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Proton Therapy FAQs for Lung Cancer

Figure 3a, left: Proton
(top panels) vs IMRT plan (bottom panels) for favorable intermediate risk prostate cancer.

The outlook for many patients diagnosed with lung cancer has improved in recent years. Through genetic sequencing and other technologies, researchers have found ways to better characterize tumors and tailor treatments to the unique tumor signature as well as the overall health of each patient. No longer are there one size fits all treatment solutions. Your treatment team will discuss with you care, strategies that might include surgery, chemotherapy, immunotherapy, targeted therapies as well as radiation and radiosurgery.


Proton therapy is a type of advanced radiation treatment. It takes advantage of a remarkable and unique characteristic of high energy particle beams and how they deposit ionizing radiation as they move through the body. Unlike conventional gamm a or X-ray beams, which do not stop as they pass through the body, the depth of proton therapy beams can be controlled.As the charged particles come to a stop,all of their energy is deposited within the tumor with little to no exit dose to the surrounding tissues.

Because the lungs are near vital organs including the heart, esophagus, and spinal cord, precise delivery of radiation is exceptionally important.This is where the precision of proton therapy comes into play.With conventional radiation the powerful doses required to kill tumor cells can also damage these sensitive structures. Avoiding radiation to the esophagus, heart and healthy lung reduces the risk of treatment related side effects including lung inflammation, scarring of the lungs, difficulties swallowing, heart complications, and pain.

With image guidance and pencil beam scanning technology, proton therapy treatment at the Johns Hopkins Proton Center is amongst the most advanced in the world. Pencil beam technology allows for “dose painting” with a precise proton beam, only a few millimeters wide to target the unique shape of individual tumors.


The Johns Hopkins Proton Therapy Center has the advanced technology lung cancer patients need to exactly target moving tumors, reducing the range of uncertainty. Because the lungs are near vital organs, proton therapy can spare exit dose radiation to adjacent structures including the heart, esophagus and spinal cord. In addition, proton therapy reduces side effects including:

  • Lung inflammation
  • Heart complications
  • Scarring of the lungs
  • Pain
  • Difficulties swallowing

These images show a comparison of exit doses for photon and proton theapy.

Many factors are taken into consideration when discussing lung cancer treatment with proton therapy. These include:

  • Is the tumor near critical organs such as esophagus, heart, and spine?
  • Has the patient received previous radiation treatment?
  • Is the patient receiving concurrent chemotherapy?
  • Does the patient suffer from poor pulmonary function due to COPD or previous smoking or other medical reasons that increase the risk of lung complications following RT?


  • Patients with stage I, II or III non-small cell lung cancer (NSCLC) and some stages of small cell lung cancer (SCLC)
  • Thoracic sarcoma, malignant mesothelioma, thymomas and thymic carcinomas
  • Inoperable non-small cell lung cancer that has not spread outside of the chest or patients who are unable to tolerate surgery may be candidates.
  • Recurrent cancer that has not spread outside the chest

Patients with disease metastasized to the brain, bone or liver are not considered candidates for proton therapy at the present.


Stage II & III Non-small Cell Lung Cancer (NSCLC)

Surgery is frequently not an option for patients with stage II and III lung cancer as the tumor maybe too large or the patient may have medical issues that make them an unsuitable candidate. Aggressive treatment with proton therapy combined with chemotherapy is an option where surgery is not possible. Because proton therapy technology with image guidance and pencil beam proton therapy reduces the radiation exposure to normal tissues, proton therapy significantly reduced dose to normal lungs, esophagus, spinal cord and heart compared with other forms of radiotherapy.

dose color

Dose color wash comparison of proton (top) and photon (bottom). Dose distribution to lung, heart, and esophagus are significantly lower in the proton plan.


In patients with limited-stage small cell lung cancer, proton therapy combined with chemotherapy provides aggressive treatment that can be less toxic than conventional X-ray radiation.This regimen could make the treatment more tolerable with less side effects, such as painful swallowing and radiation induced pneumonia.

Colaco RJ, Huh S, Nichols RC, Morris CG, D’Agostino H, Flampouri S, Li Z, Pham DC, Bajwa AA, Hoppe BS. Dosimetric rationale and early experience at UFPTI of thoracic proton therapy and chemotherapy in limited-stage small cell lung cancer. Acta Oncologica. 2013 Feb; 52(3): 506-13.


Proton therapy can help lower the risk of recurrence in patients with thymoma following surgical resection. For patients with unresectable thymoma, proton therapy combined with chemotherapy can often be curative. Compared to other forms of radiation, proton therapy helps reduce the radiation dose to the heart and lungs compared with conventional IMRT. Reducing these doses results in lower rates of complication. For young women, it can lower the radiation dose to the breast, reducing the risk of breast cancer.

Hoppe BS, Huh S, Flampouri S, Nichols RC, Oliver KR, Morris CG, Mendenhall NP, Li Z. Double-scattered proton-based stereotactic body radiotherapy for stage I lung cancer: a dosimetric comparison with photon-based stereotactic body radiother- apy. Radiother Oncol. 2010 Dec; 97(3):425- 30.

Grutters JP, Kessels AG, Pijls-Johannesma M, De Ruysscher D. Joore MA, Lambin P. Comparison of the effectiveness of radio- therapy with photons, protons, and car- bon-ions for non-small cell lung cancer: a meta-analysis. Radiother Oncol. 2010 Apr; 95(1):32-40.

Baumann BC, Mitra N,Harton JG, XiaoY,Wojcieszynski AP, Gabriel PE, Zhong H, Geng H,Doucette A,Wei J, O’Dwyer PJ, Bekelman JE, Metz JM, Comparative Effectiveness of Proton vs PhotonTherapy as Part of Concurrent Chemoradiotherapy for Locally Advanced Cancer, JAMA Oncol.2019, Dec 26

Chang JY, Komaki R, Lu C,Wen HY,Allen PK,Tsao A, Gillin M, Mohan R, Cox JD. Phase 2 study of high-dose proton therapy with concurrent chemotherapy for unresectable stage III non small cell lung cancer. Cancer. 2013 Oct; 117(20):4707-13.

Sejpal S, Komaki R,Tsao A, Chang JY, Liao Z,Wei X, Allen PK, Lu C, Gillin M, Cox JD. Early findings on toxicity of proton beam therapy with concurrent chemotherapy for non-small cell lung cancer. Cancer. 2011 Jul; 117(13): 3004-13.

Nichols RC, Huh SN, Henderson RH, Mendenhall NP, Flampouri S, Li Z, D’Agostino HJ, Cury JD, Pham DC, Hoppe BS. Proton radiation therapy offers reduced normal lung and bone marrow exposure for patients receiving dose-escalated radiation therapy for unresectable stage III non- small-cell lung cancer: a dosimetry study. Clin Lung Cancer. 2011 Jul; 12(4):252-7.

To refer a patient or find out more about the Johns Hopkins Proton Therapy Center, visit

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