About one-third of patients with locally advanced breast cancers who underwent mastectomy did not receive the recommended radiation therapy (RT) after surgery, a study of nearly 57,000 women has found.
RT is indicated for breast cancers that have spread to four or more axillary lymph nodes (N2/N3) to improve outcomes, according to guidelines from the National Comprehensive Cancer Network (NCCN) and the American Society of Clinical Oncology (ASCO).
Patients with these breast cancers are at "high risk" for recurrence and death, write lead investigator Quyen Chu, MD, MBA, from the Louisiana State University Health Sciences Center in Shreveport, and colleagues.
"We were startled and surprised that the adherence rate was not as high as we expected," Dr Chu told Medscape Medical News.
The investigators dug into the records of patients diagnosed with N2/N3 breast cancer from 1998 to 2011 in National Cancer Data Base to look for factors associated with getting the recommended and advisable RT (i.e., compliance).
They did not come up with much.
On multivariate analysis, compliance with postmastectomy RT was predicted by only three independent variables: receipt of chemotherapy (odds ratio [OR], 4.55; P < .01); readmission in the 30 days after surgery (OR, 1.14; P = .01); and being alive 30 days after surgery (OR,1.55; P = .04).
Naturally, the investigators took a look at socioeconomic factors.
Surprisingly, none of the following factors influenced compliance or noncompliance: race/ethnicity, insurance status, income level, education level, population density, or distance from the patient's residence and hospital, facility type, or location.
Also surprising: Neither age nor comorbidity was independently associated with the omission of RT.
The reasons 35% of the study patients did not receive postmastectomy RT "remain a puzzle," Dr Chu and colleagues write in their study, which was published online January 14 in the Journal of the American College of Surgeons.
They speculate about the three factors they found to be associated with compliance.
Readmission to the hospital might serve as a "safety valve" to capture patients who would have otherwise been missed for their postmastectomy RT, they explain. However, too much is unknown about these patients and their care, they report.
"From this study, we could not tease out whether patients refuse treatment or there is a lack of awareness among women and physicians about the need for radiation therapy after mastectomy for locally advanced breast cancer," Dr Chu said in a press statement from the American College of Surgeons.
Another expert hinted that a lack of awareness among clinicians is at play.
"On average, it takes 9 years from the time a new intervention is recommended as an evidence-based practice to when it is fully adopted," said Daniel P. McKellar, MD, a general surgeon in Greenville, Ohio, in the same press statement. He is chair of the American College of Surgeons Commission on Cancer (CoC).
The recommendations from the NCCN and ASCO date back to 2000.
"This study by Dr Chu's group illustrates an important issue regarding the dissemination of new research findings and their implementation into clinical practice," Dr McKellar said.
The omission of postmastectomy RT is not a first-time finding.
"Our group and others have reported findings that are, in general, similar," said Benjamin Smith, MD, a radiation oncologist from the University of Texas M.D. Anderson Cancer Center in Houston, in an email to Medscape Medical News.
However, Dr Smith suspects the problem is not "quite as a big a problem as described" by Dr Chu's team. He explained that the "use of RT is likely underascertained by the coders who abstract data for the National Cancer Data Base."
Dr Smith and the investigators point out that some patients will have legitimate contraindications to radiation, such as the development of distant metastases prior to the initiation of radiation and connective tissue disorders.
Postmastectomy RT is highly beneficial in patients with locally advanced breast cancer, reducing locoregional recurrence by 20% to 27% and increasing overall survival by 8% to 9% (absolute numbers, in both cases), the investigators report.
Univariate Factors Were More Abundant
In their study, they chose to evaluate compliance with the treatment guidelines by using the National Cancer Data Base, which captures an estimated 70% of newly diagnosed cancer cases from approximately 1500 cancer programs in the United States accredited by the CoC.
Of the 2.72 million breast cancer cases diagnosed during the study period, the team identified 56,990 women with N2 or N3 cancer.
The average patient age was 58 years, and the median follow-up was 61 months.
Median follow-up was significantly longer for patients who received postmastectomy RT than for those who did not (59.5 vs 56.6 months; P < .01).
"This implies that patients with radiation therapy were alive longer than those without radiation therapy," the investigators write.
The majority of patients were from comprehensive community cancer programs (59%), white (81%), health insurance policy holders (96%), residents of a large metropolitan area (98%), and without comorbidities (83%).
Approximately 65% of patients treated with mastectomy received postmastectomy RT.
Most of the patients (99.0%) were treated with curative intent, and 30-day mortality was low (0.3%).
Factors significantly associated with postmastectomy RT compliance on univariate analysis were tumor grade (P = .03), readmission within 30 days of surgical discharge (P = .03), receipt of chemotherapy (P < .01), receipt of hormone therapy (P < .01), 30-day mortality (P < .01), vital status at last follow-up, and length of follow-up period.
However, as noted, on multivariate analysis, only three of the factors were independent predictors of the receipt of RT.
The authors have disclosed no relevant financial relationships. Dr Smith reports financial ties with Varian Medical Systems.
J Am Coll Surg. Published online January 14, 2015. Abstract
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Cite this: 'Puzzle': 35% of High-Risk Mastectomy Patients Get No RT - Medscape - Feb 17, 2015.