The Pathologist, the Surgeon, and the Rare Phyllodes Tumor

This multi-institutional study highlights the heterogeneity of Phyllodes tumors of the breast and the importance of accurate pathology assessment and individualized surgical approaches.   LEE WILKE: This JCO podcast provides observations and commentary on the JCO article, Contemporary Multi-institutional Cohort of 550 Cases of Phyllodes Tumors from 2007 to 2017 Demonstrates a Need For More Individualized Margin Guidelines by Rosenberger, et al. My name Lee Wilke and I am a professor of surgery and the Hendrix chair in breast surgery research at the University of Wisconsin School of Medicine and Public Health in Madison, Wisconsin. My oncologist specialty is breast surgical oncology. I have no relationships to disclose related to these studies. As medical students we are asked to adopt an expanded vocabulary to describe a multitude of diseases. The word phyllodes is frequently one of those memorable medical school terms whose origin is Greek and describes a leaf-like growth. Phyllodes are rare tumors accounting for less than 1% of breast malignancies, with just over 2,000 patients diagnosed annually in the United States. Originally, the phyllodes tumor was described as cyst like and, therefore, the historic term cystosarcoma phyllodes was applied. Though these tumors are of connective tissue and fibroepithelial origin, they are infrequently cystic and not a true sarcoma. And therefore, the World Health Organization now classifies them as simply phyllodes tumors. They are importantly, for treatment approaches, sub-categorized into benign, borderline, and malignant based on detailed pathologic review of celularity, atypia, overgrowth, mitotic rate, and the borders of the tumor. Phyllodes tumors are listed in the National Institute of Health's genetic and rare diseases program. On the center's website, surgery is described as the primary treatment for these rare malignancies and 1 centimeter margins or greater are recommended for all subtypes of phyllodes tumors, with a note that these tumors are quote, "often treated with mastectomy", unquote. As specialists caring for patients with breast malignancies, we are rapidly learning that the one-size-fits-all approach is not appropriate, and the same is true for those individuals with phyllodes tumors. In the article that accompanies this podcast, to support a shift towards more individualized treatment, Dr. Laura Rosenberger from Duke University in North Carolina assembled a group of key collaborators from 11 US academic cancer centers to pool and evaluate their treatment approaches and outcomes for patients with phyllodes tumors. The investigators identified a total cohort of 550 patients with phyllodes tumors treated between 2007 and 2017. Consistent with systematic reviews of phyllodes tumor data sets, such as that by Lu et al in Annals of Surgical Oncology, with this JCO publication being the largest, the patients have a median age of 44. The malignant cohort is approximately 10%. And median tumor size is three centimeters, with a range to as high as 29 centimeters. Key facts found within this analysis are that 2% of patients underwent nodal evaluation, all with negative nodes. The addition of either a sentinel node or axillary surgery is not without risks to the patient. And unless the pre-surgical diagnosis raises the question of a simultaneous adenocarcinoma, patients undergoing surgery for a phyllodes tumor should not undergo nodal mapping or axillary surgery as these tumors are primarily local malignancies and do not metastasize via the lymphatic network. This is the first key takeaway from this paper, supporting the work of others that nodal surgery in phyllodes tumors is unnecessary. The second notable finding is the heterogeneity, even among academic medical centers, regarding the surgical approach. Approximately 38% of patients, or 209, proceeded to a second surgical intervention. 51 of these patients, or nearly 10% of the entire cohort, had negative margins at their first surgery. Of the group that underwent a second surgery, only six patients, or 3% of those proceeding to a second intervention, had residual disease. On the opposite end of the spectrum, of those patients with a positive surgical margin, which was 42% of the entire group, 74, or 32% of those with positive margins, did not proceed with a second surgery. These outcomes highlight that even among patients being treated at centers that one would assume would function similarly, patients could have everything from positive margins to additional surgery in the setting of negative margins. What is vital to note at this point, however, is that the recurrence rate for this cohort was only 3.3% or 18 patients-- 15 with a local recurrence and three with a distant recurrence. The recurrences were differentially associated with the phyllodes subtypes, with 1.3% in benign, 5.6% in borderline, and 6.9% in malignant phyllodes. In univariate logistic regression analysis, however, margin status and margin width did not predict for a recurrence and neither did type of surgery or patient age. Clearly, a one centimeter margin for a phyllodes tumor is not needed, just as we are likely finding is true for our adenocarcinomas of the breast. The authors don't go so far as to state that a positive margin is acceptable, but highlight the need for a national registry to evaluate an individualized surgical approach in this rare patient population. A final and third key point from this retrospective but important pooled patient analysis is the primary role the pathologist plays in determining the patient outcome. As I frequently comment to my cancer patients, the pathologist is the most important doctor you never meet. In Dr. Rosenberger's analysis, factors that were influential for local recurrence were all pathological variables-- grade, extent of atypia and overgrowth and tumor size. Currently, there are no College of American Pathologists guidelines for reporting phyllodes tumors. With this and other patient data sets highlighting the importance of these pathologic factors in patient outcomes, perhaps a standardization and education program for identifying each of these key findings within a phyllodes tumor should be developed. Without a good pathologist or team of pathologists, oncologic surgeons lack the tools they need to advise the patient on additional surgery and potentially adjuvant therapy. As the use of adjuvant therapy was small in this data set, conclusions could not be provided for or against radiation therapy. Thus, as with all rare tumors, a collaborative and team approach with development of a national registry is needed across community and academic institutions to standardize and evaluate the outcomes for these patients with the eventual goal of providing a more tailored treatment approach. This concludes this JCO podcast. Thank you for listening.