Epidermal growth factor receptor inhibitor-induced hypomagnesemia: a survey of practice patterns among Canadian gastrointestinal medical oncologists.

Background: The optimal management of hypomagnesemia (hMg) induced by epidermal growth factor receptor inhibitors (egfris) for advanced colorectal cancer is unclear. We surveyed gastrointestinal medical oncologists in Canada to determine practice patterns for the management of egfri-induced hMg. Methods: Based on distribution lists from the Eastern Canadian Colorectal Cancer Consensus Conference and the Western Canadian Gastrointestinal Cancer Consensus Conference, medical oncologists were invited to participate in an online questionnaire between November 2013 and February 2014. Results: From the 104 eligible physicians, 40 responses were obtained (38.5%). Panitumumab was more commonly prescribed than cetuximab by 70% of respondents, with 25% prescribing cetuximab and panitumumab equally. Most respondents obtain a serum magnesium level before initiating a patient on an egfri (92.5%) and before every treatment (90%). Most use a reactive strategy for magnesium supplementation (90%) and, when using supplementation, favour intravenous (iv) alone (40%) or iv and oral (45%) dosing. Magnesium sulfate was used for iv replacement, and the most common oral strategies were magnesium oxide (36.4%) and magnesium rougier (18.2%). Under the reactive strategy, intervention occurred at hMg grade 1 (70.3%) or grade 2 (27%). Of the survey respondents, 45% felt that 1-5 of their patients have ever developed symptoms attributable to hMg, and 35% have had to interrupt egfri therapy because of this toxicity, most commonly at grade 3 (30%) or grade 4 (45%) hMg. The most important question about egfri-induced hMg was its relevance to clinical outcomes (45%) and its symptoms (37.5%). Conclusions: In Canada, various strategies are used in the management of egfri-induced hMg, including prophylactic and reactive approaches that incorporate iv, oral, or a combination of iv and oral supplementation. Clinicians are concerned about the effect of hMg on clinical outcomes and about the symptoms that patients experience as a result of this toxicity.

Clinical outcomes of elderly patients receiving neoadjuvant chemoradiation for locally advanced rectal cancer.

BACKGROUND: Studies of clinical outcomes of elderly patients treated with neoadjuvant chemoradiation (nCRT) for locally advanced rectal cancer (LARC) are limited. Our aim was to assess the impact of age on clinical outcomes in a large multi-institutional database. PATIENTS AND METHODS: Data for patients diagnosed with LARC who received nCRT and curative-intent surgery between 2005 and 2012 were collected from five major Canadian cancer centers. Age was analyzed as a continuous and dichotomous variable (< 70 versus ≥ 70 years) and correlated with disease-free survival (DFS), cancer-specific survival (CSS) and overall survival (OS). Cox regression models were used to adjust for important prognostic factors. RESULTS: Of 1172 patients included, 295 (25%) were ≥ 70 years, and they were less likely to receive adjuvant chemotherapy (ACT; 60% versus 79%, P < 0.0001), oxaliplatin-based ACT (12% versus 31%, P < 0.0001), less likely to complete nCT (76% versus 86%, P < 0.001), and more likely to be anemic at initiation of nCRT (42% versus 30%, P = 0.0004). In multivariate analyses, age ≥ 70 years was associated with similar DFS [hazard ratio (HR) 0.93, 95% confidence interval (CI) 0.68-1.26, P = 0.63], similar CSS (HR 0.81, 95% CI 0.46-1.41, P = 0.45), and similar OS (HR 1.28, 95% CI 0.88-1.86, P = 0.20), compared with the younger age group. As a continuous variable, increasing age was not predictive of DFS (HR 1.00, 95% CI 0.99-1.02, P = 0.49) or CSS (HR 1.002, 95% CI 0.98-1.02, P = 0.88); however, it correlated with an inferior OS (HR 1.02, 95% CI 1.00-1.03, P = 0.04). CONCLUSIONS: Elderly patients (≥ 70 years) who receive nCRT followed by surgery appear to have similar outcomes compared with younger patients. Decisions regarding eligibility for nCRT and surgery should not be based on age alone.