Benefit of Radiation Boost After Whole-Breast Radiotherapy

Radiation Boost After Adjuvant Whole Breast Radiotherapy: Does Evidence Support Practice for Close Margin and Altered Fractionation?

Adding a boost to whole breast radiation (WBI) following breast-conserving surgery (BCS) may help improve local control, but it increases the total cost of treatment and may worsen cosmetic outcomes. Therefore, it is reserved for patients whose potential benefit outweighs the risks; however, current evidence is insufficient to support comprehensive and consistent guidance on how to identify these patients, leading to a potential for significant variations in practice. The use of a boost in the setting of close margins and hypofractionated radiotherapy represents two important areas where consensus guidelines, patterns of practice, and current evidence do not seem to converge. Close margins were previously routinely re-excised, but this is no longer felt to be necessary. Because of this recent practice change, good long-term data on the local recurrence risk of close margins with or without a boost is lacking. As for hypofractionation, although there is guidance recommending that the decision to add a boost be independent from the whole-breast fractionation schedule, it appears that patterns-of-practice data may show underutilization of a boost when hypofractionation is used. The use of a boost in these two common clinical scenarios represents important areas of future study for the optimization of adjuvant breast radiation.

A novel technique for treating deep seated breast cavity boosts

Breast boost irradiation is an integral component to the standard of care for early staged breast cancer. The use of reduced tangents is common for deep seating tumor bed; however, reduced tangents result in non-conformal plans delivering prescription dose to large volumes of breast tissue. To improve conformity, a novel technique of integrating a single conformal arc with reduced tangents has been developed. With this technique, a conformal arc was placed between a pair of reduced tangents to better conform the prescription dose to the target volume. This new technique improves the conformity but was also shown to potentially increase max dose to nearby critical structures, such as the heart, due to exit dose from the arc. This tangent and arc technique has been implemented at our clinic in cases where the exit dose is not critical to the heart.

Hypofractionated Whole-Breast Irradiation With or Without Boost in Elderly Patients: Clinical Evaluation of an Italian Experience

PURPOSE

To examine local control, disease-free survival (DFS), and toxicity in elderly (≥ 65 years) breast cancer patients treated with hypofractionated radiotherapy (hypo-RT) with or without a boost to the tumor bed.

PATIENTS AND METHODS

The study was conducted on 752 patients treated from April 2009 to February 2017. Patients received 42.4 Gy in 16 daily fractions (2.65 Gy per fraction). A boost was only administered in cases of grade 3 primary tumor and close or positive margins. Acute and late toxicity was prospectively assessed during and after hypo-RT, based on the Radiation Therapy Oncology Group scale. DFS and local recurrence-free survival were estimated by the Kaplan-Meier method for cumulative probability. Log-rank tests were used to identify differences by subtype. Cox proportional hazard models were used to investigate the impact of various factors on the risk of disease progression.

RESULTS

Among the 752 patients treated, 41 (5.5%) experienced disease progression, including 7 (17.1%) exclusively local recurrences; 1 (2.4%) local and nodal recurrence; 1 (2.4%) local and nodal recurrence plus metastasis; 7 (17.1%) nodal recurrences plus metastases; and 25 (61%) exclusively distant metastases. The 5-year DFS, local recurrence-free survival, breast cancer-specific survival, and overall survival rates were 91.8% (95% confidence interval [CI], 88.6-94.2), 98.0% (95% CI, 96.1-99.1), 98.2% (95% CI, 96.5-99.1), and 87.5% (95% CI, 83.8-90.5), respectively. On univariate analysis, the administration of a boost, disease grade (grades 1 and 2 vs. 3), and molecular subtype (triple negative or human epidermal growth factor receptor 2 [HER2] positive, or luminal B vs. luminal A) significantly affected disease progression (P < .01). These findings were confirmed by multivariate analysis.

CONCLUSION

Hypo-RT is effective and well tolerated in the elderly population, and the routine use of a boost for patients over 65 years is not justified. Further studies on the boost issue are strongly advocated.

Hypofractionation with simultaneous integrated boost for early breast cancer: results of the German multicenter phase II trial (ARO-2010-01)

PURPOSE

To evaluate the feasibility of hypofractionation with SIB in all settings in Germany to prepare a multicenter treatment comparison.

METHODS

Eligible patients had histopathologically confirmed breast cancer operated by BCS. Patients received WBI 40.0 Gy in 16 fractions of 2.5 Gy. A SIB with 0.5 Gy per fraction was administered to the tumor bed, thereby giving 48.0 Gy in 16 fractions to the boost-PTV sparing heart, LAD, lung, contralateral breast. The primary study objective was feasibility, administration of specified dose in 16 fractions within 22-29 days with adherence to certain dose constraints (heart; LAD; contralateral breast); secondary endpoints were toxicity, QoL.

RESULTS

151 patients were recruited from 7 institutions between 07/11-10/12. 10 patients met exclusion criteria prior to irradiation. All but two patients (99%) received the prescribed dose in the PTVs. Adherence to dose constraints and time limits was achieved in 89% (95% CI 82% to 93%). 11 AE were reported in 10 patients; five related to concurrent endocrine therapy. Two of the AEs were related to radiotherapy: grade 3 hot flushes in two cases. QoL remained unchanged.

CONCLUSION

Hypofractionation with a SIB is feasible and was well tolerated in this study.

Radiotherapy boost dose-escalation for invasive breast cancer after breast-conserving surgery: 2093 patients treated with a prospective margin-directed policy

PURPOSE

To investigate the outcome of invasive early breast cancer patients that underwent breast-conserving surgery and adjuvant radiotherapy (RT), treated with a prospective margin-directed institutional policy for RT boost dose, based on final margins status (FMS).

METHODS AND MATERIALS

A total of 2093 patients were treated between 2000 and 2008. 10 Gy boost was prescribed in case of FMS>5mm; 16 Gy boost with FMS between 2 and 5mm; 20 Gy boost in case of FMS<2mm or positive.

RESULTS

After a median follow up of 5.2 years, we recorded 41 local relapse (LR, 2%). Concerning LR free survival, age at diagnosis, nuclear grade, hormonal status, T-stage, adjuvant hormonal therapy and adjuvant chemotherapy emerged as significant parameters (p-values from log rank test <0.05). FMS, that directed the RT boost dose, did not have significant impact on LRFS (p=0.46). LR rates were 2.3% for FMS<2mm, 2.6% for 2-5mm FMS and 1.8% for FMS>5mm. At multivariate analysis, higher nuclear grade (p=0.045), triple negative subtype (p=0.036) and higher T-stage (p=0.02) resulted as the independent predictors of LR occurrence.

CONCLUSIONS

Our experience showed that a margin-directed policy of RT boost dose-escalation seems to reduce the negative impact of FMS on LR, but it is not able to overcome the unfavorable effect of higher nuclear grade, higher T stage and triple negative subtype.

Radiotherapy breast boost with reduced whole-breast dose is associated with improved cosmesis: the results of a comprehensive assessment from the St. George and Wollongong randomized breast boost trial

PURPOSE

To evaluate comprehensively the effect of a radiotherapy boost on breast cosmetic outcomes after 5 years in patients treated with breast-conserving surgery.

METHODS

The St. George and Wollongong trial (NCT00138814) randomized 688 patients with histologically proven Tis-2, N 0-1, M0 carcinoma to the control arm of 50 Gy in 25 fractions (342 patients) and the boost arm of 45 Gy in 25 fractions to the whole breast followed by a 16 Gy in 8 fraction electron boost (346 patients). Five-year cosmetic outcomes were assessed by a panel subjectively in 385 patients and objectively using pBRA (relative breast retraction assessment). A subset of patients also had absolute BRA measurements. Clinician assessment and patient self-assessment of overall cosmetic and specific items as well as computer BCCT.core analysis were also performed.

RESULTS

The boost arm had improved cosmetic overall outcomes as scored by the panel and BCCT.core software with 79% (p = 0.016) and 81% (p = 0.004) excellent/good cosmesis respectively compared with 68% in no-boost arm. The boost arm also had lower pBRA and BRA values with a mean difference of 0.60 and 1.82 mm, respectively, but was not statistically significant. There was a very high proportion of overall excellent/good cosmetic outcome in 95% and 93% in the boost and no-boost arms using patient self-assessment. However, no difference in overall and specific items scored by clinician assessment and patient self-assessment was found.

CONCLUSION

The results show the negative cosmetic effect of a 16-Gy boost is offset by a lower whole-breast dose of 45 Gy.