Breast cancer awareness has significantly improved over the past few years. More patients now present with early stage breast cancer (Stage I) mostly detected through routine health checkups. Such Stage I cancers have a very good outcome with cure rates of more than 90-95%. Breast conservation surgery (BCS) has become the standard of care for early stage breast cancers with equal survival compared to mastectomy, but with better shoulder function and quality of life. Radiotherapy (RT) to breast after BCS results in three fold reduction in cancer recurrences and significant increase in survival. Conventionally, RT is given as daily treatment, 5 days a week over 5-6 weeks. Such long course of treatment causes physical/ financial strain on the patient and family, specially in situations where patient has to travel a long distance for RT and was found to be a major deterrent for patients to choose BCS over mastectomy. However, it is possible in a subset of patients, to deliver whole course of RT in just a week by a technique called "Accelerated partial breast irradiation (APBI)".
We recently treated a 68 years old lady with APBI, the first in GKNM hospital. She presented to us with painless right breast lump. On evaluation she was diagnosed as a case of Carcinoma right breast, stage I- cT1cN0M0. Trucut biopsy showed Invasive carcinoma, ER/PR+ve, Her2 neu negative and low Ki67. Patient was planned for BCS + Sentinel lymphnode biopsy + APBI using multicatheter brachytherapy. This article gives a brief review about the technique and merits of APBI.APBI (multicatheter brachytherapy) technique:
Patient needs to be evaluated both by the surgeon and radiation oncologist pre-operatively. During surgery, patient first undergoes sentinel node biopsy and axillary node negativity has to be confirmed by frozen section, as metastatic axillary node is an absolute contraindication for APBI. After lumpectomy is performed with negative margins, multiple rigid needles are inserted under direct visualization of lumpectomy cavity. The needles are spaced approximately 1 cm from each other and placed such that the cavity is covered adequately. Needles are then replaced with flexible catheters and cavity is closed with a drain tube after securing the implants.
CT scan for simulation and RT planning are done on 2nd post op day (POD). Proper target delineation and RT planning is necessary to ensure adequate coverage of the target avoiding excessive dose to normal structures. Treatment is delivered from POD 4, using High dose rate brachytherapy at 32Gy/ 8fractions / over 4 days (twice daily radiation). Here, a miniature radioactive source (Iridium-192) traverses through the implanted catheters and treats the tumor bed ensuring high dose to the centre of cavity and rapid dose fall off beyond the target. After completion of RT, flexible catheters are removed and patient is discharged on POD-7.APBI- brief review:
Recurrence data from randomised control trials evaluating the benefit of RT in early breast cancer showed that most recurrences occur in the vicinity of tumor and recurrences in the ipsilateral breast away from tumor bed were rare. Based on this data, subsequent trials showed that shorter course of partial breast irradiation (RT to tumor bed alone) in a selected group of breast cancer patients had similar control rate compared to 5-6 weeks of whole breast irradiation.
APBI has since gained popularity and is recommended in good prognosis patients with the following criteria- Age > 50 yrs, Tumor size <3 cm, Lymphovascular invasion negative, surgical margin >2mm, axillary nodes negative, unicentric tumor and ductal histology.APBI can be delivered using four different techniques 1- Multicatheter interstitial brachytherapy
A- Intra op picture showing implantation with flexible catheters. B- 3D rendering of breast with reconstructed catheters created in treatment planning system from CT scan. C- CT slice showing isodose lines covering the target and surgical clips (arrow).