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Lacustrine δ2H and δ18O isotope proxies are powerful tools for reconstructing past climate and precipitation changes in the Arctic. However, robust paleoclimate record interpretations depend on site‐specific lake water isotope systematics, which are poorly described in the eastern Canadian Arctic due to insufficient modern lake water isotope data. We use modern lake water isotopes (δ18O and δ2H) collected between 1994–1997 and 2017–2021 from a transect of sites spanning a Québec‐to‐Ellesmere Island gradient to evaluate the effects of inflow seasonality and evaporative enrichment on the δ2H and δ18O composition of lake water. Four lakes near Iqaluit, Nunavut sampled biweekly through three ice‐free seasons reflect mean annual precipitation isotopes with slight evaporative enrichment. In a 23° latitudinal transect of 181 lakes, through‐flowing lake water δ2H and δ18O fall along local meteoric water lines. Despite variability within each region, we observe a latitudinal pattern: southern lakes reflect mean annual precipitation isotopes, whereas northern lakes reflect summer‐biased precipitation isotopes. This pattern suggests that northern lakes are more fully flushed with summer precipitation, and we hypothesize that this occurs because the ratio of runoff to precipitation increases with latitude as vegetation cover decreases. Therefore, proxy records from through‐flowing lakes in this region should reflect precipitation isotopes with minimal influence of evaporation, but vegetation changes in lake catchments across a latitudinal transect and through geologic time may influence the seasonality of lake water isotopic compositions. Thus, we recommend that future lake water isotope proxy records are considered in context with temperature and ecological proxy records. Plain Language Summary: Proxies from sediment cores that reflect the isotopic composition of lake water are commonly used to reconstruct past climate, but understanding the processes affecting lake water isotopes (e.g., the seasonal distribution of precipitation and evaporation) is key to accurate climate interpretations. However, due to accessibility issues, little is known about the seasonal isotopic composition of water in eastern Canadian Arctic lakes. Here, we compile modern lake water isotope (δ18O and δ2H) measurements spanning the eastern Canadian Arctic, with special focus on Baffin Island, collected in 1994–1996 and 2017–2021, to identify regional and seasonal patterns in lake water isotopes. Isotopes from lakes in the southern part of this transect reflect mean annual precipitation with some influence of evaporation. In contrast, lakes in the northern part of this transect reflect summer precipitation isotopes. This latitudinal trend may be caused by vegetation cover: as vegetation becomes less dense northward, relatively more precipitation in a catchment enters the lake as runoff. Despite this trend, there is some variability within each region. Therefore, quantifying lake water isotope seasonality is a critical step toward robust interpretations of lake water isotope proxy records. Key Points: Eastern Canadian Arctic lakes reflect precipitation isotopes with little influence of evaporative enrichmentPatterns in lake water isotope seasonality driven by the ratio of runoff to precipitationGroundwater is an important variable in the lake system that influences lake water isotope seasonality [ABSTRACT FROM AUTHOR]

Arctic precipitation is predicted to increase this century. Records of past precipitation seasonality provide baselines for a mechanistic understanding of the dynamics controlling Arctic precipitation. We present an approach to reconstruct Arctic precipitation seasonality using stable hydrogen isotopes (δ2H) of aquatic plant waxes in neighboring lakes with contrasting water residence times and present a case study of this approach in two lakes on western Greenland. Residence time calculations suggest that growing season lake water δ2H in one lake reflects summer precipitation δ2H, while the other reflects amount‐weighted annual precipitation δ2H and evaporative enrichment. Aquatic plant wax δ2H in the "summer lake" is relatively constant throughout the Holocene, perhaps reflecting competing effects of local summer warmth and increased distal moisture transport due to a strengthened latitudinal temperature gradient. In contrast, aquatic plant wax δ2H in the "mean annual lake" is 100‰ 2H depleted from 6 to 4 ka relative to the beginning and end of the record. Because there are relatively minor changes in summer precipitation δ2H, we interpret the 100‰ 2H depletion in mean annual precipitation to reflect an increase in winter precipitation amount, likely accompanied by changes in winter precipitation δ2H and decreased evaporative enrichment. Thus, unlike the "summer lake," the "mean annual lake" records changes in winter precipitation. This dual‐lake approach may be applied to reconstruct past changes in precipitation seasonality at sites with strong precipitation isotope seasonality and minimal lake water evaporative enrichment. Key Points: Neighboring lakes with contrasting residence times may be used to reconstruct precipitation isotopes from different seasonsWestern Greenland had wetter winters in the middle Holocene due to increased oceanic heat transport and decreased winter sea iceHolocene summer precipitation isotopes on western Greenland were relatively constant suggesting consistent summer moisture source [ABSTRACT FROM AUTHOR]

Radioimmunotherapy offers an exciting new therapeutic modality for patients with relapsed non-Hodgkin's lymphoma; however, considerable debate exists regarding the optimal dose and administration schedule for radioimmunoconjugates. Myelosuppression has been the dose-limiting toxicity of most clinical trials employing radiolabeled antibodies, and this complication has generated both high-dose and low-dose treatment strategies. 'Low-dose' strategies are nonmyeloablative and rely upon repetitive infusions to effectively eradicate tumor masses. Trials incorporating low-dose radioimmunotherapy have documented high response rates, though the durability of these responses remains unclear. The most encouraging nonmyeloablative studies have documented objective responses in 70%-80% of patients, complete responses in 30%-50% of patients, minimal toxicity, and a median response duration of 12 months. In contrast, high-dose trials performed in conjunction with autologous hematopoietic stem cell transplantation have demonstrated objective responses in 95% of patients, complete responses in 85% of patients, with a progression-free survival of 62% and an overall survival of 93% with a median follow-up of two years. Toxicities are considerably higher than those reported with nonmyeloablative regimens, but are modest compared to conventional marrow transplant conditioning regimens incorporating total body irradiation (TBI). Ongoing trials integrating high-dose radioimmuotherapy with high-dose chemotherapy in an autologous transplantation setting are testing the hypothesis that targeted radiotherapy plus chemotherapy will provide increased efficacy and diminished toxicity as compared to nonspecific external beam TBI-containing regimens.

Radioimmunotherapy offers an exciting new therapeutic modality for patients with recurrent hematologic malignancies and solid tumors resistant to conventional chemotherapy. In this review, a brief overview of tumor radiobiology as well as various obstacles to treatment is presented. Early radiolabeled antibody trials documented myelosuppression as the dose-limiting toxicity. Ongoing trials in solid tumors and hematologic malignancies are testing the hypothesis that myeloablative doses of radiation in conjunction with hematopoietic stem cell rescue will improve long-term survival. For solid tumors, there are many barriers to achieving this goal. The most encouraging trials in metastatic breast cancer have documented significant symptomatic relief and a 50% partial response in patients. In contrast, trials involving hematologic malignancies have produced more impressive results. With a median follow-up of 33 months, 67% of patients with recurrent acute myelogenous leukemia or myelodysplasia treated with radiolabeled antibodies, total-body irradiation, and high-dose chemotherapy remain disease free. Alone, myeloablative doses of radioimmunotherapy have documented a 41% complete response in patients with Hodgkin's disease. Seattle trials with recurrent non-Hodgkin's lymphoma have demonstrated objective responses in 90% of patients, complete responses in 85% of patients, a progression-free survival of 62%, and an overall survival of 93% with a median follow-up of 2 years.