RESEARCH - Permanent seed implants reduce radiotherapy burden in breast cancer

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Permanent seed implants reduce radiotherapy burden in breast cancer

1/5/2006

By: Shalmali Pal

Permanent breast seed implants were successfully used as the sole adjuvant

radiation technique for early-stage breast cancer, according to Canadian

researchers. They reported the first use of the technique, in a series of

patients, in the January issue of the International Journal of Radiation

Oncology, Biology, Physics.

Current breast radiation methods are time-consuming -- three to seven weeks'

worth of treatment -- and also carry significant side effects, such as acute

skin reactions. Permanent breast seed implants would be implanted just once,

and would deliver a therapeutic radiation dose to the tumor site, with the

radiation levels declining to harmless levels over time.

" Therefore, simpler effective treatment delivered over a shorter period of

time is required to improve the care of these women, " wrote Dr.

Jean-Philippe Pignol, Ph.D., and colleagues from Sunnybrook and Women's

College Health Sciences Centre at the University of Toronto. " We have

developed a permanent breast 103-Pd seed implant (PBSI) technique

administered under neuroleptanalgesia in a single one-hour session " (IJROBP,

January 2006, Vol. 64:1, pp. 176-181).

For this study 16 women over the age of 40 were enrolled. All were diagnosed

with an infiltrating ductal carcinoma of less than 3 cm with surgical

margins of 2 mm or more. The treatment plan included breast ultrasound to

localize and measure the size of the surgical bed, as well as measure the

distance to the skin surface.

CT simulation helped determine clinical target volume (CTV) and planned

target volume (PTV). A dose of 90 Gy was the minimal peripheral dose to

cover PTV. A 17-gauge fiducial brachytherapy needle was used for seed

implantation. This device facilitates accurate seed placement, according to

the authors.

A CT scan was done two months after the procedure to evaluate

end-of-treatment dose distributions. Patients recorded their pain levels

before and after the procedure, and answered a satisfaction questionnaire.

According to the results, the average CTV was 8.0 cc and the average PTV was

31.7 cc. The latter " is much smaller compared to PTV volumes in other

partial breast irradiation series, " the authors stated.

On average, 70 seeds were used per patient, with a seed strength ranging

from 1.59 U to 2.59 U. The V100 (relative volume receiving 100% of the

prescribed dose) significantly improved over time, coming in at 74% for the

first eight patients and climbing to 87% for the remainder. The authors

stated that this demonstrated an operator learning curve phenomenon. In

addition, the V100 and the V200 (relative volume receiving 200% of the

prescribed dose) increased between CT scans, indicating that the seeds came

closer together with time.

So far, none of the patients have evidence of their cancer returning, and

the researchers report that acute skin irritation is six times less frequent

when compared to external beam radiation.

In terms of pain, 56% of the patients reported pain during the procedure.

One week later, 37% claimed minimal pain while 31.5% experienced moderate to

significant pain. Asymptomatic hardening of the implantation site occurred

in 62.5% of the women, although complete healing occurred at two months.

The authors acknowledged that pain may be a limiting factor with PBSI, but

pointed out that 57% of the patients reported being very satisfied with the

procedure. Also, women with larger seromas (where seeds could float freely

inside the cavity) and larger tumor size (exceeding the template grid) may

not be eligible for PBSI.

However, " this technique represents an ultimate step in reducing radiation

treatment burden (and) in reducing dose delivered to the skin, " the authors

wrote. Another major advantage is that patients are discharged the same day

as the procedure, returning to a relatively normal life.

By Shalmali Pal

AuntMinnie.com staff writer

January 5, 2006

http://www.auntminnie.com/index.asp?Sec=sup & Sub=wom & Pag=dis & ItemId=69340 & wf=595

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