The Risk of Second Primary Cancers in Prostate Cancer Survivors Treated in the Modern Radiotherapy Era

The impact of baseline health factors on second primary cancer risk after radiotherapy for prostate cancer

PURPOSE

In evaluating second primary cancers (SPCs) following External Beam Radiotherapy (EBRT), the role of lifestyle factors is frequently not considered due to data limitations. We investigated the association between smoking, comorbidities, and SPC risks within EBRT-treated patients for localized prostate cancer (PCa).

PATIENTS & METHODS

The study included 1,883 PCa survivors aged 50-79, treated between 2006 and 2013, with intensity-modulated radiotherapy (IMRT) or three-dimensional conformal radiotherapy (3D-CRT). Clinical data were combined with SPC and survival data from the Netherlands Cancer Registry with a 12-month latency period. Standardized Incidence Ratios (SIRs) were calculated comparing the EBRT cohort with the general Dutch population. To explore the effect of patient and treatment characteristics on SPCs we conducted a Cox regression analysis. Lastly, we estimated cumulative incidences of developing solid SPC, pelvis SPC, and non-pelvis SPC using a competing risk analysis.

RESULTS

Significantly increased SIRs were observed for all SPC (SIR = 1.21, 95% confidence interval [CI]: 1.08-1.34), pelvis SPC (SIR = 1.46, 95% CI: 1.18-1.78), and non-pelvis SPC (SIR = 1.18, 95% CI [1.04-1.34]). Smoking status was significantly associated with pelvic and non-pelvic SPCs. Charlson comorbidity index (CCI) ≥ 1 (Hazard Ratio [HR] = 1.45, 95% CI: 1.10-1.91), cardiovascular disease (HR = 1.41, 95% CI: 1.05-1.88), and chronic obstructive pulmonary disease (COPD) (HR = 1.91, 95% CI: 1.30-2.79) were significantly associated with non-pelvis SPC. The proportion of active smoking numbers in the cohort was similar to the general population.

INTERPRETATION

We conclude that the presence of comorbidities in the EBRT population might be a relevant factor in observed excess non-pelvis SPC risk, but not for excess pelvis SPC risk.

[Does radiation therapy for prostate cancer increase the risk of second cancers?]

PURPOSE

The increased risk of second cancer after prostate radiotherapy is a debated clinical concern. The objective of the study was to assess the risk of occurrence of second cancers after prostate radiation therapy based on the analysis the literature, and to identify potential factors explaining the discrepancies in results between studies.

MATERIALS AND METHODS

A review of the literature was carried out, comparing the occurrence of second cancers in patients all presenting with prostate cancer, treated or not by radiation.

RESULTS

This review included 30 studies reporting the occurrence of second cancers in 2,112,000 patients treated or monitored for localized prostate cancer, including 1,111,000 by external radiation therapy and 103,000 by brachytherapy. Regarding external radiation therapy, the average follow-up was 7.3years. The majority of studies (80%) involving external radiation therapy, compared to no external radiation therapy, showed an increased risk of second cancers with a hazard ratio ranging from 1.13 to 4.9, depending on the duration of the follow-up. The median time to the occurrence of these second cancers after external radiotherapy ranged from 4 to 6years. An increased risk of second rectal and bladder cancer was observed in 52% and 85% of the studies, respectively. Considering a censoring period of more than 10 years after irradiation, 57% and 100% of the studies found an increased risk of rectal and bladder cancer, without any impact in overall survival. Studies of brachytherapy did not show an increased risk of second cancer. However, these comparative studies, most often old and retrospective, had many methodological biases.

CONCLUSION

Despite numerous methodological biases, prostate external radiation therapy appears associated with a moderate increase in the risk of second pelvic cancer, in particular bladder cancer, without impacting survival. Brachytherapy does not increase the risk of a second cancer.

Deep-Learning for Rapid Estimation of the Out-of-Field Dose in External Beam Photon Radiation Therapy - A Proof of Concept

PURPOSE

The dose deposited outside of the treatment field during external photon beam radiation therapy treatment, also known as out-of-field dose, is the subject of extensive study as it may be associated with a higher risk of developing a second cancer and could have deleterious effects on the immune system that compromise the efficiency of combined radio-immunotherapy treatments. Out-of-field dose estimation tools developed today in research, including Monte Carlo simulations and analytical methods, are not suited to the requirements of clinical implementation because of their lack of versatility and their cumbersome application. We propose a proof of concept based on deep learning for out-of-field dose map estimation that addresses these limitations.

METHODS AND MATERIALS

For this purpose, a 3D U-Net, considering as inputs the in-field dose, as computed by the treatment planning system, and the patient's anatomy, was trained to predict out-of-field dose maps. The cohort used for learning and performance evaluation included 3151 pediatric patients from the FCCSS database, treated in 5 clinical centers, whose whole-body dose maps were previously estimated with an empirical analytical method. The test set, composed of 433 patients, was split into 5 subdata sets, each containing patients treated with devices unseen during the training phase. Root mean square deviation evaluated only on nonzero voxels located in the out-of-field areas was computed as performance metric.

RESULTS

Root mean square deviations of 0.28 and 0.41 cGy/Gy were obtained for the training and validation data sets, respectively. Values of 0.27, 0.26, 0.28, 0.30, and 0.45 cGy/Gy were achieved for the 6 MV linear accelerator, 16 MV linear accelerator, Alcyon cobalt irradiator, Mobiletron cobalt irradiator, and betatron device test sets, respectively.

CONCLUSIONS

This proof-of-concept approach using a convolutional neural network has demonstrated unprecedented generalizability for this task, although it remains limited, and brings us closer to an implementation compatible with clinical routine.

Long-term Overall Survival after External Beam Radiotherapy for Localised Prostate Cancer

AIMS

Knowledge on survival probabilities is essential for determining optimal treatment strategies. We studied overall survival and associated prognostic factors in Dutch patients with localised prostate cancer (PCa) selected for external beam radiotherapy.

MATERIALS AND METHODS

For this single-centre retrospective cohort study, we identified all T1-T3 PCa patients (aged 55-80 years) in the radiotherapy planning database with a start date between January 2006 and December 2013, treated with 72-78 Gy in 2 Gy fractions to the prostate ± seminal vesicles (n = 1536). Long-term androgen deprivation therapy (ADT) was predominantly prescribed in the case of extracapsular disease (>T3). Overall survival was estimated using the Kaplan-Meier method. Prognostic factors were evaluated in Cox regression models for the intermediate-risk and high-risk groups.

RESULTS

The median follow-up was 12 years for patients who were alive. Ten-year survival rates were 79.0% for low-risk (n = 120), 59.9% for intermediate-risk (n = 430) and 56.8% for high-risk patients (n = 986). A higher age, higher comorbidity score, active smoking and Gleason score ≥8 had a statistically significant negative impact on overall survival at multivariable analysis. ADT was associated with superior overall survival in the high-risk group translating into overall survival rates similar to the intermediate-risk group.

CONCLUSIONS

Although PCa patients selected for external beam radiotherapy are typically in good health, their comorbidity score and smoking habits appeared to be dominant predictors for overall survival. Overall survival rates within the high-risk group varied, showing improved overall survival with ADT prescription and worse overall survival in the case of Gleason score ≥8.

Impact of Advanced External Beam Radiotherapy on Second Haematological Cancer Risk in Prostate Cancer Survivors

AIMS

External beam radiotherapy (EBRT) for prostate cancer (PCa) has rapidly advanced over the years. Advanced techniques with altered dose distributions may have an impact on second haematological cancer (SHC) risks. We assessed SHC risk after EBRT for PCa and explored whether this risk has changed over the years.

MATERIALS AND METHODS

Patients diagnosed with a T1-T3 PCa between 1990 and 2015 were selected from the Netherlands Cancer Registry. Patients treated with EBRT were assigned to EBRT eras based on the date of diagnosis. These eras represented two-dimensional radiotherapy (2D-RT; 1991-1996), three-dimensional conformal radiotherapy (3D-CRT; 1998-2005) or advanced EBRT (2008-2015). Standardised incidence ratios (SIR) and absolute excess risks (AER) were calculated overall and by EBRT era. Sub-hazard ratios (sHRs) were calculated for the comparison of EBRT versus radical prostatectomy and active surveillance.

RESULTS

PCa patients with EBRT as the primary treatment (n = 37 762) had an increased risk of developing a SHC (SIR = 1.20; 95% confidence interval 1.13-1.28) compared with the Dutch male general population. Estimated risks were highest for the 2D-RT era (SIR = 1.32; 95% confidence interval 1.14-1.67) compared with the 3D-CRT era (SIR = 1.16; 95% confidence interval 1.05-1.27) and the advanced EBRT era (SIR = 1.21; 95% confidence interval 1.07-1.36). AER were limited, with about five to six extra cases per 10 000 person-years. Relative risk analysis (EBRT versus radical prostatectomy/active surveillance) showed significant elevation with EBRT versus active surveillance (sHR = 1.17; 95% confidence interval 1.03-1.33; P = 0.017), but not for EBRT versus radical prostatectomy (sHR = 1.08; 95% confidence interval 0.94-1.23; P = 0.281).

CONCLUSION

Increased SHC risks after EBRT for PCa cancer were observed for all EBRT eras compared with the general Dutch male population. Excess risks for EBRT versus other PCa treatment groups were found for only EBRT versus active surveillance.

Dosimetric analysis of patients receiving radiotherapy with VMAT technique in localized prostate cancer and its correlation with side effects

Aim

The aim was to study the relationship between dosimetric data of localized prostate cancer patients who have been treated with curative radiotherapy (RT) and gastrointestinal (GIS), genitourinary (GUS), anal and sexual side effects, and whether there was a difference between dosimetric data and clinical findings between risk groups.

Methods

Eighty-seven patients who received curative radiotherapy for localized prostate cancer between 2014 and 2019 were included in the study. Dosimetrically; whether there was a relationship between V30, V40, V50, V60, V65, V70, V75 for rectum and bladder; D90 for the penile bulb, V72, V74, V76 for the bulbomembranous urethra, V30, V45, V53, Dmax for the anus, and V45 (cc) for the intestine data and the side effects were analyzed. It was evaluated whether there was a relationship between testosterone values and sexual side effects. The Kolmogorov-Smirnov test, one-way analysis of variance (ANOVA) (F-test), and paired-sample t-test were used as statistical methods. For statistical significance, P < 0.05 was accepted.

Results

: The mean age of the patients was 69 (50-86), the mean Prostat specific antigen (PSA) (ng/dL) before RT was 25.1 (0.9-339), the median RT dose was 76 Gy (74-78 Gy), and the mean follow-up period was 38.2 months. PTVmax, PTVmean, PTVmin, bladder V40, bladder V50, rectum V30, rectum V40, rectum V50, and intestinal V45 (cc) were determined as dosimetric data showing differences between risk groups. A statistically significant relationship was found between rectum V30 (P = 0.017), V60 (P = 0.019), V65 (P = 0.008), V70 (P = 0.007), and V75 (P = 0.034) and chronic GIS side effects. G2 GIS side effects were observed in four patients (4.6%) in the entire patient group during the acute period. A statistically significant relationship was found between the patients receiving hormonotherapy (P = 0.021) and testosterone values at the last control (P ≤ 0.001) and chronic sexual side effects.

Conclusion

Attention should be paid to the rectum V30, V60, V65, V70, and V75 values to minimize the long-term GIS side effects in patients who have undergone RT. Testosterone level and ADT status affect chronic sexual toxicity.

Advances in radiotherapy and its impact on second primary cancer risk: a multi-center cohort study in prostate cancer patients

BACKGROUND

Modelling studies suggest that advanced intensity-modulated radiotherapy may increase second primary cancer (SPC) risks, due to increased radiation exposure of tissues located outside the treatment fields. In the current study we investigated the association between SPC risks and characteristics of applied external beam radiotherapy (EBRT) protocols for localized prostate cancer (PCa).

METHODS

We collected EBRT protocol characteristics (2000-2016) from five Dutch RT institutes for the 3D-CRT and advanced EBRT era (N=7908). From the Netherlands Cancer Registry we obtained patient/tumour characteristics, SPC data, and survival information. Standardized incidence ratios (SIR) were calculated for pelvis and non-pelvis SPC. Nationwide SIRs were calculated as a reference, using calendar period as a proxy to label 3D-CRT/advanced EBRT.

RESULTS

From 2000-2006, 3D-CRT with 68-78 Gy in 2 Gy fractions, delivered with 10-23 MV and weekly portal imaging was the most dominant protocol. By the year 2010 all institutes routinely used advanced EBRT (IMRT, VMAT, tomotherapy), mainly delivering 78 Gy in 2Gy fractions, using various kV/MV imaging protocols. Sixteen percent (N=1268) developed ≥1 SPC. SIRs for pelvis and non-pelvis SPC (all institutes, advanced EBRT vs 3D-CRT) were 1.17 (1.00-1.36) vs 1.39 (1.21-1.59), and 1.01 (0.89-1.07) vs 1.03 (0.94-1.13), respectively. Nationwide non-pelvis SIR was 1.07 (1.01-1.13) vs 1.02 (0.98-1.07). Other RT protocol characteristics did not correlate with SPC endpoints.

CONCLUSION

None of the studied RT characteristics of advanced EBRT was associated with increased out-of-field SPC risks. With constantly evolving EBRT protocols, evaluation of associated SPC risks remains important.

Global trends in the epidemiology of bladder cancer: challenges for public health and clinical practice

Bladder cancer is among the ten most common cancers globally, causes considerable morbidity and mortality and is, therefore, a substantial burden for health-care systems. The incidence of bladder cancer is affected by demographic trends, most notably population growth and ageing, as well as exposure to risk factors, especially tobacco smoking. Consequently, the incidence has not been stable throughout the world over time, nor will it be in the near future. Further primary prevention efforts are of the utmost importance to reduce the medical and financial burden of bladder cancer on populations and health-care systems. Simultaneously, less-invasive and lower-cost approaches for the diagnosis of both primary and recurrent bladder cancers are required to address challenges posed by the increasing shortage of health-care professionals and limited financial resources worldwide. In this regard, urinary biomarkers have demonstrated promising diagnostic accuracy and efficiency. Awareness of the risk factors and symptoms of bladder cancer should also be increased in society, particularly among health-care professionals and high-risk groups. Studies investigating the associations between lifestyle factors and bladder cancer outcomes are scarce and should be a research priority. In this Review, we outline global trends in bladder cancer incidence and mortality, and discuss the main risk factors influencing bladder cancer occurrence and outcomes. We then discuss the implications, challenges and opportunities of these epidemiological trends for public health and clinical practice.

Proton therapy for prostate cancer: current state and future perspectives

OBJECTIVE

Localized prostate cancer can be treated with several radiotherapeutic approaches. Proton therapy (PT) can precisely target tumors, thus sparing normal tissues and reducing side-effects without sacrificing cancer control. However, PT is a costly treatment compared with conventional photon radiotherapy, which may undermine its overall efficacy. In this review, we summarize current data on the dosimetric rationale, clinical benefits, and cost of PT for prostate cancer.

METHODS

An extensive literature review of PT for prostate cancer was performed with emphasis on studies investigating dosimetric advantage, clinical outcomes, cost-effective strategies, and novel technology trends.

RESULTS

PT is safe, and its efficacy is comparable to that of standard photon-based therapy or brachytherapy. Data on gastrointestinal, genitourinary, and sexual function toxicity profiles are conflicting; however, PT is associated with a low risk of second cancer and has no effects on testosterone levels. Regarding cost-effectiveness, PT is suboptimal, although evolving trends in radiation delivery and construction of PT centers may help reduce the cost.

CONCLUSION

PT has several advantages over conventional photon radiotherapy, and novel approaches may increase its efficacy and safety. Large prospective randomized trials comparing photon therapy with proton-based treatments are ongoing and may provide data on the differences in efficacy, toxicity profile, and quality of life between proton- and photon-based treatments for prostate cancer in the modern era.

ADVANCES IN KNOWLEDGE

PT provides excellent physical advantages and has a superior dose profile compared with X-ray radiotherapy. Further evidence from clinical trials and research studies will clarify the role of PT in the treatment of prostate cancer, and facilitate the implementation of PT in a more accessible, affordable, efficient, and safe way.

Impact of Advanced Radiotherapy on Second Primary Cancer Risk in Prostate Cancer Survivors: A Nationwide Cohort Study

Purpose

External Beam Radiotherapy (EBRT) techniques dramatically changed over the years. This may have affected the risk of radiation-induced second primary cancers (SPC), due to increased irradiated low dose volumes and scatter radiation. We investigated whether patterns of SPC after EBRT have changed over the years in prostate cancer (PCa) survivors.

Materials and Methods

PCa survivors diagnosed between 1990-2014 were selected from the Netherlands Cancer Registry. Patients treated with EBRT were divided in three time periods, representing 2-dimensional Radiotherapy (RT), 3-dimensional conformal RT (3D-CRT), and the advanced RT (AdvRT) era. Standardized incidence ratios (SIR) and absolute excess risks (AER) were calculated to estimate relative and excess absolute SPC risks. Sub-hazard ratios (sHRs) were calculated to compare SPC rates between the EBRT and prostatectomy cohort. SPCs were categorized by subsite and anatomic region.

Results

PCa survivors who received EBRT had an increased risk of developing a solid SPC (SIR=1.08; 1.05-1.11), especially in patients aged <70 years (SIR=1.13; 1.09-1.16). Pelvic SPC risks were increased (SIR=1.28; 1.23-1.34), with no obvious differences between the three EBRT eras. Non-pelvic SPC were only significantly increased in the AdvRT era (SIR=1.08; 1.02-1.14), in particular for the 1-5 year follow-up period. Comparing the EBRT cohort to the prostatectomy cohort, again an increased pelvic SPC risk was found for all EBRT periods (sHRs= 1.61, 1.47-1.76). Increased non-pelvic SPC risks were present for all RT eras and highest for the AdvRT period (sHRs=1.17, 1.06-1.29).

Conclusion

SPC risk in patients with EBRT is increased and remained throughout the different EBRT eras. The risk of developing a SPC outside the pelvic area changed unfavorably in the AdvRT era. Prolonged follow-up is needed to confirm this observation. Whether this is associated with increased irradiated low-dose volumes and scatter, or other changes in clinical EBRT practice, is the subject of further research.