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Patients with low-risk in situ ductal carcinoma (DCIS) are unlikely to experience recurrence after bad-conserving surgery, but radiotherapy can further reduce this risk.
New Discoveries Presented at the American Society for Radiation Oncology. (ASTRO) 2018 showed that bad radiotherapy as a whole reduced recidivism by half compared to observation. The reduction in the recurrence rate was much greater than what the authors of the study had predicted.
"The larger than expected reduction yielded significant results even though it does not match the targeted initial accumulation," explained lead author, Beryl McCormick, MD, FASTRO, Department Head Statistical beam radiotherapy service at the Memorial Sloan Kettering Cancer Center and Professor of Radiation Oncology at Cornell University in New York City
The study involved 629 patients, with a median follow-up of 12.4 years. The cumulative incidence of local recurrence was 2.8% in the WBRT group versus 11.4% in the observation group (hazard ratio [HR] 0.26; P = .0001). The cumulative incidence of invasive local recurrence was 1.5% in the WBRT arm compared to 5.8 for the conservation arm (HR, 0.34, P = 016).
The study is the first to study exclusively postoperative radiotherapy.
"The results should inform patient-physician discussions about the risks, benefits and comfort of the patient – which varies considerably – with respect to local control with or without radiation," McCormick said.
DCIS is considered a pre-vascular or precancerous lesion that does not metastasize to other parts of the body. Before the advent of screening mammography, the DCIS was rarely diagnosed.
A recent study using data from the SEER database from 1998 to 2014 found that lumpectomy badociated with radiation therapy was badociated with a statistically significant reduction in the risk of death from bad cancer. compared to lumpectomy or mastectomy alone in women with DCIS. However, the clinical benefit is low and routine radiotherapy is not recommended.
High Risk Disease Can Benefit
Although DCIS is generally non-invasive, it is unclear which cases are most likely to progress.
"was once considered a single entity and we were convinced that not all DCIS systems are identical," McCormick said. "And we were the first to define" high risk "and" high risk, "" she said.
The current study was designed to determine whether radiotherapy would reduce the risk of local failure only in patients with low or low risk DCIS.
In this study, the authors badessed the impact of WBRT on an observation in women with high-risk DCIS after bad conservation surgery. For this trial, the DCIS at risk was defined as an occult DCIS clinically detected by mammography or accidentally. In addition, the tumor should be 2.5 cm or less; margins should be 3 mm or less; and the tumor was to be of low or intermediate nuclear grade.
Women in the cohort were randomly badigned to the WBRT with standard doses or at observation. The use of tamoxifen for 5 years was optional. Randomization took place from 1999 to 2006; Preliminary results over 7 years were reported in 2015.
In the current and updated badysis, 76% of participants were postmenopausal. The size of the pathological tumor was 0.60 cm; 61% of the tumors were 0.5 cm or less; and in 65% of cases, the width of the tumor margin was 1.0 cm or more, or a new excision specimen was completely negative for the disease. Grade 1 tumors were detected in 44% of cases; Grade 2 tumors were diagnosed in the remaining 56%. Tamoxifen was used by 58% of patients in the WBRT group and by 65% of the observation group ( P = 0.05).
In a multivariate badysis, only WBRT treatment (HR, 0.25, P = 0.0003) and tamoxifen treatment (HR, 0.50, 95% CI) %, 0.27-0.91, P = .024) were badociated with reduced local recurrence. Factors such as age (<50 years vs ≥ 50 years) and pathological tumor size were not significant in predicting local recurrence or local invasive recurrence. As expected, there were no significant differences between the two groups with respect to overall survival, disease-free survival, or mastectomy treatment.
Decision Support
Richard Bakst, MD, Associate Professor of Radiation Oncology at the Icahn School of Medicine, Mount Sinai, New York, commented that these results are very useful in guiding decision-making regarding women with high-risk DCIS.
The risk of recidivism seems to increase with time.
million. Richard Bakst
"Long-term follow-up continued to demonstrate the benefits of radiation treatment in preventing recurrence, both of DCIS and bad cancer," he said. "The risk of recidivism seems to increase over time to reach 12% at 12, which is particularly significant in decision-making for younger women and women with longer life expectancy."
Bakst adds that for "those women who elect to give up radiotherapy, the study confirmed that women could be treated at the time of recurrence without compromising their survival."
The study was funded by the National Cancer Institute. Dr. McCormick and Bakst did not reveal any relevant financial relationship.
American Society of Radiation Oncology (ASTRO) 2018. Abstract LBA 1, presented on October 21, 2018.
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