The impact of chemotherapy on toxicity and cosmetic outcome in patients receiving whole breast irradiation: an analysis within a state-wide quality consortium

Breast Irradiation Is Well Tolerated in Carriers of a Pathogenic ATM Variant

PURPOSE

There are mixed and limited data regarding radiation therapy (RT) tolerance in carriers of a germline pathogenic or likely pathogenic (P/LP) ATM variant. We investigated RT-related toxic effects in carriers of an ATM variant who received treatment for breast cancer.

METHODS AND MATERIALS

We identified 71 patients treated with adjuvant RT for breast cancer who were carriers of a variant in ATM: 15 were classified as P/LP and 56 classified as variants of unknown significance (VUS). We additionally identified 205 consecutively treated patients during a similar timeframe who were either confirmed ATM wild type or had no prior genetic testing. RT plans were reviewed. Acute and chronic toxic effects were evaluated using Common Terminology Criteria for Adverse Events version 4.0 criteria. Fisher's exact tests for count data were performed to compare toxic effects between the cohorts (P/LP vs VUS vs control). Wilcoxon rank-sum testing was performed to assess for differences in patient characteristics.

RESULTS

The median toxicity follow-up was 19.4 months; median follow-up for the subcohorts was 13.3 months (P/LP), 12.6 months (VUS), and 23.3 months (control). There were no significant differences in radiation plan heterogeneity, receipt of a boost, or size of breast/chest wall planning target volume. There was greater use of hypofractionated RT in the control cohort (P = .023). After accounting for patient- and treatment-related factors that may affect toxic effects, we found no significant differences with respect to acute dermatitis, hyperpigmentation, moist desquamation, breast/chest wall pain, or breast edema. Additionally, we found no significant differences with respect to chronic breast/chest wall pain, induration, telangiectasia, or cosmetic outcome.

CONCLUSIONS

RT as part of the management of breast cancer was well tolerated in carriers of a P/LP ATM variant, with toxic effect profiles that were similar to those seen in patients without known ATM mutations. High rates of excellent or good cosmesis were observed in carriers of a P/LP ATM variant who underwent breast conservation.

Locoregional Therapy: From Mastectomy to Reconstruction, Targeted Surgery, and Ultra-Hypofractionated Radiotherapy

Background

The past 3 decades have seen an unprecedented shift toward treatment de-escalation in surgical therapy of breast cancer.

Summary

Radical mastectomy has been replaced by breast-conserving and oncoplastic approaches in most patients, and full axillary lymph node dissection by less radical staging procedures, such as sentinel lymph node biopsy and targeted axillary dissection. Further, attempts have been made to spare healthy tissue while increasing the probability of removing the tumor with clear margins, thus improving cosmetic results and minimizing the risk of local recurrence. In this context, modern probe-guided localization techniques have been introduced to guide surgical excision. This progress was accompanied by the development of targeted systemic therapies. At the same time, radiotherapy for breast cancer has undergone significant changes. The use of hypofractionation has decreased the typical length of a treatment course from 5-6 weeks to 1-3 weeks. Partial breast irradiation is now a valid option for de-escalation in patients with low-risk features. Axillary radiotherapy achieves similar recurrence rates and decreases the risk of lymphedema in patients with limited sentinel node involvement.

Key Messages

Taken together, these advances are important steps toward individualization of locoregional management strategies. This highlights the importance of interdisciplinary approaches for de-escalation of locoregional therapies.

Near-Surface Dose Correlates With Moist Desquamation and Unplanned Reconstructive Surgery in Patients With Implant-Based Reconstruction Receiving Postmastectomy Radiation Therapy

Purpose

Postmastectomy radiation therapy (PMRT) reduces disease recurrence in appropriately selected patients but may compromise implant-based reconstruction. We investigated whether near-surface dose correlates with radiation-related toxic effects in these patients.

Methods and Materials

Patients receiving PMRT at a single institution from 2016 to 2019 were retrospectively reviewed. Patient demographics and treatment information were collected. Three near-surface structures were retrospectively generated, bound by the chest wall tangent beam as well as the skin surface and the skin-3 mm contour (SR3), skin surface and skin-5 mm contour (SR5), or skin-5 and skin-10 mm contours. Dosimetric analysis of these near-surface contours was performed in 2 Gy intervals. Univariate and multivariate analyses were used to identify predictors of moist desquamation, grade 2+ chest wall pain, use of opiate pain medication, unplanned reconstructive surgery, and implant failure. Logistic regression for each outcome and near-surface contour was performed for receiver-operator area under the curve (AUC) analysis and the Youden J Statistic was used to determine the optimal threshold for each dosimetric parameter.

Results

Of 126 patients reviewed, 109 met the study's eligibility criteria. Median follow-up was 2.3 years. Twenty-five patients (23%) underwent unplanned reconstructive surgery, and 10 (9.2%) experienced implant failure. Among clinical variables, low body mass index and history of smoking predicted unplanned surgery on univariate and multivariate analyses, and moist desquamation predicted grade 2+ chest wall pain. The top dosimetric parameters by AUC for moist desquamation, grade 2+ chest wall pain, use of opiates, unplanned reconstructive surgery, and implant failure were SR5 D10 cc (AUC = 0.701, optimal threshold 57.8 Gy, P < .001), SR3 D10 cc (AUC = 0.600, optimal threshold 56.8 Gy, P = .079), SR5 D10 cc (AUC = 0.642, optimal threshold 57.3 Gy, P = .041), SR3 V44 Gy (AUC = 0.711, optimal threshold 81%, P = .001), and SR3 V44 Gy (AUC = 0.688, optimal threshold 82%, P = .052), respectively.

Conclusions

Near-surface dose correlates with moist desquamation and unplanned reconstructive surgery after PMRT. Further evaluation of prospective optimization of dosimetric parameters related to SR3 and SR5 should be considered.