PracticeUpdate Oncology Best of 2018

CONFERENCE COVERAGE 33

American Society for Radiation Oncology 2018 Annual Meeting 21–24 OCTOBER 2018 • SAN ANTONIO, TEXAS, USA By the PracticeUpdate Editorial Team In PatientsWith DCIS, Radiotherapy Cuts LowRecurrence Risk by Half Radiotherapy slashes the already low recurrence rate of DCIS even further. R ecurrence of ductal carcinoma in situ (DCIS), which is very low fol- lowing breast conservation surgery, can be reduced even further with radia- tion therapy. According to Dr. McCormick, DCIS is not the same in every patient and does not impact life expectancy. Without radia- tion, the recurrence rate is extremely low, so patients and clinicians should have a meaningful discussion about the option to pursue additional treatment. The 12-year cumulative incidence of inva- sive local recurrence was 1.5% (95% CI 0.4% to 4.0%) of those in the WBRT arm and 5.8% (95% CI 3.2% to 9.5%) of those who did not receive radiation (HR 0.34; 95% CI 0.14–0.85; P = .016). In multivariate analysis, only those who received both WBRT (HR 0.25; 95% CI 0.12 –0.53; P = .0003) and tamoxifen (HR 0.50; 95% CI 0.27–0.91; P = .024) experienced reduced local recurrence.

©ASTRO 2018

This finding of a long-term update of a ran- domized, phase II, open-label, multicenter NRGOncology/Radiation Therapy Oncology Group trial was reported at ASTRO 2018. Beryl McCormick, MD, of the Memorial Sloan Kettering Cancer Center and Cor- nell University in New York, noted that the low recurrence rate in patients randomized to radiation therapy was very surprising. The recurrence rate was reduced by half, which was a greater impact than expected. Patients with “good risk” DCIS – cancer found on mammography only or inciden- tally during a breast biopsy for another reason – continued to experience extremely low recurrence 12 years after breast conservation surgery. Those who underwent whole breast radiation therapy (WBRT) and those who also opted to take tamoxifen experienced the lowest recur- rence rates, but even those who received no further treatment following surgery faced no life-threatening consequences. Because none of the tumors that recurred in either group appeared to pose a life-threatening risk, it was reasonable for patients to determine, in consultation with their physician, whether to continue treat- ment following surgery.

Neither age nor pathological tumor size were significant predictors of local recur- rence or invasive local recurrence. No significant differences between treatment arms in overall or disease-free survival or mastectomy were observed. During the additional 5 years following sur- gery, Dr. McCormick noted that the local recurrence rate slightly increased. Among those who received WBRT, the rate increased by just under 1%, bringing it to nearly 3% post surgery. Among those who did not receive radiation, the recurrence rate increased by one percentage point during each additional year of follow-up, climbing from just under 7% to just under 12% after 12 years. Dr. McCormick concluded that these results should inform discussions between patients and physicians, including risks, benefits, and each individual patient's comfort level. Everyone has a different defi- nition of acceptable risk, so some patients with DCIS will want radiation therapy and others may not want further treatment because of the very low risk. Both options

Eligible tumors were ≤2.5 cm, with margins ≤3 mm, and of low or intermediate nuclear grade. From 1999 to 2006, 636 patients were randomized to standard-dose WBRT or to an observation arm. A 5-year course of tamoxifen was optional. Initial results, including 7 years of follow-up, were reported in 2013 and published in 2015. The new analyses include long-term fol- low-up data for 629 patients whose median age was 58 years, including 76% postmen- opausal women. Mean pathological tumor size was 0.60 cm (61%, ≤0.5 cm; 65% with margin width ≥1.0 cm or a completely neg- ative re-excision specimen). The highest nuclear tumor grade was 1, found in 44% of patients. Grade 2 tumors were diagnosed in the remaining 56%. Overall, 58% of patients in the WBRT arm took tamoxifen; 65% of those on the observation arm (P = .05). Median follow-up duration was 12.4 years. After 12 years, the cumulative incidence of local recurrence was 2.8% (95% CI 1.1% to 5.6%) of those in the WBRT arm and 11.4% (95% CI 7.7% to 15.8%) of those in the obser- vation arm (HR 0.26; 95% CI 0.13% to 0.54%; P = .0001).

should be considered viable. www.practiceupdate.com/c/75078

VOL. 2 • NO. 4 • 2018