Radiation doses to contralateral breast during unilateral breast external beam radiotherapy


Introduction: The cost benefit of external beam radiotherapy (EBRT) in the management of patients living with cancer, especially cancer of the breast cannot be over emphasized. It improves 5-year disease free survival, local tumour control and relieves associated pain. However, EBRT for unilateral breast cancer management could predispose contralateral breast (CB), that is outside the treatment volume (TV), to unavoidable scatter radiation doses. This is of great concern in radiation protection because of high radio-sensitivity of breast tissue.

Materials and Methods: Radiation dose to CB of 20 patients, who consented to participate and be managed with EBRT from Tele-Cobalt unit for primary breast cancer were considered. The dose to CB was measured with calibrated Thermoluminescent dosimeters (TLD) placed on CB at three different positions away from the TV.

Results: The scattered radiation dose (Gy) to CB measured at position 5cm (midline), 10cm (nipple) and 15cm away from the TV were 2.515 + 0.613; 1.548 + 0.578 and 0.780 ± 0.149 respectively. The average dose to CB was 1.601 + 0.40 Gy per session and this is 43% of the prescribed dose (3.75 Gy). This is a bit higher than result from similar study, where CB was covered with lead shield.

Conclusion: It was observed that the mean scattered radiation doses to three different portions of CB during EBRT varied according to the inverse squared principle, where the portion that is closest to TV got 67% of the prescribed dose followed by 41% and the farthest portion got 21%.

Keywords: Contralateral Breast, External Beam Radiotherapy, Breast Cancer, Scattered radiation doses.

Contexte: Le rapport coût-bénéfice de la radiothérapie externe (EBRT) dans la prise en charge des patients atteints de cancer, en particulier le cancer du sein, ne peut être surestimé. Il améliore la survie sans maladie à 5 ans, le contrôle local des tumeurs et soulage la douleur associée. Cependant, l’EBRT pour la prise en charge unilatérale du cancer du sein peut prédisposer le sein controlatéral (BC), c’est-à-dire en dehors du volume de traitement (TV), à des doses de rayonnement diffus inévitables. Ceci est très préoccupant en radioprotection en raison de la radio-sensibilité élevée du tissu mammaire.

Matériel et méthodes: La dose de rayonnement à la C.-B. de 20 patientes, qui ont consenti à participer et à être prises en charge par EBRT de l’unité Tele-Cobalt pour le cancer du sein primaire a été prise en compte. La dose au CB a été mesurée avec des dosimètres thermoluminescents étalonnés (TLD) placés sur CB à trois positions différentes loin du téléviseur.

Résultats: La dose de rayonnement diffusé (Gy) au CB mesurée à la position 5 cm (ligne médiane), 10 cm (mamelon) et 15 cm du téléviseur était de 2,515 + 0,613; 1,548 + 0,578 et 0,780 ± 0,149 respectivement. La dose moyenne à CB était de 1,601 + 0,40 Gy par séance et cela correspond à 43% de la dose prescrite (3,75 Gy). C’est un peu plus élevé que le résultat d’une étude similaire, où le disjoncteur était recouvert d’un blindage en plomb.

Conclusion: Il a été observé que les doses moyennes de rayonnement diffusées sur trois parties différentes du CB pendant l’EBRT variaient selon le principe du carré inverse, où la partie la plus proche du VT recevait 67% de la dose prescrite suivie de 41% et la partie la plus éloignée. . obtenu 21%.

Mots clés: Sein controlatéral, radiothérapie externe, cancer du sein, doses de rayonnement diffusées.

Correspondence: Dr. Akinlade Bidemi I, Department of Radiation Oncology, College of Medicine, University of Ibadan, Ibadan, Nigeria. Mobile: 08066659578; E-mail: bidy2012@yahoo.com, biakinlade@com.ui.edu.ng



Jemal A, Bray F, Center MM, et al. Global cancer statistics. CA Cancer J Clin. 2011; 61: 69 90.

Torre LA, Bray F, Siegel RL, et al. A. Global cancer statistics. CA Cancer J Clin. 2012; 65: 87 108.

Freddie B., Jacques F., Isabelle S., et al. Global Cancer Statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries.

Datta K., Choudhuri M., Guha S. and Biswa J. Breast cancer scenario in a regional cancer center in Eastern India over eight years – Still a major public health problem. Asian Pacific Organization for Cancer Prevention, 2012; 13:809 – 813.

Bhatia S, Robison LL, Oberlin O., et al. ‘Breast cancer and other second neoplasms after childhood Hodgkin’s disease.’ The New England Jour. of Med. 1996; 334 (12): 745-51 9.

Mahavir S. and Babita J. Association between body mass index and risk of breast cancer among females of north India. South Asian Journal of cancer, 2013; 3:121-125.

George X., Bryan B. and Harald P. A review of dosimetry studies on external-beam radiation treatment with respect to second cancer induction’. Phys Med Biol. 2014; 53 (13): 193 – 241.

Elumelu-Kupoluyi T., Akinlade B., Abdus-salam A. and Adenipekun A. Measurement of Scattered Radiation Dose to The Eyes, Breasts and Gonads of Patients During External Beam Radiation Therapy’ Cancer Biology 2011;1(2):10 -16.

Moon K, Stukenborg GJ, Keim J. and Theodorescu D. Cancer incidence after localized therapy for prostate cancer. Cancer 2007; 109 (1): 164 - 169.

Wahba A.G. and Reham S. Radiation doses to contralateral breast during irradiation of breast cancer. Med. Jour. Cairo Univ. 2009; 77 (2) 27 – 31.

Marilyn S., Susan AS., Bryan ML, et al. WECARE Study Collaborative Group. Dose to the Contralateral Breast from Radiation Therapy and Risk of Second Primary Breast Cancer in the WECARE Study. Int. J. Radiat. Oncol. Biol. Phys. 2008; 72(4); 1021 – 1030.

Technical Report Series, TRS 398: Absorbed dose determination in External beam Radiotherapy. An International Code of Practice for Dosimetry based on standards of Absorbed dose to water. International Atomic Energy Agency, Vienna 2000: 57 – 65.

Sajad AR, Mohib-ul MH, Nazir AK and Ajaz AK. Determining the contralateral breast dose during radiotherapy of breast cancer using rainbow dosimeter. Jour Rad. Res and Appl Sci. 2014; 7 (4): 384 -389.

Keyvan J, Nazli A, Shadi B. and Alireza A. Optimizing of the tangential technique and supraclavicular fields in 3-dimensional conformal radiation therapy for breast cancer. Jour Med Signals and Sensors 2013; 3:107 - 116.

Kry S.F., Bednarz B., Howell R.M., et al. TG 158: Measurement and calculation of doses outside the treated volume from external beam radiation therapy. Med. Phys. 2017; 44 (10): 391- 429.