Intensity-modulated radiotherapy for prostate cancer implementing molecular imaging with 18F-choline PET-CT to define a simultaneous integrated boost

Focal Boost in Prostate Cancer Radiotherapy: A Review of Planning Studies and Clinical Trials

BACKGROUND

Focal boost radiotherapy was developed to deliver elevated doses to functional sub-volumes within a target. Such a technique was hypothesized to improve treatment outcomes without increasing toxicity in prostate cancer treatment.

PURPOSE

To summarize and evaluate the efficacy and variability of focal boost radiotherapy by reviewing focal boost planning studies and clinical trials that have been published in the last ten years.

METHODS

Published reports of focal boost radiotherapy, that specifically incorporate dose escalation to intra-prostatic lesions (IPLs), were reviewed and summarized. Correlations between acute/late ≥G2 genitourinary (GU) or gastrointestinal (GI) toxicity and clinical factors were determined by a meta-analysis.

RESULTS

By reviewing and summarizing 34 planning studies and 35 trials, a significant dose escalation to the GTV and thus higher tumor control of focal boost radiotherapy were reported consistently by all reviewed studies. Reviewed trials reported a not significant difference in toxicity between focal boost and conventional radiotherapy. Acute ≥G2 GU and late ≥G2 GI toxicities were reported the most and least prevalent, respectively, and a negative correlation was found between the rate of toxicity and proportion of low-risk or intermediate-risk patients in the cohort.

CONCLUSION

Focal boost prostate cancer radiotherapy has the potential to be a new standard of care.

Diagnostic efficiency of hybrid imaging using PSMA ligands, PET/CT, PET/MRI and MRI in identifying malignant prostate lesions

OBJECTIVE

The objective of this study was to assess the accuracy of 68Ga-PSMA-11 PET/MRI, 18F-PSMA-1007 PET/CT, 68Ga-PSMA-11 PET/CT, and multiparametric (mp)MRI for the delineating of dominant intraprostatic lesions (IPL).

MATERIALS AND METHODS

35 patients with organ-confined prostate cancer who were assigned to definitive radiotherapy (RT) were divided into three groups based on imaging techniques: 68Ga-PSMA-PET/MRI (n = 9), 18F-PSMA-PET/CT (n = 16) and 68Ga-PSMA-PET/CT (n = 10). All patients without PSMA-PET/MRI received an additional mpMRI. PSMA-PET-based automatic isocontours and manual contours of the dominant IPLs were generated for each modality. The biopsy results were then used to validate whether any of the prostate biopsies were positive in the marked lesion using Dice similarity coefficient (DSC), Youden index (YI), sensitivity and specificity. Factors that can predict the accuracy of IPLs contouring were analysed.

RESULTS

Diagnostic performance was significantly superior both for manual and automatic IPLs contouring using 68Ga-PSMA-PET/MRI (DSC/YI SUV70%-0.62/0.51), 18F-PSMA-PET/CT (DSC/YI SUV70%-0.67/0.53) or 68Ga-PSMA-PET/CT (DSC/YI SUV70%-0.63/0.51) compared to mpMRI (DSC/YI-0.47/0.41; p < 0.001). The accuracy for delineating IPLs was not improved by combination of PET/CT and mpMRI images compared to PET/CT alone. Significantly superior diagnostic accuracy was found for large prostate lesions (at least 15% from the prostate volume) and higher Gleason score (at least 7b) comparing to smaller lesions with lower GS.

CONCLUSION

IPL localization was significantly improved when using PSMA-imaging procedures compared to mpMRI. No significant difference for delineating IPLs was found between hybrid method PSMA-PET/MRI and PSMA-PET/CT. PSMA-based imaging technique should be considered for the diagnostics of IPLs and focal treatment modality.

PET/CT in radiation oncology

The progressive integration of positron emission tomography/computed tomography (PET/CT) imaging in radiation therapy has its rationale in the biological intertumoral and intratumoral heterogeneity of malignant lesions that require the individual adjustment of radiation dose to obtain an effective local tumor control in cancer patients. PET/CT provides information on the biological features of tumor lesions such as metabolism, hypoxia, and proliferation that can identify radioresistant regions and be exploited to optimize treatment plans. Here, we provide an overview of the basic principles of PET-based target volume selection and definition using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and then we focus on the emerging strategies of dose painting and adaptive radiotherapy using different tracers. Previous studies provided consistent evidence that integration of ¹⁸F-FDG PET/CT in radiotherapy planning improves delineation of target volumes and reduces the uncertainties and variabilities of anatomical delineation of tumor sites. PET-based dose painting and adaptive radiotherapy are feasible strategies although their clinical implementation is highly demanding and requires strong technical, computational, and logistic efforts. Further prospective clinical trials evaluating local tumor control, survival, and toxicity of these emerging strategies will promote the full integration of PET/CT in radiation oncology.

PET and PET/CT with radiolabeled choline in prostate cancer: a critical reappraisal of 20 years of clinical studies

We here aim to provide a comprehensive and critical review of the literature concerning the clinical applications of positron emission tomography/computed tomography (PET/CT) with radiolabeled choline in patients with prostate cancer (PCa). We will initially briefly summarize the historical context that brought to the synthesis of [¹¹C]choline, which occurred exactly 20 years ago. We have arbitrarily grouped the clinical studies in three different periods, according to the year in which they were published and according to their relation with their applications in urology, radiotherapy and oncology. Studies at initial staging and, more extensively, studies in patients with biochemical failure, as well as factors predicting positive PET/CT will be reviewed. The capability of PET/CT with radiolabeled choline to provide prognostic information on PCa-specific survival will also be examined. The last sections will be devoted to the use of radiolabeled choline for monitoring the response to androgen deprivation therapy, radiotherapy, and chemotherapy. The accuracy and the limits of the technique will be discussed according to the information available from standard validation processes, including biopsy or histology. The clinical impact of the technique will be discussed on the basis of changes induced in the management of patients and in the evaluation of the response to therapy. Current indications to PET/CT, as officially endorsed by guidelines, or as routinely performed in the clinical practice will be illustrated. Emphasis will be made on methodological factors that might have influenced the results of the studies or their interpretation. Finally, we will briefly highlight the potential role of positron emission tomography/magnetic resonance and of new radiotracers for PCa imaging.

PET/Computed Tomography for Radiation Therapy Planning of Prostate Cancer

This article is a short review of PET tracers, which have been used in clinical routine in single institutions. Preliminary anecdotal research supports the use of PET techniques in therapy planning of prostate cancer. The existing literature is discussed. For external beam radiation therapy, the biological target volume definition can only be based on PET imaging. There are not yet any prospective and randomized trials available; therefore, single-institution experiences cannot yet be recommended as clinical routine.

Imaging of Prostate Cancer Using 18F-Choline PET/Computed Tomography

¹⁸F-fluorocholine (FCH) PET/computed tomography (CT) is a valuable imaging modality in prostate cancer disease. Probably, its main role is restaging of patients with biochemical recurrence after radical prostatectomy or external beam radiotherapy. ¹⁸F-FCH PET/CT is strengthening its position in the initial staging, biopsy target definition, radiotherapy planning, and therapy monitoring. Gleason score and prostate-specific antigen value, doubling time, and velocity can influence positivity of ¹⁸F-FCH PET/CT. The influence of androgen deprivation therapy on choline uptake is not precisely clarified. Collaboration between nuclear medicine physicians, radiologists, urologists, oncologists, and radiotherapists is crucial to help patients with prostate cancer disease.

The delineation of intraprostatic boost regions for radiotherapy using multimodality imaging

Dose escalation to the prostate improves tumor control but at the expense of increased rectal toxicity. Modern imaging can be used to detect the most common site of recurrence, the intraprostatic lesion (IPL), which has led to the concept of focusing dose escalation to the IPL in order to improve the therapeutic ratio. Imaging must be able to detect lesions with adequate sensitivity and specificity to accurately delineate the IPL. This information must be carefully integrated into the radiotherapy planning process to ensure the dose is targeted to the IPL. This review will consider the role and challenges of multiparametric MRI and PET computed tomography in delineating a tumor boost to be delivered by external beam radiotherapy.

Early hematologic changes during prostate cancer radiotherapy predictive for late urinary and bowel toxicity

BACKGROUND

The primary objective of the study was to identify early hematologic changes predictive for radiotherapy (RT)-associated genitourinary and gastrointestinal toxicity.

METHODS

In a group of 91 prostate cancer patients presenting for primary (n = 51) or postoperative (n = 40) curative RT, blood samples (blood count, acute phase proteins, and cytokines) were analyzed before (T1), three times during (T2-T4), and 6-8 weeks after (T5) radiotherapy. Before RT (baseline), on the last day (acute toxicity), a median of 2 months and 16 months (late toxicity) after RT, patients responded to a validated questionnaire (Expanded Prostate Cancer Index Composite). Acute score changes > 20 points and late changes > 10 points were considered clinically relevant.

RESULTS

Radiotherapy resulted in significant changes of hematologic parameters, with the largest effect on lymphocytes (mean decrease of 31-45 %) and significant dependence on target volume. C-reactive protein (CRP) elevation > 5 mg/l and hemoglobin level decrease ≥ 5 G/1 at T2 were found to be independently predictive for acute urinary toxicity (p < 0.01, respectively). CRP elevation was predominantly detected in primary prostate RT (p = 0.02). Early lymphocyte level elevation ≥ 0.3G/l at T2 was protective against late urinary and bowel toxicity (p = 0.02, respectively). Other significant predictive factors for late bowel toxicity were decreasing hemoglobin levels (cut-off ≥ 5 G/l) at T2 (p = 0.04); changes of TNF-α (tumor necrosis factor; p = 0.03) and ferritin levels (p = 0.02) at T5. All patients with late bowel toxicity had interleukin (IL)-6 levels < 1.5 ng/l at T2 (63 % without; p = 0.01).

CONCLUSION

Early hematologic changes during prostate cancer radiotherapy are predictive for late urinary and bowel toxicity.

Volumetric modulated arc therapy planning for primary prostate cancer with selective intraprostatic boost determined by 18F-choline PET/CT

PURPOSE

This study evaluated expected tumor control and normal tissue toxicity for prostate volumetric modulated arc therapy (VMAT) with and without radiation boosts to an intraprostatically dominant lesion (IDL), defined by (18)F-choline positron emission tomography/computed tomography (PET/CT).

METHODS AND MATERIALS

Thirty patients with localized prostate cancer underwent (18)F-choline PET/CT before treatment. Two VMAT plans, plan79 Gy and plan100-105 Gy, were compared for each patient. The whole-prostate planning target volume (PTVprostate) prescription was 79 Gy in both plans, but plan100-105 Gy added simultaneous boost doses of 100 Gy and 105 Gy to the IDL, defined by 60% and 70% of maximum prostatic uptake on (18)F-choline PET (IDLsuv60% and IDLsuv70%, respectively, with IDLsuv70% nested inside IDLsuv60% to potentially enhance tumor specificity of the maximum point dose). Plan evaluations included histopathological correspondence, isodose distributions, dose-volume histograms, tumor control probability (TCP), and normal tissue complication probability (NTCP).

RESULTS

Planning objectives and dose constraints proved feasible in 30 of 30 cases. Prostate sextant histopathology was available for 28 cases, confirming that IDLsuv60% adequately covered all tumor-bearing prostate sextants in 27 cases and provided partial coverage in 1 case. Plan100-105 Gy had significantly higher TCP than plan79 Gy across all prostate regions for α/β ratios ranging from 1.5 Gy to 10 Gy (P<.001 for each case). There were no significant differences in bladder and femoral head NTCP between plans and slightly lower rectal NTCP (endpoint: grade ≥ 2 late toxicity or rectal bleeding) was found for plan100-105 Gy.

CONCLUSIONS

VMAT can potentially increase the likelihood of tumor control in primary prostate cancer while observing normal tissue tolerances through simultaneous delivery of a steep radiation boost to a (18)F-choline PET-defined IDL.

The role of PET-CT in radiotherapy planning of solid tumours

Background

PET-CT is becoming more and more important in various aspects of oncology. Until recently it was used mainly as part of diagnostic procedures and for evaluation of treatment results. With development of personalized radiotherapy, volumetric and radiobiological characteristics of individual tumour have become integrated in the multistep radiotherapy (RT) planning process. Standard anatomical imaging used to select and delineate RT target volumes can be enriched by the information on tumour biology gained by PET-CT. In this review we explore the current and possible future role of PET-CT in radiotherapy treatment planning. After general explanation, we assess its role in radiotherapy of those solid tumours for which PET-CT is being used most.

Conclusions

In the nearby future PET-CT will be an integral part of the most radiotherapy treatment planning procedures in an every-day clinical practice. Apart from a clear role in radiation planning of lung cancer, with forthcoming clinical trials, we will get more evidence of the optimal use of PET-CT in radiotherapy planning of other solid tumours.

¹⁸F-fluoromethylcholine or ¹⁸F-fluoroethylcholine pet for prostate cancer imaging: which is better? A literature revision

INTRODUCTION

The present review was conceived for describing the differences in biodistribution and diagnostic performance of two types of (18)F-radiolabeled choline for positron emission tomography (PET) imaging in prostate cancer (PCa), such as fluoromethylcholine (FCH) and fluoroethylcholine (FEC).

MATERIALS AND METHODS

A collection of published data about two radiopharmaceutical agents was made by using PubMed, Web of Knowledge databases and Trip Database, and then a critical revision was discussed.

RESULTS

FCH was injected in 338 and 1164 patients, while FEC was injected in 20 and 139 patients, respectively for basal staging and re-staging. The diagnostic performances of FCH and FEC for the detection of lymph node metastasis before the surgical approach are typically around 50% or less and between 0% and 39%, respectively. Conversely, both the tracers appear useful for the detection of recurrent PCa in case of increase in absolute PSA value or in case of high levels of PSA velocity and PSA doubling time (sensitivity ranged between 42.9% and 96% for FCH and between 62% and 85.7% for FEC).

CONCLUSIONS

In according with the available information, FCH appears to be a more appropriate radiocompound as compared to FEC, although more comparative data are mandatory. A well designed and prospective trial for the evaluation of biokinetic data and diagnostic performance of both radiopharmaceutical agents seems essential.

ADVANCES IN KNOWLEDGE AND IMPLICATION FOR PATIENT CARE

FCH seems to be an appropriate radiopharmaceutical agent as compared to FEC. Anyway both the radiocompounds are useful in the evaluation of recurrent disease in case of a serial increase in PSA value and their performance improves when a correct preparation and acquisition protocol is employed.

Hematologic changes during prostate cancer radiation therapy are dependent on the treatment volume

AIM

To assess hematologic changes of modern prostate radiation therapy (RT) comparing different target volumes.

PATIENTS & METHODS

Blood samples were evaluated before (T1), during (T2-T4) and 6-8 weeks after (T5) RT in a group of 113 patients. Whole-pelvic RT up to 46 Gy was applied in 27 cases. The total dose to the prostatic fossa (n = 46)/prostate (n = 67) was 66/76 Gy.

RESULTS

Erythrocyte, leukocyte and platelet levels decreased significantly relative to baseline levels at T2-T5. Neoadjuvant hormonal therapy had an impact on hemoglobin levels before and during RT. The cumulative incidence of grade 2 leukopenia was 15 versus 2% (p = 0.02) and grade 2 anemia 8 versus 0% (p = 0.03) with versus without whole-pelvic RT, respectively. Lymphocyte decrease was larger at times T2-T5 (36 vs 3% grade 3 toxicity; p < 0.01).

CONCLUSION

Prostate RT has a small but significant and longer effect on the blood count. Lower lymphocyte levels need to be considered when larger volumes are treated.

Perfusion CT is a valuable diagnostic method for prostate cancer: a prospective study of 94 patients

Purpose

The aim of this study is to assess the usefulness of perfusion computer tomography (pCT) in prostate cancer (PCa) diagnostics.

Materials and Methods

94 patients with biopsy-proven PCa were enrolled in the study. Dynamic pCT of the prostate gland was performed for 50 seconds after an intravenous injection of contrast medium. Blood flow (BF), blood volume (BV), mean transit time (MTT) and permeability surface area product (PS) were computed in the suspected PCa area and in normal prostatic tissue.

Results

PCa was visible in pCT in 90 of the 94 examined patients as a focal peripheral CT enhancement. When PCa was located in the peripheral zone (PZ), it was visible on perfusion maps, mostly showing an early peak followed by wash-out. The average values of all perfusion parameters were higher for tumour than for normal prostate tissue (p < 0.000). BV and BF were dependent on tumour grade expressed by the Gleason score (GS). All PCa cases were divided into groups, according to histological grade, as low (GS ≤ 6), medium (GS = 7), and high (GS > 7). In high-grade PCa, the mean BF value was significantly higher (p = 0.001) than the mean value of BF low- and medium-grade PCa (p = 0.011). Similar results were obtained regarding the mean values of BV; the more aggressive the cancer grade, the higher the mean BV value (p = 0.04).

Conclusion

CT quantitative perfusion imaging allows PCa to be distinguished from normal prostate tissue. The highest values for BF and BV were observed in the most aggressive PCa grade.

Transurethral resection of the prostate after radiotherapy for prostate cancer: impact on quality of life

OBJECTIVES

To evaluate the impact of transurethral resection of the prostate on quality of life after radiotherapy for prostate cancer.

METHODS

A group of 49 consecutive patients with and 487 without prior transurethral resection of the prostate responded to the Expanded Prostate Cancer Index Composite questionnaire before, on the last day, and a median time of 2 months and 16 months after external beam radiotherapy (70-78 Gy). A matched-pair analysis was used to avoid the influence of treatment-associated confounding factors, including dose, treatment volume and hormonal therapy.

RESULTS

Significantly smaller acute urinary score changes relative to baseline levels resulted with versus without prior transurethral resection of the prostate (mean function/bother score decrease of 3/6 vs 18/21 points at the end of radiotherapy; P < 0.01), affecting urinary incontinence (pads to control urinary leakage in 4% vs 24%; P = 0.03) and irritative/obstructive symptoms (big/moderate problem with weak urinary stream in 11% vs 37%; P = 0.02). As opposed to acute changes, transurethral resection of the prostate was a significant predisposing factor for a long-term urinary function score decrease >10 points (20% vs 6% of patients with vs without prior resection; P = 0.04). Urinary incontinence risk was higher for patients with a longer time from resection to radiotherapy.

CONCLUSIONS

Transurethral resection of the prostate significantly affects acute (considerably fewer symptoms) and long-term (relevant toxicity in some cases) urinary quality of life after radiotherapy for prostate cancer.

Learning curve in the application of a hydrogel spacer to protect the rectal wall during radiotherapy of localized prostate cancer

OBJECTIVE

To evaluate the effect of increasing experience on hydrogel dimensions, rectal dose, and acute toxicity, and to discuss important technical issues gained from this experience.

METHODS

Sixty-four consecutive patients with prostate cancer were included in this analysis (G1/G2 corresponding to first/second 32 patients) after injection of 10 mL spacer gel. All patients were treated with a 5-field intensity-modulated radiotherapy technique to 76-78 Gy. Treatment toxicity was evaluated with a validated quality of life questionnaire (expanded prostate cancer index composite) before and after radiotherapy.

RESULTS

Rectum volume could be entirely excluded from the planning target volume in 31% in G1 vs 56% in G2 (P = .04). Increasing symmetry was detected comparing the first 15 patients to the subsequent rest, with mean differences between right and left of 0.6 cm vs 0.3 cm at the midgland (P = .03). Mean distance between prostate and anterior rectal wall increased from 0.8 cm/1.1 cm/0.8 cm (G1) at the base/middle/apex to 1.3 cm/1.5 cm/1.2 cm (G2), respectively, so that the dose to the rectum decreased significantly (6% vs 2% of the volume inside the 70 Gy isodose; P <.01). Bowel function and bother score changes were smaller comparing baseline with last day of radiotherapy levels (mean 16/18 in G1 vs 9/12 in G2).

CONCLUSION

A learning curve could be demonstrated in our patient population, respecting improved and more symmetrical spacer placement, improved treatment planning, and less treatment-related acute toxicity. Several important technical aspects need to be considered.

Potential of [18F]-fluoromisonidazole positron-emission tomography for radiotherapy planning in head and neck squamous cell carcinomas

BACKGROUND AND PURPOSE

Positron-emission tomography (PET) with [(18)F]-fluoromisonidazole (FMISO) permits consideration of radiotherapy dose escalation to hypoxic volumes in head and neck cancers (HNC). However, the definition of FMISO volumes remains problematic. The aims of this study are to confirm that delayed acquisition at 4 h is most appropriate for FMISO-PET imaging and to assess different methods of volume segmentation.

PATIENTS AND METHODS

A total of 15 HNC patients underwent several FMISO-PET/computed tomography (CT) acquisitions 2, 3 and 4 h after FMISO injection. Three automatic methods of PET image segmentation were tested: fixed threshold, adaptive threshold based on the ratio between tumour-derived and background activities (R(T/B)) and the fuzzy locally adaptive Bayesian (FLAB) method. The hypoxic fraction (HF), which is defined as the ratio between the FMISO and CT volumes, was also calculated.

RESULTS

The R(T/B) for images acquired at 2, 3 and 4 h differed significantly, with mean values of 2.5 (1.7-2.9), 3 (2-4.5) and 3.4 (2.3-6.1), respectively. The mean tumour volume, as defined manually using CT images, was 39.1 ml (1.2-116 ml). After 4 h, the mean FMISO volumes were 18.9 (0.1-81), 9.5 (0.9-33.1) and 12.5 ml (0.9-38.4 ml) with fixed threshold, adaptive threshold and the FLAB method, respectively; median HF values were 0.47 (0.1-1.93), 0.25 (0.11-0.75) and 0.35 (0.14-1.05), respectively. FMISO volumes were significantly different.

CONCLUSION

The best contrast is obtained at the 4-hour acquisition time. Large discrepancies were found between the three tested methods of volume segmentation.

Prostate stereotactic body radiotherapy with simultaneous integrated boost: which is the best planning method?

Background

The delivery of a simultaneous integrated boost to the intra-prostatic tumour nodule may improve local control. The ability to deliver such treatments with hypofractionated SBRT was attempted using RapidArc (Varian Medical systems, Palo Alto, CA) and Multiplan (Accuray inc, Sunnyvale, CA).

Materials and methods

15 patients with dominant prostate nodules had RapidArc and Multiplan plans created using a 5 mm isotropic margin, except 3 mm posteriorly, aiming to deliver 47.5 Gy in 5 fractions to the boost whilst treating the whole prostate to 36.25 Gy in 5 fractions. An additional RapidArc plan was created using an 8 mm isotropic margin, except 5 mm posteriorly, to account for lack of intrafraction tracking.

Results

Both RapidArc and Multiplan can produce clinically acceptable boost plans to a dose of 47.5 Gy in 5 fractions. The mean rectal doses were lower for RapidArc plans (D50 13.2 Gy vs 15.5 Gy) but the number of missed constraints was the same for both planning methods (11/75). When the margin was increased to 8 mm/5 mm for the RapidArc plans to account for intrafraction motion, 37/75 constraints were missed.

Conclusions

RapidArc and Multiplan can produce clinically acceptable simultaneous integrated boost plans, but the mean rectal D50 and D20 with RapidArc are lower. If the margins are increased to account for intrafraction motion, the RapidArc plans exceed at least one dose constraint in 13/15 cases. Delivering a simultaneous boost with hypofractionation appears feasible, but requires small margins needing intrafraction motion tracking.

Pushing the limits of radiation therapy for prostate cancer: where do we go next?

There have been significant advancements in the quality and precision of radiation therapy (RT) for prostate cancer over the past two decades. The development and implementation of intensity-modulated radiation therapy has allowed for RT dose-escalation without parallel increases in treatment morbidity. Moreover, integration of androgen deprivation therapy with definitive RT has led to improvements in outcomes for certain subgroups of prostate cancer patients. In this review, we highlight several ongoing and developing technical advances that hold promise for further optimizing RT care, including proton beam therapy, inter- and intra-fractional image-guided dose-delivery, methods for improved target volume definition, and development of techniques for safely performing hypofractionation and stereotactic body radiotherapy. We also discuss the importance of investigating the potential benefit of integrating novel systemic therapies with prostate RT to further improve outcomes for patients with locally advanced prostate cancer.

Current standards and future directions for prostate cancer radiation therapy

Definitive radiation therapy is a well-recognized curative treatment option for localized prostate cancer. A suitable technique, dose, target volume and the option of a combination with androgen deprivation therapy need to be considered. An optimal standard external beam radiotherapy currently includes intensity-modulated and image-guided radiotherapy techniques with total doses of ≥76-78 Gy in conventional fractionation. Protons or carbon ions are alternatives available only in specific centers. Data from several randomized studies increasingly support the rationale for hypofractionated radiotherapy. A simultaneous integrated boost with dose escalation focused on a computed tomography/PET- or MRI/magnetic resonance spectroscopy-detected malignant lesion is one option to increase tumor control, with potentially no additional toxicity. The application of a spacer is a promising concept for optimal protection of the rectal wall.

Role of choline PET/CT in guiding target volume delineation for irradiation of prostate cancer

Choline PET/CT has shown limitations for the detection of primary prostate cancer and nodal metastatic disease, mainly due to limited sensitivity and specificity. Conversely in the restaging of prostate cancer recurrence, choline PET/CT is a promising imaging modality for the detection of local regional and nodal recurrence with an impact on therapy management. This review highlights current literature on choline PET/CT for radiation treatment planning in primary and recurrent prostate cancer. Due to limited sensitivity and specificity in differentiating between benign and malignant prostatic tissues in primary prostate cancer, there is little enthusiasm for target volume delineation based on choline PET/CT. Irradiation planning for the treatment of single lymph node metastases on the basis of choline PET/CT is controversial due to its limited lesion-based sensitivity in primary nodal staging. In high-risk prostate cancer, choline PET/CT might diagnose lymph node metastases, which potentially can be included in the conventional irradiation field. Prior to radiation treatment of recurrent prostate cancer, choline PET/CT may prove useful for patient stratification by excluding distant disease which would require systemic therapy. In patients with local recurrence, choline PET/CT can be used to delineate local sites of recurrence within the prostatic resection bed allowing a boost to PET-positive sites. In patients with lymph node metastases outside the prostatic fossa and regional metastatic lymph nodes, choline PET/CT might influence radiation treatment planning by enabling extension of the target volume to lymphatic drainage sites with or without a boost to PET-positive lymph nodes. Further clinical randomized trials are required to assess treatment outcomes following choline-based biological radiation treatment planning in comparison with conventional radiation treatment planning.

Predictive factors of [18F]-Choline PET/CT in 170 patients with increasing PSA after primary radical treatment

AIM

The purpose of this study was to evaluate the potential usefulness of [18F]-Choline PET/CT in the restaging of prostate cancer patients, who presented a rising PSA.

MATERIALS AND METHODS

We evaluated 170 prostate cancer patients, previously radically treated, that were referred for restaging with [18F]-Choline PET/CT.

RESULTS

A total of 129 patients (median PSA 4.29 ng/ml at relapse) showed one or more areas of high uptake on PET/CT scan, while 41 patients with a median PSA of 1.07 ng/ml at relapse showed negative PET/CT scans. No false negative was found, while 31 patients were identified as false positive. Specificity of Choline PET/CT in our series was 56.9 %, while sensibility was 100 %. At the time of restaging, a PSA value superior or equal to 1 ng/ml was found to be a statistically significant predictive factor of PET positivity, either at the univariate (p < 0.0001) and at the multivariate analysis (p < 0.0001).

CONCLUSIONS

Based on our findings, [18F]-Choline PET/CT is confirmed as a useful diagnostic tool to detect early recurrence, in patients with increasing PSA after primary treatment. However, in case of a mild increase in PSA, positive results must be validated with other techniques, as specificity and positive predictive value of [18F]-Choline PET/CT decrease with the lower values of PSA.

Dose-escalation using intensity-modulated radiotherapy for prostate cancer - evaluation of quality of life with and without (18)F-choline PET-CT detected simultaneous integrated boost

BACKGROUND

In comparison to the conventional whole-prostate dose escalation, an integrated boost to the macroscopic malignant lesion might potentially improve tumor control rates without increasing toxicity. Quality of life after radiotherapy (RT) with vs. without (18)F-choline PET-CT detected simultaneous integrated boost (SIB) was prospectively evaluated in this study.

METHODS

Whole body image acquisition in supine patient position followed 1 h after injection of 178-355MBq (18)F-choline. SIB was defined by a tumor-to-background uptake value ratio > 2 (GTV(PET)). A dose of 76Gy was prescribed to the prostate (PTV(prostate)) in 2Gy fractions, with or without SIB up to 80Gy. Patients treated with (n = 46) vs. without (n = 21) SIB were surveyed prospectively before (A), at the last day of RT (B) and a median time of two (C) and 19 month (D) after RT to compare QoL changes applying a validated questionnaire (EPIC - expanded prostate cancer index composite).

RESULTS

With a median cut-off standard uptake value (SUV) of 3, a median GTV(PET) of 4.0 cm(3) and PTV(boost) (GTV(PET) with margins) of 17.3 cm(3) was defined. No significant differences were found for patients treated with vs. without SIB regarding urinary and bowel QoL changes at times B, C and D (mean differences ≤3 points for all comparisons). Significantly decreasing acute urinary and bowel score changes (mean changes > 5 points in comparison to baseline level at time A) were found for patients with and without SIB. However, long-term urinary and bowel QoL (time D) did not differ relative to baseline levels - with mean urinary and bowel function score changes < 3 points in both groups (median changes = 0 points). Only sexual function scores decreased significantly (> 5 points) at time D.

CONCLUSIONS

Treatment planning with (18)F-choline PET-CT allows a dose escalation to a macroscopic intraprostatic lesion without significantly increasing toxicity.

Critical discussion of evaluation parameters for inter-observer variability in target definition for radiation therapy

BACKGROUND AND PURPOSE

Inter-observer studies represent a valid method for the evaluation of target definition uncertainties and contouring guidelines. However, data from the literature do not yet give clear guidelines for reporting contouring variability. Thus, the purpose of this work was to compare and discuss various methods to determine variability on the basis of clinical cases and a literature review.

PATIENTS AND METHODS

In this study, 7 prostate and 8 lung cases were contoured on CT images by 8 experienced observers. Analysis of variability included descriptive statistics, calculation of overlap measures, and statistical measures of agreement. Cross tables with ratios and correlations were established for overlap parameters.

RESULTS

It was shown that the minimal set of parameters to be reported should include at least one of three volume overlap measures (i.e., generalized conformity index, Jaccard coefficient, or conformation number). High correlation between these parameters and scatter of the results was observed.

CONCLUSION

A combination of descriptive statistics, overlap measure, and statistical measure of agreement or reliability analysis is required to fully report the interrater variability in delineation.

Combination of dose escalation with technological advances (intensity-modulated and image-guided radiotherapy) is not associated with increased morbidity for patients with prostate cancer

PURPOSE

The aim was to evaluate treatment-related morbidity after intensity-modulated (IMRT) and image-guided (IGRT) radiotherapy with a total dose of 76 Gy in comparison to conventional conformal radiotherapy (3DCRT) up to 70.2-72 Gy for patients with prostate cancer.

PATIENTS AND METHODS

All patients were prospectively surveyed prior to, on the last day, as well as after a median time of 2 and 16 months after RT using a validated questionnaire (Expanded Prostate Cancer Index Composite). Criteria for the 78 matched pairs after IMRT vs. 3DCRT were patient age, use of antiandrogens, treatment volume (± whole pelvis), prognostic risk group, and urinary/bowel/sexual quality of life (QoL) before treatment.

RESULTS

QoL changes after dose-escalated IMRT were found to be similar to QoL changes after 3DCRT in all domains. Only sexual function scores more than 1 year after RT decreased slightly more after 3DCRT in comparison to IMRT (mean 9 vs. 6 points; p = 0.04), with erections firm enough for intercourse in 14% vs. 30% (p = 0.03). Painful bowel movements were reported more frequently after 3DCRT vs. IMRT 2 months after treatment (≥ once a day in 10% vs. 1%; p = 0.03), but a tendency for higher rectal bleeding rates was found after IMRT vs. 3DCRT more than 1 year after RT (≥ rarely in 20% vs. 9%; p = 0.06).

CONCLUSION

Combination of dose escalation with technological advances (IMRT and IGRT) is not associated with increased morbidity for patients with prostate cancer.