The title of the article by Portnow et al. 1 is not suitable because there is uneven coverage of the development of PET imaging devices and inadequate coverage of radiopharmaceuticals or their translational applications. There are some key conceptual and factual errors as well.Contrary to the authors' contention, half-life of Carbon-14 is approximately 5,730 years, while halflife of Fluorine-18 is only 110 minutes: the latter's half-life is shorter-not longer-than the former's. Moreover, there was a need for an alternative agent for glucose imaging because Carbon-14 decays by beta particle formation and beta particles cannot penetrate the human body for image formation. Gamma rays formed after the positron decay of fluorine-18 and other positron emitters can penetrate the human body to enable emission imaging in living humans. Additionally, authors show an image of a " 18 F-spiperone" scan but do not mention the pioneering studies by Wagner et al.2,3 on neuroreceptor imaging in the brain with 3-N-[11 C] methylspiperone. Dr. Wagner is considered a forefather of nuclear medicine. 4 Finally, PET can also be used for cerebellar and brainstem imaging-in addition to cerebral imaging-which is of relevance for several brain disorders.Author Response: Michael Okun, Leah Portnow, David Vaillancourt, Gainesville, FL: We appreciate the comments by Dr. Singhal. Dr. Singhal is correct that we should have used the word "shorter half-life" instead of "longer half-life" when describing the half-life of FDG compared with 14CDG. We are grateful that this error was noticed. We also agree that other elements of PET imaging including radiopharmaceuticals and the translational applications should have been included. In prior drafts, we had a more developed version consistent with these suggestions, but with the word count limits we were constrained to focus on key areas that were of particular interest to our research.

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For angiosarcomas treated with radiotherapy, outcome varies widely and is impacted by tumor site, size, and resectability. In amenable sites, aggressive treatment with resection and hyperfractionated radiotherapy may offer the best prognosis.

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Objectives and Rationale: For breast cancer patients receiving neoadjuvant chemotherapy (NAC) and undergoing pre-NAC axillary lymph node biopsy, NCCN guidelines recommend biopsy marker (clip) placement. This recommendation is based on reports that retrieval of the clipped node after NAC minimizes the false negative rate of sentinel lymph node biopsy (SLNB). Prior studies examining this practice in cN1 patients have reported that the clipped node is a non-SLN 20% of the time. There is limited data regarding if the clipped node needs to be retrieved among cN0 patients, and how often the post-NAC pathologic status of the clipped node has potential to change adjuvant therapy decisions. Here we aim to determine: 1) how often the clipped node is a non-SLN among both cN0 and cN1 patients, and 2) how often the retrieved, clipped node is a non-SLN and is the only positive node after NAC, potentially impacting adjuvant treatment recommendations. Methods: A consecutive cohort of 147 patients treated with NAC and surgery at our institution between January 2019-May 2020 was prospectively examined. Prior to NAC, all patients underwent routine axillary ultrasound (AxUS). For those with an abnormal appearing node, biopsy was performed of the most suspicious lymph node and a clip was placed. All cN0 patients underwent SLNB without localization of the clipped node. Patients who converted from cN1 to cN0 underwent radioactive seed localization of the clipped node and SLNB with dual tracers (radioactive tracer and blue dye). All lymph nodes were analyzed by IHC. Any residual disease, including ITCs, was considered pathologic node positive (ypN+). Patients with DCIS/unknown breast tumor histology (N = 3), those without AxUS (N = 9), those treated with neoadjuvant endocrine therapy (N = 9) and cN1 patients without a clip (N = 2) were excluded. Descriptive analyses were performed to examine the rate of ypN+ disease among cN0 and cN1 patients, and how often the clipped node was a non-SLN containing residual disease. In the cN0 population, if the clipped node was not obtained during SLNB it was considered a non-SLN. Results: Of 124 patients meeting study criteria, 61 were cN0 and 63 cN1. Among cN0 patients, 21 (34%) had suspicious lymph nodes on AxUS which were biopsied (negative) and clipped. All cN0 patients underwent successful SLNB, with a median of 2 SLNs removed (range 1-10). Of these, 5 (8%) were ypN+. Of the 21 patients with clipped nodes, 14 (67%) of the clipped nodes were non-SLN. If <3 SLNs were sampled, the clipped non-SLN rate was 82% (9/11). If ≥3 were sampled, the clipped non-SLN rate was 50% (5/10). Among patients with clipped nodes and ypN+ disease, there were no cases in which the clipped node was the only positive node. Among 63 cN1 patients with clipped nodes, 55 (87%) converted to cN0 and underwent SLNB. SLNB was successful in 52/55 (95%) and a median of 3 SLNs were removed (range 1-8). Overall, 28/55 (51%) were ypN+. Of the 52 with successful SLNB, 15 (29%) of the clipped nodes were non-SLN. If <3 SLNs were sampled, the clipped non-SLN rate was 46% (6/13). If ≥3 were sampled, the clipped non-SLN rate was 23% (9/39). In one of 52 (2%) patients, the clipped non-SLN was the only positive node. Conclusions: In this prospective study, among cN0 patients with negative pre-NAC lymph node biopsies, the clipped node was frequently a non-SLN and pathologic status of the clipped node alone did not impact management. Among cN1 patients suitable for SLNB after NAC, although the clipped node was a non-SLN 29% of the time, it was the only positive node in only one patient. The finding that the post-NAC pathologic status of the clipped lymph node alone potentially changed adjuvant treatment recommendations in only 2% (1/52) of patients warrants further investigation. Citation Format: Anna Weiss, Claire King, Samantha Grossmith, Leah Portnow, Sughra Raza, Faina Nakhlis, Laura Dominici, Elizabeth A. Mittendorf, Tari A. King. How often does retrieval of a clipped lymph node change adjuvant therapy recommendations? A prospective consecutive patient cohort [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD4-06.