Potential gains: Comparison of a mono-isocentric three-dimensional conformal radiotherapy (3D-CRT) planning technique to hybrid intensity-modulated radiotherapy (hIMRT) to the whole breast and supraclavicular fossa (SCF) region.

INTRODUCTION: Until late 2018, standard of practice at the Northern Sydney Cancer Centre (NSCC) for breast and nodal treatment was a conformal mono-isocentric technique. A planning study comparing an existing mono-isocentric three-dimensional conformal radiotherapy (3D-CRT) planning technique to a hybrid intensity-modulated radiotherapy (hIMRT) approach for the whole breast and supraclavicular fossa (SCF) region was undertaken with the aim to improve plan quality by improving dose conformity/homogeneity across target volumes and reducing hotspots outside the target. METHODS: A cohort of 17 patients was retrospectively planned using the proposed hIMRT technique, keeping the same planning constraints as the original treated breast and SCF 3D-CRT plan and normalising the 3D-CRT plans to achieve minimum breast/SCF target coverage to compare organs at risk (OARs). Normal tissue index (NTI) and homogeneity index (HI) were compared for plan quality as well as for evaluating OARs. RESULTS: The hIMRT technique showed statistically significant improvements in NTI and HI, as well as improvement in maximum brachial plexus and thyroid doses. There was a negligible increase in maximum oesophagus dose which could be improved if used in optimisation. Other OAR doses in the irradiated region were comparable to the 3D-CRT plans, however maximum doses were reduced overall. CONCLUSION: The hIMRT planning technique maintained clinically acceptable doses to OARs and reduced normal tissue dose while maintaining equivalent dose coverage to breast and SCF planning target volumes with improved conformity and homogeneity. The reduction in maximum doses promotes a favourable toxicity profile, with potential benefit of improved long-term cosmesis.

Patterns of negative seroconversion in ongoing surveys of SARS-CoV-2 antibodies among workers in New York's largest healthcare system.

OBJECTIVES: Given the importance of continued COVID-19 surveillance, our objective was to present findings from a short follow-up survey of workforce SARS-CoV-2 antibody testing in previously seropositive participants and describe associations between work locations and negative seroconversion. METHODS: We conducted a follow-up cross-sectional survey on previously seropositive healthcare workers, using questionnaires and serology testing. Eligible employees previously consented to be contacted were invited by email to participate in a survey and laboratory blood draws. SAS V.9.4 was used to describe employee characteristics and seroconversion status. Binomial regression models were used to calculate unadjusted and adjusted prevalence ratios (PRs) of seronegativity. The multivariable analyses included age, gender, race/ethnicity, region of residence, work location, prior diagnosis/PCR results and days between antibody tests. Unadjusted and adjusted PRs 95% CIs and p values were reported. RESULTS: Of the 3990 employees emailed in the follow-up, 1631 completed an exposure survey and generated a blood-draw requisition form. Average time between serology testing was 4 months. Of the 955 employees with complete serology results, 79.1% were female, 53.4% were white and 46.4% resided in Long Island; 176 participants seroconverted to negative. In multivariable regression analyses adjusted for gender, race/ethnicity and region of residence, younger employees (<20-30 years), intensive care unit workers and those with no/negative prior PCR results were more likely to have negative seroconversion. CONCLUSIONS AND RELEVANCE: Patterns of negative seroconversion showed significant differences by sociodemographic and workplace characteristics. These results contribute information to workplace serosurveillance.

A clip-based protocol for breast boost radiotherapy provides clear target visualisation and demonstrates significant volume reduction over time.

INTRODUCTION: The clinical target volume (CTV) for early stage breast cancer is difficult to clearly identify on planning computed tomography (CT) scans. Surgical clips inserted around the tumour bed should help to identify the CTV, particularly if the seroma has been reabsorbed, and enable tracking of CTV changes over time. METHODS: A surgical clip-based CTV delineation protocol was introduced. CTV visibility and its post-operative shrinkage pattern were assessed. The subjects were 27 early stage breast cancer patients receiving post-operative radiotherapy alone and 15 receiving post-operative chemotherapy followed by radiotherapy. The radiotherapy alone (RT/alone) group received a CT scan at median 25 days post-operatively (CT1rt) and another at 40 Gy, median 68 days (CT2rt). The chemotherapy/RT group (chemo/RT) received a CT scan at median 18 days post-operatively (CT1ch), a planning CT scan at median 126 days (CT2ch), and another at 40 Gy (CT3ch). RESULTS: There was no significant difference (P = 0.08) between the initial mean CTV for each cohort. The RT/alone cohort showed significant CTV volume reduction of 38.4% (P = 0.01) at 40 Gy. The Chemo/RT cohort had significantly reduced volumes between CT1ch: median 54 cm(3) (4-118) and CT2ch: median 16 cm(3), (2-99), (P = 0.01), but no significant volume reduction thereafter. CONCLUSION: Surgical clips enable localisation of the post-surgical seroma for radiotherapy targeting. Most seroma shrinkage occurs early, enabling CT treatment planning to take place at 7 weeks, which is within the 9 weeks recommended to limit disease recurrence.