Partial Breast Radiation Reduces Side Effects in Lumpectomy Surgery


CME NUGGETS

Ed Susman

Mr. Susman is a freelance medical writer based in Florida, USA. He travels worldwide to report from medical conferences, writing regularly for wire services, internet websites, and medical journals such as the Journal of the National Cancer Institute and AIDS.

For comments, edwardsusman@cs.com


SAN ANTONIO, Texas – A faster, intense course of radiation therapy given to women who undergo breast cancer lumpectomy appears to have similar results as a longer treatment period, researchers reported here at the annual San Antonio Breast Cancer Symposium.

Under the accelerated partial breast irradiation protocol, women are given 5 treatments that have a total radiation dose of 30 Gray over a 12-day period. Ten years later their risk of relapse is 3.9 percent compared to 2.6 percent relapse rate (P=0.39) in women who have whole breast irradiation that is conducted over 5-6 weeks and includes 50 Gray in 25 fractions, reported Icro Meattini, MD, associate professor of radiation oncology at the University of Florence, Italy.

“We found that acute and late toxicity and cosmesis evaluations significantly favor the accelerated partial breast irradiation arm of this trial,” Dr. Meattini. “Accelerated partial breast irradiation might be considered a standard alternative to whole breast irradiation in low risk early breast cancer patients,” he suggested.

The APBI IMRT trial enrolled 520 women over age 40 who had either stage 1 or stage 2 breast cancer. Between 2005 and 2013, the patients were randomly assigned to receive either partial breast irradiation or whole breast irradiation. The majority of the patients had hormone receptor-positive, HER2-negative breast cancer, and most were over age 50. The women were eligible for the shortened course of treatment if their tumors were 2.5 cm or less, and if surgical margins were clear, Dr. Meattini reported.

Overall survival at 10 years was not significantly different either, Dr. Meattini said. At 10 years, overall survival was 92.7 percent among the women who received accelerated partial breast irradiation compared with a 93.3 percent overall survival among the women who were given whole breast irradiation (P=0.37), he said.

Breast-cancer specific survival was 97.6 percent for those who received accelerated partial breast irradiation and 97.5 percent for those who received whole breast irradiation. The distant metastasis-free survival rate was 96.9 percent in both arms of the trial.

About 95.5 percent of the women receiving the short-course of therapy avoided skin toxicity while 70 percent had no skin toxicity if they were receiving whole breast toxicity.

“Accelerated partial breast irradiation is one of the primary examples of de-escalation of treatment in breast oncology,” Dr. Meattini said. “For many patients, partial breast irradiation may be an optimal choice optimal choice that is cost-effective, safe, and efficacious.”

Residual disease burden score

In another study at the meeting, researchers suggested that use of a residual cancer burden calculator can be helpful in determining prognosis of breast cancer patients.

The calculator showed accuracy in predicting risk of dying of breast cancer 12 years after initial surgery based on how much cancer remained after initial neoadjuvant therapy and included data from 12 clinical trials that represented 5,100 patients from clinics around the world, reported W. Fraser Symmans, MD, professor and director of research operations in pathology at the University of Texas MD Anderson Cancer center, Houston.

The calculator (available online at the website of the University of Texas MD Anderson Cancer Center: http://www.mdanderson.org/breastcancer_ RCB ) assesses residual cancer burden in the tumor bed and in lymph nodes and then determines its score – a 0 score is akin to a pathological complete response, and then the grade rise to 1, 2 or 3. The long-term outcome indicates that in most breast cancer types a 0 score is the best prognosis; a score of 3 is the worst prognosis.

Dr. Symmans reviewed results for major breast cancer phenotypes:

For hormone receptor-positive/HER2-negative, 11 percent of patients were classified as having a pathological complete response (pCR); 11 percent as Residual Cancer Burden (RCB-I); 53 percent as RCB-II, and 25 percent as RCB-III. At the 10-year follow-up, 19 percent of the pCR group had had a recurrence or had died; compared with 14 percent of the RCB-I group; 31 percent of the RCB-II group; and 48 percent of the RCB-III group.

For hormone receptor-positive/HER2-positive, 38 percent of patients were classified as having a pCR; 20 percent as RCB-I; 33 percent as RCBII; and 8 percent as RCB-III. At the 10-year follow-up, 9 percent of the pCR group had had a recurrence or had died; compared with 17 percent of the RCB-I group; 36 percent of the RCB-II group; and 55 percent of the RCB-III group.

For hormone receptor-negative/HER2-positive, 69 percent of patients were classified as having a pCR; 11 percent as RCB-I; 16 percent as RCBII; and 4 percent as RCB-III. At the 10-year follow-up, 7 percent of the pCR group had had a recurrence or had died; compared with 15 percent of the RCB-I group; 37 percent of the RCB-II group; and 40 percent of the RCB-III group.

For hormone receptor-negative/HER2-negative, 43 percent of patients were classified as having a pCR; 12 percent as RCB-I; 33 percent as RCBII; and 11 percent as RCB-III. At the 10-year follow-up, 14 percent of the pCR group had had a recurrence or had died; compared with 25 percent of the RCB-I group; 39 percent of the RCB-II group; and 75 percent of the RCB-III group.

Dr. Symmans noted that while the residual cancer burden and risk of recurrence or death generally followed a liner path, there were some non-linear curves. But, he said, “The calculator gives strong potential to calibrate an individual’s residual cancer burden index to residual prognostic risk.”

Oral paclitaxel improves outcomes

An oral formulation of paclitaxel appears to extend survival and reduce neuropathy when compared to intravenous treatment of the drug for a population of metastatic breast cancer patients, researchers suggested.

But taking the oral form of paclitaxel isn’t as simple as taking one pill a day, and, in fact, it is a process that can take up half a day, researchers described at the annual San Antonio Breast Cancer Symposium.

For the primary endpoint of the study – objective response to treatment, 40.4 percent of the 265 patients assigned to receive the oral formula achieved a confirmed tumor response compared with 25.6 percent of the 137 patients who were treated with conventional intravenous paclitaxel (P=0.005), said Gerardo Antonio Umanzor Funez, MD, medical oncologist at Centro Oncologico Integral, who conducted the study with DEMEDICA of San Pedro Sula, Honduras.

The study was conducted among 45 sites in Central and South America.

“This oral form of paclitaxel provides a new therapeutic option for patients, in particular, for those who cannot easily travel,” Dr. Umanzor said. “While blood counts still need to be monitored, oral administration allows patients to remain home during therapy, and avoid spending significant time in the chemotherapy unit.“We were pleasantly surprised that responses were durable, conferring an early survival advantage with minimal neuropathy,” he continued.

Dr. Umanzor also reported that the median overall survival with oral paclitaxel was 27.9 months compared with 16.9 months median overall survival for women treated with standard delivery of the drug – an 11 month difference that was statistically significant (P=0.035). He also reported a trend in favor of oral paclitaxel in median progression free survival – 9.3 months with the oral formulation and 8.3 months with the intravenous form (P=0.077).

The oral paclitaxel regimen involves a lot of pills and a lot of time, Umanzor explained. The patients take the medication 3 times a week. After fasting for at least 4 hours – or when awakening in the morning, the patients takes the drug encequidor, a highly specific, potent inhibitor of the P-glycoprotein pump. The P-glycoprotein pump excretes paclitaxel so encequidor stops the pump from working, allowing for oral paclitaxel to be absorbed. The 15 mg tablet is taken first, and then patient waits an hour and then takes the oral paclitaxel in tablets of 30 mg. The number of tablets of oral paclitaxel is based on a dose of 205 mg/m2. The regimen then requires patients to fast another 4 hours before taking a second table of encequidor. Umanzor suggested that each day the average woman would be taking about 11 tablets of the 2 drugs. That regimen is followed for 3 days a week, for 3 weeks, which completes one cycle of treatment.

The researchers selected a regimen of the Food and Drug Administration approved dosing for intravenous paclitaxel for metastatic breast cancer: 175 mg/m2 every 3 weeks. Umanzor acknowledged that in clinical practice in the United States, clinicians administer 80 mg/m2 weekly. In the trial, patients underwent 6 cycles of treatment, and then they entered an extension phase of the trial for another 3 cycles.

“We had our doubts about compliance at the beginning of the trial,” Dr. Umanzor said. “But patients were so excited that they were getting an oral treatment that we really didn’t have a problem with adherence. We did give them a course in how to take the medicine but after that there were no problems. They would take their first dose at the clinic and we would work with them there, and then they would take the rest of the treatments at home.”

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