Conclusion

Our results were not able to show any significant correlation between increasing convenience with QUANTEC limits and lower rectal toxicity. Conclusively, new dosimetric definitions are warranted to predict acute rectal toxicity more accurately in prostate cancer patients during IMRT treatment.

Differentially Expressed Genes and Molecular Pathways in an Autochthonous Mouse Prostate Cancer Model

Prostate cancer remains a major public health problem and the second leading cause of cancer-related deaths in men in the United States. The present study aims to understand the molecular pathway(s) of prostate cancer which is essential for early detection and treatment. Dorsolateral prostate from 20 week transgenic adenocarcinoma of the mouse prostate (TRAMP) mice, which spontaneously develops prostate cancer and recapitulates human disease and age-matched non-transgenic littermates were utilized for microarray analysis. Mouse genome network and pathway analyses were mapped to the human genome using the Ingenuity Pathway Analysis (IPA) database for annotation, visualization, and integrated discovery. In total, 136 differentially expressed genes, including 32 downregulated genes and 104 upregulated genes were identified in the dorsolateral prostate of TRAMP, compared to non-transgenic mice. A subset of differentially expressed genes were validated by qRT-PCR. Alignment with human genome database identified 18 different classes of proteins, among these, 36% were connected to the nucleic acid binding, including ribosomal proteins, which play important role in protein synthesis—the most enriched pathway in the development of prostate cancer. Furthermore, the results suggest deregulation of signaling molecules (9%) and enzyme modulators (8%) affect various pathways. An imbalance in other protein classes, including transporter proteins (7%), hydrolases (6%), oxidoreductases, and cytoskeleton proteins (5%), contribute to cancer progression. Our study evaluated the underlying pathways and its connection to human prostate cancer, which may further help assess the risk of disease development and progression and identify potential targets for therapeutic intervention.

Nomogram to predict rectal toxicity following prostate cancer radiotherapy

BACKGROUND

To identify predictors of acute and late rectal toxicity following prostate cancer radiotherapy (RT), while integrating the potential impact of RT technique, dose escalation, and moderate hypofractionation, thus enabling us to generate a nomogram for individual prediction.

METHODS

In total, 972 patients underwent RT for localized prostate cancer, to a total dose of 70 Gy or 80 Gy, using two different fractionations (2 Gy or 2.5 Gy/day), by means of several RT techniques (3D conformal RT [3DCRT], intensity-modulated RT [IMRT], or image-guided RT [IGRT]). Multivariate analyses were performed to identify predictors of acute and late rectal toxicity. A nomogram was generated based on the logistic regression model used to predict the 3-year rectal toxicity risk, with its accuracy assessed by dividing the cohort into training and validation subgroups.

RESULTS

Mean follow-up for the entire cohort was 62 months, ranging from 6 to 235. The rate of acute Grade ≥2 rectal toxicity was 22.2%, decreasing when combining IMRT and IGRT, compared to 3DCRT (RR = 0.4, 95%CI: 0.3-0.6, p<0.01). The 5-year Grade ≥2 risks for rectal bleeding, urgency/tenesmus, diarrhea, and fecal incontinence were 9.9%, 4.5%, 2.8%, and 0.4%, respectively. The 3-year Grade ≥2 risk for overall rectal toxicity increased with total dose (p<0.01, RR = 1.1, 95%CI: 1.0-1.1) and dose per fraction (2Gy vs. 2.5Gy) (p = 0.03, RR = 3.3, 95%CI: 1.1-10.0), and decreased when combining IMRT and IGRT (RR = 0.50, 95% CI: 0.3-0.8, p<0.01). Based on these three parameters, a nomogram was generated.

CONCLUSIONS

Dose escalation and moderate hypofractionation increase late rectal toxicity. IMRT combined with IGRT markedly decreases acute and late rectal toxicity. Performing combined IMRT and IGRT can thus be envisaged for dose escalation and moderate hypofractionation. Our nomogram predicts the 3-year rectal toxicity risk by integrating total dose, fraction dose, and RT technique.

Comparison of different contouring definitions of the rectum as organ at risk (OAR) and dose-volume parameters predicting rectal inflammation in radiotherapy of prostate cancer: which definition to use?

OBJECTIVE

The objective of this retrospective planning study was to find a contouring definition for the rectum as an organ at risk (OAR) in curative three-dimensional external beam radiotherapy (EBRT) for prostate cancer (PCa) with a predictive correlation between the dose-volume histogram (DVH) and rectal toxicity.

METHODS

In a pre-study, the planning CT scans of 23 patients with PCa receiving definitive EBRT were analyzed. The rectum was contoured according to 13 different definitions, and the dose distribution was correlated with the respective rectal volumes by generating DVH curves. Three definitions were identified to represent the most distinct differences in the shapes of the DVH curves: one anatomical definition recommended by the Radiation Therapy Oncology Group (RTOG) and two functional definitions based on the target volume. In the main study, the correlation between different relative DVH parameters derived from these three contouring definitions and the occurrence of rectal toxicity during and after EBRT was studied in two consecutive collectives. The first cohort consisted of 97 patients receiving primary curative EBRT and the second cohort consisted of 66 patients treated for biochemical recurrence after prostatectomy. Rectal toxicity was investigated by clinical investigation and scored according to the Common Terminology Criteria for Adverse Events. Candidate parameters were the volume of the rectum, mean dose, maximal dose, volume receiving at least 60 Gy (V₆₀), area under the DVH curve up to 25 Gy and area under the DVH curve up to 75 Gy in dependence of each chosen rectum definition. Multivariable logistic regression considered other clinical factors such as pelvine lymphatics vs local target volume, diabetes, prior rectal surgery, anticoagulation or haemorrhoids too.

RESULTS

In Cohort 1 (primary EBRT), the mean rectal volumes for definitions "RTOG", planning target volume "(PTV)-based" and "PTV-linked" were 100 cm³ [standard deviation (SD) 43 cm³], 60 cm³ (SD 26 cm³) and 74 cm³ (SD 31 cm³), respectively (p < 0.01; analysis of variance). The mean rectal doses according to these definitions were 35 Gy (SD 8 Gy), 48 Gy (SD 4 Gy) and 44 Gy (SD 5 Gy) (p < 0.01). In Cohort 2 (salvage EBRT), the mean rectal volumes were 114 cm³ (SD 47 cm³), 64 cm³ (SD 26 cm³) and 81 cm³ (SD 30 cm³) (p < 0.01) and the mean doses received by the rectum were 36 Gy (SD 8 Gy), 49 Gy (SD 5 Gy) and 44 Gy (SD 5 Gy) (p < 0.01). Acute or subacute rectal inflammation occurred in 69 (71.9%) patients in Cohort 1 and in 43 (70.5%) in Cohort 2. We did not find a correlation between all investigated DVH parameters and rectal toxicity, irrespective of the investigated definition. By adding additional variables in multivariate analysis, the predictive ability was substantially improved. Still, there was essentially no difference in the probability of predicting rectal inflammation occurrence between the tested contouring definitions.

CONCLUSION

The RTOG anatomy-based recommendations are questionable in comparison with functional definitions, as they result in higher variances in several relative DVH parameters. Moreover, the anatomy-based definition is no better and no worse in the predictive value concerning clinical end points. Advances in knowledge: Functional definitions for the rectum as OAR are easier to apply, faster to contour, have smaller variances and do not offer less information than the anatomy-based RTOG definition.

Identification of a rectal subregion highly predictive of rectal bleeding in prostate cancer IMRT

BACKGROUND AND PURPOSE

To identify rectal subregions at risks (SRR) highly predictive of 3-year rectal bleeding (RB) in prostate cancer IMRT.

MATERIALS AND METHODS

Overall, 173 prostate cancer patients treated with IMRT/IGRT were prospectively analyzed, divided into "training" (n=118) and "validation" cohorts (n=53). Dose-volume histograms (DVHs) were calculated in three types of rectal subregions: "geometric", intuitively defined (hemi-rectum,…); "personalized", obtained by non-rigid registration followed by voxel-wise statistical analysis (SRRp); "generic", mapped from SRRps, located within 8×8 rectal subsections (SRRg). DVHs from patients with and without RB were compared and used for toxicity prediction.

RESULTS

Training cohort SRRps were primarily within the inferior anterior hemi-rectum and upper anal canal, with 3.8Gy mean dose increase for Grade⩾1 RB patients. The SRRg, representing 15% of the absolute rectal volume, was located in 10 inferior-anterior rectal subsections. V18-V70 for SRRps and V58-V65 for SRRg were significantly higher for RB patients than non-RB. Maximum areas under the curve (AUCs) for SRRp and SRRg RB prediction were 71% and 64%, respectively. The validation cohort confirmed the predictive value of SRRg for Grade⩾1 RB. The total cohort confirmed the predictive value of SRRg for Grade⩾2 RB. Geometrical subregions were not RB predictors.

CONCLUSION

The inferior-anterior hemi anorectum was highly predictive of RB.

No increase in toxicity of pelvic irradiation when intensity modulation is employed: clinical and dosimetric data of 208 patients treated with post-prostatectomy radiotherapy

OBJECTIVE

To compare the toxicity of image-guided intensity-modulated radiotherapy (IG-IMRT) to the pelvis or prostate bed (PB) only. To test the hypothesis that the potentially injurious effect of pelvic irradiation can be counterbalanced by reduced irradiated normal tissue volume using IG-IMRT.

METHODS

Between February 2010 and February 2012, 208 patients with prostate cancer were treated with adjuvant or salvage IG-IMRT to the PB (102 patients, Group PB) or the pelvis and prostate bed (P) (106 patients, Group P). The Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer criteria were used to evaluate toxicity.

RESULTS

Median follow-up was 27 months. Toxicity G ≥ 2 in Group PB: in the bowel acute and late toxicities were 11.8% and 10%, respectively; urinary acute and late toxicities were 10.8% and 15%, respectively. Toxicity G ≥ 2 in Group P: in the bowel acute and late toxicities were both 13.2%; urinary acute and late toxicities were 13.2% and 15.1%, respectively. No statistical difference in acute or late toxicity between the groups was found (bowel: p = 0.23 and p = 0.89 for acute and late toxicity, respectively; urinary: p = 0.39 and p = 0.66 for acute and late toxicity, respectively). Of the clinical variables, only previous abdominal surgery was correlated with acute bowel toxicity. Dosimetric parameters that correlated with bowel toxicity were identified.

CONCLUSION

The toxicity rates were low and similar in both groups, suggesting that IG-IMRT allows for a safe post-operative irradiation of larger volumes. Further investigation is warranted to exclude bias owing to non-randomized character of the study.

ADVANCES IN KNOWLEDGE

Our report shows that modern radiotherapy technology and careful planning allow maintaining the toxicity of pelvic lymph node treatment at the acceptable level, as it is in the case of PB radiotherapy.

Outcome modeling techniques for prostate cancer radiotherapy: Data, models, and validation

Prostate cancer is a frequently diagnosed malignancy worldwide and radiation therapy is a first-line approach in treating localized as well as locally advanced cases. The limiting factor in modern radiotherapy regimens is dose to normal structures, an excess of which can lead to aberrant radiation-induced toxicities. Conversely, dose reduction to spare adjacent normal structures risks underdosing target volumes and compromising local control. As a result, efforts aimed at predicting the effects of radiotherapy could invaluably optimize patient treatments by mitigating such toxicities and simultaneously maximizing biochemical control. In this work, we review the types of data, frameworks and techniques used for prostate radiotherapy outcome modeling. Consideration is given to clinical and dose-volume metrics, such as those amassed by the QUANTEC initiative, and also to newer methods for the integration of biological and genetic factors to improve prediction performance. We furthermore highlight trends in machine learning that may help to elucidate the complex pathophysiological mechanisms of tumor control and radiation-induced normal tissue side effects.

Urinary adverse effects of pelvic radiotherapy

Objective

Radiation is an integral part of the treatment of many pelvic tumors. The cellular death induced by radiotherapy (RT) benefits cancer control but can also result in adverse effects (AEs) on the organ being treated or those adjacent to it. RT for cancers of the pelvis (bladder, prostate, rectum, uterus or cervix) can result in AEs in the urinary tract. While the acute urinary AEs of pelvic RT are well described, late AEs are less well characterized. The burden of treatment for late AEs may be large given the prevalence of tumors in the pelvis and the high utilization of RT to treat them.

Review

For prostate cancer, grade 1 and 2 urinary AEs following external beam radiation therapy (EBRT) are reported to occur in 20-43% and 7-19%, respectively, with a follow up of 10 years. Three-year cumulative risk for grade ≥2 urinary AEs is 28-30%. Following brachytherapy (BT), rates of urinary AEs at 5 years are reported to be 36%, 24%, 6.2% and 0.1% for Radiation Therapy Oncology Group (RTOG) grade 1, 2, 3, and 4, respectively. For bladder cancer, with a median follow-up of 5 years, 7-12% of patients who receive RT experience urinary AEs of grade 3 or more. For cervical cancer, there remains a 0.25% per year risk of severe AEs for at least 25 years following RT, and ureteral stricture is a well-described AE. For endometrial cancer, severe urinary AEs are rare, but at 13 years of follow up, patients report a significantly worse quality of life with respect to urinary function. In rectal cancer, preoperative RT has a lower risk of AEs than postoperative RT, and few urinary AEs are reported in the literature.

Conclusions

Urinary AEs can manifest long after RT, and there is a paucity of studies describing rates of these long-term AEs. It is important that the possible complications of RT are recognized by providers and properly communicated to patients so that they are able to make informed decisions about their cancer treatment.

Incorporating Genetic Biomarkers into Predictive Models of Normal Tissue Toxicity

There is considerable variation in the level of toxicity patients experience for a given dose of radiotherapy, which is associated with differences in underlying individual normal tissue radiosensitivity. A number of syndromes have a large effect on clinical radiosensitivity, but these are rare. Among non-syndromic patients, variation is less extreme, but equivalent to a ±20% variation in dose. Thus, if individual normal tissue radiosensitivity could be measured, it should be possible to optimise schedules for individual patients. Early investigations of in vitro cellular radiosensitivity supported a link with tissue response, but individual studies were equivocal. A lymphocyte apoptosis assay has potential, and is currently under prospective validation. The investigation of underlying genetic variation also has potential. Although early candidate gene studies were inconclusive, more recent genome-wide association studies are revealing definite associations between genotype and toxicity and highlighting the potential for future genetic testing. Genetic testing and individualised dose prescriptions could reduce toxicity in radiosensitive patients, and permit isotoxic dose escalation to increase local control in radioresistant individuals. The approach could improve outcomes for half the patients requiring radical radiotherapy. As a number of patient- and treatment-related factors also affect the risk of toxicity for a given dose, genetic testing data will need to be incorporated into models that combine patient, treatment and genetic data.

Exploiting biological and physical determinants of radiotherapy toxicity to individualize treatment

The recent advances in radiation delivery can improve tumour control probability (TCP) and reduce treatment-related toxicity. The use of intensity-modulated radiotherapy (IMRT) in particular can reduce normal tissue toxicity, an objective in its own right, and can allow safe dose escalation in selected cases. Ideally, IMRT should be combined with image guidance to verify the position of the target, since patients, target and organs at risk can move day to day. Daily image guidance scans can be used to identify the position of normal tissue structures and potentially to compute the daily delivered dose. Fundamentally, it is still the tolerance of the normal tissues that limits radiotherapy (RT) dose and therefore tumour control. However, the dose-response relationships for both tumour and normal tissues are relatively steep, meaning that small dose differences can translate into clinically relevant improvements. Differences exist between individuals in the severity of toxicity experienced for a given dose of RT. Some of this difference may be the result of differences between the planned dose and the accumulated dose (DA). However, some may be owing to intrinsic differences in radiosensitivity of the normal tissues between individuals. This field has been developing rapidly, with the demonstration of definite associations between genetic polymorphisms and variation in toxicity recently described. It might be possible to identify more resistant patients who would be suitable for dose escalation, as well as more sensitive patients for whom toxicity could be reduced or avoided. Daily differences in delivered dose have been investigated within the VoxTox research programme, using the rectum as an example organ at risk. In patients with prostate cancer receiving curative RT, considerable daily variation in rectal position and dose can be demonstrated, although the median position matches the planning scan well. Overall, in 10 patients, the mean difference between planned and accumulated rectal equivalent uniform doses was -2.7 Gy (5%), and a dose reduction was seen in 7 of the 10 cases. If dose escalation was performed to take rectal dose back to the planned level, this should increase the mean TCP (as biochemical progression-free survival) by 5%. Combining radiogenomics with individual estimates of DA might identify almost half of patients undergoing radical RT who might benefit from either dose escalation, suggesting improved tumour cure or reduced toxicity or both.

Predictive value of PAK6 and PSMB4 expression in patients with localized prostate cancer treated with dose-escalation radiation therapy and androgen deprivation therapy

PURPOSE

The present study analyzed the expression by immunochemistry of the novel markers P21-activated protein kinase 6 (PAK6) and proteasome beta-4 subunit (PSMB4) in men with localized prostate cancer (PC) who were treated with dose-escalation radiotherapy (RT) and androgen deprivation therapy.

MATERIALS AND METHODS

Between 1996 and 2004, a cohort of 129 patients with PC who underwent diagnostic biopsies pretreatment and 24 to 36 months following RT were enrolled in this study. Suitable archival diagnostic tissue was obtained from 89 patients. Median follow-up was 129 months (48-198). Correlation analysis was done to assess association between PAK6 and PSMB4 expression and clinical outcome.

RESULTS

PAK6 and PSMB4 were expressed in the cytoplasm in 62% and 96.7% of diagnostic biopsies, respectively. Increased staining for PAK6 was significantly (P = 0.04) correlated with higher Gleason scores. In the multivariate analysis, the intensity of PSMB4 staining was an independent predictor of local relapse (hazard ratio = 8.6, P = 0.04).

CONCLUSIONS

To our knowledge, this is the first description of PAK6 and PSMB4 expression in the diagnostic specimens of men with PC who were treated with RT. If confirmed by further studies, increased expression of these genes could be used to identify patients at a high risk of developing local failure following high-dose RT, thus better tailoring treatments for the individual patient.

Long term rectal function after high-dose prostatecancer radiotherapy: results from a prospective cohort study

PURPOSE

To prospectively evaluate long-term late rectal bleeding (lrb) and faecal incontinence (linc) after high-dose radiotherapy (RT) for prostate cancer in the AIROPROS 0102 population, and to assess clinical/dosimetric risk factors.

MATERIALS AND METHODS

Questionnaires of 515 patients with G0 baseline incontinence and bleeding scores (follow-up ≥6 years) were analysed. Correlations between lrb/linc and many clinical and dosimetric parameters were investigated by univariate and multivariate logistic analyses. The correlation between lrb/linc and symptoms during the first 3 years after RT was also investigated.

RESULTS

Of 515 patients lrb G1, G2 and G3 was found in 32 (6.1%), 2 (0.4%) and 3 (0.6%) patients while linc G1, G2 and G3 was detected in 50 (9.7%), 3 (0.6%) and 3 (0.6%), respectively. The prevalence of G2-G3 lrb events was significantly reduced compared to the first 3-years (1% vs 2.7%, p=0.016) ≥G1 lrb was significantly associated with V75 Gy (OR=1.07). In multivariate analysis, ≥G1 linc was associated with V40 Gy (OR=1.015), use of antihypertensive medication (OR=0.38), abdominal surgery before RT (OR=4.7), haemorrhoids (OR=2.6), and G2-G3 acute faecal incontinence (OR=4.4), a nomogram to predict the risk of long-term ≥G1 linc was proposed. Importantly, the prevalence of ≥G1 linc was significantly correlated with the mean incontinence score during the first 3 years after RT (OR=16.3).

CONCLUSIONS

Long-term (median: 7 years) rectal symptoms are prevalently mild and strongly correlated with moderate/severe events occurring in the first 3 years after RT. Linc was associated with several risk factors.

Reducing rectal injury during external beam radiotherapy for prostate cancer

Rectal bleeding and faecal incontinence are serious injuries that men with prostate cancer who receive radiotherapy can experience. Although technical advances--including the use of intensity-modulated radiotherapy coupled with image-guided radiotherapy--have enabled the delivery of dose distributions that conform to the shape of the tumour target with steep dose gradients that reduce the dose given to surrounding tissues, radiotherapy-associated toxicity can not be avoided completely. Many large-scale prospective studies have analysed the correlations of patient-related and treatment-related parameters with acute and late toxicity to optimize patient selection and treatment planning. The careful application of dose-volume constraints and the tuning of these constraints to the individual patient's characteristics are now considered the most effective ways of reducing rectal morbidity. Additionally, the use of endorectal balloons (to reduce the margins between the clinical target volume and planning target volume) and the insertion of tissue spacers into the region between the prostate and anterior rectal wall have been investigated as means to further reduce late rectal injury. Finally, some drugs and other compounds are also being considered to help protect healthy tissue. Overall, a number of approaches exist that must be fully explored in large prospective trials to address the important issue of rectal toxicity in prostate cancer radiotherapy.

Management of intestinal complications in patients with pelvic radiation disease

Gastrointestinal toxicity after radiotherapy for pelvic cancer is a major complication-the most commonly reported symptoms include rectal bleeding, diarrhea, and fecal incontinence, which substantially impair patients' quality of life. Management of these symptoms can be a challenge, although available treatment strategies generally are ignored or underused. Radiation-induced symptoms have multiple mechanisms of pathogenesis; the first step for the correct management is to identify the mechanism that is causing the symptoms. Optimal management requires close liaisons among physicians, gastroenterologists with specialist interests, radiotherapists, oncologists, dieticians, nurses, and surgeons. Patients should be reassured that treatment options (medical, endoscopic, and surgical) exist and are in most cases successful if patients are referred to experts in pelvic radiation disease. However, although new therapeutic approaches are not yet always supported by high-quality trials, research projects are underway to improve management of patients. Clinicians should focus on using proven treatments correctly and avoiding misuse.

(Radio)biological optimization of external-beam radiotherapy

“Biological optimization” (BIOP) means planning treatments using (radio)biological criteria and models, that is, tumour control probability and normal-tissue complication probability. Four different levels of BIOP are identified: Level I is “isotoxic” individualization of prescription dose D_presc at fixed fraction number. D_presc is varied to keep the NTCP of the organ at risk constant. Significant improvements in local control are expected for non-small-cell lung tumours. Level II involves the determination of an individualized isotoxic combination of D_presc and fractionation scheme. This approach is appropriate for “parallel” OARs (lung, parotids). Examples are given using our BioSuite software. Hypofractionated SABR for early-stage NSCLC is effectively Level-II BIOP. Level-III BIOP uses radiobiological functions as part of the inverse planning of IMRT, for example, maximizing TCP whilst not exceeding a given NTCP. This results in non-uniform target doses. The NTCP model parameters (reflecting tissue “architecture”) drive the optimizer to emphasize different regions of the DVH, for example, penalising high doses for quasi-serial OARs such as rectum. Level-IV BIOP adds functional imaging information, for example, hypoxia or clonogen location, to Level III; examples are given of our prostate “dose painting” protocol, BioProp. The limitations of and uncertainties inherent in the radiobiological models are emphasized.

[Role of hypofractionated radiotherapy in the treatment of prostate cancer: a review]

BACKGROUND

Radiotherapy of prostate cancers, over the last few years, has been an alternative choice to radical prostatectomy in the case of localised cancers as well as being the preferred treatment in both advanced localised cancers and those of the elderly. A conventional course of prostate radiotherapy consisting of four to five sessions a week, lasts between 7 and 8 weeks plus about one week of preparation.

MATERIALS AND METHODS

A systematic review of the scientific literature based on Pubmed, along with an exhaustive review of randomised studies presented at international congresses, have made it possible to analyse the numerous therapeutic regimens available other than the conventional normofractioned one (i.e. with doses per session ranging between 1.8 and 2.2 grays).

RESULTS

Five randomised trials reported since 2005, plus several thousand patients treated by stereotaxic radiotherapy, have given rise to numerous scientific questions; these alternative hypofractioned courses (dose per fraction higher than 2.2 grays) have a potentially enhanced antitumoral efficacity along with the practical advantages of a shortened duration of radiotherapy.

CONCLUSION

The aim of this analysis of the scientific literature on hypofractioning in prostate cancer radiotherapy is to gather all the scientific evidence we currently have at our disposal. Further mature results of future randomised trials will have to be examined before modifying current practice.

A bioinformatics filtering strategy for identifying radiation response biomarker candidates

The number of biomarker candidates is often much larger than the number of clinical patient data points available, which motivates the use of a rational candidate variable filtering methodology. The goal of this paper is to apply such a bioinformatics filtering process to isolate a modest number (<10) of key interacting genes and their associated single nucleotide polymorphisms involved in radiation response, and to ultimately serve as a basis for using clinical datasets to identify new biomarkers. In step 1, we surveyed the literature on genetic and protein correlates to radiation response, in vivo or in vitro, across cellular, animal, and human studies. In step 2, we analyzed two publicly available microarray datasets and identified genes in which mRNA expression changed in response to radiation. Combining results from Step 1 and Step 2, we identified 20 genes that were common to all three sources. As a final step, a curated database of protein interactions was used to generate the most statistically reliable protein interaction network among any subset of the 20 genes resulting from Steps 1 and 2, resulting in identification of a small, tightly interacting network with 7 out of 20 input genes. We further ranked the genes in terms of likely importance, based on their location within the network using a graph-based scoring function. The resulting core interacting network provides an attractive set of genes likely to be important to radiation response.

Late rectal bleeding after 3D-CRT for prostate cancer: development of a neural-network-based predictive model

The aim of this study was to develop a model exploiting artificial neural networks (ANNs) to correlate dosimetric and clinical variables with late rectal bleeding in prostate cancer patients undergoing radical radiotherapy and to compare the ANN results with those of a standard logistic regression (LR) analysis. 718 men included in the AIROPROS 0102 trial were analyzed. This multicenter protocol was characterized by the prospective evaluation of rectal toxicity, with a minimum follow-up of 36 months. Radiotherapy doses were between 70 and 80 Gy. Information was recorded for comorbidity, previous abdominal surgery, use of drugs and hormonal therapy. For each patient, a rectal dose-volume histogram (DVH) of the whole treatment was recorded and the equivalent uniform dose (EUD) evaluated as an effective descriptor of the whole DVH. Late rectal bleeding of grade ≥ 2 was considered to define positive events in this study (52 of 718 patients). The overall population was split into training and verification sets, both of which were involved in model instruction, and a test set, used to evaluate the predictive power of the model with independent data. Fourfold cross-validation was also used to provide realistic results for the full dataset. The LR was performed on the same data. Five variables were selected to predict late rectal bleeding: EUD, abdominal surgery, presence of hemorrhoids, use of anticoagulants and androgen deprivation. Following a receiver operating characteristic analysis of the independent test set, the areas under the curves (AUCs) were 0.704 and 0.655 for ANN and LR, respectively. When evaluated with cross-validation, the AUC was 0.714 for ANN and 0.636 for LR, which differed at a significance level of p = 0.03. When a practical discrimination threshold was selected, ANN could classify data with sensitivity and specificity both equal to 68.0%, whereas these values were 61.5% for LR. These data provide reasonable evidence that results obtained with ANNs are superior to those achieved with LR when predicting late radiotherapy-related rectal bleeding. The future introduction of patient-related personal characteristics, such as gene expression profiles, might improve the predictive power of statistical classifiers. More refined morphological aspects of the dose distribution, such as dose surface mapping, might also enhance the overall performance of ANN-based predictive models.

Is it time to tailor the prediction of radio-induced toxicity in prostate cancer patients? Building the first set of nomograms for late rectal syndrome

PURPOSE

Development of user-friendly tools for the prediction of single-patient probability of late rectal toxicity after conformal radiotherapy for prostate cancer.

METHODS AND MATERIALS

This multicenter protocol was characterized by the prospective evaluation of rectal toxicity through self-assessed questionnaires (minimum follow-up, 36 months) by 718 adult men in the AIROPROS 0102 trial. Doses were between 70 and 80 Gy. Nomograms were created based on multivariable logistic regression analysis. Three endpoints were considered: G2 to G3 late rectal bleeding (52/718 events), G3 late rectal bleeding (24/718 events), and G2 to G3 late fecal incontinence (LINC, 19/718 events).

RESULTS

Inputs for the nomogram for G2 to G3 late rectal bleeding estimation were as follows: presence of abdominal surgery before RT, percentage volume of rectum receiving >75 Gy (V75Gy), and nomogram-based estimation of the probability of G2 to G3 acute gastrointestinal toxicity (continuous variable, which was estimated using a previously published nomogram). G3 late rectal bleeding estimation was based on abdominal surgery before RT, V75Gy, and NOMACU. Prediction of G2 to G3 late fecal incontinence was based on abdominal surgery before RT, presence of hemorrhoids, use of antihypertensive medications (protective factor), and percentage volume of rectum receiving >40 Gy.

CONCLUSIONS

We developed and internally validated the first set of nomograms available in the literature for the prediction of radio-induced toxicity in prostate cancer patients. Calculations included dosimetric as well as clinical variables to help radiation oncologists predict late rectal morbidity, thus introducing the possibility of RT plan corrections to better tailor treatment to the patient's characteristics, to avoid unnecessary worsening of quality of life, and to provide support to the patient in selecting the best therapeutic approach.

Ubiquitin-proteasome genes as targets for modulation of cisplatin sensitivity in fission yeast

Background

The ubiquitin(Ub)-proteasome pathway is implicated in the regulation of a variety of cellular functions and plays a major role in stress response in eukaryotic cells, by targeting misfolded and damaged proteins for degradation. In addition, in the presence of DNA damage, the Ub-proteasome system regulates proteins involved in sensing, repairing, and/or tolerating the damage. Antitumor agents such as cisplatin can activate the pathway, but the role of specific pathway components in cell sensitivity/response to the drug is not known. Since platinum compounds represent clinically relevant antitumor agents and a major limitation to their use is the development of drug resistance, there is an urgent need for identifying targets for improving their efficacy.

Results

In the present study, we performed a genome-wide screening for sensitivity to cisplatin using non-essential haploid deletion mutants of the fission yeast Schizosaccharomyces pombe, belonging to a collection of haploid strains constructed through homologous recombination. Using this approach, we identified three Ub-proteasome mutants exhibiting hypersensitivity to cisplatin (ubp16, ubc13 and pmt3) and ten mutants (including ufd2, beta7 20S, rpt6/let1) resistant to the drug. In addition, the importance of lub1 gene emerged from the comparison between the present screening and gene expression profile data previously obtained in fission yeast.

Conclusions

The factors identified in the present study allowed us to highlight most finely the close relationship between the Ub-proteasome system and DNA damage response mechanisms, thus establishing a comprehensive framework of regulators likely relevant also in higher eukaryotes. Our results provide the proof of principle of the involvement of specific genes modulated by cisplatin treatment in cell response to the drug, suggesting their potential role as targets for modulating cisplatin sensitivity. In this regard, the prospective identification of novel targets for modulation of cisplatin sensitivity in an eukaryotic model organism appears particularly intriguing towards the discovery of strategies to overcome cisplatin resistance in human tumors.

Predictors of acute bowel toxicity in patients treated with IMRT whole pelvis irradiation after prostatectomy

PURPOSE/OBJECTIVE

Whole pelvis irradiation with IMRT (WPRT-IMRT) after prostatectomy is efficient in reducing acute toxicity: however, a number of patients still experience moderate acute bowel toxicity.

MATERIALS AND METHODS

Ninety-six patients treated with WPRT-IMRT after prostatectomy with adjuvant or salvage intent were analysed. A number of parameters were individually recovered, including the DVHs of the intestinal cavity outside PTV and of the loops referred to both the WPRT phase and the whole treatment. Correlation between clinical-dosimetric parameters and acute bowel toxicity was investigated by logistic analyses. Best predictive cut-off values for continuous variables were assessed by ROC curves.

RESULTS

15/96 (15.6%) Patients experienced grade 2 toxicity (no grade 3). Best dose-volume predictors were the fraction of loops receiving more than 45, 50 and 55 Gy (respectively, V45TL ≥ 50cc, V50TL ≥ 13cc, V55TL ≥ 3cc; p-values ranging from 0.005 to 0.027). Age, GU acute toxicity, rectal acute toxicity and time between prostatectomy and IMRT were also predictors of acute bowel toxicity. Multivariate analysis showed that the most predictive independent parameters were age (OR: 1.13; 95%CI: 1.02-1.25; p=0.021) and V50TL (≥ 13cc, OR: 8.2; 95%CI: 1.7-40; p=0.009).

CONCLUSIONS

The risk of moderate acute uGI toxicity during WPRT-IMRT for post-operatively treated patients increases with age; the risk is substantially reduced in patients with small overlap between PTV and loops.