Faculty Bibliography

Purpose: To determine feasibility and explore the clinical efficacy of concurrent radiotherapy and carboplatin as adjuvant treatment of triple negative breast cancer (TNBC). Patients and Methods: Women with Stage I-II TNBC were treated after surgery in a phase I-II prospective trial [NCT01289353]. Weekly carboplatin (AUC = 2.0) was delivered for 6 weeks. Concurrent radiotherapy was delivered in the prone position during weeks 2-4, for a total dose of 40.5 Gy in 15 fractions to the breast, and 46.5 Gy in 17 fractions to the tumor bed. Adverse events (AE) were assessed weekly during treatment, once at 45-60 d, and every 6 mo thereafter, using the Common Terminology Criteria for AE (CTCAE) v3.0. Results: A total of 39 patients accrued and 36 received treatment. Eight patients (22%, exact 95% CI: 10%, 39%) developed grade 2 or greater acute radiation dermatitis. Overall, grade 2 AE were seen in nine and grade 3 in two patients. Twenty-three patients (64%) received additional adjuvant chemotherapy. With a median follow-up of 48 mo, 34/36 (94%) are alive and disease free. One patient died of pulmonary failure with possible but unproven breast cancer recurrence, and one patient died of pelvic malignancy. One patient recurred locally and is alive and disease free after surgical management. Brisk lymphocytic infiltrate was present pre-treatment in 39% of 18 patients with evaluable tumor. Conclusions: Adjuvant concurrent carboplatin and prone accelerated radiotherapy is a well-tolerated and promising treatment of early stage TNBC. The observed 3% compares favorably with the expected 30% recurrence rate within 1-4 y from treatment, warranting further studies.

The optimal radiation dose and fractionation to induce anti-tumor immunity remain elusive. We recently found that the exonuclease TREX1 abrogates the immunogenicity of irradiated cancer cells by degrading interferon-stimulatory cytosolic dsDNA. TREX1 upregulation by radiation dose per fraction beyond a threshold of 10-12 Gy results in poor synergy with immune checkpoint blockers.

PURPOSE: Maximum dose to the left anterior descending artery (LADmax) is an important physical constraint to reduce the risk of cardiovascular toxicity. We generated a simple algorithm to guide the positioning of the tangent fields to reliably maintain LADmax <10 Gy. METHODS AND MATERIALS: Dosimetric plans from 146 consecutive women treated prone to the left breast enrolled in prospective protocols of accelerated whole breast radiation therapy, with a concomitant daily boost to the tumor bed (40.5 Gy/15 fraction to the whole breast and 48 Gy to the tumor bed), provided the training set for algorithm development. Scatter plots and correlation coefficients were used to describe the bivariate relationships between LADmax and several parameters: distance from the tumor cavity to the tangent field edge, cavity size, breast separation, field size, and distance from the tangent field. A logistic sigmoid curve was used to model the relationship of LADmax and the distance from the tangent field. Furthermore, we tested this prediction model on a validation data set of 53 consecutive similar patients. RESULTS: A lack of linear relationships between LADmax and distance from cavity to LAD (-0.47), cavity size (-0.18), breast separation (-0.02), or field size (-0.28) was observed. In contrast, distance from the tangent field was highly negatively correlated to LADmax (-0.84) and was used in the models to predict LADmax. From a logistic sigmoid model we selected a cut-point of 2.46 mm (95% confidence interval, 2.19-2.74 mm) greater than which LADmax is <10 Gy (95% confidence interval, 9.30-10.72 Gy) and LADmean is <3.3 Gy. CONCLUSIONS: Placing the edge of the tangents at least 2.5 mm from the closest point of the contoured LAD is likely to assure LADmax is <10 Gy and LADmean is <3.3 Gy in patients treated with prone accelerated breast radiation therapy.

PURPOSE: To identify differences in breast cancer patient-reported quality of life (QOL) between 2 radiation tumor bed boost dose regimens. METHODS AND MATERIALS: Four hundred patients with stage 0, I, or II breast cancer who underwent segmental mastectomy with sentinel node biopsy and/or axillary node dissection were treated with either a daily or weekly boost. Patients were treated prone to 40.5 Gy/15 fractions to the whole breast, 5 days per week. Patients were randomized to a concomitant daily boost to the tumor bed of 0.5 Gy, or a weekly boost of 2 Gy on Friday. Patients completed 6 validated QOL survey instruments at baseline, last week of treatment (3 weeks), 45-60 days from the completion of radiation treatment, and at 2-year follow-up. RESULTS: There were no statistically significance differences in responses to the 6 QOL instruments between the daily and weekly radiation boost regimens, even after adjustment for important covariates. However, several changes in responses over time occurred in both arms, including worsening functional status, cosmetic status, and breast-specific pain at the end of treatment as compared with before and 45 to 60 days after the conclusion of treatment. CONCLUSIONS: Whole-breast, prone intensity modulated radiation has similar outcomes in QOL measures whether given with a daily or weekly boost. This trial has generated the foundation for a current study of weekly versus daily radiation boost in women with early breast cancer in which 3-dimensional conformal radiation is allowed as a prospective stratification factor.

PURPOSE: To report the results of a prospective randomized trial comparing a daily versus weekly boost to the tumor cavity during the course of accelerated radiation to the breast with patients in the prone position. METHODS AND MATERIALS: From 2009 to 2012, 400 patients with stage 0 to II breast cancer who had undergone segmental mastectomy participated in an institutional review board-approved trial testing prone breast radiation therapy to 40.5 Gy in 15 fractions 5 d/wk to the whole breast, after randomization to a concomitant daily boost to the tumor bed of 0.5 Gy, or a weekly boost of 2 Gy, on Friday. The present noninferiority trial tested the primary hypothesis that a weekly boost produced no more acute toxicity than did a daily boost. The recurrence-free survival was estimated for both treatment arms using the Kaplan-Meier method; the relative risk of recurrence or death was estimated, and the 2 arms were compared using the log-rank test. RESULTS: At a median follow-up period of 45 months, no deaths related to breast cancer had occurred. The weekly boost regimen produced no more grade >/=2 acute toxicity than did the daily boost regimen (8.1% vs 10.4%; noninferiority Z = -2.52; P=.006). No statistically significant difference was found in the cumulative incidence of long-term fibrosis or telangiectasia of grade >/=2 between the 2 arms (log-rank P=.923). Two local and two distant recurrences developed in the daily treatment arm and three local and one distant developed in the weekly arm. The 4-year recurrence-free survival rate was not different between the 2 treatment arms (98% for both arms). CONCLUSIONS: A tumor bed boost delivered either daily or weekly was tolerated similarly during accelerated prone breast radiation therapy, with excellent control of disease and comparable cosmetic results.

PURPOSE: To test clinical feasibility, safety, and toxicity of prone hypofractionated breast, chest wall, and nodal radiation therapy. METHODS AND MATERIALS: Following either segmental or total mastectomy with axillary node dissection, patients were treated in an institutional review board-approved prospective trial of prone radiation therapy to the breast, chest wall, and supraclavicular and level III axillary lymph nodes. A dose of 40.5 Gy/15 fractions with a concomitant daily boost to the tumor bed of 0.5 Gy (total dose, 48 Gy) was prescribed. In postmastectomy patients, the same treatment was prescribed, but without a tumor bed boost. The primary endpoint was incidence of >grade 2 acute skin toxicity. The secondary endpoints were feasibility of treatment using prone set-up, compliance with protocol-defined dosimetric constraints, and incidence of late toxicity. A dosimetric comparison was performed between protocol plans (prone) and nonprotocol plans (supine), targeting the same treatment volumes. RESULTS: Sixty-nine patients with stage IB-IIIA breast cancer enrolled in this trial. Surgery was segmental mastectomy (n = 45), mastectomy (n = 23), and bilateral mastectomy (n = 1), resulting in 70 cases. None experienced >grade 2 acute skin toxicity according to the Common Terminology Criteria for Adverse Events, v 3.0, meeting our primary endpoint. Ninety-six percent of patients could be treated with this technique prone. However, 17 plans (24%) exceeded protocol constraints to the brachial plexus. Maximum long-term toxicity was 1 grade 2 arm lymphedema, 1 grade 3 breast retraction, and no occurrence of brachial plexopathy. Dosimetric comparison of protocol with nonprotocol plans demonstrated significantly decreased lung and heart doses in prone plans. CONCLUSIONS: Prone hypofractionated breast, chest wall, and nodal radiation therapy is safe and well tolerated in this study. Although the initial pattern of local and regional control is encouraging, longer follow-up is warranted for efficacy and late toxicity assessment, particularly to the brachial plexus.

Immune checkpoint inhibitors are effective in cancer treatment. A pre-existing immune response demonstrated by significant pretreatment tumor lymphocytic infiltration is a pre-requisite for response. Within such infiltrated tumors, referred as "hot", immune checkpoint inhibitors rescue anti-tumor T cells activity. In contrast, "cold" tumors lack lymphocytic infiltration and are refractory to immunotherapy. Preclinical data show that radiotherapy sensitizes refractory tumors to immune checkpoint inhibitors by recruiting anti-tumor T cells. Despite the growing number of clinical studies testing radiation's ability to enhance immunotherapy, clinical evidence that it converts cold tumors into responsive ones remains elusive. Here we review evidence that radiotherapy is not only an occasional enhancer of immunotherapy's effects but a "game changer", and propose a blueprint to test this.