Discussion
Quality assurance is integral to modern day delivery of RT and focusses on metrics related to processes, logistics and timing. RT protocol compliance is one aspect of quality assurance and adult and paediatric studies have confirmed that RT protocol deviation leads to increased treatment failure (7,8). There is no accepted universal definition of deviations and this varies by cancer and protocol but would generally include one or more of the following; dose, volume, field, timing of start and overall treatment time (7,8).
In our audit of children with cancer who received RT at our institute we found that approximately one in two children had a deviation in one parameter with one in four children having deviation in TTS and TTC but only one in 17 having deviation in TDD. A recent study from the Dominican Republic with a relatively smaller sample size (19 children with Wilms tumour, rhabdomyosarcoma, retinoblastoma and nasopharyngeal carcinoma) is the only other study from LMIC which has previously studied this and found that 95% of children had at least one deviation (they also examined an additional parameter of field) with greatest deviation in TTC 79% followed by TTS 53% and finally TDD 42%.(9)
These findings are concerning because the published literature provides evidence to the importance of these parameters. Delay in starting RT impacts outcome of children with Ewing sarcoma(10-12), Wilms tumour(13) and medulloblastoma(14) and excess time taken to complete RT has an adverse impact on children with medulloblastoma.(15) Similarly dose deviations have had an adverse impact in children with rhabdomyosarcoma(16), medulloblastoma(17) and Ewing sarcoma.(18) A limitation of our study is that we did not have follow-up for each patient to determine if deviations had an impact on outcomes but it would not be incorrect to assume some detrimental impact.
Factors associated with deviations may be demographic, disease or treatment related. We found the greatest deviations in TTS in sarcomas in comparison to leukemia, lymphoma and CNS tumours. This may be due to involvement of both, surgery and chemotherapy as modalities before radiation and toxicities related to these modalities. In carcinoma nasopharynx and brainstem glioma, in which radiation was primary mode of treatment, treatment was started within days of diagnosis.
Additionally, healthcare related factors, which may be specific to our institution as well as the wider context of healthcare delivery in the country, may impact these deviations. 31% of the children who received RT had their preceding treatment (surgery and/or chemotherapy) outside our institute and their deviation in TTS was double of those who had preceding treatment at our institute. This highlights the lack of access to RT and the need to move to different locations, compromising delivery of quality care. Once RT commenced at our institute, preceding treatment ceased to be a significant factor in deviation of TTC as our infrastructure is geared to deliver uninterrupted treatment if the child remains well.
Similarly deviations in TDD were only around 6% and less likely to be impacted by any of the factors mentioned above. Although most of our patients are not on prospective clinical studies, we do use national and international recommendations and protocols to deliver the correct doses. Our data does show that there was TDD deviation in brainstem gliomas which received a mean dose of 52.6 Gray against a recommended dose of 54 to 60 Gray. We are now putting in guidelines to correct this.
We did see significant association of cancer type with TTC with the high degree of deviation seen in medulloblastoma where craniospinal irradiation (CSI) would lead to myelotoxicity. This challenge has also been highlighted in another publication from India where 73% of patients had interruptions in CSI.(19) In contrast experience from USA suggests that interruptions even in this group of patients can be as low as 2.5%.(20) We plan to review our practice of CSI including thresholds for interrupting RT and use of growth factors to address this.
In conclusion, our study adds to the limited literature on RT quality for children with cancer in LMIC. It highlights that one in four children have deviation in TTS and TTC RT and provides us areas to improve within our practice. Our work is limited by the fact that we did not examine the parameter of volume or field. Also our study is retrospective and dependent on the quality of record keeping and so we cannot comment on the individual circumstances which may have led to the deviation (e.g. site and stage of tumour, treatment intensity, etc.).