Induced second cancers after prostate-cancer radiotherapy: No cause for concern?

Metastatic prostate adenocarcinoma and high-grade appendiceal mucinous neoplasm mimicking acute appendicitis in a post-radiation therapy patient

Prostate cancer is the most common visceral malignancy diagnosed in males. Surveillance for post-treatment neoplasms is very crucial. Here we report the first case of recurrent metastatic prostate cancer presenting as acute appendicitis in a background of a high-grade appendiceal mucinous neoplasm. In addition, this case also includes an unusually early presentation of a secondary primary malignancy after radiation therapy. A 70-year-old male with a history of prostate adenocarcinoma status post-proton radiation therapy presented with recurrent poorly differentiated prostate adenocarcinoma with disease progression and extra-prostatic extension. He underwent salvage proton therapy and testosterone replacement therapy. Two years later, the patient presented with right lower quadrant pain. A computed tomography scan showed perforated acute appendicitis with intra-abdominal abscess, which was treated with interval appendectomy. Upon histologic analysis, metastatic prostatic adenocarcinoma was noted in the appendiceal wall and mesoappendix. In addition, an incidental background of high-grade appendiceal mucinous neoplasm was found. Four months later, he presented with persistent abdominal pain, rapid weight loss, fatigue, and fever for 3 months. An abdominal CT scan revealed a 6.1 cm rectal mass. Pathologic analysis diagnosed an aggressive post-radiation spindle cell sarcoma, intermediate to high grade. The patient opted for palliative care. This case shows that a clinical presentation of acute appendicitis in an older patient may sometimes portend a neoplastic rather than infectious etiology. Clinical history and patient epidemiology should always be considered when evaluating an older patient with clinical signs and symptoms of acute appendicitis.

Overall survival and second primary malignancies in men with metastatic prostate cancer

Background

Among prostate cancer (PC) patients, over 90% of distant metastases occur in the bone. PC treatments may be associated with side effects, including second primary malignancies (SPM). There is limited information on the incidence of SPM among men with bone metastatic PC (mPC) and among men with bone metastatic castration-resistant PC (mCRPC). We estimated overall survival and the incidence of SPM in men with mPC and mCRPC.

Methods

In the Prostate Cancer data Base Sweden, the National Prostate Cancer Register was linked to other national health care registers, 15,953 men with mPC in 1999–2011 were identified. Further, 693 men with mCRPC were identified. Outcomes were evaluated using stratified incidence rates, Kaplan-Meier estimators and Cox models.

Results

The mean age among men with mPC was 73.9 years and in men with mCRPC 70.0 years. The median respective survivals were 1.5 (13,965 deaths) and 1.14 years (599 deaths), and average times since PC diagnosis 1.8 and 4.7 years. We observed 2,669 SPMs in men with mPC and 100 SPMs in men with mCRPC. The incidence rate of SPM per 1,000 person-years was 81.8 (78.8–85.0) for mPC and 115.6 (95.1–140.7) for mCRPC. High age, prior neoplasms, urinary tract infection, congestive heart failure, diabetes and renal disease were most strongly associated with increased mortality risk. Prior neoplasms and prior use of antineoplastic agents were most strongly associated with increased SPM risk. Several factors associated with increased mortality and SPM risks were more prevalent in the mCRPC cohort.

Conclusions

Our results on mortality for men with mPC and mCRPC are in line with previous studies from the same time period. Investigation of factors associated with mortality and SPM in men with mPC and mCRPC can help to further understand these outcomes in the era prior to several new treatments have come available.

Metachronous Malignancies in Men with Previous Prostate Cancer in Umbria, Italy, 1994–2003

Data about second primary tumors after prostate carcinoma are controversial. Some authors emphasize an increased incidence of some cancer sites, others an overall diminution. With the aim to provide further information to define the issue, we have analyzed the frequency of second metachronous primary malignancies in patients with diagnosed prostate cancer in the Umbria region of Italy. A total of 410 metachronous cancers among 4528 prostate cancer patients were abstracted from incident cases of the RTUP, over the period 1994–2003. This cohort was compared with all cases (except prostate cancers) recorded in the RTUP archive. The expected number of cases was obtained from indirect standardization with regional incidence rates of several sites. The significance of the observed/expected ratios and the corresponding 95% confidence intervals were based on the Poisson distribution. A significant standardized incidence ratio was found for all sites but prostate, with 410/351 observed/expected cases. The significance disappears considering all sites except prostate and skin non-melanomas. Among several sites, significant standardized incidence ratios were found for skin non-melanomas, for bladder, for rectum, but not for colon cancers. Kidney, ureter and urethra showed a nonsignificant standardized incidence ratio. Nasopharynx showed a significant standardized incidence ratio, but the result was based on a very small number of cases. In our data, the increase in urinary bladder and rectal cancers, after prostate cancer diagnosis, seems to be real: it is plausible that the number of second cancers may be due to increased urologist surveillance, which, in our Region, does not seem to be reduced in elderly men.

Secondary Urethral Malignancies Following Prostate Brachytherapy

OBJECTIVE

To understand urethral secondary malignancies among patients treated with brachytherapy (BRT) for primary prostate cancer.

PATIENTS AND METHODS

Institutional retrospective review identified 13 patients evaluated from 2003 to 2014 with urethral cancer and history of BRT monotherapy for prostate cancer. All patients were biochemically free of their primary disease and radiation-associated secondary malignancies (RASMs) were confirmed pathologically to be histologically distinct from primary tumor. BRT characteristics, patient age, presentation, staging workup, and clinical course were evaluated.

RESULTS

The mean time from BRT to presenting symptoms of hematuria, urinary retention, and/or renal failure was 71 months. Symptom onset to RASM diagnosis interval was 24 months. Mean time from BRT to RASM diagnosis was 95 months. Eighty-five percent of patients had an undetectable prostate-specific antigen level (<0.2 ng/mL) at last follow-up. Types of RASM included sarcomatoid carcinoma (6), small cell carcinoma (2), urothelial carcinoma with squamous differentiation (2), squamous cell carcinoma (1), rhabdomyosarcoma (1), and urothelial carcinoma (1). A majority of patients were diagnosed with advanced disease with either distant metastases (54%) or local progression (23%). Ten patients died during this study period with median time to death after RASM diagnosis of 6 months.

CONCLUSION

RASMs localized to the posterior urethra displayed advanced disease and high mortality rates. Refractory lower urinary tract symptoms, hematuria, and history of prostate BRT should raise suspicion for urethral RASMs. Further studies are warranted to determine patient and disease characteristics that correlate with disease-specific mortality of secondary urethral malignancies.

Evaluation of Imaging Dose From Different Image Guided Systems During Head and Neck Radiotherapy: A Phantom Study

This work evaluated and compared the absorbed doses to selected organs in the head and neck region from the three image guided radiotherapy systems: cone-beam computed tomography (CBCT) and kilovoltage (kV) planar imaging using the On-board Imager® (OBI) as well as the ExacTrac® X-ray system, all available on the Varian Novalis TX linear accelerator. The head and neck region of an anthropomorphic phantom was used to simulate patients' head within the imaging field. Nanodots optically stimulated luminescent dosemeters were positioned at selected sites to measure the absorbed doses. CBCT was found to be delivering the highest dose to internal organs while OBI-2D gave the highest doses to the eye lenses. The setting of half-rotation in CBCT effectively reduces the dose to the eye lenses. Daily high-quality CBCT verification was found to increase the secondary cancer risk by 0.79%.

Use of image guided radiation therapy techniques and imaging dose measurement at Indian hospitals: A survey

A national survey was conducted to obtain information about the use of image-guided radiotherapy (IGRT) techniques and IGRT dose measurement methods being followed at Indian radiotherapy centers. A questionnaire containing parameters relevant to use of IGRT was prepared to collect the information pertaining to (i) availability and type of IGRT delivery system, (ii) frequency of image acquisition protocol and utilization of these images for different purpose, and (iii) imaging dose measurement. The questionnaire was circulated to 75 hospitals in the country having IGRT facility, and responses of 51 centers were received. Survey results showed that among surveyed hospitals, 86% centers have IGRT facility, 78% centers have kilo voltage three-dimensional volumetric imaging. 75% of hospitals in our study do not perform computed tomography dose index measurements and 89% of centers do not perform patient dose measurements. Moreover, only 29% physicists believe IGRT dose is additional radiation burden to patient. This study has brought into focus the need to design a national protocol for IGRT dose measurement and development of indigenous tools to perform IGRT dose measurements.

Intravesical Liposomal Tacrolimus Protects against Radiation Cystitis Induced by 3-Beam Targeted Bladder Radiation

PURPOSE

We primarily determined whether the small animal radiation research platform could create a rat radiation cystitis model via targeted bladder irradiation (phase I). The response to treating early phase radiation cystitis in rats with transurethral catheter instillation of liposomal tacrolimus was also examined (phase II).

MATERIALS AND METHODS

In phase I 16 adult female Sprague Dawley® rats were used. Metabolic urination patterns were analyzed before and after exposure to 20, 30 or 40 Gy radiation. In phase II irradiated rats were randomly assigned to receive a single instillation of saline or liposomal tacrolimus.

RESULTS

The 40 Gy radiation dose induced statistically significant reductions in the intermicturition interval compared to the lower radiation doses. By approximately 20 minutes 40 Gy radiation caused a significant decrease in the mean intermicturition interval (p < 0.0001). Histological analysis revealed degenerative epithelial changes and urothelial swelling with evidence of pseudocarcinomatous epithelial hyperplasia. Therefore, 40 Gy were chosen for the phase II efficacy study. There was no measurable change in total voided urine volume after irradiation, or after liposomal tacrolimus or saline instillation. Liposomal tacrolimus significantly increased the post-irradiation intermicturition interval by approximately 30 minutes back to baseline (p < 0.001).

CONCLUSIONS

The radiation cystitis rat model showed a dose dependent decrease in the intermicturition interval without inducing short-term skin or gastrointestinal damage. This study demonstrates that liposomal tacrolimus may be a promising new intravesical therapy for the rare, serious condition of radiation cystitis.

Comparison of low-dose, half-rotation, cone-beam CT with electronic portal imaging device for registration of fiducial markers during prostate radiotherapy

This study evaluated the agreement of fiducial marker localization between two modalities — an electronic portal imaging device (EPID) and cone‐beam computed tomography (CBCT) — using a low‐dose, half‐rotation scanning protocol. Twenty‐five prostate cancer patients with implanted fiducial markers were enrolled. Before each daily treatment, EPID and half‐rotation CBCT images were acquired. Translational shifts were computed for each modality and two marker‐matching algorithms, seed‐chamfer and grey‐value, were performed for each set of CBCT images. The localization offsets, and systematic and random errors from both modalities were computed. Localization performances for both modalities were compared using Bland‐Altman limits of agreement (LoA) analysis, Deming regression analysis, and Cohen's kappa inter‐rater analysis. The differences in the systematic and random errors between the modalities were within 0.2 mm in all directions. The LoA analysis revealed a 95% agreement limit of the modalities of 2 to 3.5 mm in any given translational direction. Deming regression analysis demonstrated that constant biases existed in the shifts computed by the modalities in the superior–inferior (SI) direction, but no significant proportional biases were identified in any direction. Cohen's kappa analysis showed good agreement between the modalities in prescribing translational corrections of the couch at 3 and 5 mm action levels. Images obtained from EPID and half‐rotation CBCT showed acceptable agreement for registration of fiducial markers. The seed‐chamfer algorithm for tracking of fiducial markers in CBCT datasets yielded better agreement than the grey‐value matching algorithm with EPID‐based registration.

PACS numbers: 87.55.km, 87.55.Qr

[Second neoplasm after treatment of localized prostate cancer]

INTRODUCTION

Prostate cancer (PC) treatment in early stages is radical prostatectomy (RP) or external radiotherapy (ER). There is some uncertainty regarding the development of new ER induced malignant tumors or second primary tumor (SPT), a fact influencing the choice of therapy. The purpose of this study is to determine the best therapeutic alternative for localized PC, in regards to incidence and time of development of.

MATERIAL AND METHODS

A systematic review of the literature is proposed by means of evaluation of studies conducted with localized PC and treated with RP or ER, published between 1990 and 2010. The Mega searchers used were Cochrane Library and Trip Database, and the data bases used were MEDLINE, OVID, Science Direct, SciELO and LiLACS, using MeSH terms and free words. The studies selected were analyzed using the MINCIR score of methodological quality (MQ) to compare articles with different design. The variables were considered to be number of patients treated, localization of lesions, global incidence of STP and MQ of the studies. Averages, medians and weighted averages (WA) were calculated. The study groups were compared using the 95% confidence intervals of the medians.

RESULTS

Eleven articles fulfilled the screening criteria (retrospective cohorts and case series); providing 13 series for the study. The average of MQ was 14.7 points (13 and 16 points). The most frequent localizations of STP were bladder, rectum and long. The WA of the global incidence of STP for the series was 3.6% (4.1% for ER and 2.2% RP) CONCLUSION: The information existing did not make it possible to demonstrated an association between the appearance of STP and therapies for localized PC, it even though there was a superior tendency in irradiated patients.

Secondary malignancies following radiotherapy for prostate cancer

Human exposure to sources of radiation as well as the use of radiation-derived therapeutic and diagnostic modalities for medical reasons has been ongoing for the last 60 years or so. The carcinogenetic effect of radiation either due to accidental exposure or use of radiation for the treatment of cancer has been undoubtedly proven during the last decades. The role of radiation therapy in the treatment of patients with prostate cancer is constantly increasing as less-invasive treatment modalities are sought for the management of this widely, prevalent disease. Moreover the wide adoption of screening for prostate cancer has led to a decrease in the average age that patients are diagnosed with prostate cancer. Screening has also resulted in the diagnosis of low-grade, less-aggressive prostate cancers which would probably never lead to complications or death from the disease. Radiotherapy for prostate cancer has been linked to the late occurrence of second malignancies both in the true pelvis and outside the targeted area due to low-dose radiation scatter. Secondary malignancies following prostate irradiation include predominantly bladder cancer and, to a lesser extent, colon cancer. Those secondary radiation-induced bladder tumors are usually aggressive and sometimes lethal. Care should be given to the long-term follow up of patients under radiation therapy for prostate cancer, while the indications for its use in certain cases should be reconsidered.

Clinical cancer genetics: Part I: Gastrointestinal

There is an increasing recognition of the importance of genetic and familial cancer syndromes in routine clinical practice. Although most of gastrointestinal cancers are sporadic, a number of important cancer predisposition syndromes are now recognized and well characterized. In this review, we discuss some of the basic principles of clinical cancer genetics and clinically relevant aspects of the more common gastrointestinal cancer syndromes from the perspective of practicing radiation oncologists.

A comparative study on the risk of second primary cancers in out-of-field organs associated with radiotherapy of localized prostate carcinoma using Monte Carlo-based accelerator and patient models

PURPOSE

A physician's decision regarding an ideal treatment approach (i.e., radiation, surgery, and/or hormonal) for prostate carcinoma is traditionally based on a variety of metrics. One of these metrics is the risk of radiation-induced second primary cancer following radiation treatments. The aim of this study was to investigate the significance of second cancer risks in out-of-field organs from 3D-CRT and IMRT treatments of prostate carcinoma compared to baseline cancer risks in these organs.

METHODS

Monte Carlo simulations were performed using a detailed medical linear accelerator model and an anatomically realistic adult male whole-body phantom. A four-field box treatment, a four-field box treatment plus a six-field boost, and a seven-field IMRT treatment were simulated. Using BEIR VII risk models, the age-dependent lifetime attributable risks to various organs outside the primary beam with a known predilection for cancer were calculated using organ-averaged equivalent doses.

RESULTS

The four-field box treatment had the lowest treatment-related second primary cancer risks to organs outside the primary beam ranging from 7.3 x 10(-9) to 2.54 x 10(-5)%/MU depending on the patients age at exposure and second primary cancer site. The risks to organs outside the primary beam from the four-field box and six-field boost and the seven-field IMRT were nearly equivalent. The risks from the four-field box and six-field boost ranged from 1.39 x 10(-8) to 1.80 x 10(-5)%/MU, and from the seven-field IMRT ranged from 1.60 x 10(-9) to 1.35 x 10(-5)%/MU. The second cancer risks in all organs considered from each plan were below the baseline risks.

CONCLUSIONS

The treatment-related second cancer risks in organs outside the primary beam due to 3D-CRT and IMRT is small. New risk assessment techniques need to be investigated to address the concern of radiation-induced second cancers from prostate treatments, particularly focusing on risks to organs inside the primary beam.

A comprehensive study on decreasing the kilovoltage cone-beam CT dose by reducing the projection number

The objective of this study was to evaluate the effect of kilovoltage cone‐beam computed tomography (CBCT) on registration accuracy and image qualities with a reduced number of planar projections used in volumetric imaging reconstruction. The ultimate goal is to evaluate the possibility of reducing the patient dose while maintaining registration accuracy under different projection‐number schemes for various clinical sites. An Elekta Synergy Linear accelerator with an onboard CBCT system was used in this study. The quality of the Elekta XVI cone‐beam three‐dimensional volumetric images reconstructed with a decreasing number of projections was quantitatively evaluated by a Catphan phantom. Subsequently, we tested the registration accuracy of imaging data sets on three rigid anthropomorphic phantoms and three real patient sites under the reduced projection‐number (as low as 1/6th) reconstruction of CBCT data with different rectilinear shifts and rotations. CBCT scan results of the Catphan phantom indicated the CBCT images got noisier when the number of projections was reduced, but their spatial resolution and uniformity were hardly affected. The maximum registration errors under the small amount transformation of the reference CT images were found to be within 0.7 mm translation and 0.3° rotation. However, when the projection number was lower than one‐fourth of the full set with a large amount of transformation of reference CT images, the registration could easily be trapped into local minima solutions for a nonrigid anatomy. We concluded, by using projection‐number reduction strategy under conscientious care, imaging‐guided localization procedure could achieve a lower patient dose without losing the registration accuracy for various clinical sites and situations. A faster scanning time is the main advantage compared to the mA decrease‐based, dose‐reduction method.

PACS numbers: 87.57.C‐, 87.57.cf, 87.57.cj, 87.57.cm, 87.57.cp, 87.57.N‐, 87.57.nf, 87.57.nj

Monte Carlo simulation and patient dosimetry for a kilovoltage cone-beam CT unit

PURPOSE

The purpose of this work is to characterize the x-ray volume imager (XVI), the cone-beam computed tomography (CBCT) unit mounted on the Elekta Synergy linac, with F1 bowtie filter and to calculate the three-dimensional dose delivered to patients using volumetric acquisition.

METHODS

The XVI is modeled in detail using a new Monte Carlo (MC) code, BEAMPP, under development at the National Research Council Canada. In this investigation, a new component module is developed to accurately model the unit's bowtie filter used in conjunction with the available beam collimators at the clinical energy of 120 kV. The modeling is compared against percentage depth dose (PDD) and profile measurements. Kilovoltage radiation beams' phase space files are also analyzed. The authors also describe a method for the absolute dose calibration of the MC model of the CBCT unit when used in a clinical volumetric acquisition mode. Finally, they calculate three-dimensional patient dose from CBCT image acquisition in three clinical cases of interest: Pelvis, lung, and head and neck.

RESULTS

The agreement between measurement and MC is shown to be very good: Within +/- 2% for the PDD and within +/- 3.5% inside the radiation field for all the collimators with the F1 bowtie filter. A full account of the absolute calibration method is given and dose calculation is validated against ion chamber measurements in different locations of a plastic phantom. Calculations and experiments agree within +/- 2% or better in both at the center and the periphery of the phantom, with worst agreement of 4.5% at the surface of the phantom and for one specific combination of collimator and filter. Patient dose from CBCT scan reveals that dose to tissue is between 2 and 2.5 cGy for a pelvis or a lung full acquisition. For H&N dose to tissue is 5 cGy, with the unit presets used in this work. Dose to bony structures can be two to three times higher than dose to tissue.

CONCLUSIONS

The XVI CBCT unit has been fully modeled including the F1 bowtie filter. Absolute dose distribution from the unit has been successfully validated. Full MC patient dose calculation has shown that the three-dimensional dose distribution from CBCT is complex. Patient dose from CBCT exposure cannot be completely accounted for by using a numerical factor as an estimate of the dose at the center of the body. Furthermore, additional dose to bone should be taken into account when adopting any IGRT strategy and weighed vs the unquestionable benefits of the technique in order to optimize treatment. Full three-dimensional dose calculation is recommended if patient dose from CBCT is to be integrated in any adaptive planning strategy.

Prostate cancer as a first and second cancer: effect of family history

BACKGROUND

Diagnosis with prostate cancer has been reported to increase the risk of subsequent tumours. However, specific data on individuals with a parental history are not available so far.

METHODS

On the basis of the nationwide Swedish Family-Cancer Database including 18,207 primary invasive prostate cancers, standardised incidence ratios (SIRs) were used to estimate the relative risks of subsequent tumours after prostate cancer in the general population and among individuals with a parental history of cancer.

RESULTS

A significantly increased SIR of colorectal cancer was found among prostate cancer patients with a parental history of colorectal cancer (2.26, 11 cases). The SIRs of parental concordant (same site) tumours after prostate cancer were also increased for urinary bladder cancer (4.42, 4 cases) and chronic lymphoid leukaemia (38.0, 2 cases).

CONCLUSION

A higher than additive and multiplicative interaction was observed between the individual history of prostate cancer and parental history of colorectal and urinary bladder cancers, although the number of cases did not permit the rejection of any interaction model. The results suggest that the occurrence of second tumours, for example bladder after prostate or prostate after bladder tumours, is mostly related to shared genetic and non-genetic risk factors rather than treatment of first cancer.

Phenomenological modelling of second cancer incidence for radiation treatment planning

It is still an unanswered question whether a relatively low dose of radiation to a large volume or a higher dose to a small volume produces the higher cancer incidence. This is of interest in view of modalities like IMRT or rotation therapy where high conformity to the target volume is achieved at the cost of a large volume of normal tissue exposed to radiation. Knowledge of the shape of the dose response for radiation-induced cancer is essential to answer the question of what risk of second cancer incidence is implied by which treatment modality. This study therefore models the dose response for radiation-induced second cancer after radiation therapy of which the exact mechanisms are still unknown. A second cancer risk estimation tool for treatment planning is presented which has the potential to be used for comparison of different treatment modalities, and risk is estimated on a voxel basis for different organs in two case studies. The presented phenomenological model summarises the impact of microscopic biological processes into effective parameters of mutation and cell sterilisation. In contrast to other models, the effective radiosensitivities of mutated and non-mutated cells are allowed to differ. Based on the number of mutated cells present after irradiation, the model is then linked to macroscopic incidence by summarising model parameters and modifying factors into natural cancer incidence and the dose response in the lower-dose region. It was found that all principal dose-response functions discussed in the literature can be derived from the model. However, from the investigation and due to scarcity of adequate data, rather vague statements about likelihood of dose-response functions can be made than a definite decision for one response. Based on the predicted model parameters, the linear response can probably be rejected using the dynamics described, but both a flattening response and a decrease appear likely, depending strongly on the effective cell sterilisation of the mutated cells. Thus insights could be gained into the impact of parameters describing the effective mutation or cell sterilisation of non-mutated as well as of mutated cells, which constitute precursors of cancer. The biggest drawbacks in the estimation of second cancer incidence remain the low statistical power of clinical studies on radiation induction of cancer and the inability to isolate the effect due to radiation alone - if the latter is possible at all. We conclude that at the present stage of knowledge, further investigations have to be carried out in order to really compare treatment modalities with respect to the second cancer risk they imply.

The management of imaging dose during image-guided radiotherapy: report of the AAPM Task Group 75

Radiographic image guidance has emerged as the new paradigm for patient positioning, target localization, and external beam alignment in radiotherapy. Although widely varied in modality and method, all radiographic guidance techniques have one thing in common--they can give a significant radiation dose to the patient. As with all medical uses of ionizing radiation, the general view is that this exposure should be carefully managed. The philosophy for dose management adopted by the diagnostic imaging community is summarized by the acronym ALARA, i.e., as low as reasonably achievable. But unlike the general situation with diagnostic imaging and image-guided surgery, image-guided radiotherapy (IGRT) adds the imaging dose to an already high level of therapeutic radiation. There is furthermore an interplay between increased imaging and improved therapeutic dose conformity that suggests the possibility of optimizing rather than simply minimizing the imaging dose. For this reason, the management of imaging dose during radiotherapy is a different problem than its management during routine diagnostic or image-guided surgical procedures. The imaging dose received as part of a radiotherapy treatment has long been regarded as negligible and thus has been quantified in a fairly loose manner. On the other hand, radiation oncologists examine the therapy dose distribution in minute detail. The introduction of more intensive imaging procedures for IGRT now obligates the clinician to evaluate therapeutic and imaging doses in a more balanced manner. This task group is charged with addressing the issue of radiation dose delivered via image guidance techniques during radiotherapy. The group has developed this charge into three objectives: (1) Compile an overview of image-guidance techniques and their associated radiation dose levels, to provide the clinician using a particular set of image guidance techniques with enough data to estimate the total diagnostic dose for a specific treatment scenario, (2) identify ways to reduce the total imaging dose without sacrificing essential imaging information, and (3) recommend optimization strategies to trade off imaging dose with improvements in therapeutic dose delivery. The end goal is to enable the design of image guidance regimens that are as effective and efficient as possible.

Secondary cancer after radiotherapy for prostate cancer: should we be more aware of the risk?

OBJECTIVES

As the number of prostate cancer survivors is increasing, the long-term health of prostate cancer patients has become a significant health issue. Radiation is known to induce malignant transformation, and prostate cancer radiotherapy is suggested to induce secondary malignancies. This report reviews the available data regarding the risk of secondary cancer after radiation for prostate cancer.

METHODS

Epidemiological studies of the secondary cancer risk in patients with a history of prostate cancer radiation and the literature regarding radiation-induced carcinogenesis were reviewed.

RESULTS

Prostate cancer is not associated with an increased number of additional malignancies. The data suggests a modest increase in secondary cancers associated with radiation for prostate cancer, as approximately one in 70 patients undergoing radiation and surviving more than 10 yr will develop secondary cancer. The most common sites for secondary cancers are bladder and rectum. In addition to the cancers adjacent to the radiation field, there is also an increase of cancers in distant sites, such as lung. The increased risk for secondary cancers is reported after external radiation, not after brachytherapy. The available data originated from studies of patients undergoing conventional radiotherapy. New treatment methods, such as intensity-modulated radiotherapy, may be associated with a higher risk of secondary cancers.

CONCLUSION

Although the incidence of secondary cancers after prostate cancer radiotherapy is not dramatically different from the overall population, patients should be informed about this risk. Other treatment modalities should be considered for patients with long life expectancy and for patients with additional risk factors.