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Hypofracfionated radiation to breast: Photon versus Electron: Results from a tertiary cancer care centre.

Publisher : KBCCC2014 (Kyoto Breast Cancer Conference)

Campus : Kochi

School : School of Medicine

Verified : Yes

Year : 2014

Abstract : Background: Sensitivity of breast cancer tissue to high dose fractionation has been proved. The results of UK Standardization of breast radiotherapy (START) randomized trials and Ontario trials showed benefits of hypofractionation. The START trials used photon energy for treating chest wall and breast, and electron boost for tumour bed. We, at our tertiary cancer care centre, have been using hypofractionated protocols from 2009, and this is a retrospective analysis of patients treated with this regime. Methods: Details of breast cancer patients treated with external beam radiation after surgery, using hypofractionated regimen from 2009 to June 2013, were retrieved from electronic medical records and were analysed . Results: Out of 828 breast cancer patients treated with adjuvant external beam radiation, from 2009 to June, 2013, 185 were offered hypofractionated schedule. Except for 2, all were females. Left sided lesions were 92 and right 93 (49.7% 50.3%). Breast conservation surgery was done for 76 patients and 109 had modified radical mastectomy. Adjuvant treatment (chemotherapy I hormones) was decided based on histopathology findings. All patients received a dose of 40Gy in 15 fractions (266.66cGylfraction) to chest wall I breast, and a tumour bed boost of 10 Gy in 5 fractions (200 cGy / fraction), where indicated using 3DCRT. Electrons were used in 91 patients (49.2%) and photons in 94. In photon group, 6MV photons were used in all except one (4MV), and dose was prescribed to 100% isodose line. Single enface electron field was used for chest wall in MRM patients, and the energy ranged from 6 MeV to 12 Mev (6 MeV- 43.95%, 8 MeV- 40.65%, 10 MeV- 14.28% 12 MeV- 1.09%). Isodoses were rescaled to get homogenous chest-wall coverage. A dose variation of 95% to 105% was noticed. In most patients treatment volume encompassed less than 2cm of lung. Photons or electrons were used for boost fields. The dose distributions were verified, in weekly institutional chart-rounds, and modified when indicated. Of the 185 patients, 18 (9.7%) had grade 1 - 2 skin reactions over the irradiated area, on completing treatment. Patients on follow up were assessed for loco-regional recurrence, chest wall, breast or upper limb oedema, brachial neuralgia, pulmonary and cardiac symptoms, and cosmetic results. None had developed chest wall recurrence. No cardiac or pulmonary adverse events were recorded. Thirty of the 185 patients had arm oedema after treatment, which was graded as mild (18/185 - 9.7%), moderate (8/185 - 4.3%) and severe (4/185 - 2.2%). Twenty patients treated with electrons (20/91- 21%), and 10 treated with photons, (9 BCS, 1 MRM) had arm oedema. The increased incidence of arm oedema in MRM patients could be because of combined surgical and radiation morbidity. The 5 year overall survival was 94.65%. Conclusion: Hypofractionation is accepted as standard of care in adjuvant breast radiation, and is cost effective. Electrons can be considered as an alternative to photons. Single enface electron field is well tolerated, and 3DCRT planning ensures homogenous chest wall coverage, respecting dose constraints to organs-at-risk.

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