Factors May Predict Which DCIS Likely to Be Upstaged

Might help with sentinel node decision

Nick Mulcahy

November 17, 2010

November 17, 2010 — In a new study, Australian researchers have found that 17.3% of patients with a percutaneous core needle biopsy (CNB) finding of ductal carcinoma in situ (DCIS) were subsequently upstaged to invasive cancer.

This rate is comparable to those found in previous studies (about 20%), say the researchers, led by Emil D. Kurniawan, BMedSc, from the Department of Surgery at the Royal Melbourne Hospital and the University of Melbourne in Victoria, Australia. Their study appears in the November issue of the Archives of Surgery.

The uniqueness of the study arises from a question that the investigators pursue: Is there a way to predict which subgroups of DCIS patients are likely to be upstaged and thus need a sentinel lymph node biopsy at the initial surgery? That would be very desirable because, as it is, these patients have to go back for reoperation to have their sentinel nodes assessed, which is inefficient and difficult for the patient.

In an analysis of 396 women with a CNB diagnosis of DCIS, the investigators found that microinvasion on CNB (carcinoma less than 1 mm) and palpability "strongly predict" upstaging.

They also found that in patients with impalpable DCIS on CNB, factors significantly associated with upstaging are the presence of a mass, density, or architectural distortion on mammogram; larger mammographic size (≥20 mm); and screening interval of 3 years or longer.

The authors propose an algorithm in which patients with 2 or more risk factors would be considered high risk, and in which routine sentinel lymph node biopsy would be offered to this group and to patients with invasive cancer on CNB.

However, this proposed management of DCIS is problematic, according to an American breast cancer expert.

"Most of the factors that the algorithm is based on have a low incidence in the study population, which makes any related decision-making a tough call. For instance, only 5% of the patients had palpable lesions and only 6% of the patients with impalpable lesions had a screening lapse of 3 or more years," said Quyen Chu, MD, professor of surgery and director of surgical oncology at the Louisiana State University Health Sciences Center-Shreveport.

"The data are not compelling enough for me to change my practice," he summarized in an interview with Medscape Medical News.

In Dr. Chu's practice, 2 factors, when found together, drive the decision-making about DCIS lesions found with screening and CNB. "Traditionally, we base our decision on size — the lesion must be greater than 2 cm on mammogram — and palpability," he said. Those patients go on to be resected and receive a sentinel lymph node biopsy as well. The others undergo resection alone. As part of the standard of care, the excised tissue is then checked for clean margins and for evidence of invasion. If patients are upstaged to invasive cancer at this point, they then have a sentinel lymph node biopsy, he said.

Study Findings

In the study, patients with a CNB diagnosis of DCIS or DCIS with microinvasion (DCISM) from January 1, 1994 through December 31, 2006 were identified from the records of North Western BreastScreen, a public screening program in Melbourne.

The investigators set out to identify preoperative demographic, mammographic, and pathologic factors that predict underestimation of invasive cancer when CNB shows DCIS. There were 390 cases of DCIS — 375 were pure DCIS and 15 were DCISM.

After surgery, 11 of the 15 cases of DCISM (73.3%) and 65 of the 375 cases of pure DCIS (17.3%) were upstaged to invasive cancer.

The presence of microinvasion on CNB was strongly associated with upstaging to invasive cancer (< .001); therefore, patients with this characteristic should have axillary assessment, the authors report.

In terms of the palpable DCIS, this type of disease was an "uncommon finding," with only 21 such cases, the authors say. Notably, 10 of 21 palpable DCIS lesions (47.6%) were found to have microinvasion. The authors note that previous studies have also reported the link between palpability and invasion, and it is "reasonable" to suggest routine sentinel lymph node biopsy for all palpable cancers.

In terms of impalpable DCIS, a multivariate analysis showed that 3 preoperative features were associated with upstaging: noncalcific mammographic features — mass, architectural distortion, and nonspecific density (odds ratio [OR], 2.00; 95% confidence interval [CI], 1.02 - 3.94); mammographic size of 20 mm or greater (OR, 2.80; 95% CI, 1.46 - 5.38); and prolonged screening interval of 3 years or longer (OR, 4.41; 95% CI, 1.60 - 12.13).

These findings "are consistent with the most commonly reported significant predictors of invasive disease," explain the authors.

In total, the findings, if confirmed when applied to other datasets, "suggest a possible management algorithm":

  • In patients with none of the above risk factors, the chance of invasive cancer is less than 10%, and therefore sentinel lymph node biopsy is unnecessary.

  • Patients with 2 or 3 of the risk factors have an incidence of underestimation of around 40%, and therefore biopsy "would be appropriate."

  • Management of cases "in which the patient has a single risk factor would require individual judgment, and SNB may be appropriate in selected cases."

Sentinel lymph node biopsy is not needed in all patients with DCIS, especially those at very low risk of having invasive cancer, the authors emphasize. "While SNB is undoubtedly a great advance over routine axillary dissection in clinically node-negative patients, it is not a trivial or harmless procedure," they point out.

The researchers have disclosed no relevant financial relationships.

Arch Surg. 2010;145:1098-1104. Abstract

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