Long-term outcomes following proton therapy for prostate cancer in young men with a focus on sexual health

Dosimetric evaluation of dose shaping by adaptive aperture and its impact on plan quality

Mevion's single-room HYPERSCAN proton therapy system employs a proton multileaf collimator called the adaptive aperture (AA), which collimates individual spots in the proton delivery as determined by the Treatment Planning System (TPS). The purpose of this study is to assess the dosimetric benefits of the AA, specifically in the dynamic aperture (DA) mode, and evaluate its impact on proton treatment plan quality as compared to a traditional pencil beam scanning (PBS) system (Varian ProBeam). The spot dose distributions with dynamic collimation (DA), a unique AA shape for each energy layer, and with static collimation (SA), a single AA collimation shape shared by all energy layers per field, were calculated and compared with the spot dose distribution of the Varian ProBeam proton therapy system. The lateral and distal dose falloff gradients and their dependence on air gap were evaluated quantitatively. Treatment plans for ten arbitrarily selected intracranial target image sets were created, and the HYPERSCAN and ProBeam beam models were compared. The spot sizes of the HYPERSCAN system are significantly larger than ProBeam system, especially at low energy. With the help of DA, the lateral dose penumbra of the HYPERSCAN is dramatically improved at lower energy and comparable at higher to ProBeam PBS beams. While the ProBeam spot size does not change with the air gap, beam penumbra of the HYPERSCAN with DA increases with the air gap. The distal dose falloff gradient for the HYPERSCAN with or without DA remains consistently around 4.8 mm through all energies due to the beamline design, not substantially varying with energy or air gap. Treatment plans of ten randomly selected intracranial cases demonstrated favorable OAR sparing but unfavorable dose uniformity for the HYPERSCAN with DA compared to ProBeam. Dose shaping by adaptive aperture substantially improves the lateral penumbra without a significant change in the distal dose gradient. The dose gradients of the multiple beam DA plans with layer-by-layer blocking are improved compared with SA plans and are close to the ProBeam plans for the ten randomly selected brain cases. With layer-by-layer DA blocking, the HYPERSCAN plans have similar plan conformality indices as the ProBeam plans, but the overall plan quality indices are lower than ProBeam plans, largely due to the lower dose homogeneity. In some cases, DA blocking was found to be superior in sparing OAR surrounding the target.

Sexual health and treatment-related sexual dysfunction in sexual and gender minorities with prostate cancer

Prostate cancer treatment has substantial effects on sexual health and function. Sexual function is a vital aspect of human health and a critical component of cancer survivorship, and understanding the potential effects of different treatment modalities on sexual health is crucial. Existing research has extensively described the effects of treatment on male erectile tissues necessary for heterosexual intercourse; however, evidence regarding their effects on sexual health and function in sexual and gender minority populations is minimal. These groups include sexual minority - gay and bisexual - men, and transgender women or trans feminine people in general. Such unique effects in these groups might include altered sexual function in relation to receptive anal and neovaginal intercourse and changes to patients' role-in-sex. Sexual dysfunctions following prostate cancer treatment affecting quality of life in sexual minority men include climacturia, anejaculation, decreased penile length, erectile dysfunction, and problematic receptive anal intercourse, including anodyspareunia and altered pleasurable sensation. Notably, clinical trials investigating sexual outcomes after prostate cancer treatment do not collect sexual orientation and gender identity demographic data or outcomes specific to members of these populations, which perpetuates the uncertainty regarding optimal management. Providing clinicians with a solid evidence base is essential to communicate recommendations and tailor interventions for sexual and gender minority patients with prostate cancer.

Current Knowledge on Radiation-Therapy-Induced Erectile Dysfunction in Prostate-Cancer Patients: A Narrative Review

Prostate cancer is the most frequently diagnosed cancer in men in the United States. Among the different available treatment options, radiation therapy is recommended for localized or even advanced disease. Erectile dysfunction (ED) often occurs after radiation therapy due to neurological, vascular, and endocrine mechanisms resulting in arterial tone alteration, pudendal-nerve neuropraxia, and lastly fibrosis. Considering the influence of quality of life on patients’ treatment choice, radiation-therapy-induced ED prevention and treatment are major issues. In this narrative review, we briefly summarize and discuss the current state of the art on radiation-therapy-induced ED in PCa patients in terms of pathophysiology and available treatment options.

Better preservation of erectile function in localized prostate cancer patients with modern proton therapy: Is it cost-effective?

BACKGROUND

Stereotactic body radiation therapy (SBRT) has gradually been recognized as favorable curative treatment for localized prostate cancer (PC). However, the high rate of erectile dysfunction (ED) after traditional photon-based SBRT remains an ongoing challenge that greatly impacts the quality of life of PC survivors. Modern proton therapy allows higher conformal SBRT delivery and has the potential to reduce ED occurrence but its cost-effectiveness remains uninvestigated.

METHODS

A Markov decision model was designed to evaluate the cost-effectiveness of proton SBRT versus photon SBRT in reducing irradiation-related ED. Base-case evaluation was performed on a 66-year-old (median age of PC) localized PC patient with normal pretreatment erectile function. Further, stratified analyses were performed for different age groups (50, 55, 60, 65, 70, and 75 years) and threshold analyses were conducted to estimate cost-effective scenarios. A Chinese societal willingness-to-pay (WTP) threshold (37,653 US dollars [$])/quality-adjusted life-year [QALY]) was adopted.

RESULTS

For the base case, protons provided an additional 0.152 QALY at an additional cost of $7233.4, and the incremental cost-effectiveness ratio was $47,456.5/QALY. Protons was cost-effective for patients ≤62-year-old at the WTP of China (≤66-year-old at a WTP of $50,000/QALY; ≤73-year-old at a WTP of $100,000/QALY). For patients at median age, once the current proton cost ($18,000) was reduced to ≤$16,505.7 or the patient had a life expectancy ≥88 years, protons were cost-effective at the WTP of China.

CONCLUSIONS

Upon assumption-based modeling, the results of current study support the use of proton SBRT in younger localized PC patients who are previously potent, for better preservation of erectile function. The findings await further validation using data from future comparative clinical trials.

Clinical Efficacy and Safety of Proton and Carbon Ion Radiotherapy for Prostate Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Carbon ion radiotherapy (CIRT) and proton beam therapy (PBT) are promising methods for prostate cancer, however, the consensus of an increasing number of studies has not been reached. We aimed to provide systematic evidence for evaluating the efficacy and safety of CIRT and PBT for prostate cancer by comparing photon radiotherapy.

MATERIALS AND METHODS

We searched for studies focusing on CIRT and PBT for prostate cancer in four online databases until July 2021. Two independent reviewers assessed the quality of included studies and used the GRADE approach to rate the quality of evidence. R 4.0.2 software was used to conduct the meta-analysis. A meta-regression test was performed based on the study design and tumor stage of each study.

RESULTS

A total of 33 studies including 13 CIRT- and 20 PBT-related publications, involving 54,101, participants were included. The quality of the included studies was found to be either low or moderate quality. Random model single-arm meta-analysis showed that both the CIRT and PBT have favorable efficacy and safety, with similar 5-year overall survival (OS) (94 vs 92%), the incidence of grade 2 or greater acute genitourinary (AGU) toxicity (5 vs 13%), late genitourinary (LGU) toxicity (4 vs 5%), acute gastrointestinal (AGI) toxicity (1 vs 1%), and late gastrointestinal (LGI) toxicity (2 vs 4%). However, compared with CIRT and PBT, photon radiotherapy was associated with lower 5-year OS (72-73%) and a higher incidence of grade 2 or greater AGU (28-29%), LGU (13-14%), AGI (14-19%), and LGI toxicity (8-10%). The meta-analysis showed the 3-, 4-, and 5-year local control rate (LCR) of CIRT for prostate cancer was 98, 97, and 99%; the 3-, 4-, 5-, and 8-year biochemical relapse-free rate (BRF) was 92, 91, 89, and 79%. GRADE assessment results indicated that the certainty of the evidence was very low. Meta-regression results did not show a significant relationship based on the variables studied (P<0.05).

CONCLUSIONS

Currently available evidence demonstrated that the efficacy and safety of CIRT and PBT for prostate cancer were similar, and they may significantly improve the OS, LCR, and reduce the incidence of GU and GI toxicity compared with photon radiotherapy. However, the quantity and quality of the available evidence are insufficient. More high-quality controlled studies are needed in the future.

Health-related quality of life in Japanese patients with prostate cancer following proton beam therapy: an institutional cohort study

Objective

Many treatment options have guaranteed long-term survival in patients with localized prostate cancer and health-related quality of life has become a greater concern for those patients. The purpose of this study was to reveal the health-related quality of life after proton beam therapy and to clarify the differences from other treatment modalities for prostate cancer.

Methods

Between January 2011 and April 2016, 583 patients were enrolled in the study and health-related quality of life outcomes using the Expanded Prostate Cancer Index Composite questionnaire were evaluated and compared with previous research targeted at Japanese patients.

Results

We found a significant decrease in the least square mean scores for urinary and bowel domains excluding the incontinence subscale after proton beam therapy (P < 0.0001) and recovery at a year following treatment. The scores for sexual function in patients without androgen deprivation therapy decreased each year after proton beam therapy (P < 0.0001). The scores for hormones in patients without androgen deprivation therapy remained high and those of patients with androgen deprivation therapy were lower before treatment but were comparable to those of non-androgen deprivation therapy patients at 2 years post-treatment. We found that the impact of radiotherapy including proton beam therapy on urinary condition and sexual function was lower than that of surgery.

Conclusions

For the first time in Japan, we investigated health-related quality of life using Expanded Prostate Cancer Index Composite questionnaires in patients with prostate cancer after proton beam therapy and compared it with other treatment modalities.

Risk of erectile dysfunction after modern radiotherapy for intact prostate cancer

BACKGROUND

Erectile dysfunction (ED) is a prevalent side effect of prostate cancer treatment. We hypothesized that the previously reported rates of ED may have improved with the advent of modern technology. The purpose of this project was to evaluate modern external beam radiotherapy and brachytherapy techniques to determine the incidence of radiotherapy (RT) induced ED.

METHODS

A systematic review of the literature published between January 2002 and December 2018 was performed to obtain patient reported rates of ED after definitive external beam radiotherapy, ultrafractionated stereotactic radiotherapy, and brachytherapy (BT) to the prostate in men who were potent prior to RT. Univariate and multivariate analyses of radiation dose, treatment strategy, and length of follow-up were analyzed to ascertain their relationship with RT-induced ED.

RESULTS

Of 890 articles reviewed, 24 met inclusion criteria, providing data from 2714 patients. Diminished erectile function status post RT was common and similar across all studies. The median increase in men reporting ED was 17%, 26%, 23%, and 23%, 3DCRT, IMRT, low dose rate BT, and SBRT, respectively, at 2-year median follow-up.

CONCLUSION

ED is a common side effect of RT. Risk of post-RT ED is similar for both LDR brachytherapy and external beam RT with advanced prostate targeting and penile-bulb sparing techniques utilized in modern RT techniques.

Challenges in Reporting the Effect of Radiotherapy on Erectile Function

BACKGROUND

Erectile dysfunction (ED) is the most common side effect of prostate radiotherapy (RT), but reported rates over time and across modalities have varied widely.

AIM

To evaluate the published literature between 2002 and 2018 for high quality data utilizing prospectively gathered patient-reported ED, and to summarize the challenges in reporting of RT-induced ED (RIED).

METHODS

A PubMed search and literature review was performed to identify articles describing rates of ED before and after definitive external beam RT or brachytherapy without androgen deprivation.

OUTCOMES

Patient-reported ED, patient and treatment variables, and study follow-up constituted the main outcomes of this study.

RESULTS

24 articles were identified, reporting RIED rates between 17% and 90%. Variables contributing to this range included patient, treatment, and study characteristics known to impact ED reporting.

CLINICAL IMPLICATIONS

For future studies, we recommend the use of validated patient-reported questionnaires and reporting of baseline function and comorbidities, RT type and dose, and use of androgen deprivation therapy and erectile aids at the time of ED measurement. With sufficient follow-up to understand the late nature of RIED, these recommendations will improve comparison of results between studies and the applicability of results to patients undergoing pretreatment counseling regarding the risks of RIED.

STRENGTHS & LIMITATIONS

The literature search and formulation of results were based on a broad understanding of the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines and the literature, but because of the focus on data reporting, a comprehensive systematic review of all RIED literature was not performed.

CONCLUSION

Reported rates of ED after RT vary widely due to differences in patients' baseline reported erectile function, age, comorbidities, and characteristics of the treatment delivered. The methodology of ED measurement has significant impact on the applicability and comparability of results to other studies and clinical practice. Nukala V, Incrocci L, Hunt AA, et al. Challenges in Reporting the Effect of Radiotherapy on Erectile Function. J Sex Med 2020;17:1053-1059.

Prostatic irradiation-induced sexual dysfunction: a review and multidisciplinary guide to management in the radical radiotherapy era (Part I defining the organ at risk for sexual toxicities)

Prostate cancer is the most common malignancy and the second leading cause of cancer-related death in men. Radiotherapy is a curative option that is administered via external beam radiation, brachytherapy, or in combination. Erectile, ejaculatory and orgasm dysfunction(s) is/are known potential and common toxicities associated with prostate radiotherapy. Our multidisciplinary team of physicians and/or scientists have written a three (3) part comprehensive review of the pathogenesis and management radiation-induced sexual dysfunction. Part I reviews pertinent anatomy associated with normal sexual function and then considers the pathogenesis of prostate radiation-induced sexual toxicities. Next, our team considers the associated radiobiological (including the effects of time, dose and fractionation) and physical (treatment planning and defining a novel Organ at Risk (OAR)) components that should be minded in the context of safe radiation treatment planning. The authors identify an OAR (i.e., the prostatic plexus) and provide suggestions on how to minimize injury to said OAR during the radiation treatment planning process.

Extreme hypofractionated proton radiotherapy for prostate cancer using pencil beam scanning: Dosimetry, acute toxicity and preliminary results

INTRODUCTION

Extreme hypofractionated radiotherapy for prostate cancer is a common modality in photon therapy. Pencil beam scanning (PBS) in similar fractionation allows better dose distribution and makes proton therapy more available for such patients. The purpose of this study is the feasibility of extreme proton hypofractionated radiotherapy and publication of early clinical results.

METHODS

Two hundred patients with early-stage prostate cancer were treated with IMPT (intensity-modulated proton therapy), extreme hypofractionated schedule (36.25 GyE in five fractions) between February 2013 and December 2015. Mean age of the patients was 64.3 years, and the mean value of prostate-specific antigen (PSA) before treatment was 6.83 μg/L (0.6-17.3 μg/L). Ninety-three patients (46.5%) were in the low-risk group. One hundred and seven patients (53.5%) were in the intermediate-risk group. Twenty-nine patients (14.5%) had neoadjuvant hormonal therapy, and no patients had adjuvant hormonal therapy. Acute toxicity, late toxicity and short-term results were evaluated.

RESULTS

All patients finished radiotherapy without interruptions. The median follow-up time was 36 months. The mean treatment time was 9.5 days (median 9 days). Acute toxicity according to Common Terminology Criteria for Adverse Events (CTCAE) v 4.0 was (gastrointestinal toxicity) GI (grade) G1-17%, G2-3.5%; (genitourinary toxicity) GU G1-40%, G2-19%; and no G3 toxicity was observed. Late toxicity was GI G1-19%, G2-5.5%; GU G1-17%, G2-4%; and no G3 toxicity was observed. PSA relapse was observed in one patient (1.08%) in the low-risk group (pelvic lymph node involvement was detected) and in seven patients (6.5%) in the intermediate-risk group (three lymph node metastases, two lymph node and bone metastases, two PSA relapses). No patient died of prostate cancer, and three patients died from other reasons. No local recurrence of cancer in the prostate was observed.

CONCLUSIONS

Proton beam radiotherapy for prostate cancer is feasible with a low rate of acute toxicity and promising late toxicity and effectivity.

Longitudinal Trends of AMS and IIEF-5 Scores in Randomly-Selected Community Men 40 to 80 Years Old: Preliminary Results

INTRODUCTION

Most of conclusions on the relationship between age and reproductive health in aging men relied on cross-sectional data.

AIM

To better characterize the natural degradation trajectory of reproductive health of aging men based on longitudinal data.

METHODS

A community cohort study was performed in randomly selected men 40 to 80 years old, initiated in 2012 and followed up in 2014 and 2016. Participants were investigated by face-to-face structured interview, including demographic information and International Index of Erectile Function (IIEF-5) and Aging Males' Symptoms (AMS) scales.

MAIN OUTCOME MEASURES

The differences among the 3 assessments of IIEF-5 and AMS were analyzed, and progression trajectories were traced.

RESULTS

The high degree of variability on AMS and IIEF-5 was evident across individual subjects, as was the variability within individuals. The average IIEF-5 score of 248 subjects decreased from 16.9 to 14.1 during the 4 years, and the total AMS score increased from 22.6-27.0 (P < .001). Longitudinal data, both of individuals and of groups, showed the more rapid increase or decrease on AMS or IIEF-5 scores over 4 years in the 61-70 age group than in other age groups.

CLINICAL IMPLICATION

The evidence of the greatest changes on AMS and IIEF-5 scores in the 61-70 age group prompts the importance of early intervention to postpone the degradation of reproductive health.

STRENGTH & LIMITATIONS

Compared with cross-sectional data, longitudinal data can provide a more natural progression trajectory of reproductive health of aging male individuals. The low follow-up rate might affect the parameter estimation to some extent.

CONCLUSION

Cohort data over 4 years' follow-up showed more abrupt changes on AMS and IIEF-5 scores in the 61-70 age group than in other age groups. Zheng J-B, Liang Q-F, Li J-H, et al. Longitudinal Trends of AMS and IIEF-5 Scores in Randomly-Selected Community Men 40 to 80 Years Old: Preliminary Results. J Sex Med 2019;16:1567-1573.

Proton versus photon-based radiation therapy for prostate cancer: emerging evidence and considerations in the era of value-based cancer care

BACKGROUND

Advances in radiation technology have transformed treatment options for patients with localized prostate cancer. The evolution of three-dimensional conformal radiation therapy and intensity-modulated radiation therapy (IMRT) have allowed physicians to spare surrounding normal organs and reduce adverse effects. The introduction of proton beam technology and its physical advantage of depositing its energy in tissue at the end-of-range maximum may potentially spare critical organs such as the bladder and rectum in prostate cancer patients. Data thus far are limited to large, observational studies that have not yet demonstrated a definite benefit of protons over conventional treatment with IMRT. The cost of proton beam treatment adds to the controversy within the field.

METHODS

We performed an extensive literature review for all proton treatment-related prostate cancer studies. We discuss the history of proton beam technology, as well as its role in the treatment of prostate cancer, associated controversies, novel technology trends, a discussion of cost-effectiveness, and an overview of the ongoing modern large prospective studies that aim to resolve the debate between protons and photons for prostate cancer.

RESULTS

Present data have demonstrated that proton beam therapy is safe and effective compared with the standard treatment options for prostate cancer. While dosimetric studies suggest lower whole-body radiation dose and a theoretically higher relative biological effectiveness in prostate cancer compared with photons, no studies have demonstrated a clear benefit with protons.

CONCLUSIONS

Evolving trends in proton treatment delivery and proton center business models are helping to reduce costs. Introduction of existing technology into proton delivery allows further control of organ motion and addressing organs-at-risk. Finally, the much-awaited contemporary studies comparing photon with proton-based treatments, with primary endpoints of patient-reported quality-of-life, will help us understand the differences between proton and photon-based treatments for prostate cancer in the modern era.

Proton beam therapy for cancer in the era of precision medicine

Precision radiotherapy, which accurately delivers the dose on a tumor and confers little or no irradiation to the surrounding normal tissue and organs, results in maximum tumor control and decreases the toxicity to the utmost extent. Proton beam therapy (PBT) provides superior dose distributions and has a dosimetric advantage over photon beam therapy. Initially, the clinical practice and study of proton beam therapy focused on ocular tumor, skull base, paraspinal tumors (chondrosarcoma and chordoma), and unresectable sarcomas, which responded poorly when treated with photon radiotherapy. Then, it is widely regarded as an ideal mode for reirradiation and pediatrics due to reducing unwanted side effects by lessening the dose to normal tissue. During the past decade, the application of PBT has been rapidly increasing worldwide and gradually expanding for the treatment of various malignancies. However, to date, the role of PBT in clinical settings is still controversial, and there are considerable challenges in its application. We systematically review the latest advances of PBT and the challenges for patient treatment in the era of precision medicine.