Surgical margins in lumpectomy: How much is enough?

When it comes to the "surgical margin" required in a breast cancer lumpectomy - the amount of normal tissue surrounding the tumor that must be removed along with the cancer to ensure that there are no residual cancer cells left in the breast - the answer is surprisingly unclear. Dr. Monica Morrow, Chief of Breast Surgery at Memorial Sloan-Kettering Cancer Center in New York, addresses this is a commentary in the New England Journal of Medicine from the July 5, 2012 issue. (Unfortunately, the full text is available only to NEJM subscribers and institutions; however, I covered many of Dr. Morrow's points in my free podcast from Cancer.Net where I summarized her talk on the same subject at the ASCO Annual Meeting June 2012.) Interestingly, published surveys have shown that even surgeons and radiation oncologists themselves cannot agree more than 50% of the time. At Johns Hopkins we tend to prefer 2 mm margins, but at our tumor boards we are always agreeing and disagreeing with that figure, mostly when discussing whether a particular patient should have additional surgery to try to achieve a larger negative margin. And that's the main issue. Should a "negative margin" be defined only as one where the tumor does not cross the inked border of the surgical specimen? Or should an additional amount of normal tissue also be taken out to achieve a wider "negative" margin? What if that requires the patient to undergo a second or even third surgical procedure and compromises the cosmetic outcome of the lumpectomy, an important goal for many patients? Studies have not uniformly shown larger negative margins are associated with a lower risk of local recurrence than a margin in which tumor simply is not touching the inked edge of the surgical specimen. For example, when MRI imaging is used in addition to mammography and ultrasound, additional tumor is frequently found, often resulting in the decision to move to mastectomy rather than lumpectomy; however, even then local recurrence rates and certainly long term outcomes are not uniformly improved.

This is not to say that lumpectomy margins are unimportant or that meticulous surgical technique should somehow not be practiced. Morrow gives some examples of clinical situations where re-excision of a close margin is highly appropriate (e.g., extensive DCIS). It is devastating when a patient undergoing a lumpectomy and radiation told upfront that she has a "good" prognosis breast cancer then goes on to experience a recurrence in the same breast months or years later, usually necessitating mastectomy.

Finally, Morrow points out that surgery and radiation are not the only treatments that reduce local recurrence. Hormonal therapy such as tamoxifen, chemotherapy, and trastuzumab (Herceptin) in HER2 positive patients, have all decreased the rate of recurrence in the breast in the modern era, compared to the 1980's and before (3-6% now vs. 10-15% prior to the wider use of drug therapy post lumpectomy, especially tamoxifen or AI's). When counseling patients it is important to emphasize these up-to-date statistics to counter a common misconception that mastectomy is always a "safer" choice.