The risk of second primary cancers due to peripheral photon and neutron doses received during prostate cancer external beam radiation therapy

Second Primary Malignancy in Patients with Hypopharyngeal Carcinoma: A SEER-Based Study

Background

A population-based analysis of the risk of secondary primary malignancy (SPM) in patients with hypopharyngeal carcinoma (HPC) has been lacking in the literature. Therefore, we conducted this study to determine the risk factors and assess the effects of SPM on the overall survival (OS) and cancer-specific survival (CSS) of patients with HPC.

Methods

Data on selected patients diagnosed with HPC from the Surveillance, Epidemiology and End Results (SEER) database between 1973 and 2015 were examined through logistic regression, Cox regression and nomogram methods.

Results

The overall risk of SPM in patients with HPC was higher than that in the general population (SIR: 2.77; P < 0.05). The specific-site, including the oral cavity, pharynx, digestive system, respiratory system and endocrine system, had a relatively higher risk of SPM. The overall risks of the subgroup of people 55–75 years of age and all subgroups of sex, race and latency were significantly elevated. In addition, patients with HPC were more likely to have been diagnosed in 2010–2015 (vs 2004–2009; P = 0.002), to be unmarried (vs married; P = 0.008), to have distant metastasis (vs no metastasis; P = 0.016) and to have had no surgery for the first tumor (vs surgery for the first tumor; P = 0.021), and these aspects were associated with a significantly elevated risk of developing SPM. SPM was independently associated with better OS and CSS. The OS and CSS in patients with HPC with SPM were better than those in patients without SPM (log rank P < 0.0001). The C indexes of the nomogram constructed with ten influencing factors including SPM were 0.681:0.699 for OS and 0.705:0.724 for CSS (training cohort:validation cohort).

Conclusion

Although the overall risk of SPM in patients with HPC was elevated, SPM did not decrease the OS and CSS in patients with HPC. This finding is inconsistent with clinical observations and thus requires further research and exploration. It possibly because HPC might have a shorter survival time, or the follow-up time was not long enough.

Comparison of Clinical Outcomes of Radical Prostatectomy versus IMRT with Long-Term Hormone Therapy for Relatively Young Patients with High- to Very High-Risk Localized Prostate Cancer

Simple Summary

That the definitive optimal treatments for relatively young men (aged ≤ 65 years) with high- or very high-risk localized prostate cancer (HR/VHR-LPC) are radical prostatectomy (RP) or radiation plus antiandrogen therapy (RT-ADT) is controversial. To the best of our knowledge, our study is the first and largest to examine biochemical failure (BF), all-cause death, locoregional recurrence, and distant metastasis in relatively young men with HR/VHR-LPC as defined by National Comprehensive Cancer Network risk strata. After head-to-head propensity score matching was used to balance the potential confounders, a multivariable Cox proportional hazards regression model was used to analyze oncologic outcomes. In relatively young men with HR/VHR-LPC, RP and RT-ADT yielded similar oncologic outcomes and RP reduced the risk of BF compared with RT-ADT.

Abstract

That intensity-modulated radiotherapy (IMRT) plus antiandrogen therapy (IMRT-ADT) and radical prostatectomy (RP) are the definitive optimal treatments for relatively young patients (aged ≤ 65 years) with high- or very high-risk localized prostate cancer (HR/VHR-LPC), but remains controversial. We conducted a national population-based cohort study by using propensity score matching (PSM) to evaluate the clinical outcomes of RP and IMRT-ADT in relatively young patients with HR/VHR-LPC. Methods: We used the Taiwan Cancer Registry database to evaluate clinical outcomes in relatively young (aged ≤ 65 years) patients with HR/VHR-LPC, as defined by the National Comprehensive Cancer Network risk strata. The patients had received RP or IMRT-ADT (high-dose, ≥72 Gy plus long-term, 1.5–3 years, ADT). Head-to-head PSM was used to balance potential confounders. A Cox proportional hazards regression model was used to analyze oncologic outcomes. Results: High-dose IMRT-ADT had a higher risk of biochemical failure (adjusted hazard ratio [aHR] = 2.03, 95% confidence interval [CI] 1.56–2.65, p < 0.0001) compared with RP; IMRT-ADT did not have an increased risk of all-cause death (aHR = 1.2, 95% CI 0.65–2.24, p = 0.564), locoregional recurrence (aHR = 0.88, 95% CI 0.67–1.06, p = 0.3524), or distant metastasis (aHR = 1.03, 95% CI 0.56–1.9, p = 0.9176) compared with RP. Conclusion: In relatively young patients with HR/VHR-LPC, RP and IMRT-ADT yielded similar oncologic outcomes and RP reduced the risk of biochemical failure compared with IMRT-ADT.

Calculation of Photoneutron Contamination of Varian Linac in ICRU Soft-Tissue Phantom Using MCNPX Code

Purpose

The aim of this research was to calculate the fluence, dose equivalent (DE), and kerma of thermal, epithermal and fast photoneutrons separately, within ICRU soft-tissue-equivalent phantom in the radiotherapy treatment room, using MCNPX Monte Carlo code.

Materials and Methods

For this purpose, 18 MV Varian Linac 2100 C/D machine was simulated and desired quantities were calculated on the central axis and transverse directions at different depths.

Results

Maximum fluence, DE and kerma of total photoneutrons on central axis of the phantom were 43.8 n.cm^-2.Gy^-1, 0.26, and 3.62 mGy.Gy^-1, at depths 2, 0.1, 0.1 cm, respectively. At any depth, average of fluence, DE and kerma in the outer area of the field were less than the inner area and in general were about 72%, 52%, and 45%, respectively.

Conclusion

According to this research, within the phantom; variation of fluence, DE and kerma in transverse direction were mild, and along the central axis at shallow area were sharp. DE of fast photoneutrons at shallow and deep areas were one order of magnitude greater than thermal photoneutrons.

Out-of-field organ doses and associated risk of cancer development following radiation therapy with photons

Innovations in cancer treatment have contributed to the improved survival rate of these patients. Radiotherapy is one of the main options for cancer management nowadays. High doses of ionizing radiation are usually delivered to the tumor site with high energy photon beams. However, the therapeutic radiation exposure may lead to second cancer induction. Moreover, the introduction of intensity-modulated radiation therapy over the last decades has increased the radiation dose to out-of-field organs compared to that from conventional irradiation. The increased organ doses might result in elevated probabilities for developing secondary malignancies to critical organs outside the treatment volume. The organ-specific dosimetry is considered necessary for the theoretical second cancer risk assessment and the proper analysis of data derived from epidemiological reports. This study reviews the methods employed for the measurement and calculation of out-of-field organ doses from exposure to photons and/or neutrons. The strengths and weaknesses of these dosimetric approaches are described in detail. This is followed by a review of the epidemiological data associated with out-of-field cancer risks. Previously published theoretical cancer risk estimates for adult and pediatric patients undergoing radiotherapy with conventional and advanced techniques are presented. The methodology for the theoretical prediction of the probability of carcinogenesis to out-of-field sites and the limitations of this approach are discussed. The article also focuses on the factors affecting the magnitude of the probability for developing radiotherapy-induced malignancies. The restriction of out-of-field doses and risks through the use of different types of shielding equipment is presented.

The risk and prognosis of secondary primary malignancy in lung cancer: a population-based study

Aim: To assess and predict risk and prognosis of lung cancer (LC) patients with second primary malignancy (SPM). Methods: LC patients diagnosed from 1992 to 2016 were obtained through the Surveillance, Epidemiology, and End Results database. Standardized incidence ratios were calculated to evaluate SPM risk. Cox regression and competing risk models were applied to assess the factors associated with overall survival, SPM development and LC-specific survival. Nomograms were built to predict SPM probability and overall survival. Results & conclusion: LC patients remain at higher risk of SPM even though the incidence declines. Patients with SPM have a better prognosis than patients without SPM. The consistency indexes for nomograms of SPM probability and overall survival are 0.605 (95% CI: 0.598-0.611) and 0.644 (95% CI: 0.638-0.650), respectively.

Secondary malignancy risk for patients with localized prostate cancer after intensity-modulated radiotherapy with and without flattening filter

Men treated for localized prostate cancer by radiotherapy have often a remaining life span of 10 yr or more. Therefore, the risk for secondary malignancies should be taken into account. Plans for ten patients were evaluated which had been performed on an Oncentra® treatment planning system for a treatment with an Elekta Synergy™ linac with Agility™ head. The investigated techniques involved IMRT and VMTA with and without flattening filter. Different dose response models were applied for secondary carcinoma and sarcoma risk in the treated region and also in the periphery. As organs at risk we regarded for carcinoma risk urinary bladder, rectum, colon, esophagus, thyroid, and for sarcoma risk bone and soft tissue. The excess absolute risk (EAR) was found very similar in the treated region for both techniques (IMRT and VMAT) and also for both with and without flattening filter. The secondary sarcoma risk resulted about one magnitude smaller than the secondary carcinoma risk. The EAR to the peripheral organs was statistically significant reduced by application of the flattening filter free mode concerning the flattening filter as main source of scattered dose. Application of flattening filter free mode can thus support to reduce second malignancy risk for patients with localized prostate cancer.

NOVEL 'PHOTONEUTRON VOLUME DOSE EQUIVALENT' HYPOTHESIS AND METHODOLOGY FOR SECOND PRIMARY CANCER RISK ESTIMATION IN HIGH-ENERGY X-RAY MEDICAL ACCELERATORS

A novel 'photoneutron (PN) volume dose equivalent' methodology was hypothesized and applied for the first time for estimating PN second primary cancer (PN-SPC) risks in high-energy X-ray medical accelerators. Novel position-sensitive mega-size polycarbonate dosimeters with 10B converter (with or without cadmium covers) were applied for determining fast, epithermal and thermal PN dose equivalents at positions on phantom surface and depths. The methodology was applied to sites of tumors such as brain, stomach and prostate in 47 patients. The PN-SPC risks were estimated for specific organs/tissues using linear International Commission on Radiological Protection cancer risks and were compared with some available data. The corresponding PN-SPC risk estimates ranged from 1.450 × 10-3 to 1.901 cases per 10 000 persons per Gray. The method was applied to 47 patients for estimating PN-SPC risks in patients undergoing radiotherapy. The PN-SPC risk estimates well match those calculated by simulation but are comparatively different from those estimated by 'PN point dose equivalent' methods, as expected.

Second primary malignancy in patients with cholangiocarcinoma: a population-based study

Background

A population-based estimate of risk of second primary malignancy (SPM) in patients with cholangiocarcinoma (CCA) is still lacking.

Objectives

To investigate the overall and site-specific risk of SPM in patients with CCA. To identify risk factors of SPM and further evaluate the impact of SPM on overall survival (OS) and disease specific survival (DSS) in patients with CCA.

Methods

Patients with histologically diagnosed CCA between 1973 and 2015 were identified from the Surveillance, Epidemiology and End Results database. Standardized incidence ratio (SIR) was calculated. Risk factors for SPM and CCA survival were evaluated by logistic, Cox, and nomogram methods.

Results

We found that the overall risk of SPM in patients with CCA was significantly higher than that in the general population (SIR =1.27, 95% CI =1.03–1.55, P<0.05). The risk of SPM was significantly increased at specific sites, including transverse colon, intrahepatic bile duct, other biliary, and thyroid. A significant increase in overall risk was characterized in the subgroups of patients aged ≤29, patients aged 30–59 years, females, whites, and patients with latency ≤11 months (63.41, 2.45, 1.4, 1.3, and 2.6-fold, respectively). In patients with CCA, not having undergone surgery for the first primary malignancy (vs having undergone surgery for the first primary malignancy; HR =0.269; 95% CI =0.211–0.342; P<0.001) was associated with significantly decreased risk of SPM. Patients with SPM had better OS and DSS than those without SPM (Log rank P<0.001). Absence of SPM was an independent risk factor for poorer OS and DSS.

Conclusion

Although the risk of SPM in patients with CCA was significantly increased, the presence of SPM did not shorten OS and DSS of patients with CCA, possibly due to the relatively poorer survival of patients with CCA.

Risk of secondary rectal cancer and colon cancer after radiotherapy for prostate cancer: a meta-analysis

PURPOSE

To investigate whether radiotherapy for prostate cancer increases the risk of therapy-related rectal cancer and colon cancer.

METHODS

A systematic literature search was carried out using the Medline (PubMed), EMBASE, and the Cochrane Library to identify studies examining the association between radiotherapy for prostate cancer and secondary colorectal cancer (rectal cancer and colon cancer) published before March 19, 2018. The risk of second colorectal cancer after radiotherapy was summarized using unadjusted odds ratio (OR) and adjusted hazard ratio (HR) with their 95% confidence interval (CI). Subgroup and sensitivity analyses were conducted to detect potential bias and heterogeneity.

RESULTS

After study selection, 16 reports were retrieved for analysis. When patients received radiotherapy compared with those unexposed to radiation, there was an increased risk of the rectal cancer (OR 1.37, 95%CI 1.01 to 1.85), but not colon cancer. According to adjusted HR, there was an increased risk of the rectal cancer (HR 1.64, 95%CI 1.39 to 1.94), and colon cancer (HR 1.33, 95%CI 1.02 to 1.76). The OR for rectal cancer showed an increased risk with longer latent period (5 years lag time versus 10 years lag time, OR: 1.56 versus 2.22). Brachytherapy had no association with second cancer across all analyses.

CONCLUSIONS

Radiotherapy was associated with an increased risk of subsequent rectal cancer compared with patients unexposed to radiation. Colon may be free from the damage of radiation. Brachytherapy had no association with second rectal cancer or colon cancer.

A Monte Carlo study of organ and effective doses of cone beam computed tomography (CBCT) scans in radiotherapy

Cone-beam CT (CBCT) scans utilised for image guided radiation therapy (IGRT) procedures have become an essential part of radiotherapy. The aim of this study was to assess organ and effective doses resulting from new CBCT scan protocols (head, thorax, and pelvis) released with a software upgrade of the kV on-board-imager (OBI) system. Organ and effective doses for protocols of the new software (V2.5) and a previous version (V1.6) were assessed using Monte Carlo (MC) simulations for the International Commission on Radiological Protection (ICRP) adult male and female reference computational phantoms. The number of projections and the mAs values were increased and the size of the scan field was extended in the new protocols. Influence of these changes on organ and effective doses of the scans was investigated. The OBI system was modelled in EGSnrc/BEAMnrc, and organ doses were estimated using EGSnrc/DOSXYZnrc. The MC model was benchmarked against experimental measurements. Organ doses resulting from the V2.5 protocols were higher than those of V1.6 for organs that were partially or fully inside the scans fields, and increased by (3-13)%, (10-77)%, and (13-21)% for the head, thorax, and pelvis protocols for both phantoms, respectively. As a result, effective doses rose by 14%, 17%, and 16% for the male phantom, and 13%, 18%, and 17% for the female phantom for the three scan protocols, respectively. The scan field extension for the V2.5 protocols contributed significantly in the dose increases, especially for organs that were partially irradiated such as the thyroid in head and thorax scans and colon in the pelvic scan. The contribution of the mAs values and projection numbers was minimal in the dose increases, up to 2.5%. The field size extension plays a major role in improving the treatment output by including more markers in the field of view to match between CBCT and CT images and hence setting up the patient precisely. Therefore, a trade-off between the risk and benefits of CBCT scans should be considered, and the dose increases should be monitored. Several recommendations have been made for optimisation of the patient dose involved for IGRT procedures.