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.).