Recommendations on post-mastectomy RT in breast cancer

Recommendations on post-mastectomy RT in breast cancer

20 Sep 2016

Post mastectomy radiation therapy (PMRT) reduces the risk of breast cancer recurrence and mortality, but the absolute benefit and benefit:risk ratio vary substantially from patient to patient, requiring careful counseling, an expert panel concluded.

Some low-risk patients "likely" derive minimal benefit from PMRT, such that the potential toxicities may outweigh the absolute benefit. Before recommending radiotherapy, clinicians should carefully consider factors that can reduce the benefit and increase the likelihood of complications, representatives of three oncology organizations advised in a clinical guideline update.

“Decision making must fully involve the patient”

"The decision to recommend post mastectomy radiation therapy or not requires a great deal of clinical judgment," concluded representatives of the American Society of Clinical Oncology (ASCO), American Society for Radiation Oncology, and Society of Surgical Oncology. "Decision making must fully involve the patient, whose values as to what constitutes sufficient benefit and how to weigh the risk of complications against this in light of the best information the treating physicians can provide regarding post mastectomy radiation therapy must be respected and incorporated into the final treatment choice," they added.

The updated guideline can inform decision making but does not replace clinician judgment, the authors emphasized. "We still don't have a single, validated formula that can determine who needs PMRT, but we hope that the research evidence summarized in this guideline update will help doctors and patients make more informed decisions," expert panel co-chair Stephen B. Edge, MD, of Roswell Park Cancer Institute in Buffalo, N.Y., added. The focused update of the guideline adheres to the principles of personalized or precision medical practice.

"In an era of personalized medicine, we want to be sure that we offer the right care to the right patients," said panel co-chair Abram Recht, MD, of Beth Israel Deaconess Medical Center in Boston. "Thanks to advances in systemic therapy, fewer women need radiation therapy after a mastectomy. This means we can be more selective when recommending this treatment to our patients."

How did the panel draw this conclusion?

The recommendations came from a review encompassing literature that has emerged since ASCO published the original clinical guideline on the issue 15 years ago. In developing the update, the panel addressed four questions:

1. Is PMRT indicated in patients with T1-2 tumors with one to three positive axillary lymph nodes who undergo axillary lymph node dissection (ALND)?
2. Is PMRT indicated in patients with T1-2 tumors and a positive sentinel node biopsy who do not undergo ALND?
3. Is PMRT indicated in patients presenting with clinical stage I or II cancers who have received neoadjuvant systemic therapy?
4. Should regional nodal irradiation (RNI) include the internal mammary and/or supraclavicular-axillary apical nodes when PMRT is used in patients with T1-2 tumors with one to three positive axillary nodes?

With regard to the first question, the panel "unanimously agreed" that PMRT reduces the risk of failure, recurrence, and mortality. However, current evidence did not allow for distinctions between various degrees of risk to identify patients who might safely avoid PMRT. The panel called for more research to determine an individual patient's risk of loco regional failure and, by extension, the potential reductions in failure risk and breast cancer mortality.

Panelists advised clinicians to consider factors that alter the benefit:risk ratio, both favorably and unfavorably. Patient-specific factors included older age, high comorbidity burden, and limited life expectancy. Pathologic findings associated with low tumor burden included T1 tumor size, absence of lymphovascular invasion, a single positive node, and small nodal metastases. Biologic characteristics associated with better outcomes included tumor type, low tumor grade, and strong hormonal sensitivity.

Which were the recommendations of the panel?

In answer to the second question, the panel acknowledged that "some clinicians omit axillary dissection with one or two positive sentinel nodes in patients treated with mastectomy." However, the practice evolved from extrapolation of data from randomized trials of breast-conserving therapy and whole-breast irradiation with or without axillary irradiation. If clinicians and patients opt to omit ALND, the panel recommended PMRT "only if there is already sufficient information to justify its use without needing to know that additional axillary nodes are involved."

With regard to the third question, the panel recommended PMRT indicated for any patient who has persistent axillary-node involvement after neoadjuvant therapy. The panel concluded that evidence is insufficient to know whether PMRT should be administered to patients who have clinically negative nodes and receive neoadjuvant therapy, or who have complete pathologic response to neoadjuvant therapy. Such patients warrant consideration for randomized trials examining the question.

Finally, the panel recommended RNI encompassing both the internal mammary and supraclavicular-axillary apical nodes, in addition to the chest wall or reconstructed breast, for patients with positive axillary lymph nodes. Acknowledging that some low-risk patients will derive little or no benefit from treating both nodal areas, the panel found data lacking to identify such patients.

 

Source: MedPage Today