Lung cancer [LC] is the leading cause of cancer death worldwide. The standard treatment of locally advanced lung cancer unresectable or marginally resectable is combination therapy with radical or preoperative chemoradiation. The local control rates and survival with this treatment modality have increased by more than 30%. Radiotherapy [RT] with technical molded 3D [3D-CRT, Three-Dimensional Conformal Radiation Therapy] or IMRT [intensity-modulated radiation therapy] has allowed that the total dose of radiation has increased which leads to a direct benefit on the results treatment.

Between 17-30% of patients are susceptible to pneumonitis due to radiation [NR]. This complication may appear at the end of the RT or up to 6 months after the treatment. In severe cases, mortality can reach 50%.

It's well known that in various diseases, functional abnormalities precede the clinical manifestations. The degree of pulmonary failure secondary to RT is measured following the standards of the Radiation Therapy Oncology Group who ranks in degrees [0 to 4].

Not precisely known factors that influence the development of NR.

Objectives:

To evaluate the effect of chemotherapy and thoracic radiotherapy on pulmonary function and identify predictors of radiation pneumonitis in locally advanced lung cancer [stages IIIA and IIIB].

Hypothesis:

Respiratory function tests may predict the development of radiation pneumonitis in patients with locally advanced lung cancer who receive radical treatment with chemoradiation.

Methods Prospective cohort study with patients with locally advanced lung cancer of the Lung Cancer Clinic of the National Cancer Institute [INCAN]. Patients will receive weekly paclitaxel 50 mg and carboplatin AUC 2 with concomitant radiotherapy 44-63 Gy (22-33 fractions). Followup of lung function tests at baseline, during treatment with radiotherapy and will be carried out on 4 more occasions.

Inclusion Criteria:

• Candidates must have understood and signed informed consent
• Histopathological diagnosis of locally advanced lung cancer [IIIA-cT2N1-2, cT3N1-2, cT4N0, M0o IIIB: cT2N3, cT3N3, cT4N1-3, M0]. They may also include patients with oligometastatic disease[M1] candidates for chemoradiation
• Any histology
• Medical tests: white blood cell count ≥ plasma 3,000 / mm3, platelets ≥ 100,000 / mm 3, hemoglobin ≥ 12 g / dl, serum creatinine ≤ 1.5 mg / dl, total bilirubin ≤ 1.5, transaminases [ ≤ 2.5 times the upper limit of normal [ULN], alkaline phosphatase <5 ULN.
• Age ≥ 18 years.
• General condition score according to ECOG 0 to 2 or a ≥ 60% Karnofsky.
• Estimated life expectancy with treatment of at least 24 weeks.

Exclusion criteria:

• Uncontrolled concurrent diseases.
• History of previous radiotherapy to the primary site.
• Pregnant or breast-feeding.
• Use of anticoagulants in therapeutic doses
• Intercurrent Malignancies, except dormant basal cell carcinoma in skin, carcinoma in situ of the cervix
• Invasive cancer unless the background was at least 5 years and the disease-free status.](streamdown:incomplete-link)

Patients with locally advanced lung cancer candidates to receive treatment with chemoradiation that will receive treatment in the National Cancer Institute in Mexico City.