|LETTER TO THE EDITOR
|Year : 2021 | Volume
| Issue : 4 | Page : 774-775
Transitioning from 3DCRT to volumetric modulated arc therapy: Is more really better?
Ashwathy Susan Mathew
Department of Radiation Oncology, Apollo Proton Cancer Centre, Chennai, Tamil Nadu, India
|Date of Submission||01-Nov-2021|
|Date of Decision||11-Nov-2021|
|Date of Acceptance||15-Nov-2021|
|Date of Web Publication||29-Dec-2021|
Ashwathy Susan Mathew
Apollo Proton Cancer Centre, 100 Feet Road, Tharamani, Chennai - 600 041, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Mathew AS. Transitioning from 3DCRT to volumetric modulated arc therapy: Is more really better?. Cancer Res Stat Treat 2021;4:774-5
I must commend Dora et al. for adding to the literature on esophageal radiotherapy in India with a retrospective audit of outcomes of definitive chemoradiation for locally advanced esophageal cancer, during a period of transition from conformal treatments to volumetric modulated arc therapy (VMAT) in their department. The accompanying editorial by Talapatra also summarized the current state of the art in radiation therapy for esophageal cancers quite succinctly.
Treatment of esophageal cancer with radical intent concurrent chemoradiation is a technically and clinically demanding procedure, as the patients are usually malnourished with multiple other comorbidities (which preclude offering surgery). They often require intensive nutritional rehabilitation before, during, and after chemoradiation, to ensure they complete the treatment successfully. It would therefore have been sobering to also have an account of the denominator from which the authors selected those patients who “successfully completed” radical chemoradiation and the baseline nutritional status of these patients. Considering the primary objective of the study, a mention of the toxicity rates with respect to the lung and heart was expected despite the retrospective nature of the study. Typical series report acute toxicity (Grade 2 or higher radiation pneumonitis) in the range of 14%–35%. It is also surprising that the use of concurrent chemotherapy seemed to significantly affect the overall survival (OS) without impacting the disease-free survival. Hence, the conclusions drawn by the authors regarding the OS and disease-free survival and the factors affecting them, including concurrent chemotherapy significantly prolonging the survival, seemed to be a little premature due to the small sample size, retrospective nature of the audit, and the short duration of follow-up, with the disease status of almost 25% of patients unknown (due to various reasons) in both the arms.
It is commendable to note that with the transition to VMAT, radiation doses to the heart could be reduced without impacting the lung doses; as technically speaking, an attempt to reduce doses to the heart could have increased the intermediate-to-low doses to the lungs. In addition, the authors have successfully demonstrated that dose-escalated radiotherapy was safely deliverable using modern radiotherapy techniques such as VMAT and resulted in a 2-year OS of 36%–40%. However, whether this dose escalation will translate into more meaningful outcomes for patients in terms of OS is uncertain. The reported OS in this study does not seem to be significantly different from that of the historical cohorts reporting an OS of 38% in a similar group of patients receiving only 50 Gy dose of radiation. Several recent studies have also supported this philosophy, and so we may need to critically look at dose escalation in esophageal cancer radiotherapy, even in squamous cell cancers.
Of course, the next question is if not dose escalation, then what do we do to improve these dismal outcomes? Biomarkers to select radio-resistant tumors, the use of radio-sensitizers, and techniques that reduce toxicity further (e.g., proton beam therapy) are all being researched on to improve the outcomes, and we eagerly await some light at the end of the long tunnel!
| References|| |
Dora TK, Deshmukh J, Chatterjee A, Goel A, Bose S, Singh A, et al.
Conformal radiation therapy versus volumetric arc therapy in high dose concurrent chemoradiotherapy for carcinoma esophagus: A retrospective analysis. Cancer Res Stat Treat 2021;4:456-65. [Full text]
Talapatra K. Radiation therapy in esophageal cancer: Shifting paradigms. Cancer Res Stat Treat 2021;4:538-40. [Full text]
Asakura H, Hashimoto T, Zenda S, Harada H, Hirakawa K, Mizumoto M, et al.
Analysis of dose-volume histogram parameters for radiation pneumonitis after definitive concurrent chemoradiotherapy for esophageal cancer. Radiother Oncol 2010;95:240-4.
Herskovic A, Martz K, Al-Sarraf M, Leichman L, Brindle J, Vaitkevicius V, et al.
Combined chemotherapy and radiotherapy compared with radiotherapy alone in patients with cancer of the esophagus. N Engl J Med 1992;326:1593-8.
Hulshof MC, Geijsen ED, Rozema T, Oppedijk V, Buijsen J, Neelis KJ, et al.
Randomized study on dose escalation in definitive chemoradiation for patients with locally advanced esophageal cancer (ARTDECO Study). J Clin Oncol 2021;39:2816-24.