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Japanese Journal of Clinical Oncology Advance Access published online on August 2, 2008
Japanese Journal of Clinical Oncology, doi:10.1093/jjco/hyn063
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© The Author (2008). Published by Oxford University Press. All rights reserved

Radiation Pneumonitis Caused by a Migrated Brachytherapy Seed Lodged in the Lung

Noriyoshi Miura1, Yoshito Kusuhara1, Kousaku Numata1, Akitomi Shirato1, Katsuyoshi Hashine1, Yoshiteru Sumiyoshi1, Masaaki Kataoka2 and Shinsuke Takechi3

1 Department of Urology
2 Department of Radiation Oncology, Shikoku Cancer Center, Ehime
3 Department of Urology, Takechi Clinic, Ehime, Japan

For reprints and all correspondence: Noriyoshi Miura, 160-Minamiumemoto, Matsuyama, Ehime 791-0280, Japan. E-Mail: nmiura{at}shikoku-cc.go.jp

Received February 7, 2008; accepted June 24, 2008


   Abstract
TOP
 Abstract
INTRODUCTION
 DISCUSSION
 References
 
We report a case of radiation pneumonitis caused by a migrated seed lodged in the lung after prostate brachytherapy. A 71-year-old man underwent transperineal interstitial permanent prostate brachytherapy for localized prostate cancer. On the day after brachytherapy, a routine postimplant chest X-ray revealed migration of one seed to the lower lobe of the left lung. After 1 month, pulmonary opacities were observed in the left lower lobe but not near the seed. He was diagnosed with bacterial pneumonia, and antibiotic therapy was commenced. Two months after brachytherapy, the patient's symptoms, laboratory data and pulmonary opacities improved; however, an abnormal shadow (consolidation) developed around the migrated seed. Lung consolidation disappeared almost completely 12 months after brachytherapy without any medical treatment. The abnormal shadow probably represented radiation pneumonitis. To the best of our knowledge, this is the first report of radiation pneumonitis caused by a migrated brachytherapy seed in the lung.

Key Words: prostate cancer • radiation pneumonitis • brachytherapy • seed migration


   INTRODUCTION
TOP
 Abstract
 INTRODUCTION
DISCUSSION
 References
 
Prostate brachytherapy is an increasingly popular treatment method for early-stage prostate carcinoma. During the follow-up of prostate carcinoma patients who have been treated with brachytherapy, we have often detected migrated seeds in the lung. However, to the best of our knowledge, no report has addressed any side effect of seed migration to the lungs. Here, we report our experience in an abnormal shadow in the lung, probably indicative of radiation pneumonitis due to a migrated seed.

Case Report
A 71-year-old man was diagnosed with prostate carcinoma [clinical-stage T1cN0M0; prostate-specific antigen (PSA) level, 6.839 ng/ml; Gleason score, 3 + 4 = 7]. In December 2005, he underwent transperineal interstitial permanent prostate brachytherapy as a treatment for localized prostate adenocarcinoma. Treatment planning was carried out using the planning system, VariSeed 7.1 (Varian Medical Systems, Palo Alto, CA, USA). A modified peripheral loading technique was used. The 55–125-iodine loose radioactive seeds were implanted in the prostate. The radioactive source strength was 0.343 mCi per seed. The prescribed dose to be administered as monotherapy was 145 Gy. On the day after brachytherapy, a routine postimplant chest X-ray revealed the migration of one seed to the lower lobe of the left lung. After 1 month, he developed cough and subsequently facial oedema.

Computed tomography (CT) of the lung revealed pulmonary opacities in the left lower lobe but no abnormal shadow around the seed. The white blood cell count had increased to 9000/mm2 (normal range, 3500–8500/mm2) and the C-reactive protein level had increased to 2.4 ng/dl (normal range, <0.3 ng/dl). He was diagnosed with bacterial pneumonia, and antibiotic therapy was commenced. Two months after brachytherapy, his symptoms improved, the laboratory data normalized and pulmonary opacities regressed (Fig. 1). However, CT revealed an abnormal shadow around the migrated seed. Since there was no respiratory symptom, the patient was followed-up without any treatment. CT performed at 4 months after brachytherapy revealed a spontaneous decrease in the consolidation, and the consolidation almost disappeared 12 months after brachytherapy (Fig. 2).


Figure 1
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  		Figure 1. Bacterial pneumonia 1 month later of the brachytherapy, pulmonary opacities occurred in the left lower lobe but not near the seed. Two months later of the brachytherapy, the symptom improved, the laboratory data became normal and pulmonary opacities improved. Computed tomography (CT) obtained (a) before the brachytherapy, (b) 1 month after the brachytherapy, (c) 2 months after the brachytherapy and (d) 4 months after the brachytherapy.

 

Figure 2
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  		Figure 2. Radiation pneumonitis two months after the brachytherapy, CT showed the consolidation occurred around the migrated seed. This shadow reduced gradually after that without any treatment. CT obtained (a) before the brachytherapy, (b) 1 month after the brachytherapy, (c) 2 months after the brachytherapy, (d) 4 months after the brachytherapy, (e) 1 year after the brachytherapy.

 

   DISCUSSION
TOP
 Abstract
 INTRODUCTION
 DISCUSSION
References
 
During the past decade, prostate brachytherapy has been increasingly used for the management for low-grade, low-stage prostate cancer. Pulmonary seed migration was identified in 1991 (1). Kunos et al. (2) examined 120 patients in whom free seeds were implanted; postoperative pulmonary migration of seeds was detected in 36% of the patients. It has also been reported that free seeds have an embolism rate of 10.9–55.0%, whereas linked seeds have an embolism rate of 0–21.4% (3–5). Reed et al. (6) performed a prospective randomized comparison of stranded versus loose 125I seeds, and showed a strong trend toward a decrease in postimplant seed loss with stranded seeds. Migration of seeds to the parts other than the lungs has also been reported. Davis et al. (7) reported a case in which seeds were lodged in the right ventricle. Nguyen (8) reported a case of relocation of implanted seeds to the heart and left-hepatic lobe. These patients did not experience any clinical symptoms due to seed migration.

The abnormal shadow observed in our case probably indicated radiation pneumonitis. To the best of our knowledge, this is the first report of radiation pneumonitis caused by a migrated seed lodged in the lung after prostate brachytherapy. The diagnosis of radiation pneumonitis can be explained as follows: first, the shadow was characteristic, in that it extended radially around the seed. CT performed 2 months after brachytherapy showed a metallic density at the centre of the consolidation; this metallic density was the migrated seed. Second, radiation pneumonitis typically occurs within 4–12 weeks after the completion of radiation therapy (9). In our case, the abnormal shadow around the migrated seed developed 8 weeks after brachytherapy, and this shadow decreased spontaneously without any medical treatment. Third, there always exists a theoretical risk of radiation pneumonitis. The total dose of radiation delivered is important. Radiological manifestations of radiation pneumonitis rarely appear at doses lower than 20 Gy and are almost always evidenced in patients who have received doses greater than 40 Gy (9). For the induction of radiation pneumonitis, Prasad et al. calculated a dose of more than 30.73 Gy to the lung at a distance of less than 0.5 cm along the transverse radius of 125I seed with a strength of 0.34 mCi (10,11). We calculate based on the data reported by Kirov et al. (12) and show radial dose function in water for 125I seed (Fig. 3).


Figure 3
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  		Figure 3. Radial dose function in water for 125I seed. We calculated based on the data reported by Kirov et al. (12).

 
Are there any other possibilities other than radiation pneumonitis?, for example, allergy and bacterial pneumonia. We think that the possibility of allergy is too low because these seeds are tiny hollow biocompatible titanium capsules with the radioactive material contained within. The possibility of bacterial pneumonia is also low. Abnormal shadow around the migrated seed had enlarged, although the symptoms improved and the laboratory data were normal. We consider that there is not the relationship between first episode of bacterial pneumonia and radiation pnuemonitis, therefore, it should be considered that two kinds of pneumonia probably occurred independently at a different place and timing.

This case was found by follow-up CT to observe bacterial pneumonia incidentally. We recommend routine chest X-ray at 3 months and 1 year after brachytherapy in case of seed migration to lung, because radiation pneumonitis typically occurs within 4–12 weeks after the completion of radiation therapy. Moreover, Ankem et al. (5) recommend a chest X-ray every 2 years as a part of the standard follow-up because there is a possible risk of lung cancer in these patients.

In conclusion, to the best of our knowledge, this is probably the first report of radiation pneumonitis caused by a migrated seed lodged in the lung. Further, the long-term implications of lung irradiation by embolized seeds are not known; therefore, long-term follow-up of such patients is required.

Conflict of interest statement None declared.


   References
TOP
 Abstract
 INTRODUCTION
 DISCUSSION
 References
 
1 Steinfeld AD, Donahue BR, Plaine L. Pulmonary embolization of iodine-125 seeds following prostate implantation. Urology (1991) 37:149–50.[CrossRef][Web of Science][Medline]

2 Kunos CA, Resnick MI, Kinsella TJ, Ellis RJ. Migration of implanted free radioactive seeds for adenocarcinoma of the prostate using a Mick applicator. Brachytherapy (2004) 3:71–7.[CrossRef][Medline]

3 Older RA, Synder B, Krupski TL, Glembocki DJ, Gillenwater JY. Radioactive implant migration in patients treated for localized prostate cancer with interstitial brachytherapy. J Urol (2001) 165:1590–2.[CrossRef][Web of Science][Medline]

4 Stone NN, Stock RG. Reduction of pulmonary migration of permanent interstitial sources in patients undergoing prostate brachytherapy. Urology (2005) 66:119–23.[CrossRef][Web of Science][Medline]

5 Ankem MK, DeCarvalho VS, Harangozo AM, Hartanto VH, Perrotti M, Han KR, et al. Implications of radioactive seed migration to the lungs after prostate brachytherapy. Urology (2002) 59:555–9.[CrossRef][Web of Science][Medline]

6 Reed DR, Wallner KE, Merrick GS, Arthurs S, Mueller A, Cavanagh W, et al. A prospective randomized comparison of stranded vs. loose 125I seeds for prostate brachytherapy. Brachytherapy (2007) 6:129–34.[CrossRef][Web of Science][Medline]

7 Davis BJ, Pfeifer EA, Wilson TM, King BF, Eshleman JS, Pisansky TM. Prostate brachytherapy seed migration to the right ventricle found at autopsy following acute cardiac dysrhythmia. J Urol (2000) 164:1661.[CrossRef][Web of Science][Medline]

8 Nguyen BD. Cardiac and hepatic seed implant embolization after prostate brachytherapy. Urology (2006) 68:673.e17–673.e19.

9 Choi YW, Munden RF, Erasmus J, Park KJ, Chung WK, Jeon SC, et al. Effects of radiation therapy on the lung: radiologic appearances and differential diagnosis. Radiographics (2004) 24:985–97.[Abstract/Free Full Text]

10 Tapen EM, Blasko JC, Grimm PD, Ragde H, Luse R, Clifford S, et al. Reduction of radioactive seed embolization to the lung following prostate brachytherapy. Int J Radiat Oncol Biol Phys (1998) 42:1063–7.[CrossRef][Web of Science][Medline]

11 Prasad SC, Bassano DA, Peng JG. Lung density effect on I-125 dose distributions. Med Phys (1985) 12:99–100.[CrossRef][Web of Science][Medline]

12 Kirov AS, Williamson JF. Monte Carlo-aided dosimetry of the Source Tech Medical Model STM1251 I-125 interstitial brachytherapy source. Med Phys (2001) 28:764–72.[CrossRef][Web of Science][Medline]


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