METHODS
The sample consisted of 585 patients that underwent radiotherapy and chemotherapy with the diagnosis
of Stage III lung cancer. OS prediction was undertaken in 324 cases, survival time prediction in
241 that died due to lung cancer, and prediction of time to progression in 223 that showed progression
during follow-up. Twenty-seven variables were evaluated, and logistic regression, multilayer perceptron
classifier (MLP), extreme gradient boosting, support vector clustering, random forest classifier (RFC),
Gaussian Naive Bayes, and light gradient boosting machine algorithms were used to construct prediction
models.
RESULTS
In OS prediction, over a median 21-month follow-up, 255 of 324 cases died and the median OS was 20
(2-101) months. The best predictive algorithms belonged to logistic regression for OS (accuracy rate:
70%, confidence interval [CI]: 0.60-0.82, area under curve [AUC]: 0.76), MLP classifier for 12- and
20-month survival times (67%, CI: 0.54-0.81, AUC: 0.64 and 71%, CI: 0.59-0.84, AUC: 0.61, respectively),
and RFC for time to progression (76%, CI: 0.66-0.86, AUC: 0.78).
CONCLUSION
Considering high treatment costs, potential serious toxicity, the harm of early progression, and low
survival in cases of ineffective treatment, machine learning-based predictive systems are promising.
Personalizing prognosis and treatment using these algorithms can improve oncological results.
Keywords: Lung cancer; machine learning; overall survival; progression-free survival; radiotherapy
Artificial intelligence (AI) is a branch of computer
science that aims to emulate human-like intelligence
in machines using computer software and algorithms
without direct human stimuli to perform certain
tasks.[
It is important to predict survival and progression
in cases diagnosed with cancer to improve treatment
and provide patients and clinicians with information.
Considering the data set of lung cancer patients with
specific demographic, tumor and treatment information,
it is essential to determine if any parameter can be
used to predict whether the patient will survive or the
disease will recur.
The current study aimed to predict OS, survival
time, and time to progression using ML in patients
diagnosed with Stage III lung cancer and treated at
the Radiation Oncology and Chest Diseases departments
of Eskişehir Osmangazi University Faculty of
Medicine.
The inclusion criteria were as follows: A
histopathological diagnosis of lung cancer, no diagnosis
of distant metastasis or multiple primary neoplasia,
Karnofsky Performance Scale (KPS) score
≥60, age >18, having completed all planned radiotherapy
(RT) and chemotherapy schemes, and regularly
attending the follow-up sessions. Staging was
performed according to the American Joint Committee
on Cancer Staging System, eighth edition.[
Treatment Characteristics
Concurrent chemotherapy was applied to the appropriate
cases. In the non-SCLC group, cisplatin (40
mg/m2) or paclitaxel (45-50 mg/m2)+carboplatin (area
under curve [AUC]: 2) was administered weekly. In the
patients with SCLC, cisplatin (40 mg/m2) was administered
weekly or cisplatin (75 mg/m2)+etoposide (100
mg/m2) every 21 days. The patients attended the outpatient
clinic every week.
Chemotherapy
Post-treatment Follow-up
ML, Statistical Analysis, and Application
Statistical Analysis and Application
Synthetic minority over-sampling involves developing
predictive models based on unbalanced classification
data sets with severe class imbalance. The difficulty
in working with unbalanced data sets is that most
ML techniques do not take into account the minority
class and perform poorly, but typically the most important
performance belongs to the minority class. One
approach to unbalanced data sets is to over-sample the
minority class. The simplest approach is the duplication
of samples in the minority class; however, these
samples do not add any new information to the model;
rather, new samples can be synthesized from existing
samples.[
Cross validation is a model validation technique
that tests what results will be obtained from a statistical
analysis performed on an independent data set.
Its main use is to predict what accuracy a prediction
system will have in practice. In a prediction problem,
the model is usually trained with a "known data set"
(training set) and tested with an "unknown data set"
(verification or test set). The purpose of this test is to
measure the ability of the trained model to generalize
new data and to identify problems of over-compliance
or selection bias.[
Radiotherapy and concurrent chemotherapy
The patients were immobilized in a supine position
using T-bar/Wingboard with their hands above their
head, and planning CT was performed with the Somatom
Definition AS® device with a 3-5-mm crosssection.
The images were fused with the FDG-PET/
thoracic CT images at the time of diagnosis and current
thorax CT images after chemotherapy in cases that
underwent chemotherapy before RT. The gross tumor
volume (GTV) was determined after fusion. In cases
receiving chemotherapy before RT, GTVtumor was determined
as the post-chemotherapy volume, and GTVlymph
node as the pre-chemotherapy volume. The clinical
target volume (CTV) margin was set according to tumor
histopathology: CTVtumor was taken as 0.8 cm for
adenocarcinoma, 0.6 cm for squamous cell carcinoma,
and 0.5 cm for other histologies. CTVlymph node was determined
as 0.5 cm. No elective nodal irradiation was
performed. For the planning target volume (PTV), the
CTVtumor and CTVlymph node, the volumes were given a
0.5-cm margin, and the cases were treated with imageguided
radiation therapy after 2014. Radiation therapy
was applied with daily fractions ranging from 1.8-2
Gy to 45-68 Gy depending on various criteria, such as
tumor localization and size, lung volume, and tumor
volume, under the guidance of 3DCRT/IMRT/VMAT
using a Varian Trilogy®/TrueBeam® or Elekta Precise?
device. In SCLC cases with good treatment response,
25 Gy (2.5 Gy/day×10 fractions) prophylactic cranial
irradiation was applied.
In squamous cell lung cancer, gemcitabine, paclitaxel,
or vinorelbine was used in primary and secondary chemotherapy, either alone or in combination with
platinum. The first-line chemotherapy of adenocarcinoma
was the same as given in the section above, but
pemetrexed was applied as the second-line therapy.
In patients with epidermal growth factor receptor,
anaplastic lymphoma receptor tyrosine kinase gene
translocation, or ROS proto-oncogene 1 receptor tyrosine
kinase gene rearrangement, first-line chemotherapy
was the same as in the previous section, and
the second-line therapy was arranged as the targeted
therapy specific to the genetic change. In patients with
recurrent/progressive disease, a chemotherapy regimen
that had not previously been used was applied,
taking into account the clinical performance ability
and comorbidities of the patient; therefore, the decision
to continue this therapy was taken according to
the patient response. In the treatment of SCLC, etoposide
combined with platinum was used as the firstline
chemotherapy regimen, and irinotecan or the
combination of vincristine+cyclophosphamide+adriablastina
was used as the second-line regimen in cases
that did not respond to treatment or recurred.
At the 1st month after the end of treatment, anamnesis,
a physical examination, thorax CT, and response to
treatment were evaluated. The follow-up evaluations of
anamnesis, physical examination, and thorax CT were
performed every 3 months for the following 3 years,
and every 6 months for the 4th and 5th years. After the
5th year, annual follow-up was undertaken. In suspected
cases of recurrence/metastasis, abdominal CT/
brain MR and/or PET CT was also conducted.
In the prediction of both OS and time to progression,
the following 27 variables were evaluated: Age, gender,
KPS score, body mass index, smoking history, presence
of chronic obstructive pulmonary disease, histopathology,
tumor localization, tumor size, lymph node site,
lymph node involvement (single level/multilevel), T
stage, N stage, TNM stage, surgical history, presence of
concurrent chemotherapy, concurrent chemotherapy
scheme, number of chemotherapy cycles before RT,
GTV, PTV, total RT dose, RT fraction dose, prognostic
nutritional index, pretreatment serum albumin and hemoglobin
values, neutrophil lymphocyte ratio (NLR),
and advanced lung cancer inflammation index. These
parameters were determined by considering previous
prognosis studies related to lung cancer.[
Extreme value analysis is a branch of statistics that
deals with extreme deviations from the median of
probability distributions. It aims to assess the likelihood
of more extreme events than those previously
observed from a particular sequential example of a
certain random variable. Excessive values decrease
predictive performance, and there are different methods
for detecting extreme values, but in simple terms,
values that deviate a certain amount from the mean are
considered as extreme.[
In the prediction of OS time, 241 Stage III lung cancer
cases that died were evaluated. The median age was 62
(range, 44-80) years. The median RT dose was 60 (range,
50-68) Gy. Concurrent chemotherapy was applied in 180
cases. The median number of concurrent chemotherapy
is 4 (min: 0, max: 6). RT timing was with the first cycle
of chemotherapy in 17 patients. The characteristics of the
patients and tumors are summarized in Table
For the prediction of time to progression, 223 cases
that showed progression during the follow-up were
evaluated. The median age was 61 (range, 44-80) years.
The median RT dose was 60 (range, 50-68) Gy. Concurrent
chemotherapy was applied to 172 cases. RT timing
was with the first cycle of chemotherapy in 11 patients.
The median number of concurrent chemotherapy is 4
(min: 0, max: 6). Patient and tumor characteristics are
summarized in Table
OS and Progression-free OS
The OS evaluation was conducted with 324 cases, and
over a median follow-up of 21 months, 255 patients
died. The prediction of OS time was performed with
241 of the patients that died, and the median survival
time of this group was 20 (2-101) months. The median
survival times for substages IIIA, IIIB, and IIIC were 25 (6-101), 19.5 (5-70), and 15 (2-65) months,
respectively. The prediction of time to progression was
undertaken with 223 cases that showed progression
during the follow-up. The median time from the end
of treatment to progression was 9 (0-96) months. The
median values for substages IIIA, IIIB, and IIIC were
10 (0-96), 9 (0-68), and 7 (1-28) months, respectively.
ML Prediction
OS prediction
Significant variables were determined as PTV, lymph node
site, and KPS score. Figure
NLR: Neutrophil-to-lymphocyte ratio; KPS: Karnofsky performance scale; ALI: Advance lung cancer inflammation index.
BMI: Body mass index; GTV: Gross tumor volume; PTV: Planning target volume; RT: Radiotherapy; PNI: Prognostic nutritional index;
NLR: Neutrophil-to-lymphocyte ratio; KPS: Karnofsky performance scale; ALI: Advance lung cancer inflammation index.
OS time prediction
Twelve-month survival prediction
Significant variables were identified as GTV, lymph
node site, surgical history, and histopathology. Figure
Twenty-month survival prediction
Significant variables were identified as GTV, lymph
node site, and T stage. In Figure
Prediction of time to progression
Significant variables were determined as NLR, lymph
node site, age, and T stage. In Figure
ROC: Receiver operating characteristic; SVC: Support vector classification; MLP: Multilayer perceptron classifier; LGBM: Light gradient
boosting machine.
Today, many hospitals store data in a digital environment. By evaluating these large data sets with ML techniques, it could become possible to predict the treatment results of patients, plan individualized patient treatment, improve institutional performance, and regulate health insurance. The accurate prediction of survival in cancer patients continues to be a problem due to the increased heterogeneity and complexity of cancer, various treatment options, and different patient characteristics (age, KPS score, comorbidities, etc.). If reliable estimates are obtained by ML, it can help achieve personalized care and treatment.
There is a growing interest in studies on prognosis
prediction based on ML using patient, tumor and treatment
data.[
Gupta et al.[
The N stage, which is also used in TNM staging,
affects the treatment decision and prognosis. In a
previous study, the 5-year OS was examined according
to the Nclinical and Npathological stages, and these rates
were found to be 60% and 75%, respectively, for N0,
37% and 49%, respectively, for N1, 23% and 36%, respectively,
for N2, and 9% and 20%, respectively, for
N3.[
In a study conducted with 207 cases diagnosed
with inoperable lung cancer, Bradley et al.[
In the current study, in the prediction of OS time,
the cases that survived for ≤20 months were successfully
predicted by the MLP algorithm at an accuracy rate
of 91%, and this algorithm had an accuracy of 31% for
those surviving for >20 months. The same algorithm had
a 48% accuracy rate in predicting patients surviving for
≤12 months and 82% accuracy rate in predicting those
surviving for more than 12 months. These results may
be associated with the patient data set including a low
number of cases surviving for <12 months or more than
20 months. There is a need for larger case studies on ML.
Gupta et al.[
ML is becoming part of people's lives day by day,
and its use in the health area can both improve treatment
outcome and reduce treatment costs. However, large data sets are required for ML, and data size and
diversity are important to achieve an effective algorithm.
There is still no standard ML algorithm to predict
prognosis, treatment outcome, or toxicity rate in
oncology, and multicenter large-scale data are required
to create the most appropriate algorithm. Thus, in future
work, it is planned to establish big data and re-evaluate
the results by increasing the number of patients
and collaborating with other centers.
Peer-review: Externally peer-reviewed.
Conflict of Interest: All authors declared no conflict of interest.
Ethics Committee Approval: The study was approved by the Eskişehir Osmangazi University Non-Invasive Clinical Research Ethics Committee (No: 29, Date: 17/12/2019).
Financial Support: None declared.
Authorship contributions: Concept - D.E., M.Y., M.M., G.A., Ş.Y.; Design - D.E., M.Y., M.M.; Supervision - D.E., M.Y.; Funding - D.E., M.Y., Ş.Y.; Materials - M.Y., Ş.Y.; Data collection and/or processing - M.Y., Ş.Y.; Data analysis and/ or interpretation - D.E., M.Y., Ş.Y., M.M., G.A., Ö.Ç.; Literature search - D.E., M.Y. Ş.Y., M.M., G.A.; Writing - D.E., M.Y. Ş.Y., M.M., G.A., Ö.Ç.; Critical review - D.E., M.Y. Ş.Y., M.M., G.A., Ö.Ç.