The Special Medical Physics Consult Process for Reirradiation Patients

Abstract

To present a systematic approach to the reirradiation special medical physics consult (ReRT-SMPC) process. Materials and Methods: An in-house reirradiation committee of physicians and physicists was formed to develop a streamlined and well-documented approach to ReRT-SMPCs. Dosimetric goals and considerations for tissue repair were generated by the committee with input from the literature, clinical trial guidelines, and physician experience. Procedural workflow was also defined. Results: The total number of ReRT-SMPCs performed in our department in 2018 was 401, corresponding to 369 unique patients and 16% of the total number of patients receiving external beam radiation in our department that year. This constituted a large increase over the 183 ReRT-SMPCs performed in 2017. We have found that a standardized ReRT-SMPC workflow helps to safeguard patients, documents the clinical decision-making process for medical and legal purposes, and facilitates the peer-review process. The data being collected from each consult along with toxicity and outcomes data can be used to help inform future re-treatment guidelines. Conclusions: As the number of patients returning for additional courses of radiation continues to increase, a uniform method for the ReRT-SMPC workflow and analysis is a powerful tool for ensuring patient safety, understanding and predicting treatment toxicity, and refining reirradiation dosimetric limits.

A surveillance study of patterns of reirradiation practice using external beam radiotherapy in Japan

“…The possibility of unacceptably high severe toxicity, even lethal catastrophic arterial rupture, carotid blow-out syndrome [ 21 ] or rupture of the thoracic aorta [ 22 ], should be anticipated. Recently, a few dose volume constraints for each organ at risk from Re-RT have been proposed [ 23 , 24 ], one of which included considering temporally-based dose recovery parameters, or ‘discount’ factors with time [ 23 ].…”

“…When considering Re-RT, ROs must make difficult clinical decisions, which depend mainly on their own experience due to the lack of high-level evidence for Re-RT. There are several considerations that could be drawn from this study to help in decision-making, such as (i) normal tissue tolerability [ 23 , 24 ], (ii) availability of technical data from the first RT, (iii) palliative or radical intent relating to prognosis, and (iv) Re-RT schedule and dose fractionation-volume relationship. Such treatment decisions must be made only by multidisciplinary teams with expertise in radiotherapy and implemented on carefully selected patients.…”

Practical Clinical Implementation of the Special Physics Consultation Process in the Re-irradiation Environment

“…Paradis et al presented a very thorough methodology as implemented by a large academic institution for using the special physics consultation to address issues associated with patients undergoing reirradiation. 3 Their emphasis on consistent structure is key to providing safe, effective treatments for these patients.…”

Acknowledge uncertainties

“…Modern dose calculation algorithms are quite impressive, but rely on CT Hounsfield numbers to infer the material composition of the medium. Other examples of common uncertainties include, but are not limited to, deformable and rigid image registration, 8 applicability of OAR dose objectives when combining different fractionation regimens and/or previous treatment, 9 motion management uncertainties, peripheral target coverage with single‐isocenter multitarget techniques, or 4D binning artifacts from irregular breathing patterns. The list could go on and on.…”