DISCUSSION
Oncological diseases account for 80-90% of the reported cases of SVCS. The frequency of mediastinal mass in T-LBL/T-ALL ranges from 66-90% in adult studies and is more in mature T-ALL phenotypes (6). One study identified that almost 50% of children with mediastinal masses presented in emergency with respiratory distress, dyspnea, cyanosis, and they needed immediate intervention (7). Of our patients, 48% of the T-ALL/T-LBL patients presented with SVCS. The most common reason for this presentation is due to the mechanical obstruction caused by the mediastinal mass. Additionally, pleural and/or pericardial effusions may be present which may be diagnosed clinically or radiologically.
SVCS is an oncological emergency requiring prompt commencement of treatment aimed at rapid tumor debulking with intensive chemotherapy and/or radiation therapy, as indicated or feasible. PICU support includes managing airway and circulation , renal replacement therapy etc. (8).
In our cohort, mediastinal widening on X-ray was noted in all patients. 72% of patients required PICU stay. Supplemental oxygen was required in 82%, and endotracheal intubation was required in 18% of our patients. None of our patients required inotrope support or renal replacement therapy. Morin et al. described the clinical presentation and critical care needs of 50 cancer patients (60% hematological malignancy and 40% solid tumor), median age 37 years(25-29years), presenting with SVCS. Pleural effusion, pulmonary atelectasis and pulmonary embolism were seen in 66%, 32%, and 10% patients respectively. Pericardial effusion on echocardiography was noted in 44% patients. Critical care unit interventions like intubation was required in 30%, inotrope infusion in 14% and renal replacement therapy in 6%. Pleural and pericardial drainage was performed in 26%, and 8% patients, respectively (9). Another study from India analyzed 55 patients of T-LBL patients with mediastinal mass with a median age of 18years, 36/55 presented with SVCS. Pleural effusion was seen in 71%, and pericardial effusion was seen in 52% (10).
These patients at presentation are very sick and need urgent commencement of treatment for onset of relief. Invasive painful procedures like bone marrow test or trucut biopsy to reach a diagnosis that requires anesthesia/sedation may not be desirable and feasible since SVCS may confer a higher risk of airway collapse and difficult intubation and ventilation. Also, delays that happen in the process of doing diagnostic tests may be circumvented when these tests can be done reliably on accessible body fluid samples like peripheral blood/ pleural fluid/ pericardial fluid. In our patients, pleurocentesis and pericardiocentesis were done in 36% patients each as therapeutic measure and the fluid was sent for morphology and Flow cytometry which helped in prompt diagnosis. Flow cytometry could identify blasts on peripheral blood and pericardial/ pleural fluid in 90% of patients.
Flow cytometry has long been known to detect blasts in peripheral blood and bone marrow aspirate; however, its efficacy in the detection of blasts on non-hematic body fluids is less well established. Several published data have shown the indispensable role on Flow cytometry in diagnosis and early initiation of treatment including that by Bhaker et al. who evaluated 15 samples from pediatric patients (6-15 years) with Precursor T-cell Lymphoma, and, Czader et al. who analyzed 115 serous cavity effusions from patients aged 2-80yeras of age( mean age- 56 years) with malignant effusion (11) (12). Cesana et al. on 2 different occasions has also demonstrated the same (13) (14).
After initial stabilization, most of the patients in our cohort had an expected course of treatment during the remaining part of the induction chemotherapy. Out of the 11 patients, 3 patients abandoned treatment at various time points. Of the remaining 8 patients, 6 are alive and in remission at last follow-up. Treatment related mortality was noted in only 1 patient. The OS and EFS of the cohort was 75%. Morin et al. studied 50 patients with cancer and SVCS aged 25-59 years, median 37 years) and reported an overall mortality rate at 6 months of 48% (9). Tilak et al. in their study of 55 de novo T-LBL ( age 3-36 years, median 18 years), have reported a 5-year OS of 59.8% (10). In a systematic review of pediatric SVCS cases by Nossair et al. the overall morbity and mortality was 30% and 18% respectively (15). In our study, 3/11(27%) patients abandoned treatment at various time points. Various other studies have also shown that treatment abandonment is a big barrier to improving outcomes for children with cancer in the developing world (16) (17). Treatment related mortality is also another major hurdle to improving the outcomes of pediatric oncology patients. In our cohort we lost one patient to treatment related complication.
Pediatric data of the presentation, course, management, outcome, and critical care needs of this cohort are limited, and it is difficult to approach such children safely. In our study, flow cytometry on peripheral blood and non-hematological fluids served as a valuable tool in diagnosing patients and prompt initiation of treatment. Despite the life-threatening initial presentations, timely initiation of specific therapy and effective critical care supportive treatment could improve the outcomes of this cohort.
Patients with SVCS, despite their life-threatening presentations of airway collapse, cardiac tamponade and shock, can have improved outcomes with good intensive care treatment and timely interventions. Utilizing flow cytometry for detection of blasts in peripheral blood/pleural fluid/pericardial fluid and delaying invasive procedures like bone marrow test and tissue biopsy in a clinically unstable child is a preferable option.
Disclosure – All authors have nothing to declare.