NSABP sentinel node study

NSABP-B-32 is a large, randomized trial comparing sentinel node resection followed by conventional axillary node dissection with an accrual goal of approximately 5,400 patients. Many surgeons question whether we still need to prove that sentinel node biopsy is the standard of care. I believe until we have the results from larger, randomized trials, it will depend on the surgeon’s level of experience. If the surgeon has performed hundreds of these procedures and convincingly demonstrated a very low false-negative rate and a high identification rate, then it’s reasonable for that surgeon to perform sentinel node biopsy alone in a subgroup of patients with a low risk for axillary involvement.

NSABP partial breast irradiation trial

We are developing a trial to compare partial breast radiotherapy versus whole breast radiotherapy. The eligibility criteria will be broad and will include totally resected DCIS as well as invasive breast cancers up to three centimeters in size. We want to conduct this study now because there may only be a small window of opportunity before partial breast radiotherapy is widely adopted.

In this study, partial breast irradiation can be administered by brachytherapy catheters, the MammoSite® device or conformal external beam radiation therapy to only a portion of the breast. The physician and the hospital will determine which method is utilized, and it needs to be declared before randomization, although it can be changed if a patient is not eligible for a certain procedure. All three options are done in 10 fractions over five days, as opposed to the five or six weeks it takes to administer whole breast radiotherapy, with or without a boost. We hope to not only make it more convenient for patients but to increase the breast conservation rate, since some patients choose mastectomy because they can’t travel to a radiotherapy facility.

There may be other subtle advantages of partial breast radiotherapy. Some data suggest that if we delay radiotherapy we may increase local recurrence, but on the other hand, when we delay systemic therapy we increase systemic recurrence — so we choose to use systemic therapy first. Partial breast radiation takes only five days and is then followed by adjuvant chemotherapy. By moving radiotherapy earlier into the treatment schedule, we may actually decrease local recurrences.

The endpoint in this study is ipsilateral breast tumor recurrence (IBTR) and, based on our trials, we expect approximately six percent of the patients in the control arm will experience IBTR. We’re trying to rule out approximately a 50 percent increase in the IBTR rate. Patients may be willing to accept this in order to receive partial breast irradiation. Because only a small portion of the breast is radiated, if they do experience IBTR, salvage therapy may consist of re-excision and full-breast radiotherapy rather than mastectomy, which is the current standard in patients who experience tumor recurrence after full breast radiotherapy. In addition, because partial breast irradiation delivers a higher dose in the vicinity of the tumor bed, it may even be more effective than whole breast radiotherapy.

NSABP-B-35: Tamoxifen versus anastrozole in patients with DCIS

The NSABP study comparing tamoxifen and anastrozole for patients with DCIS is essentially a trial aimed at preventing invasive breast cancer. Aromatase inhibitors have emerged as very good agents in the treatment of metastatic breast cancer, both second- and first-line, and the pivotal results from the ATAC trial demonstrated adjuvant anastrozole was more effective than tamoxifen in reducing recurrence rates and contralateral breast cancers. If patients with DCIS fail, it’s usually in the ipsilateral or contralateral breast rather than in the regional nodes or distant sites.

Aromatase inhibitors are very well-tolerated in general. In the ATAC trial, the safety profile of anastrozole was impressive. Patients had fewer thromboembolic events, endometrial cancers and menopausal symptoms than with tamoxifen, but with aromatase inhibitors we need to monitor bone density and fractures.

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