Partial breast irradiation

Refers to brachytherapy for breast cancer after breast conserving surgery.

Referred to as partial or accelerated partial breast irradiation.

Intraoperative radiotherapy is a form of partial breast radiotherapy.

Breast brachytherapy temporarily implants a irradiation source within a single or multi-channel balloon catheter within a lumpectomy cavity or within a parallel array of implanted interstitial catheters.

Multiple techniques including catheter based interstitial brachytherapy, applicator-based brachytherapy, and external beam techniques can deliver PBI.

Allows larger and fewer radiation dose fractions directly to the breast tissue around the local excision site.

Can reduce or even eliminate need for WBI.

PBI Tell me limited in time range from one day to three weeks.

Has potential to reduce normal tissue toxicity by avoiding radiation to the skin and limits radiation to the surrounding normal breast tissue since it is a form of partial breast irradiation.

Because brachytherapy involves surgical implantation of catheters and is associated with high surface radiation doses to and around a lumpectomy cavity it may increase skin reactions, infections and wound complications

Acute complications include skin toxicity, infections, fat necrosis, seromas and catheter failures.

After one year, wound and skin complications were significantly increased compared to whole breast radiation (Presley CJ et al ).

Intraoperative radiotherapy reduces doses to the heart, lungs, and ribs by utilizing electron or low-energy x-ray.

Treatment of part of the breast containing the tumor bed accomplished by brachytherapy or external bean radiation techniques.

Treating a limited areas includes surgical cavity and a 1.5-2cm margin and allowing for a shortened course of treatment.

Rationale for use of this technique comes from the knowledge that 5-10 years following breast conserving treatment with whole breast irradiation most recurrences are at or near the original tumor bed, whereas a larger proportion of recurrences occur at later years in other quadrant, reflecting new primaries.

Studies show that new primaries and elsewhere recurrences in whole breast irradiated patients similar to contralateral breast, suggesting treatment of nontarget breast tissue outside the original tumor site adds no additional benefit.

In patients having reexcision after partial breast irradiation for a lumpectomy treated lesion a margin of 10 mm around the tumor is adequate in more than 90% of cases.

Interstitial implantation traditionally used for a boost therapy after completing whole breast irradiation can be used to treat the breast with partial radiation.

Interstitial brachytherapy consists of placing needles into the breast under anesthesia at the time of lumpectomy or after surgery.

Interstitial brachytherapy consists of placing 10 or more catheters at 1-1.5 cm intervals covering the target volume with a 2-3 cm margin.

Implants can deliver low-dose or high-dose rate treatment.

Low-rate implants can deliver 45-60 Gy over 4-6 days.

High-dose rate application provides a dose between 3.4-5.2 Gy per fraction, usually delivered twice per day with a minimum 6 hour interfraction interval for total dose of 32-37 Gy over 4-5 days.

Treatment tolerated well with minimal analgesics, low recurrence rates with excellent cosmesis.

Data demonstrating improved outcomes compared to whole breast irradiation or is still lacking despite its incorporation into clinical practice (2013).

Risk-local recurrence rates range from 0-4% with 88-100% good to excellent satisfaction concerning cosmesis.

Complications are rare and include infections and bleeding.

Incidence of fat necrosis as high as 33% in some clinical studies.

MammoSite radiotherapy system consisting of a balloon with double lumen catheter able to provide radiation to tumor site is effective partial breast irradiation technique.

Intraoperative radiation may be performed at the time of lumpectomy, but definitive pathological information regarding lymph node status, tumor margins and other prognostic factors may not be known.

Uses a shielding device to cover the chest wall to further reduce radiation dose to deeper normal tissues.

Three dimensional conformal radiation (3D-CRT) can also be used for partial irradiation.

3D-CRT non invasive, associated with greater dose homogeneity than brachytherapy.

In a retrospective study in older women with invasive BC treated with lumpectomy followed by RT: brachytherapy was associated with higher risk for subsequent mastectomy with a five-year cumulative incidence of 3.95 percent compared with 2.18% in patients who received WBI (Smith G et al).

In the above study brachytherapy was associated with high risk for infectious and noninfectious postoperative complications 27.5% versus 16.9% and was associated with a higher risk for complications within five years of radiation 24.9% versus 18.8% for WBI.

In the above study overall survival was similar.

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